fix: SQLite 'database is locked' under concurrent writes

[he-yufeng]

Problem

AstrBot frequently hits (sqlite3.OperationalError) database is locked when multiple async operations (agent responses, metrics inserts, session updates) write to SQLite concurrently. This affects both Windows and Linux deployments and is especially noticeable after importing personas or during rapid conversations.

Root Cause

create_async_engine() in BaseDatabase.__init__ doesn't set a busy timeout:

self.engine = create_async_engine(
    self.DATABASE_URL,
    echo=False,
    future=True,
    # no connect_args → SQLite default timeout is 5s (or 0 depending on driver)
)

SQLite only supports one writer at a time. Without a timeout, the second concurrent write fails immediately instead of waiting for the lock to be released.

Fix

Add connect_args={"timeout": 30} for SQLite engines. This tells the driver to wait up to 30 seconds for the write lock before raising an error — more than enough to handle the typical concurrent write bursts.

Combined with the existing WAL journal mode (set in SQLiteDatabase.initialize()), this provides concurrent reads + serialized writes with proper backpressure.

Fixes #6443

Summary by Sourcery

Bug Fixes:

• Prevent frequent sqlite3.OperationalError: database is locked errors during concurrent SQLite writes by adding a busy timeout to async engine creation.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves frequent 'database is locked' errors encountered in AstrBot when multiple asynchronous operations attempt to write to SQLite concurrently. The fix introduces a 30-second busy timeout for SQLite database connections, allowing the driver to wait for write locks to be released. This significantly improves the stability and resilience of concurrent database interactions without altering the existing WAL journal mode, ensuring proper backpressure for serialized writes.

Highlights

• SQLite Database Locking Fix: Implemented a solution to prevent sqlite3.OperationalError: database is locked by configuring a busy timeout for SQLite connections, allowing concurrent write operations to wait for locks instead of failing immediately.
• Conditional Connection Arguments: Added `connect_args={\

Changelog

• astrbot/core/db/init.py
  • Added logic to detect SQLite database URLs and conditionally apply connect_args.
  • Introduced a timeout of 30 seconds within connect_args for SQLite engines to handle concurrent write contention.
  • Included detailed comments explaining the necessity and function of the SQLite busy timeout.

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• Using "sqlite" in self.DATABASE_URL to detect SQLite is a bit fragile; consider checking the URL scheme/driver name (e.g., via SQLAlchemy URL parsing or startswith "sqlite:" / "sqlite+") to avoid accidental matches.
• The timeout=30 value is currently hardcoded; it might be useful to make this configurable (e.g., via settings/env) so deployments with different concurrency patterns can tune it without code changes.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Using `"sqlite" in self.DATABASE_URL` to detect SQLite is a bit fragile; consider checking the URL scheme/driver name (e.g., via SQLAlchemy URL parsing or startswith `"sqlite:"` / `"sqlite+"`) to avoid accidental matches.
- The `timeout=30` value is currently hardcoded; it might be useful to make this configurable (e.g., via settings/env) so deployments with different concurrency patterns can tune it without code changes.

## Individual Comments

### Comment 1
<location path="astrbot/core/db/__init__.py" line_range="41" />
<code_context>
+        # second write is attempted.  Setting timeout=30 tells SQLite to
+        # wait up to 30 s for the lock, which is enough to ride out brief
+        # write bursts from concurrent agent/metrics/session operations.
+        is_sqlite = "sqlite" in self.DATABASE_URL
+        connect_args = {"timeout": 30} if is_sqlite else {}
         self.engine = create_async_engine(
</code_context>
<issue_to_address>
**suggestion:** Use a stricter check for SQLite URLs instead of a substring search.

`"sqlite" in self.DATABASE_URL` can match non-SQLite URLs (e.g., if `sqlite` appears in credentials or query params). Consider parsing the URL and checking the scheme (e.g. via `sqlalchemy.engine.make_url(...).drivername`) or at least using `self.DATABASE_URL.startswith("sqlite")` so the timeout is only applied for real SQLite connections.

Suggested implementation:

```python
from sqlalchemy.engine import make_url
from sqlalchemy.ext.asyncio import create_async_engine

```

```python
        # SQLite only supports a single writer at a time.  Without a busy
        # timeout the driver raises "database is locked" instantly when a
        # second write is attempted.  Setting timeout=30 tells SQLite to
        # wait up to 30 s for the lock, which is enough to ride out brief
        # write bursts from concurrent agent/metrics/session operations.
        url = make_url(self.DATABASE_URL)
        is_sqlite = url.drivername.startswith("sqlite")
        connect_args = {"timeout": 30} if is_sqlite else {}

```
</issue_to_address>

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[sourcery-ai]

suggestion: Use a stricter check for SQLite URLs instead of a substring search.

"sqlite" in self.DATABASE_URL can match non-SQLite URLs (e.g., if sqlite appears in credentials or query params). Consider parsing the URL and checking the scheme (e.g. via sqlalchemy.engine.make_url(...).drivername) or at least using self.DATABASE_URL.startswith("sqlite") so the timeout is only applied for real SQLite connections.

Suggested implementation:

from sqlalchemy.engine import make_url
from sqlalchemy.ext.asyncio import create_async_engine

        # SQLite only supports a single writer at a time.  Without a busy
        # timeout the driver raises "database is locked" instantly when a
        # second write is attempted.  Setting timeout=30 tells SQLite to
        # wait up to 30 s for the lock, which is enough to ride out brief
        # write bursts from concurrent agent/metrics/session operations.
        url = make_url(self.DATABASE_URL)
        is_sqlite = url.drivername.startswith("sqlite")
        connect_args = {"timeout": 30} if is_sqlite else {}

[gemini-code-assist]

Code Review

This pull request correctly addresses the database is locked error with SQLite by introducing a busy timeout. The implementation is clear and directly solves the problem of concurrent writes. I've provided one suggestion to make the logic for detecting an SQLite connection more robust, which will prevent potential issues if other database URLs happen to contain 'sqlite' in their string.

[gemini-code-assist]

For improved robustness and conciseness, these lines can be combined. Using startswith("sqlite") is more reliable than checking for containment with in. This change prevents misidentifying a non-SQLite database that might have "sqlite" in its name or path, which could lead to errors if that database driver does not support the timeout connection argument.

Suggested change

	is_sqlite = "sqlite" in self.DATABASE_URL
	connect_args = {"timeout": 30} if is_sqlite else {}
	connect_args = {"timeout": 30} if self.DATABASE_URL.startswith("sqlite") else {}