fix(postgres-driver): handle connection termination errors gracefully

[igorlukanin]

Add error handlers to pool clients to prevent unhandled error events from crashing the process when PostgreSQL connections are terminated unexpectedly (e.g., when max connections are reached).

Check List

• Tests have been run in packages where changes have been made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Issue Reference this PR resolves

Fixes #10142

Conversation with Claude

claude.txt

[Copilot]

Pull request overview

This PR addresses unhandled error events from PostgreSQL connections that can crash the Node.js process when database connections are terminated unexpectedly (e.g., due to max connections being reached). The changes replace direct console.log calls with the proper databasePoolError method and add error handlers to individual pool clients.

• Replaces console.log statements with calls to databasePoolError method in pool error handlers
• Adds error event listeners to individual pool clients to prevent unhandled errors from crashing the process
• Applies the same fix consistently across both PostgresDriver and QuestDriver

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/cubejs-postgres-driver/src/PostgresDriver.ts	Updated pool error handler to use databasePoolError and added client error handlers in stream() and queryResponse() methods
packages/cubejs-questdb-driver/src/QuestDriver.ts	Updated pool error handler to use databasePoolError and added client error handler in queryResponse() method

---

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[Copilot]

The error listener is being attached each time a connection is acquired from the pool, but it's never removed. When connections are reused from the pool, this will result in multiple identical error listeners accumulating on the same connection object, causing a memory leak. Consider using conn.once('error', ...) instead of conn.on('error', ...) to ensure the listener is automatically removed after the first error, or explicitly remove the listener in the finally block or release callback.

Suggested change

	conn.on('error', (err) => {
	conn.once('error', (err) => {

[Copilot]

The error listener is being attached each time a connection is acquired from the pool, but it's never removed. When connections are reused from the pool, this will result in multiple identical error listeners accumulating on the same connection object, causing a memory leak. Consider using conn.once('error', ...) instead of conn.on('error', ...) to ensure the listener is automatically removed after the first error, or explicitly remove the listener in the finally block.

[Copilot]

The error listener is being attached each time a connection is acquired from the pool, but it's never removed. When connections are reused from the pool, this will result in multiple identical error listeners accumulating on the same connection object, causing a memory leak. Consider using conn.once('error', ...) instead of conn.on('error', ...) to ensure the listener is automatically removed after the first error, or explicitly remove the listener in the finally block.

Suggested change

	conn.on('error', (err) => {
	conn.once('error', (err) => {

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.17%. Comparing base (df8161c) to head (003c146).
⚠️ Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (df8161c) and HEAD (003c146). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (df8161c)	HEAD (003c146)
cubesql	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #10277       +/-   ##
===========================================
- Coverage   83.27%   55.17%   -28.11%     
===========================================
  Files         248      221       -27     
  Lines       74448    17202    -57246     
  Branches        0     3521     +3521     
===========================================
- Hits        61999     9491    -52508     
+ Misses      12449     7216     -5233     
- Partials        0      495      +495     

Flag	Coverage Δ
cube-backend	55.17% <ø> (?)
cubesql	?

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