TypeError in #monitor: Cannot read properties of undefined (reading 'filter')

[hmwill]

Description

In pg-boss v12.9.0, the #monitor method in boss.ts throws a recurring TypeError during the supervise cycle:

TypeError: Cannot read properties of undefined (reading 'filter')
    at #monitor (file:///app/node_modules/.pnpm/pg-boss@12.9.0/node_modules/pg-boss/dist/boss.js:138:45)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async Boss.supervise (file:///app/node_modules/.pnpm/pg-boss@12.9.0/node_modules/pg-boss/dist/boss.js:120:17)
    at async #onSupervise (file:///app/node_modules/.pnpm/pg-boss@12.9.0/node_modules/pg-boss/dist/boss.js:88:32)

The error fires approximately every minute via the error event.

Root Cause

In src/boss.ts line ~183, #monitor calls cacheQueueStats and destructures the result:

const { rows: rowsCacheStats } = await this.#executeSql(cacheStatsSql)

Then immediately calls .filter() on it:

const warnings = rowsCacheStats.filter(i => i.queuedCount > (i.warningQueueSize || WARNINGS.LARGE_QUEUE.size))

When #executeSql returns a result where rows is undefined, this throws the TypeError.

A similar issue was fixed in commit 3805bb6 ("fix: unwrap sql result in case it returns array during supervise"), but that fix addressed a different code path and didn't cover the cacheQueueStats call in #monitor.

Impact

• Non-critical — all scheduled jobs continue to execute and complete successfully
• Noisy — the error fires every ~1 minute, polluting logs
• Observed in a production deployment on Azure Container Apps with PostgreSQL (Azure Flexible Server)

Environment

• pg-boss: 12.9.0 (also verified the code path is unchanged through 12.11.2)
• Node.js: 24
• PostgreSQL: 16 (Azure Flexible Server)

Suggested Fix

Add a guard or default for rowsCacheStats similar to the pattern used in the supervise fix:

const warnings = (rowsCacheStats || []).filter(i => i.queuedCount > (i.warningQueueSize || WARNINGS.LARGE_QUEUE.size))

[timgit]

Are you using a custom db client driver?