Add support for on-disk SQLite store in computerd

[aron-cf]

computerd keeps the workspace in memory. When it restarts, the store is gone and the durable object sends every path again before any command can run. For unsynced directories like node_modules this requires a full re-build.

Set COMPUTERD_DB to an absolute path to use a SQLite DB on disk, this can then be backed up and restored across container instances.

COMPUTERD_DB=memory                      # default, unchanged
COMPUTERD_DB=/var/lib/computerd/state.db # on disk, survives a restart

The path must be absolute and must sit outside MOUNT_POINT. A database the mount also shows would feed its writes back to itself. computerd refuses to start on either mistake.

The cloudflared process then starts back knowing what it was already sent, so only the difference needs to be synced.

import { Database, initializeSchema } from "@cloudflare/dofs";
import { NodeSQLiteStorage } from "@cloudflare/dofs/node";

const storage = new NodeSQLiteStorage({ location: "/var/lib/computerd/state.db" });
const db = new Database(storage);
initializeSchema(db, Date.now);

storage.checkpoint(); // { walFrames, sizeBytes, durationMs }
storage.close();

POST /__computerd/checkpoint collapses the write-ahead log back into the database file, so a snapshot holds one file instead of two. The same happens on SIGTERM, after the mount is released — the mount writes buffered bytes as it closes each file, so it has to go first. GET /__computerd/info reports the store in use, and GET /__computerd/stats reports its size.

Restart by hand

PORT=8080 MOUNT_POINT=/workspace FUSE_MOUNT=fuse \
  COMPUTERD_DB=/var/lib/computerd/state.db computerd &

echo hello > /workspace/a.txt
curl -X POST localhost:8080/__computerd/checkpoint
kill %1

PORT=8080 MOUNT_POINT=/workspace FUSE_MOUNT=fuse \
  COMPUTERD_DB=/var/lib/computerd/state.db computerd &

cat /workspace/a.txt                    # hello
curl -s localhost:8080/api/watermarks   # positions kept, not zeroed

Tests cover the storage layer, the new setting, and the point of the change: restart on a file store and the files and sync positions are still there, restart in memory and they are not. The unmount-then-checkpoint order has its own test, since reversing it would lose the last writes quietly. The computerd README covers the setting and its limits, and the performance document carries the numbers.

---

[changeset-bot]

🦋 Changeset detected

Latest commit: aa4f984

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@cloudflare/dofs	Minor
@cloudflare/computer	Minor
@cloudflare/computer-rpc	Minor
@cloudflare/computerd	Minor

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commit: aa4f984

[devin-ai-integration]

✅ Devin Review: No Issues Found

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