docs/usage.md

@@ -229,6 +229,20 @@ what changed at the source in between.
 - **Sieve scripts** are matched by name, and the target's is replaced when
   its content differs from the archive's.
 
+Messages go in batches, as many to an `Email/import` as the target's
+`maxObjectsInSet` allows, up to 50, with their blobs uploaded several at a
+time -- the target's `maxConcurrentUpload`, and no more than `--threads`.
+Each message is still counted on its own: one the target rejects fails
+alone, and the rest of its batch lands. A batch that ends without a clear
+answer -- a dropped connection, a gateway timeout -- is never sent again as
+it was. The target is read first, the messages that arrived are counted as
+created, and only the rest are imported again, so none is ever doubled.
+
+While it runs, export prints a line every few seconds for mail, contacts and
+events: how many of how many, how fast, and about how long is left. Each
+type ends with a line of what was created, updated, left unchanged and
+failed.
+
 `--prune` also deletes what is on the target and not in the archive. It asks
 first; `--yes` answers for it, for scripts. Export speaks JMAP only.
 

src/jmap/http.rs

@@ -97,6 +97,10 @@ impl Inner {
 #[derive(Debug, Clone, Copy)]
 enum Kind {
     Api,
+    /// An API call that must not be sent twice: a write the server may
+    /// already have applied when the connection failed. A transport error is
+    /// returned to the caller, which checks the target instead of resending.
+    ApiOnce,
     Upload,
 }
 
@@ -220,6 +224,23 @@ impl HttpClient {
             .map_err(|e| JmapError::Malformed(format!("response is not valid json: {e}")))
     }
 
+    /// As `post_json`, but a transport failure is not retried: the request
+    /// may have reached the server, and sending it again could apply it twice.
+    /// Throttling and `503` answers, which mean it was not processed, are still
+    /// retried.
+    pub fn post_json_once(&self, url: &str, body: &Value) -> Result<Value, JmapError> {
+        let payload = serde_json::to_vec(body)?;
+        let raw = self.execute(
+            Kind::ApiOnce,
+            "POST",
+            url,
+            Some(&payload),
+            Some("application/json"),
+        )?;
+        serde_json::from_slice(&raw)
+            .map_err(|e| JmapError::Malformed(format!("response is not valid json: {e}")))
+    }
+
     pub fn upload(
         &self,
         upload_url: &str,
@@ -298,6 +319,16 @@ impl HttpClient {
                                 body: truncate(&body),
                             });
                         }
+                        // A gateway error may come back after the server
+                        // behind it applied the write: not safe to resend.
+                        StatusOutcome::Retryable
+                            if matches!(kind, Kind::ApiOnce) && matches!(status, 502 | 504) =>
+                        {
+                            return Err(JmapError::HttpStatus {
+                                status,
+                                body: truncate(&body),
+                            });
+                        }
                         StatusOutcome::Retryable => {
                             attempt += 1;
                             self.inner.retries_total.fetch_add(1, Ordering::Relaxed);
@@ -344,6 +375,7 @@ impl HttpClient {
                         }
                     }
                 }
+                Attempt::Transport(err) if matches!(kind, Kind::ApiOnce) => return Err(err),
                 Attempt::Transport(err) => match transport_disposition(&err) {
                     Disposition::Fatal => return Err(err),
                     Disposition::Retryable => {
@@ -659,6 +691,90 @@ mod tests {
     use super::*;
     use crate::net::CertOverride;
 
+    /// A server that reads each request and hangs up without answering: a
+    /// transport failure after the request has been sent. Returns its URL and
+    /// the count of requests it has seen.
+    fn hang_up_server() -> (String, Arc<AtomicU64>) {
+        use std::io::Read;
+        let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+        let url = format!("http://{}/jmap/api", listener.local_addr().unwrap());
+        let seen = Arc::new(AtomicU64::new(0));
+        let counter = seen.clone();
+        std::thread::spawn(move || {
+            for stream in listener.incoming() {
+                let Ok(mut stream) = stream else { break };
+                let mut buf = [0u8; 4096];
+                let _ = stream.read(&mut buf);
+                counter.fetch_add(1, Ordering::SeqCst);
+            }
+        });
+        (url, seen)
+    }
+
+    fn quick_retries(max_retries: u32) -> RetryPolicy {
+        RetryPolicy {
+            max_retries,
+            base: Duration::from_millis(1),
+            cap: Duration::from_millis(2),
+        }
+    }
+
+    #[test]
+    fn a_write_sent_once_is_not_resent_after_a_transport_failure() {
+        let (url, seen) = hang_up_server();
+        let client = HttpClient::new(
+            Auth::Bearer { token: "t".into() },
+            quick_retries(2),
+            CertOverride::none(),
+        );
+        let err = client
+            .post_json_once(&url, &serde_json::json!({}))
+            .unwrap_err();
+        assert!(matches!(err, JmapError::Transport(_)), "{err}");
+        assert_eq!(seen.load(Ordering::SeqCst), 1, "sent exactly once");
+
+        let (url, seen) = hang_up_server();
+        let _ = client.post_json(&url, &serde_json::json!({}));
+        assert_eq!(
+            seen.load(Ordering::SeqCst),
+            3,
+            "an ordinary call retries twice"
+        );
+    }
+
+    #[test]
+    fn a_write_sent_once_is_not_resent_after_a_gateway_timeout_but_is_after_503() {
+        let mut server = mockito::Server::new();
+        let url = format!("{}/jmap/api", server.url());
+        let client = HttpClient::new(
+            Auth::Bearer { token: "t".into() },
+            quick_retries(2),
+            CertOverride::none(),
+        );
+        let gateway = server
+            .mock("POST", "/jmap/api")
+            .with_status(504)
+            .expect(1)
+            .create();
+        let err = client
+            .post_json_once(&url, &serde_json::json!({}))
+            .unwrap_err();
+        assert!(
+            matches!(err, JmapError::HttpStatus { status: 504, .. }),
+            "{err}"
+        );
+        gateway.assert();
+        gateway.remove();
+
+        let busy = server
+            .mock("POST", "/jmap/api")
+            .with_status(503)
+            .expect(3)
+            .create();
+        let _ = client.post_json_once(&url, &serde_json::json!({}));
+        busy.assert();
+    }
+
     #[test]
     fn invalid_certificates_are_accepted_only_for_the_named_host() {
         let client = HttpClient::new(

src/jmap/request.rs

@@ -131,6 +131,14 @@ impl Request {
         let value = client.post_json(api_url, &self.envelope()?)?;
         Response::parse(value)
     }
+
+    /// As `send`, for a write that must not be applied twice: a transport
+    /// failure comes back as an error instead of being resent (see
+    /// `HttpClient::post_json_once`).
+    pub fn send_once(&self, client: &HttpClient, api_url: &str) -> Result<Response, JmapError> {
+        let value = client.post_json_once(api_url, &self.envelope()?)?;
+        Response::parse(value)
+    }
 }
 
 #[derive(Debug)]

src/sync/export.rs

@@ -7,6 +7,9 @@
 
 use std::collections::{HashMap, HashSet};
 use std::io::{IsTerminal, Write};
+use std::path::PathBuf;
+use std::sync::Mutex;
+use std::sync::atomic::{AtomicUsize, Ordering};
 
 use rusqlite::Connection;
 use serde_json::{Map, Value, json};
@@ -134,6 +137,77 @@ impl<'a> Uploader<'a> {
         Ok(id)
     }
 
+    /// Uploads several stored blobs at once, on up to `Net::upload_workers`
+    /// threads, and returns each one's result in the order given. Each thread
+    /// reads its blobs through its own read-only connection to the archive, so
+    /// at most one blob per thread is held in memory. With one worker, or in a
+    /// dry run, it is `upload_with` in a loop.
+    fn upload_many(
+        &mut self,
+        local_ids: &[i64],
+        content_type: &str,
+    ) -> Vec<Result<JmapId, JmapError>> {
+        if self.net.dry_run || self.net.upload_workers <= 1 {
+            return local_ids
+                .iter()
+                .map(|id| self.upload_with(*id, content_type))
+                .collect();
+        }
+        self.touched.extend_from_slice(local_ids);
+        let mut todo: Vec<i64> = Vec::new();
+        for id in local_ids {
+            if !self.cache.contains_key(id) && !todo.contains(id) {
+                todo.push(*id);
+            }
+        }
+        let net = self.net;
+        let results = run_bounded(
+            &todo,
+            net.upload_workers,
+            || {
+                rusqlite::Connection::open_with_flags(
+                    &net.archive,
+                    rusqlite::OpenFlags::SQLITE_OPEN_READ_ONLY,
+                )
+            },
+            |conn, local_id| {
+                let conn = conn
+                    .as_ref()
+                    .map_err(|e| JmapError::malformed(format!("archive not readable: {e}")))?;
+                let bytes = db::blobs::blob_bytes(conn, *local_id)?.ok_or_else(|| {
+                    JmapError::malformed(format!("blob local id {local_id} missing"))
+                })?;
+                blobxfer::upload_bytes(
+                    &net.client,
+                    &net.session,
+                    &net.account,
+                    content_type,
+                    &bytes,
+                )
+            },
+        );
+        let mut failed: HashMap<i64, JmapError> = HashMap::new();
+        for (local_id, result) in todo.into_iter().zip(results) {
+            match result {
+                Ok(id) => {
+                    self.cache.insert(local_id, id);
+                }
+                Err(e) => {
+                    failed.insert(local_id, e);
+                }
+            }
+        }
+        local_ids
+            .iter()
+            .map(|id| match self.cache.get(id) {
+                Some(blob) => Ok(blob.clone()),
+                None => Err(failed.get(id).map(clone_error).unwrap_or_else(|| {
+                    JmapError::malformed(format!("blob local id {id} not uploaded"))
+                })),
+            })
+            .collect()
+    }
+
     fn invalidate(&mut self, local_id: i64) {
         self.cache.remove(&local_id);
     }
@@ -147,6 +221,58 @@ impl<'a> Uploader<'a> {
     }
 }
 
+/// A copy of an upload error for each archive row that shares the blob. The
+/// errors that carry meaning for the caller -- the size limits -- keep their
+/// kind; the rest keep their message.
+fn clone_error(e: &JmapError) -> JmapError {
+    match e {
+        JmapError::RequestTooLarge => JmapError::RequestTooLarge,
+        JmapError::SingleObjectTooLarge(m) => JmapError::SingleObjectTooLarge(m.clone()),
+        other => JmapError::Transport(other.to_string()),
+    }
+}
+
+/// Runs `f` over `jobs` on at most `workers` threads and returns the results
+/// in job order. Each thread builds its own state once with `init`, such as a
+/// connection of its own to the archive.
+fn run_bounded<J, S, R>(
+    jobs: &[J],
+    workers: usize,
+    init: impl Fn() -> S + Sync,
+    f: impl Fn(&mut S, &J) -> R + Sync,
+) -> Vec<R>
+where
+    J: Sync,
+    R: Send,
+{
+    let workers = workers.clamp(1, jobs.len().max(1));
+    if workers == 1 {
+        let mut state = init();
+        return jobs.iter().map(|j| f(&mut state, j)).collect();
+    }
+    let next = AtomicUsize::new(0);
+    let slots: Mutex<Vec<Option<R>>> = Mutex::new((0..jobs.len()).map(|_| None).collect());
+    std::thread::scope(|scope| {
+        for _ in 0..workers {
+            scope.spawn(|| {
+                let mut state = init();
+                loop {
+                    let i = next.fetch_add(1, Ordering::SeqCst);
+                    let Some(job) = jobs.get(i) else { break };
+                    let r = f(&mut state, job);
+                    slots.lock().expect("result slots")[i] = Some(r);
+                }
+            });
+        }
+    });
+    slots
+        .into_inner()
+        .expect("result slots")
+        .into_iter()
+        .map(|r| r.expect("every job ran"))
+        .collect()
+}
+
 impl BlobBytes for Uploader<'_> {
     fn bytes(&self, local_id: i64) -> Result<Vec<u8>, JmapError> {
         db::blobs::blob_bytes(self.conn, local_id)?
@@ -162,6 +288,11 @@ struct Net {
     limits: Limits,
     session: Session,
     dry_run: bool,
+    /// The archive's path, for the upload threads' own connections.
+    archive: PathBuf,
+    /// Blobs uploaded at once: the server's `maxConcurrentUpload`, and no
+    /// more than `--threads`.
+    upload_workers: usize,
 }
 
 fn has_rows(conn: &Connection, ty: ObjectType) -> bool {
@@ -185,6 +316,10 @@ pub fn run(common: CommonConfig, config: ExportConfig) -> Result<Summary, Error>
         limits: connected.limits,
         session: connected.session.clone(),
         dry_run: ctx.dry_run(),
+        archive: ctx.common.archive.clone(),
+        upload_workers: (connected.limits.max_concurrent_upload as usize)
+            .min(ctx.common.threads)
+            .max(1),
     };
 
     let work = work_list(&ctx.conn, &config, &connected, &logger);
@@ -198,6 +333,7 @@ pub fn run(common: CommonConfig, config: ExportConfig) -> Result<Summary, Error>
         if logger.enabled(LEVEL_DEFAULT) {
             eprintln!("export: {} ...", ty.jmap_name());
         }
+        let started = std::time::Instant::now();
         let mut counts = TypeCounts::default();
         let res = reconcile_type(
             &ctx,
@@ -217,6 +353,16 @@ pub fn run(common: CommonConfig, config: ExportConfig) -> Result<Summary, Error>
                 Plan::default()
             }
         };
+        if logger.enabled(LEVEL_DEFAULT) && !ctx.dry_run() {
+            eprintln!(
+                "{}",
+                crate::sync::progress::done_line(
+                    &format!("export: {}", ty.jmap_name()),
+                    &counts,
+                    started.elapsed()
+                )
+            );
+        }
         plans.insert(*ty, plan);
         counts_per_type.insert(*ty, counts);
     }
@@ -635,3 +781,49 @@ mod common {
         outcome
     }
 }
+
+#[cfg(test)]
+mod pool_tests {
+    use super::run_bounded;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::time::Duration;
+
+    #[test]
+    fn never_more_workers_at_once_than_the_cap_and_results_keep_job_order() {
+        let jobs: Vec<usize> = (0..24).collect();
+        let running = AtomicUsize::new(0);
+        let most = AtomicUsize::new(0);
+        let inits = AtomicUsize::new(0);
+        let out = run_bounded(
+            &jobs,
+            3,
+            || inits.fetch_add(1, Ordering::SeqCst),
+            |_, j| {
+                let now = running.fetch_add(1, Ordering::SeqCst) + 1;
+                most.fetch_max(now, Ordering::SeqCst);
+                std::thread::sleep(Duration::from_millis(5));
+                running.fetch_sub(1, Ordering::SeqCst);
+                j * 2
+            },
+        );
+        assert_eq!(out, jobs.iter().map(|j| j * 2).collect::<Vec<_>>());
+        let most = most.load(Ordering::SeqCst);
+        assert!(most <= 3, "{most} ran at once");
+        assert!(most > 1, "work ran in parallel");
+        assert_eq!(
+            inits.load(Ordering::SeqCst),
+            3,
+            "state built once per worker"
+        );
+    }
+
+    #[test]
+    fn one_worker_or_one_job_runs_in_place() {
+        let out = run_bounded(&[1, 2, 3], 1, || (), |_, j| j + 1);
+        assert_eq!(out, vec![2, 3, 4]);
+        let out = run_bounded(&[7], 8, || (), |_, j| j + 1);
+        assert_eq!(out, vec![8]);
+        let out: Vec<i32> = run_bounded(&[], 4, || (), |_, j: &i32| *j);
+        assert!(out.is_empty());
+    }
+}

src/sync/export/email.rs

@@ -21,6 +21,7 @@ use crate::jmap::wire::JmapId;
 use crate::logging::Logger;
 use crate::sync::import_jmap::mapping::{EMAIL_SELECT, EmailRow, TargetResolver, row_to_email};
 use crate::sync::keys::{EmailIndex, EmailKey, email_index, email_keys, index_from_json};
+use crate::sync::progress::Progress;
 use crate::sync::{Context, TypeCounts};
 use crate::types::ObjectType;
 
@@ -61,45 +62,7 @@ pub fn reconcile(
     logger: &Logger,
 ) -> Result<Plan, Error> {
     let ty = ObjectType::Email;
-
+    let (targets, target_keys) = target_emails(net).map_err(Error::from)?;
-    let target_min = target_query_get(
-        net,
-        ty,
-        Some(&["messageId", "size", "mailboxIds", "keywords"]),
-    )
-    .map_err(Error::from)?;
-    let mut indices: Vec<EmailIndex> = target_min.iter().map(server_index).collect();
-
-    let fallback_ids: Vec<JmapId> = target_min
-        .iter()
-        .zip(indices.iter())
-        .filter(|(_, i)| i.mids.is_empty())
-        .filter_map(|(v, _)| jid(v).map(JmapId))
-        .collect();
-    if !fallback_ids.is_empty() {
-        let got = get_objects::<Value>(
-            &net.client,
-            &net.api,
-            &net.account,
-            ty.jmap_name(),
-            &fallback_ids,
-            Some(&["messageId", "from", "subject", "sentAt", "to"]),
-            &net.limits,
-        )
-        .map_err(Error::from)?;
-        let by_id: HashMap<String, &Value> = got
-            .list
-            .iter()
-            .filter_map(|v| jid(v).map(|i| (i, v)))
-            .collect();
-        for (v, slot) in target_min.iter().zip(indices.iter_mut()) {
-            if let Some(full) = jid(v).and_then(|i| by_id.get(&i)) {
-                *slot = server_index(full);
-            }
-        }
-    }
-    let targets: Vec<TargetEmail> = target_min.iter().map(TargetEmail::from_value).collect();
-    let target_keys = email_keys(&indices);
 
     let mut local: Vec<(i64, EmailRow)> = {
         let mut stmt = ctx
@@ -134,28 +97,334 @@ pub fn reconcile(
 
     let migrated = maps.targets_of(ObjectType::Mailbox);
     let mut updates: Vec<(String, Value)> = Vec::new();
+    let mut creates: Vec<usize> = Vec::new();
     for (i, unit) in units.iter().enumerate() {
         match pairs[i] {
             Some(t) => match email_patch(&unit.row, &targets[t], maps, &migrated) {
                 Some(patch) => updates.push((targets[t].id.clone(), patch)),
                 None => counts.skipped += 1,
             },
-            None => export_one(
+            None => creates.push(i),
-                net,
-                &mut uploader,
-                maps,
-                unit.local_id,
-                &unit.row,
-                counts,
-                logger,
-            ),
         }
     }
+    let mut progress = Progress::new("export: Email", creates.len() as u64, logger);
+    import_units(
+        net,
+        &mut uploader,
+        maps,
+        &units,
+        &creates,
+        counts,
+        logger,
+        &mut progress,
+    );
     update_batch(net, ty, updates, counts, logger);
 
     Ok(Plan::default())
 }
 
+/// The emails already on the target, and the key each one matches by.
+fn target_emails(net: &Net) -> Result<(Vec<TargetEmail>, Vec<EmailKey>), JmapError> {
+    let ty = ObjectType::Email;
+    let target_min = target_query_get(
+        net,
+        ty,
+        Some(&["messageId", "size", "mailboxIds", "keywords"]),
+    )?;
+    let mut indices: Vec<EmailIndex> = target_min.iter().map(server_index).collect();
+
+    let fallback_ids: Vec<JmapId> = target_min
+        .iter()
+        .zip(indices.iter())
+        .filter(|(_, i)| i.mids.is_empty())
+        .filter_map(|(v, _)| jid(v).map(JmapId))
+        .collect();
+    if !fallback_ids.is_empty() {
+        let got = get_objects::<Value>(
+            &net.client,
+            &net.api,
+            &net.account,
+            ty.jmap_name(),
+            &fallback_ids,
+            Some(&["messageId", "from", "subject", "sentAt", "to"]),
+            &net.limits,
+        )?;
+        let by_id: HashMap<String, &Value> = got
+            .list
+            .iter()
+            .filter_map(|v| jid(v).map(|i| (i, v)))
+            .collect();
+        for (v, slot) in target_min.iter().zip(indices.iter_mut()) {
+            if let Some(full) = jid(v).and_then(|i| by_id.get(&i)) {
+                *slot = server_index(full);
+            }
+        }
+    }
+    let targets: Vec<TargetEmail> = target_min.iter().map(TargetEmail::from_value).collect();
+    let keys = email_keys(&indices);
+    Ok((targets, keys))
+}
+
+/// The most emails one `Email/import` carries: the server's
+/// `maxObjectsInSet`, but no more than this, so that a request that fails
+/// without a clear answer leaves few messages to check.
+const IMPORT_BATCH_CAP: usize = 50;
+
+/// One message ready to import: its creation id, its place in `units`, and
+/// the `Email/import` entry.
+struct Pending {
+    cid: String,
+    unit: usize,
+    item: Value,
+}
+
+/// Writes the messages the target does not have yet. They go in batches of
+/// up to `maxObjectsInSet` (capped by `IMPORT_BATCH_CAP`), their blobs
+/// uploaded at once up to `maxConcurrentUpload`. Each message is still
+/// counted on its own: one rejected in a batch fails alone. A batch that
+/// fails without a clear answer is never resent blindly -- the target is
+/// checked first, and only what did not arrive is imported again.
+#[allow(clippy::too_many_arguments)]
+fn import_units(
+    net: &Net,
+    uploader: &mut Uploader,
+    maps: &Maps,
+    units: &[Unit],
+    creates: &[usize],
+    counts: &mut TypeCounts,
+    logger: &Logger,
+    progress: &mut Progress,
+) {
+    let batch = (net.limits.max_objects_in_set as usize).clamp(1, IMPORT_BATCH_CAP);
+    let mut unclear: Vec<Pending> = Vec::new();
+    for chunk in creates.chunks(batch) {
+        let mut ready: Vec<(usize, Map<String, Value>)> = Vec::new();
+        for &i in chunk {
+            let row = &units[i].row;
+            match build_mailbox_ids(row, maps) {
+                Some(mids) => ready.push((i, mids)),
+                None => {
+                    logger.warn(&format!(
+                        "Email/import e{} ({}) skipped: mailbox not on target",
+                        units[i].local_id,
+                        blob_hint(uploader, row)
+                    ));
+                    counts.failed += 1;
+                }
+            }
+        }
+        let blobs: Vec<i64> = ready
+            .iter()
+            .map(|(i, _)| units[*i].row.blob_local_id)
+            .collect();
+        let uploaded = uploader.upload_many(&blobs, "message/rfc822");
+        let mut pending: Vec<Pending> = Vec::new();
+        for ((i, mids), result) in ready.into_iter().zip(uploaded) {
+            let row = &units[i].row;
+            let cid = format!("e{}", units[i].local_id);
+            match result {
+                Ok(blob) => pending.push(Pending {
+                    cid,
+                    unit: i,
+                    item: import_item(blob.0, mids, build_keywords(row), &row.received_at),
+                }),
+                Err(e) => {
+                    logger.warn(&format!(
+                        "Email/import {cid} ({}) blob upload failed: {e}{}",
+                        blob_hint(uploader, row),
+                        size_note(&e)
+                    ));
+                    counts.failed += 1;
+                }
+            }
+        }
+        if net.dry_run {
+            counts.created += pending.len() as u64;
+        } else {
+            send_batch(
+                net,
+                uploader,
+                maps,
+                units,
+                pending,
+                counts,
+                logger,
+                &mut unclear,
+            );
+        }
+        progress.add(chunk.len() as u64);
+    }
+    if !unclear.is_empty() {
+        settle_unclear(net, uploader, maps, units, unclear, counts, logger);
+    }
+}
+
+/// Sends one `Email/import` for `batch` and counts each message's outcome.
+/// A request too large for the server is split in two; a method error that
+/// rejects the whole call is retried one message at a time, so the one at
+/// fault fails alone. Anything that leaves it unclear whether the server
+/// applied the call goes to `unclear`.
+#[allow(clippy::too_many_arguments)]
+fn send_batch(
+    net: &Net,
+    uploader: &mut Uploader,
+    maps: &Maps,
+    units: &[Unit],
+    batch: Vec<Pending>,
+    counts: &mut TypeCounts,
+    logger: &Logger,
+    unclear: &mut Vec<Pending>,
+) {
+    if batch.is_empty() {
+        return;
+    }
+    let mut emails = Map::new();
+    for p in &batch {
+        emails.insert(p.cid.clone(), p.item.clone());
+    }
+    let mut req = Request::new();
+    req.call(
+        "Email/import",
+        json!({ "accountId": net.account, "emails": Value::Object(emails) }),
+        "i",
+    );
+    let cids: Vec<&str> = batch.iter().map(|p| p.cid.as_str()).collect();
+    let sent = req.fits(&net.limits).and_then(|()| {
+        retry_method_call(
+            &net.client,
+            MethodCallKind::SingleObjectWrite,
+            logger,
+            || {
+                let resp = req.send_once(&net.client, &net.api)?;
+                let mr = resp.first()?;
+                check_method_error(mr)?;
+                Ok(cids
+                    .iter()
+                    .map(|cid| interpret_import_for(mr, cid, cids.len()))
+                    .collect::<Vec<_>>())
+            },
+        )
+    });
+    match sent {
+        Ok(outcomes) => {
+            for (p, outcome) in batch.into_iter().zip(outcomes) {
+                let row = &units[p.unit].row;
+                match outcome {
+                    SingleImport::Created => counts.created += 1,
+                    SingleImport::Skipped => counts.skipped += 1,
+                    SingleImport::NotCreated { error_type, .. } if error_type == "blobNotFound" => {
+                        retry_after_reupload(net, uploader, maps, &p.cid, row, counts, logger);
+                    }
+                    SingleImport::NotCreated { detail, .. } => {
+                        logger.warn(&format!(
+                            "Email/import {} ({}) failed: {detail}",
+                            p.cid,
+                            blob_hint(uploader, row)
+                        ));
+                        counts.failed += 1;
+                    }
+                }
+            }
+        }
+        Err(JmapError::RequestTooLarge | JmapError::SingleObjectTooLarge(_)) if batch.len() > 1 => {
+            let mut batch = batch;
+            let second = batch.split_off(batch.len() / 2);
+            send_batch(net, uploader, maps, units, batch, counts, logger, unclear);
+            send_batch(net, uploader, maps, units, second, counts, logger, unclear);
+        }
+        Err(e) if applied_unknown(&e) => {
+            logger.warn(&format!(
+                "Email/import of {} message(s) ended without a clear answer ({e}); the target is checked before any is sent again",
+                batch.len()
+            ));
+            unclear.extend(batch);
+        }
+        Err(JmapError::Method { .. }) if batch.len() > 1 => {
+            for p in batch {
+                send_batch(net, uploader, maps, units, vec![p], counts, logger, unclear);
+            }
+        }
+        Err(e) => {
+            for p in batch {
+                logger.warn(&format!(
+                    "Email/import {} ({}) send failed: {e}{}",
+                    p.cid,
+                    blob_hint(uploader, &units[p.unit].row),
+                    size_note(&e)
+                ));
+                counts.failed += 1;
+            }
+        }
+    }
+}
+
+/// Whether the server may have applied a call that failed with `e`: the
+/// connection broke after the request was sent, the answer was unreadable, or
+/// the server said it applied part of it.
+fn applied_unknown(e: &JmapError) -> bool {
+    match e {
+        JmapError::Transport(_)
+        | JmapError::RetriesExhausted(_)
+        | JmapError::Malformed(_)
+        | JmapError::HttpStatus { .. } => true,
+        JmapError::Method { error_type, .. } => error_type == "serverPartialFail",
+        _ => false,
+    }
+}
+
+/// Settles messages whose import ended without a clear answer: reads the
+/// target again, counts those that arrived as created, and imports the rest
+/// one at a time. If the target cannot be read, they are counted as failed --
+/// the next export matches whatever did arrive, so none is ever doubled.
+fn settle_unclear(
+    net: &Net,
+    uploader: &mut Uploader,
+    maps: &Maps,
+    units: &[Unit],
+    unclear: Vec<Pending>,
+    counts: &mut TypeCounts,
+    logger: &Logger,
+) {
+    let (targets, target_keys) = match target_emails(net) {
+        Ok(t) => t,
+        Err(e) => {
+            logger.warn(&format!(
+                "could not read the target to settle {} message(s) ({e}); they count as failed, and the next export matches whatever arrived",
+                unclear.len()
+            ));
+            counts.failed += unclear.len() as u64;
+            return;
+        }
+    };
+    let keys: Vec<EmailKey> = email_keys(
+        &unclear
+            .iter()
+            .map(|p| index_from_json(&units[p.unit].row.message_match))
+            .collect::<Vec<_>>(),
+    );
+    let sizes: Vec<Option<u64>> = unclear
+        .iter()
+        .map(|p| uploader.blob_len(units[p.unit].row.blob_local_id))
+        .collect();
+    let pairs = pair_with_targets(&keys, &sizes, &target_keys, &targets);
+    for (p, found) in unclear.into_iter().zip(pairs) {
+        if found.is_some() {
+            counts.created += 1;
+            continue;
+        }
+        let unit = &units[p.unit];
+        export_one(
+            net,
+            uploader,
+            maps,
+            unit.local_id,
+            &unit.row,
+            counts,
+            logger,
+        );
+    }
+}
+
 /// One message to write: the archive rows that hold the same bytes, folded
 /// together. A source that files one message in several folders (IMAP and
 /// Maildir copies, Gmail labels) leaves one archive row per folder; on the
@@ -521,6 +790,13 @@ fn send_single_import(
 
 fn interpret_import(mr: &MethodCall, cid: &str) -> Result<SingleImport, JmapError> {
     check_method_error(mr)?;
+    Ok(interpret_import_for(mr, cid, 1))
+}
+
+/// One message's outcome in an `Email/import` answer. With a single message
+/// in the call, any `created` entry is taken as its own, as servers may key it
+/// differently.
+fn interpret_import_for(mr: &MethodCall, cid: &str, in_call: usize) -> SingleImport {
     if let Some(err) = mr
         .args
         .get("notCreated")
@@ -533,25 +809,21 @@ fn interpret_import(mr: &MethodCall, cid: &str) -> Result<SingleImport, JmapErro
             .unwrap_or("")
             .to_owned();
         if error_type == "alreadyExists" {
-            return Ok(SingleImport::Skipped);
+            return SingleImport::Skipped;
         }
-        return Ok(SingleImport::NotCreated {
+        return SingleImport::NotCreated {
             error_type,
             detail: err.to_string(),
-        });
+        };
     }
-    if mr
+    let created = mr.args.get("created").and_then(Value::as_object);
-        .args
+    if created.is_some_and(|c| c.contains_key(cid) || (in_call == 1 && !c.is_empty())) {
-        .get("created")
+        return SingleImport::Created;
-        .and_then(Value::as_object)
-        .is_some_and(|c| !c.is_empty())
-    {
-        return Ok(SingleImport::Created);
     }
-    Ok(SingleImport::NotCreated {
+    SingleImport::NotCreated {
         error_type: String::new(),
         detail: format!("Email/import returned neither created nor notCreated for {cid}"),
-    })
+    }
 }
 
 #[cfg(test)]

src/sync/export/uidtype.rs

@@ -17,6 +17,7 @@ use crate::logging::Logger;
 use crate::sync::import_jmap::mapping::{
     CALENDAR_EVENT_SELECT, CONTACT_CARD_SELECT, calendar_event_to_wire, contact_card_to_wire,
 };
+use crate::sync::progress::Progress;
 use crate::sync::prune::{TargetObj, candidates};
 use crate::sync::{Context, TypeCounts};
 use crate::types::ObjectType;
@@ -79,7 +80,13 @@ pub fn reconcile(
     let mut matched_uids: HashSet<String> = HashSet::new();
     let mut updates: Vec<(String, Value)> = Vec::new();
     let blobs = Uploader::new(net, &ctx.conn);
+    let mut progress = Progress::new(
+        format!("export: {}", ty.jmap_name()),
+        rows.len() as u64,
+        logger,
+    );
     for (local, uid) in &rows {
+        progress.add(1);
         if let Some((tid, existing)) = by_uid.get(uid) {
             maps.insert(ty, *local, crate::jmap::wire::JmapId(tid.clone()));
             matched_uids.insert(uid.clone());

src/sync/mod.rs

@@ -16,6 +16,7 @@ pub mod import_maildir;
 pub mod import_managesieve;
 pub mod import_takeout;
 pub mod keys;
+pub mod progress;
 pub mod prune;
 
 use std::path::PathBuf;

src/sync/progress.rs

@@ -0,0 +1,196 @@
+/*
+ * SPDX-FileCopyrightText: 2026 John Coffey <[email protected]>
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ */
+
+//! A progress line for long runs: how many of how many, how fast, and about
+//! how long is left. Printed to stderr at the default log level, at most once
+//! per interval, so a large export shows it is moving without flooding the
+//! terminal.
+
+use std::time::{Duration, Instant};
+
+use crate::logging::{LEVEL_DEFAULT, Logger};
+
+/// How often a progress line is printed while work continues.
+pub const PROGRESS_INTERVAL: Duration = Duration::from_secs(5);
+
+pub struct Progress {
+    label: String,
+    total: u64,
+    done: u64,
+    started: Instant,
+    last: Instant,
+    interval: Duration,
+    enabled: bool,
+}
+
+impl Progress {
+    /// `label` names the work, e.g. "export: Email". Nothing is printed when
+    /// the logger is quiet or there is nothing to do.
+    pub fn new(label: impl Into<String>, total: u64, logger: &Logger) -> Progress {
+        let now = Instant::now();
+        Progress {
+            label: label.into(),
+            total,
+            done: 0,
+            started: now,
+            last: now,
+            interval: PROGRESS_INTERVAL,
+            enabled: logger.enabled(LEVEL_DEFAULT) && total > 0,
+        }
+    }
+
+    /// Records `n` more items done, and prints a line once the interval has
+    /// passed since the last one.
+    pub fn add(&mut self, n: u64) {
+        self.done = (self.done + n).min(self.total);
+        if !self.enabled {
+            return;
+        }
+        let now = Instant::now();
+        if now.duration_since(self.last) >= self.interval {
+            self.last = now;
+            eprintln!("{}", self.line(now.duration_since(self.started)));
+        }
+    }
+
+    fn line(&self, elapsed: Duration) -> String {
+        progress_line(&self.label, self.done, self.total, elapsed)
+    }
+}
+
+/// `export: Email 1,200/5,000 (24%), 40/s, about 1m35s left`. The rate and
+/// the time left are left out until there is enough to estimate them from.
+pub fn progress_line(label: &str, done: u64, total: u64, elapsed: Duration) -> String {
+    let pct = (done * 100).checked_div(total).unwrap_or(100);
+    let mut out = format!("{label} {}/{} ({pct}%)", thousands(done), thousands(total));
+    let secs = elapsed.as_secs_f64();
+    if done > 0 && secs >= 1.0 {
+        let rate = done as f64 / secs;
+        out.push_str(&format!(", {}/s", format_rate(rate)));
+        let left = (total - done) as f64 / rate;
+        if total > done && left.is_finite() {
+            out.push_str(&format!(
+                ", about {} left",
+                format_duration(Duration::from_secs_f64(left))
+            ));
+        }
+    }
+    out
+}
+
+/// A duration as `45s`, `1m35s` or `2h03m`.
+pub fn format_duration(d: Duration) -> String {
+    let total = d.as_secs();
+    if total < 60 {
+        format!("{total}s")
+    } else if total < 3600 {
+        format!("{}m{:02}s", total / 60, total % 60)
+    } else {
+        format!("{}h{:02}m", total / 3600, (total % 3600) / 60)
+    }
+}
+
+/// The line printed when a type is finished: `export: Email done: 120
+/// created, 3 updated, 5,000 unchanged, 0 failed (2m03s)`.
+pub fn done_line(label: &str, counts: &crate::sync::TypeCounts, elapsed: Duration) -> String {
+    format!(
+        "{label} done: {} created, {} updated, {} unchanged, {} failed ({})",
+        thousands(counts.created),
+        thousands(counts.updated),
+        thousands(counts.skipped),
+        thousands(counts.failed),
+        format_duration(elapsed)
+    )
+}
+
+fn format_rate(rate: f64) -> String {
+    if rate >= 10.0 {
+        format!("{:.0}", rate)
+    } else {
+        format!("{:.1}", rate)
+    }
+}
+
+pub fn thousands(n: u64) -> String {
+    let digits = n.to_string();
+    let mut out = String::with_capacity(digits.len() + digits.len() / 3);
+    for (i, c) in digits.chars().enumerate() {
+        if i > 0 && (digits.len() - i).is_multiple_of(3) {
+            out.push(',');
+        }
+        out.push(c);
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn a_line_has_count_rate_and_time_left() {
+        let line = progress_line("export: Email", 1200, 5000, Duration::from_secs(30));
+        assert!(
+            line.starts_with("export: Email 1,200/5,000 (24%)"),
+            "{line}"
+        );
+        assert!(line.contains("40/s"), "{line}");
+        assert!(line.contains("about 1m35s left"), "{line}");
+    }
+
+    #[test]
+    fn no_estimate_before_there_is_something_to_estimate_from() {
+        assert_eq!(
+            progress_line("export: Email", 0, 10, Duration::from_secs(5)),
+            "export: Email 0/10 (0%)"
+        );
+        assert_eq!(
+            progress_line("export: Email", 3, 10, Duration::from_millis(200)),
+            "export: Email 3/10 (30%)"
+        );
+    }
+
+    #[test]
+    fn a_finished_run_shows_no_time_left() {
+        let line = progress_line("export: Email", 10, 10, Duration::from_secs(4));
+        assert!(!line.contains("left"), "{line}");
+        assert!(line.contains("(100%)"), "{line}");
+    }
+
+    #[test]
+    fn durations_and_counts_read_naturally() {
+        assert_eq!(format_duration(Duration::from_secs(45)), "45s");
+        assert_eq!(format_duration(Duration::from_secs(95)), "1m35s");
+        assert_eq!(format_duration(Duration::from_secs(7380)), "2h03m");
+        assert_eq!(thousands(0), "0");
+        assert_eq!(thousands(999), "999");
+        assert_eq!(thousands(1_000), "1,000");
+        assert_eq!(thousands(1_234_567), "1,234,567");
+    }
+
+    #[test]
+    fn the_done_line_names_every_count() {
+        let counts = crate::sync::TypeCounts {
+            created: 120,
+            updated: 3,
+            skipped: 5000,
+            failed: 1,
+            ..Default::default()
+        };
+        assert_eq!(
+            done_line("export: Email", &counts, Duration::from_secs(123)),
+            "export: Email done: 120 created, 3 updated, 5,000 unchanged, 1 failed (2m03s)"
+        );
+    }
+
+    #[test]
+    fn a_quiet_logger_or_empty_job_prints_nothing() {
+        let p = Progress::new("x", 10, &Logger::from_flags(true, 0));
+        assert!(!p.enabled);
+        let p = Progress::new("x", 0, &Logger::from_flags(false, 0));
+        assert!(!p.enabled);
+    }
+}

tests/mock_export_batch.rs

@@ -0,0 +1,342 @@
+/*
+ * SPDX-FileCopyrightText: 2026 John Coffey <[email protected]>
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ */
+
+//! Batched `Email/import` on export: batches honor the server's limits, one
+//! rejected message fails alone, and a batch that ends without a clear answer
+//! is settled against the target instead of being sent again.
+
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use inbuxa_migrate::db;
+use inbuxa_migrate::jmap::account::AccountSelector;
+use inbuxa_migrate::jmap::http::Auth;
+use inbuxa_migrate::logging::Logger;
+use inbuxa_migrate::sync::{self, CommonConfig, ConnectConfig, ExportConfig, TypeCounts};
+use mockito::Matcher;
+use serde_json::{Value, json};
+
+const API: &str = "/jmap/api";
+
+fn tmp() -> PathBuf {
+    static SEQ: AtomicUsize = AtomicUsize::new(0);
+    let n = SEQ.fetch_add(1, Ordering::Relaxed);
+    let mut p = std::env::temp_dir();
+    p.push(format!(
+        "inbuxa-migrate-exportbatch-{}-{:?}-{n}.sqlite",
+        std::process::id(),
+        std::thread::current().id(),
+    ));
+    let _ = std::fs::remove_file(&p);
+    p
+}
+
+fn session(base: &str, max_objects_in_set: u64, max_concurrent_upload: u64) -> String {
+    json!({
+        "apiUrl": format!("{base}{API}"),
+        "uploadUrl": format!("{base}/jmap/upload/{{accountId}}/"),
+        "downloadUrl": format!("{base}/jmap/dl/{{accountId}}/{{blobId}}/{{type}}/{{name}}"),
+        "capabilities": { "urn:ietf:params:jmap:core": {
+            "maxObjectsInGet": 500, "maxObjectsInSet": max_objects_in_set,
+            "maxCallsInRequest": 16, "maxConcurrentRequests": 4,
+            "maxConcurrentUpload": max_concurrent_upload,
+            "maxSizeRequest": 10000000, "maxSizeUpload": 50000000
+        } },
+        "accounts": { "w": { "name": "alice",
+            "accountCapabilities": { "urn:ietf:params:jmap:mail": {} } } }
+    })
+    .to_string()
+}
+
+/// An archive with one Inbox and `n` distinct messages, `<m-1@h>` .. `<m-n@h>`.
+fn seed(n: usize) -> PathBuf {
+    let archive = tmp();
+    let conn = db::init::open(&archive).unwrap();
+    conn.execute(
+        "INSERT INTO mailboxes (id,name,parent_id,role) VALUES (1,'Inbox',NULL,'inbox')",
+        [],
+    )
+    .unwrap();
+    for i in 1..=n {
+        let raw = format!("From: a@x\r\nSubject: m{i}\r\nMessage-ID: <m-{i}@h>\r\n\r\nbody {i}");
+        let blob = db::blobs::intern_blob(&conn, raw.as_bytes()).unwrap();
+        let mm = inbuxa_migrate::sync::keys::index_to_json(
+            &inbuxa_migrate::sync::emailmeta::email_index_from_blob(raw.as_bytes()),
+        );
+        conn.execute(
+            "INSERT INTO emails (blob_id,received_at,mailbox_ids,keywords,message_match)
+             VALUES (?1,'2020-01-01T00:00:00Z','[1]','[]',?2)",
+            rusqlite::params![blob, mm],
+        )
+        .unwrap();
+    }
+    archive
+}
+
+/// The session, an Inbox already on the target, and uploads. The target's
+/// email list is left to each test.
+fn mock_target(server: &mut mockito::ServerGuard, session_body: String) -> Vec<mockito::Mock> {
+    vec![
+        server.mock("GET", "/").with_status(404).create(),
+        server
+            .mock("GET", "/.well-known/jmap")
+            .with_body(session_body)
+            .create(),
+        server
+            .mock("POST", API)
+            .match_body(Matcher::Regex("Mailbox/query".into()))
+            .with_body(
+                json!({"methodResponses":[["Mailbox/query",
+                    {"accountId":"w","ids":["t1"]},"q"]]})
+                .to_string(),
+            )
+            .create(),
+        server
+            .mock("POST", API)
+            .match_body(Matcher::AllOf(vec![
+                Matcher::Regex("Mailbox/query".into()),
+                Matcher::Regex("anchor".into()),
+            ]))
+            .with_body(
+                json!({"methodResponses":[["Mailbox/query",
+                    {"accountId":"w","ids":[]},"q"]]})
+                .to_string(),
+            )
+            .create(),
+        server
+            .mock("POST", API)
+            .match_body(Matcher::Regex("Mailbox/get".into()))
+            .with_body(
+                json!({"methodResponses":[["Mailbox/get",{"accountId":"w","list":[
+                    {"id":"t1","name":"Inbox","role":"inbox","parentId":null,
+                     "myRights":{"mayDelete":true}}],"notFound":[]},"g"]]})
+                .to_string(),
+            )
+            .create(),
+        server
+            .mock("POST", Matcher::Regex("/jmap/upload/".into()))
+            .with_body(json!({"blobId":"UP"}).to_string())
+            .create(),
+    ]
+}
+
+fn empty_email_query(server: &mut mockito::ServerGuard) -> mockito::Mock {
+    server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/query".into()))
+        .with_body(
+            json!({"methodResponses":[["Email/query",{"accountId":"w","ids":[]},"q"]]}).to_string(),
+        )
+        .create()
+}
+
+/// The creation ids of the emails in an `Email/import` request body.
+fn import_cids(body: &[u8]) -> Vec<String> {
+    let v: Value = serde_json::from_slice(body).unwrap_or(Value::Null);
+    v["methodCalls"][0][1]["emails"]
+        .as_object()
+        .map(|m| m.keys().cloned().collect())
+        .unwrap_or_default()
+}
+
+/// An `Email/import` answer: each id in `cids` created, except those in
+/// `rejected`, which come back as `invalidEmail`.
+fn import_answer(cids: &[String], rejected: &[&str]) -> Vec<u8> {
+    let mut created = serde_json::Map::new();
+    let mut not_created = serde_json::Map::new();
+    for cid in cids {
+        if rejected.contains(&cid.as_str()) {
+            not_created.insert(cid.clone(), json!({"type":"invalidEmail"}));
+        } else {
+            created.insert(
+                cid.clone(),
+                json!({"id": format!("T{cid}"), "blobId":"b","threadId":"t","size":10}),
+            );
+        }
+    }
+    json!({"methodResponses":[["Email/import",
+        {"accountId":"w","created":created,"notCreated":not_created},"i"]]})
+    .to_string()
+    .into_bytes()
+}
+
+fn run_export(archive: &Path, base: &str, threads: usize) -> TypeCounts {
+    let summary = sync::export::run(
+        CommonConfig {
+            archive: archive.to_path_buf(),
+            threads,
+            dry_run: false,
+            max_retries: 1,
+            allow_invalid_certs: false,
+            logger: Logger::from_flags(true, 0),
+        },
+        ExportConfig {
+            connect: ConnectConfig {
+                url: base.to_owned(),
+                auth: Auth::Basic {
+                    user: "u".into(),
+                    password: "p".into(),
+                },
+                account: AccountSelector::Id("w".into()),
+            },
+            objects: None,
+            prune: false,
+            yes: true,
+        },
+    )
+    .expect("export run");
+    summary
+        .per_type
+        .iter()
+        .find(|(t, _)| *t == "Email")
+        .map(|(_, c)| c.clone())
+        .expect("email counts")
+}
+
+#[test]
+fn imports_are_batched_up_to_max_objects_in_set() {
+    let mut server = mockito::Server::new();
+    let base = server.url();
+    let archive = seed(5);
+    let _base_mocks = mock_target(&mut server, session(&base, 2, 4));
+    let _eq = empty_email_query(&mut server);
+
+    let sizes = Arc::new(std::sync::Mutex::new(Vec::new()));
+    let seen = sizes.clone();
+    let imports = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/import".into()))
+        .with_body_from_request(move |req| {
+            let cids = import_cids(req.body().unwrap());
+            seen.lock().unwrap().push(cids.len());
+            import_answer(&cids, &[])
+        })
+        .expect(3)
+        .create();
+
+    let email = run_export(&archive, &base, 4);
+    assert_eq!(email.created, 5);
+    assert_eq!(email.failed, 0);
+    imports.assert();
+    let mut sizes = sizes.lock().unwrap().clone();
+    sizes.sort_unstable();
+    assert_eq!(
+        sizes,
+        vec![1, 2, 2],
+        "no call carries more than maxObjectsInSet"
+    );
+    let _ = std::fs::remove_file(&archive);
+}
+
+#[test]
+fn a_rejected_message_in_a_batch_fails_alone() {
+    let mut server = mockito::Server::new();
+    let base = server.url();
+    let archive = seed(3);
+    let _base_mocks = mock_target(&mut server, session(&base, 50, 4));
+    let _eq = empty_email_query(&mut server);
+
+    let rejected = Arc::new(std::sync::Mutex::new(String::new()));
+    let pick = rejected.clone();
+    let imports = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/import".into()))
+        .with_body_from_request(move |req| {
+            let cids = import_cids(req.body().unwrap());
+            let mut sorted = cids.clone();
+            sorted.sort();
+            let middle = sorted[1].clone();
+            *pick.lock().unwrap() = middle.clone();
+            import_answer(&cids, &[middle.as_str()])
+        })
+        .expect(1)
+        .create();
+
+    let email = run_export(&archive, &base, 1);
+    assert_eq!(email.created, 2, "the other two land");
+    assert_eq!(email.failed, 1, "only {} fails", rejected.lock().unwrap());
+    imports.assert();
+    let _ = std::fs::remove_file(&archive);
+}
+
+#[test]
+fn an_unclear_batch_is_settled_against_the_target_not_resent() {
+    let mut server = mockito::Server::new();
+    let base = server.url();
+    let archive = seed(2);
+    let _base_mocks = mock_target(&mut server, session(&base, 50, 4));
+
+    // First look: the target is empty. After the unclear batch: m-1 arrived.
+    let queries = Arc::new(AtomicUsize::new(0));
+    let q = queries.clone();
+    let _eq = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/query".into()))
+        .with_body_from_request(move |req| {
+            // A page after the first (it carries an anchor) is empty.
+            let paged = String::from_utf8_lossy(req.body().unwrap()).contains("anchor");
+            let ids = if paged || q.fetch_add(1, Ordering::SeqCst) == 0 {
+                json!([])
+            } else {
+                json!(["arrived"])
+            };
+            json!({"methodResponses":[["Email/query",{"accountId":"w","ids":ids},"q"]]})
+                .to_string()
+                .into_bytes()
+        })
+        .create();
+    let _eg = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/get".into()))
+        .with_body(
+            json!({"methodResponses":[["Email/get",{"accountId":"w","list":[
+                {"id":"arrived","messageId":["m-1@h"],"mailboxIds":{"t1":true},"keywords":{}}
+            ],"notFound":[]},"g"]]})
+            .to_string(),
+        )
+        .create();
+
+    // The batch carries both messages and gets a gateway timeout, so it may
+    // or may not have been applied. mockito answers with the first matching
+    // mock still owed hits, so this answers the first import only; every
+    // later import is created by the next mock, which records what it sees.
+    let gateway = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/import".into()))
+        .with_status(504)
+        .expect(1)
+        .create();
+    let later = Arc::new(std::sync::Mutex::new(Vec::new()));
+    let later_seen = later.clone();
+    let _created = server
+        .mock("POST", API)
+        .match_body(Matcher::Regex("Email/import".into()))
+        .with_body_from_request(move |req| {
+            let cids = import_cids(req.body().unwrap());
+            later_seen.lock().unwrap().push(cids.clone());
+            import_answer(&cids, &[])
+        })
+        .create();
+
+    let email = run_export(&archive, &base, 1);
+    gateway.assert();
+    assert!(
+        queries.load(Ordering::SeqCst) >= 2,
+        "the target is read again before anything is resent"
+    );
+    assert_eq!(
+        *later.lock().unwrap(),
+        vec![vec!["e2".to_owned()]],
+        "only the message that did not arrive is sent again, on its own"
+    );
+    assert_eq!(
+        email.created, 2,
+        "one found on the target, one imported again"
+    );
+    assert_eq!(email.failed, 0);
+    let _ = std::fs::remove_file(&archive);
+}

tests/mock_sync.rs

@@ -487,150 +487,6 @@ fn export_mailbox_already_exists_maps_existing_id() {
     let _ = std::fs::remove_file(&archive);
 }
 
-#[test]
-fn email_export_sends_one_email_per_import_call() {
-    let mut server = mockito::Server::new();
-    let base = server.url();
-    let api = "/jmap/api";
-
-    let archive = tmp();
-    {
-        let conn = db::init::open(&archive).unwrap();
-        conn.execute(
-            "INSERT INTO mailboxes (id,name,parent_id,role) VALUES (1,'Inbox',NULL,'inbox')",
-            [],
-        )
-        .unwrap();
-        for n in 1..=2 {
-            let raw =
-                format!("From: a@x\r\nSubject: m{n}\r\nMessage-ID: <m-{n}@h>\r\n\r\nbody {n}",);
-            let blob = db::blobs::intern_blob(&conn, raw.as_bytes()).unwrap();
-            conn.execute(
-                "INSERT INTO emails (blob_id,received_at,mailbox_ids,keywords)
-                 VALUES (?1,'2020-01-01T00:00:00Z','[1]','[]')",
-                rusqlite::params![blob],
-            )
-            .unwrap();
-        }
-    }
-
-    let _root = server.mock("GET", "/").with_status(404).create();
-    let _wk = server
-        .mock("GET", "/.well-known/jmap")
-        .with_body(session_body(&base))
-        .create();
-
-    let _mq = server
-        .mock("POST", api)
-        .match_body(Matcher::Regex("Mailbox/query".into()))
-        .with_body(
-            json!({"methodResponses":[["Mailbox/query",
-                {"accountId":"w","ids":["t1"]},"q"]]})
-            .to_string(),
-        )
-        .expect_at_least(1)
-        .create();
-    let _mq_empty = server
-        .mock("POST", api)
-        .match_body(Matcher::AllOf(vec![
-            Matcher::Regex("Mailbox/query".into()),
-            Matcher::Regex("anchor".into()),
-        ]))
-        .with_body(
-            json!({"methodResponses":[["Mailbox/query",
-                {"accountId":"w","ids":[]},"q"]]})
-            .to_string(),
-        )
-        .create();
-    let _mg = server
-        .mock("POST", api)
-        .match_body(Matcher::Regex("Mailbox/get".into()))
-        .with_body(
-            json!({"methodResponses":[["Mailbox/get",{"accountId":"w","list":[
-                {"id":"t1","name":"Inbox","role":"inbox","parentId":null,
-                 "myRights":{"mayDelete":true}}],"notFound":[]},"g"]]})
-            .to_string(),
-        )
-        .expect_at_least(1)
-        .create();
-    let _eq = server
-        .mock("POST", api)
-        .match_body(Matcher::Regex("Email/query".into()))
-        .with_body(
-            json!({"methodResponses":[["Email/query",
-                {"accountId":"w","ids":[]},"q"]]})
-            .to_string(),
-        )
-        .expect_at_least(1)
-        .create();
-
-    let _ups = server
-        .mock("POST", Matcher::Regex("/jmap/upload/".into()))
-        .with_body(json!({"blobId":"UP1"}).to_string())
-        .expect(2)
-        .create();
-
-    let single_only = server
-        .mock("POST", api)
-        .match_body(Matcher::AllOf(vec![
-            Matcher::Regex("Email/import".into()),
-            Matcher::Regex("e1".into()),
-            Matcher::Regex("e2".into()),
-        ]))
-        .expect(0)
-        .create();
-
-    let imports = server
-        .mock("POST", api)
-        .match_body(Matcher::Regex("Email/import".into()))
-        .with_body(
-            json!({"methodResponses":[["Email/import",
-                {"accountId":"w","created":{"e":{"id":"x","blobId":"b","threadId":"t","size":10}}},"i"]]})
-            .to_string(),
-        )
-        .expect(2)
-        .create();
-
-    let summary = sync::export::run(
-        CommonConfig {
-            archive: archive.clone(),
-            threads: 1,
-            dry_run: false,
-            max_retries: 0,
-            allow_invalid_certs: false,
-            logger: Logger::from_flags(true, 0),
-        },
-        ExportConfig {
-            connect: ConnectConfig {
-                url: base.clone(),
-                auth: Auth::Basic {
-                    user: "u".into(),
-                    password: "p".into(),
-                },
-                account: AccountSelector::Id("w".into()),
-            },
-            objects: None,
-            prune: false,
-            yes: true,
-        },
-    )
-    .expect("export run");
-
-    let email = summary
-        .per_type
-        .iter()
-        .find(|(t, _)| *t == "Email")
-        .map(|(_, c)| c.clone())
-        .expect("email counts");
-    assert_eq!(email.created, 2, "both emails imported in per-item rounds");
-    assert_eq!(email.failed, 0, "no per-unit failure");
-    assert!(!summary.any_failed(), "no whole-run failure");
-
-    single_only.assert();
-    imports.assert();
-    let _ = std::fs::remove_file(&archive);
-}
-
 #[test]
 fn export_email_blob_not_found_reuploads_and_retries() {
     let mut server = mockito::Server::new();