knexjs Query Instrumentation

metrics.ts

import { UpDownCounter, ValueRecorder } from '@opentelemetry/api-metrics';
import { hrTime, hrTimeDuration } from '@opentelemetry/core';

type QueryEvent = {
  sql: string;
  __knexUid: string;
  __knexTxId?: string;
};

export function install(db: Knex): void {
  const queryStarts: Map<string, [number, number]> = new Map();

  const activeQueries = getActiveQueries();
  const queryLatency = getQueryLatency();

  db.on('query', queryStart);
  db.on('query-error', queryComplete);
  db.on('query-response', (_: unknown, data: QueryEvent) => queryComplete(data));

  function queryStart(data: QueryEvent): void {
    queryStarts.set(data.__knexUid, hrTime());
    activeQueries.add(1);
  }

  function queryComplete(data: QueryEvent, error?: Error): void {
    const start = queryStarts.get(data.__knexUid);
    if (!start) {
      // Unable to track query, we don't have a start time.
      return;
    }

    queryStarts.delete(data.__knexUid);
    activeQueries.add(-1);
    queryLatency.record(hrTimeToSeconds(hrTimeDuration(start, hrTime())), {
      sql: data.sql,
      error: String(!!error),
    });
  }
}

function hrTimeToSeconds(hrTime: HrTime): number {
  return Math.round(hrTime[0] + hrTime[1] / 1e9);
}

function getActiveQueries(): UpDownCounter {
  // .. snip ..
}

function getQueryLatency(): ValueRecorder {
  // .. ship ..
}