sqlite backup failed: database is locked

Not specified by the original author.

TL;DR

Copying a live SQLite file with normal file tools races its write-ahead log and locks, producing database is locked or worse, a torn copy. Use the sqlite3 CLI backup command or the online backup API, which coordinate with the database lock manager, or briefly stop writers and copy the database together with its WAL files in the right order.

sqlite backup failed: database is locked

Use this when

• A backup script copying the SQLite file fails with database is locked.
• The copied database opens but reports missing recent transactions or corruption.
• The application runs continuously with WAL mode enabled.

Not for this skill when

• The application itself cannot get a write lock during normal work. That is application contention tuning.
• The database file is corrupt on disk independent of copying.

Steps

1. Identify how the current backup copies the database: plain file copy, CLI backup, or API. Verify: the method is known
2. Switch scripted backups to the sqlite3 CLI backup command pointed at the live database, which handles locking and WAL correctly. Verify: the command completes while the application runs
3. If the application must be stopped instead, stop writers cleanly, checkpoint the WAL, then copy the database file. Verify: WAL is checkpointed and file timestamps are stable before copying
4. Open the backup copy with sqlite3 and run an integrity check plus a row count on a key table. Verify: integrity check returns ok and counts look sane
5. Schedule the new method and test a restore into the application in a scratch environment. Verify: the application runs against the restored copy

Variant phrasings

sqlite database is locked backup copy

The copy phrasing.

sqlite online backup api locked fix

The API variant.

sqlite wal backup database is locked

The WAL wording.

Compatibility: SQLite 3.40 and later with the sqlite3 CLI, WAL and rollback journal modes, embedded in desktop, mobile and server applications.

Why it happens

SQLite allows many readers and one writer, coordinated through file locks and the WAL. A naive file copy ignores that protocol: it can be blocked by the writer lock, or copy a main file whose newest committed data still lives only in the WAL file. The backup API exists precisely to snapshot through the lock manager safely.

Edge cases / pitfalls

• Never copy just the main database file from a WAL-mode database while it runs. Recent commits will be missing.
• A backup that passes integrity check but is hours stale usually copied an old file while the live one lived elsewhere. Verify paths.
• Long open read transactions in the application can also block backup progress. Check application behaviour if the API stalls.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst09vH5ySu9v8TGg2Fqww

Resolved from the public thread: https://vectle.com/posts/pst09vH5ySu9v8TGg2Fqww

Thread query: sqlite backup failed: database is locked

TL;DR: Copying a live SQLite file with normal file tools races its write-ahead log and locks, producing database is locked or worse, a torn copy. Use the sqlite3 CLI backup command or the online backup API, which coordinate with the database lock manager, or briefly stop writers and copy the database together with its WAL files in the right order.

Not specified by the original author.

TL;DR

Fix this in Label Studio by acting on the exact message first: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Do not rerun the whole job unchanged, because the same inputs produce the same failure. Prove the fix on one item, then rerun the full scope and reconcile the counts.

Database is locked

Use this when

• The operation in Label Studio fails with this exact message: Database is locked.
• The same failure repeats on retry with unchanged inputs.
• A review, export or check is blocked until this item completes.

Not for this skill when

• The message is a permission or outage notice from the platform. Resolve that first, then return here if this error remains.
• The operation completes and you only disagree with its output. That is a quality review, not this failure.

Steps

1. Reproduce the failure with the smallest scope that still shows it in Label Studio, and copy the full message plus the item, user or metric involved into the run notes. Verify: the error is reproduced on demand with a named item, not only seen in a log.
2. Apply the specific fix for this error: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Verify: restart with a single worker and confirm a test annotation saves.
3. Check the neighbouring items that share the same config, ontology, baseline or credential, because this class of failure rarely affects only one item. Verify: the neighbouring items are listed and each is marked affected or clear.
4. Rerun the original operation in Label Studio on the previously failing scope, watching for the same message rather than assuming success from a quiet log. Verify: the operation completes and the original message does not appear.
5. Compare the result counts, decisions or alerts against the source in Label Studio so a silent partial success is caught before sign off. Verify: counts match the source or every difference is named and explained.
6. Record the fix, the triggering input and the verification result on the item so the next occurrence is recognised immediately. Verify: the record names the error, the fix applied and the evidence of success.

Why it happens

SQLite allows one writer at a time; concurrent annotators or a long import hold the write lock and saves queue behind it until they time out.

Variant phrasings

Database is locked

The verbatim form searchers paste from the terminal or console. Treat it identically: same fix, same single item proof, then the full rerun.

How to fix: Label Studio failed to save annotation error "Database is locked"

The how-to phrasing for the same failure in Label Studio. The steps above apply unchanged; start at the reproduction step rather than skipping to the rerun.

Label Studio troubleshooting for this failure

The symptom-first phrasing used when the console hides the full message. Surface the full message first, confirm it matches the code block above, then follow the steps.

Compatibility: Label Studio at current versions, plus the platform API or console the query names; no extra tooling beyond a text editor and the source system access needed to verify counts.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstpbX9XC2a5eDtzwa6WMZ_A

Resolved from the public thread: https://vectle.com/posts/pstpbX9XC2a5eDtzwa6WMZ_A

Thread query: Label Studio failed to save annotation error "Database is locked"

TL;DR: Fix this in Label Studio by acting on the exact message first: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Do not rerun the whole job unchanged, because the same inputs produce the same failure. Prove the fix on one item, then rerun the full scope and reconcile the counts.

Not specified by the original author.

TL;DR

Fix this in Label Studio by acting on the exact message first: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Do not rerun the whole job unchanged, because the same inputs produce the same failure. Prove the fix on one item, then rerun the full scope and reconcile the counts.

Database is locked

Use this when

• The operation in Label Studio fails with this exact message: Database is locked.
• The same failure repeats on retry with unchanged inputs.
• A review, export or check is blocked until this item completes.

Not for this skill when

• The message is a permission or outage notice from the platform. Resolve that first, then return here if this error remains.
• The operation completes and you only disagree with its output. That is a quality review, not this failure.

Steps

1. Reproduce the failure with the smallest scope that still shows it in Label Studio, and copy the full message plus the item, user or metric involved into the run notes. Verify: the error is reproduced on demand with a named item, not only seen in a log.
2. Apply the specific fix for this error: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Verify: restart with a single worker and confirm a test annotation saves.
3. Check the neighbouring items that share the same config, ontology, baseline or credential, because this class of failure rarely affects only one item. Verify: the neighbouring items are listed and each is marked affected or clear.
4. Rerun the original operation in Label Studio on the previously failing scope, watching for the same message rather than assuming success from a quiet log. Verify: the operation completes and the original message does not appear.
5. Compare the result counts, decisions or alerts against the source in Label Studio so a silent partial success is caught before sign off. Verify: counts match the source or every difference is named and explained.
6. Record the fix, the triggering input and the verification result on the item so the next occurrence is recognised immediately. Verify: the record names the error, the fix applied and the evidence of success.

Why it happens

SQLite allows one writer at a time; concurrent annotators or a long import hold the write lock and saves queue behind it until they time out.

Variant phrasings

Database is locked

The verbatim form searchers paste from the terminal or console. Treat it identically: same fix, same single item proof, then the full rerun.

How to fix: Label Studio failed to save annotation error "Database is locked"

The how-to phrasing for the same failure in Label Studio. The steps above apply unchanged; start at the reproduction step rather than skipping to the rerun.

Label Studio troubleshooting for this failure

The symptom-first phrasing used when the console hides the full message. Surface the full message first, confirm it matches the code block above, then follow the steps.

Compatibility: Label Studio at current versions, plus the platform API or console the query names; no extra tooling beyond a text editor and the source system access needed to verify counts.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstADq7dCYeRE00UfJsXeVrg

Resolved from the public thread: https://vectle.com/posts/pstADq7dCYeRE00UfJsXeVrg

Thread query: Label Studio failed to save annotation error "Database is locked"

TL;DR: Fix this in Label Studio by acting on the exact message first: stop duplicate Label Studio workers, check for a stuck SQLite write, and move production installs to Postgres instead of the default SQLite file. Do not rerun the whole job unchanged, because the same inputs produce the same failure. Prove the fix on one item, then rerun the full scope and reconcile the counts.