30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
---
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title: MySQL Connection Pool Runbook
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keywords: [MySQL connection pool, pool exhausted, max_connections, HikariCP]
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summary: Diagnose exhausted MySQL connection pools and distinguish application leaks from database limits.
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category: database
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source: mysql-connection-pool
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breadcrumb: Database > MySQL > Connection Pool
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kb_scope: rag-eval
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covers: [mysql, connection pool, database capacity]
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when_to_retrieve: Use when MySQL clients report exhausted pools, connection acquisition timeout, max_connections pressure, or HikariCP saturation.
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---
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# Database
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## MySQL
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### Connection Pool
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When MySQL connection pool is exhausted, first compare application pool usage with database `max_connections`.
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For HikariCP, check `active`, `idle`, `pending`, and connection acquisition timeout metrics.
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Recommended diagnosis:
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1. Verify whether HikariCP active connections stay near maximum while pending threads grow.
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2. Check MySQL `Threads_connected`, `Threads_running`, and `max_connections`.
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3. Inspect slow SQL and long transactions that keep connections checked out.
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4. If the database is healthy, look for application connection leaks or missing transaction boundaries.
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Use this runbook as evidence for connection pool, max_connections, and HikariCP incidents.
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