import { executeQuery } from '../db/index.js';
import { formatSuccess, formatError } from '../utils/formatters.js';
import type { ToolResponse } from '../types.js';
/**
* Tool: monitor_blocking
* Monitor blocking sessions and lock chains
*/
export async function monitorBlocking(): Promise<ToolResponse> {
try {
const query = `
SELECT
w.pid AS "blockedSessionId",
w.locktype AS "lockType",
w.mode AS "waitMode",
w.relation::regclass::text AS "relation",
a.usename AS "blockedLogin",
a.application_name AS "blockedProgram",
a.query AS "blockedQuery",
a.query_start AS "blockedQueryStart",
b.pid AS "blockingSessionId",
b.usename AS "blockingLogin",
b.application_name AS "blockingProgram",
b.query AS "blockingQuery"
FROM pg_locks w
JOIN pg_stat_activity a ON a.pid = w.pid
JOIN pg_locks bl ON bl.locktype = w.locktype
AND bl.database IS NOT DISTINCT FROM w.database
AND bl.relation IS NOT DISTINCT FROM w.relation
AND bl.page IS NOT DISTINCT FROM w.page
AND bl.tuple IS NOT DISTINCT FROM w.tuple
AND bl.virtualxid IS NOT DISTINCT FROM w.virtualxid
AND bl.transactionid IS NOT DISTINCT FROM w.transactionid
AND bl.classid IS NOT DISTINCT FROM w.classid
AND bl.objid IS NOT DISTINCT FROM w.objid
AND bl.objsubid IS NOT DISTINCT FROM w.objsubid
AND bl.pid <> w.pid
AND bl.granted
JOIN pg_stat_activity b ON b.pid = bl.pid
WHERE NOT w.granted
ORDER BY a.query_start DESC
`;
const result = await executeQuery(query, {}, 100);
// Truncate long queries
const blockingInfo = result.rows.map((row) => {
const info = row as { blockedQuery?: string; blockingQuery?: string; blockingSessionId?: number };
if (info.blockedQuery && info.blockedQuery.length > 1000) {
info.blockedQuery = info.blockedQuery.substring(0, 1000) + '... [truncated]';
}
if (info.blockingQuery && info.blockingQuery.length > 1000) {
info.blockingQuery = info.blockingQuery.substring(0, 1000) + '... [truncated]';
}
return info;
});
const headBlockers = Array.from(
new Set(
blockingInfo
.map((row) => row.blockingSessionId)
.filter((id): id is number => typeof id === 'number')
)
);
return formatSuccess({
blocking: blockingInfo,
headBlockers,
count: result.rowCount,
});
} catch (error) {
return formatError(error);
}
}
/**
* Tool definition for monitor_blocking
*/
export const monitorBlockingDefinition = {
name: 'monitor_blocking',
description:
'Monitor blocking sessions and lock chains. Shows which sessions are blocking others and identifies head blockers.',
inputSchema: {
type: 'object' as const,
properties: {},
},
};
