[MO] How to log your queries duration with Knex

SUMMARY.MD

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       - [1. Cache your routes using varnish](/performance/backend/cache-routes-using-varnish.mo.md)
       - [2. Serve images as static files](/performance/backend/serve-images-as-static-files.mo)
       - [3. Minimize your number of SQL queries](/performance/backend/minimize-number-sql-queries.mo.md)
+      - [4. Log queries durations with Knex](/performance/backend/log-queries-durations-with-knex.mo.md)
     - Front
       - 1.  Pure components **-> [To do]**
   - Have you a mean of keeping the performance under control?

performance/backend/log-queries-durations-with-knex.mo.md

@@ -0,0 +1,60 @@
+# [MO] How to log your queries durations with Knex (~10)
+
+## Owner: [Guillaume Renouvin](https://github.com/GuillaumeRenouvin)
+## Creation date: August, 1st 2018
+## Update date: August, 1st 2018
+
+## Context
+- You want to log your database requests durations using Knex query builder
+
+## Prerequisites
+- Have Knex installed
+
+## Steps
+
+### Log your queries informations (~5min)
+- After your Knex instantiation add listeners on each query, query response and query errors
+```javascript
+db.on('query', query => {
+  console.log(query.sql);
+})
+ .on('query-response', (response, query) => {
+   console.log(query.sql);
+ })
+ .on('query-error', err => {
+   console.log(err);
+ });
+```
+> Check: Launch your server, call an API route and you should see your queries on the logs
+
+### Log query duration (~5min)
+
+```javascript
+import now from 'performance-now';
+
+const durations = {};
+
+knex
+ .on('query', query => {
+   durations[query.__knexQueryUid] = {
+     query,
+     startTime: now(),
+   };
+ })
+ .on('query-response', (response, query) => {
+   durations[query.__knexQueryUid].endTime = now();
+
+   console.log(query.sql, ',', `[${query.bindings ? query.bindings.join(',') : ''}]`);
+   console.log(
+     `Time: ${(
+       durations[query.__knexQueryUid].endTime - durations[query.__knexQueryUid].startTime
+     ).toFixed(3)} ms\n`
+   );
+   delete durations[uid];
+ });
+
+  ```
+> Check: Launch your server, call an API route and you should see your queries durations on the logs
+
+### Sources
+- [Timing Your Queries in Knex.js for Node.js](https://spin.atomicobject.com/2017/03/27/timing-queries-knexjs-nodejs/)