fix(cloud-sql): update unclear configuration in postgres connection sample (#1746)

* updated timeout, backoff, and lifetime region tags for clarity

* moved idleTimeoutMillis to timeout region tag

Author: shubha-rajan

cloud-sql/postgres/knex/server.js

@@ -75,26 +75,27 @@ const connect = () => {
   // Additional connections will be established to meet this value unless the pool is full.
   knex.client.pool.min = 5;
   // [END cloud_sql_postgres_knex_limit]
+
   // [START cloud_sql_postgres_knex_timeout]
-  // 'acquireTimeoutMillis' is the maximum number of milliseconds to wait for a connection checkout.
-  // Any attempt to retrieve a connection from this pool that exceeds the set limit will throw an
-  // SQLException.
+  // 'acquireTimeoutMillis' is the number of milliseconds before a timeout occurs when acquiring a 
+  // connection from the pool. This is slightly different from connectionTimeout, because acquiring 
+  // a pool connection does not always involve making a new connection, and may include multiple retries.
+  // when making a connection
+  knex.client.pool.acquireTimeoutMillis = 60000; // 60 seconds
+  // 'createTimeoutMillis` is the maximum number of milliseconds to wait trying to establish an
+  // initial connection before retrying. 
+  // After acquireTimeoutMillis has passed, a timeout exception will be thrown.
   knex.client.pool.createTimeoutMillis = 30000; // 30 seconds
-  // 'idleTimeoutMillis' is the maximum amount of time a connection can sit in the pool. Connections that
-  // sit idle for this many milliseconds are retried if idleTimeoutMillis is exceeded.
+  // 'idleTimeoutMillis' is the number of milliseconds a connection must sit idle in the pool 
+  // and not be checked out before it is automatically closed.
   knex.client.pool.idleTimeoutMillis = 600000; // 10 minutes
   // [END cloud_sql_postgres_knex_timeout]
+
   // [START cloud_sql_postgres_knex_backoff]
+  // 'knex' uses a built-in retry strategy which does not implement backoff.
   // 'createRetryIntervalMillis' is how long to idle after failed connection creation before trying again
   knex.client.pool.createRetryIntervalMillis = 200; // 0.2 seconds
   // [END cloud_sql_postgres_knex_backoff]
-  // [START cloud_sql_postgres_knex_lifetime]
-  // 'acquireTimeoutMillis' is the maximum possible lifetime of a connection in the pool. Connections that
-  // live longer than this many milliseconds will be closed and reestablished between uses. This
-  // value should be several minutes shorter than the database's timeout value to avoid unexpected
-  // terminations.
-  knex.client.pool.acquireTimeoutMillis = 600000; // 10 minutes
-  // [START cloud_sql_postgres_knex_lifetime]
 
   // [END_EXCLUDE]
   return knex;