/**
* 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";
import { LOW_PRIORITY } from "../../../utils/resourceAnnotations.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",
annotations: LOW_PRIORITY,
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,
};
},
};
}
