/**
* Locks Resource
*
* Lock contention detection and blocking query identification.
*/
import type { PostgresAdapter } from '../PostgresAdapter.js';
import type { ResourceDefinition, RequestContext } from '../../../types/index.js';
interface LockWarning {
severity: 'HIGH' | 'MEDIUM' | 'INFO';
message: string;
recommendation?: string;
}
interface LockRow {
locktype: string;
mode: string;
granted: boolean;
pid: number;
usename: string;
application_name: string;
client_addr: string;
state: string;
wait_event_type: string;
wait_event: string;
relation: string;
query_preview: string;
query_duration_seconds: number;
}
export function createLocksResource(adapter: PostgresAdapter): ResourceDefinition {
return {
uri: 'postgres://locks',
name: 'Lock Information',
description: 'Current lock information with contention detection',
mimeType: 'application/json',
handler: async (_uri: string, _context: RequestContext) => {
// Get lock information
const locksResult = await adapter.executeQuery(`
SELECT
l.locktype,
l.mode,
l.granted,
l.pid,
a.usename,
a.application_name,
a.client_addr::text as client_addr,
a.state,
a.wait_event_type,
a.wait_event,
COALESCE(r.relname, l.relation::text) as relation,
LEFT(a.query, 100) as query_preview,
EXTRACT(EPOCH FROM age(now(), a.query_start)) as query_duration_seconds
FROM pg_locks l
LEFT JOIN pg_stat_activity a ON l.pid = a.pid
LEFT JOIN pg_class r ON l.relation = r.oid
WHERE l.pid != pg_backend_pid()
ORDER BY l.granted, a.query_start NULLS LAST
LIMIT 50
`);
const locks = (locksResult.rows ?? []) as unknown as LockRow[];
// Get active session count for context
const sessionResult = await adapter.executeQuery(`
SELECT COUNT(*) as count FROM pg_stat_activity
WHERE pid != pg_backend_pid()
AND state = 'active'
`);
const activeSessions = Number(sessionResult.rows?.[0]?.['count'] ?? 0);
// Analyze locks
const blockingLocks = locks.filter((lock: LockRow) => !lock.granted);
const activeLocks = locks.filter((lock: LockRow) => lock.granted);
// Generate warnings
const warnings: LockWarning[] = [];
if (blockingLocks.length > 0) {
warnings.push({
severity: 'HIGH',
message: blockingLocks.length.toString() + ' blocked queries detected',
recommendation: 'Review blocking queries and consider terminating long-running transactions'
});
}
if (locks.length > 100) {
warnings.push({
severity: 'MEDIUM',
message: 'High number of locks (' + locks.length.toString() + ') - showing top 50',
recommendation: 'May indicate lock contention or long-running transactions'
});
}
if (warnings.length === 0) {
warnings.push({
severity: 'INFO',
message: 'No lock contention detected'
});
}
// Generate summary message
const summary = locks.length === 0
? `No locks detected. ${String(activeSessions)} active sessions. Empty result is normal when queries complete quickly.`
: `${String(locks.length)} locks held by ${String(new Set(locks.map(l => l.pid)).size)} processes. ${String(activeSessions)} active sessions.`;
return {
totalLocks: locks.length,
activeLocks: activeLocks.length,
blockingLocks: blockingLocks.length,
activeSessions,
lockDetails: locks,
warnings,
summary
};
}
};
}
