/**
* Pool Resource
*
* MCP server connection pool statistics with external pooler detection.
*/
import type { PostgresAdapter } from '../PostgresAdapter.js';
import type { ResourceDefinition, RequestContext } from '../../../types/index.js';
interface ExternalPoolerInfo {
detected: boolean;
type: 'pgbouncer' | 'pgpool' | 'none';
hint?: string;
}
export function createPoolResource(adapter: PostgresAdapter): ResourceDefinition {
return {
uri: 'postgres://pool',
name: 'Connection Pool',
description: 'MCP server connection pool statistics with external pooler detection',
mimeType: 'application/json',
handler: async (_uri: string, _context: RequestContext) => {
const pool = adapter.getPool();
if (!pool) {
return { error: 'Pool not initialized' };
}
const stats = pool.getStats();
const health = await pool.checkHealth();
// Determine pool status
let status: 'idle' | 'active' | 'busy' | 'empty';
if (stats.total === 0) {
status = 'empty';
} else if (stats.active > 0 && stats.active >= stats.total - 1) {
status = 'busy';
} else if (stats.active > 0) {
status = 'active';
} else {
status = 'idle';
}
// Detect external poolers
const externalPooler: ExternalPoolerInfo = {
detected: false,
type: 'none'
};
try {
// Check for pgbouncer by looking for its admin database or signature
const pgbouncerCheck = await adapter.executeQuery(`
SELECT COUNT(*) as count FROM pg_database WHERE datname = 'pgbouncer'
`);
const hasPgbouncerDb = Number(pgbouncerCheck.rows?.[0]?.['count'] ?? 0) > 0;
if (hasPgbouncerDb) {
externalPooler.detected = true;
externalPooler.type = 'pgbouncer';
externalPooler.hint = 'pgbouncer database detected. Use "SHOW POOLS" on pgbouncer admin database for pooler stats.';
}
// Alternative detection: check for pgbouncer in application_name patterns
if (!hasPgbouncerDb) {
const appNameCheck = await adapter.executeQuery(`
SELECT COUNT(*) as count FROM pg_stat_activity
WHERE application_name ILIKE '%pgbouncer%' OR application_name ILIKE '%pgpool%'
`);
const hasPoolerConnections = Number(appNameCheck.rows?.[0]?.['count'] ?? 0) > 0;
if (hasPoolerConnections) {
externalPooler.detected = true;
externalPooler.type = 'pgbouncer';
externalPooler.hint = 'Connections via external pooler detected. This resource shows MCP internal pool stats only.';
}
}
} catch {
// Detection failed, continue with default
}
// Build contextual note
let note = 'Reports the MCP server internal connection pool.';
if (status === 'empty' || status === 'idle') {
note += ' Values of 0 are normal when the pool is idle.';
}
if (externalPooler.detected) {
note += ` External pooler (${externalPooler.type}) detected - see externalPooler.hint for querying pooler stats.`;
} else {
note += ' For external poolers like PgBouncer, query the pgbouncer admin database directly.';
}
return {
stats,
health,
isInitialized: pool.isInitialized(),
status,
externalPooler,
note
};
}
};
}
