Add support for batch sync to workerd

[aron-cf]

Commands currently wait for the full post-command pull before returning. That works for small changes, but an npm install can create thousands of files and run over a request budget. The default sync filter recently dropped node_modules, so installed packages now survive a replacement workspace runtime.

Sync can now move a fixed number of entries or bytes at a time and resume from a path within one revision. Workspace.push() and Workspace.pull() keep their existing behavior unless the caller selects batch mode. Commands also accept sync: "deferred".

Deferred mode is intended to batch work across several messages/cycles to avoid CPU saturation. The host can call retryPendingSync() from its durable object alarm until the captured target is complete. Though for now the default remains inline sync.

Deferred targets are captured after pending filesystem writes settle. Later commands extend an existing target, successful batches do not consume the failure retry limit, and cancellation waits for the command to finish before recording its target. Runtime replacement and stale cursor handling keep retries from reporting success against the wrong container.

An example of a container-backed workspace that has a SyncRetryScheduler configured:

const handle = await workspace.runtime.exec("npm install", {
  sync: "deferred",
});

const result = await handle.result();
console.log(result.sync.status); // "pending"

let retry = await workspace.retryPendingSync();
while (retry.status === "pending") {
  retry = await workspace.retryPendingSync();
}

After the retry reports "complete", replacing the runtime and running a command that reads node_modules should use the installed files from the workspace store.

[changeset-bot]

⚠️ No Changeset found

Latest commit: bc54994

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@cloudflare/computer@116

commit: bc54994

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.