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DashBoard/openspec/specs/slow-query-concurrency-control/spec.md
egg d8e91624d4 feat(qc-gate): add Package column to LOT detail table + archive 3 completed changes 
Add PACKAGE_LEF as a dedicated `package` field in the QC-GATE API payload
and display it as a new column after LOT ID in LotTable.vue. Archive
qc-gate-lot-package-column, historical-query-slow-connection, and
msd-multifactor-backward-tracing changes with their delta specs synced
to main specs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-02 08:44:26 +08:00

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Purpose

Define stable requirements for slow-query-concurrency-control.

Requirements

Requirement: Configurable slow query timeout

The system SHALL read DB_SLOW_CALL_TIMEOUT_MS from environment/config to determine the default call_timeout for read_sql_df_slow. The default value SHALL be 300000 (300 seconds).

Scenario: Default timeout when no env var set

  • WHEN DB_SLOW_CALL_TIMEOUT_MS is not set in environment
  • THEN read_sql_df_slow uses 300 seconds as call_timeout

Scenario: Custom timeout from env var

  • WHEN DB_SLOW_CALL_TIMEOUT_MS is set to 180000
  • THEN read_sql_df_slow uses 180 seconds as call_timeout

Scenario: Caller overrides timeout

  • WHEN caller passes timeout_seconds=120 to read_sql_df_slow
  • THEN the function uses 120 seconds regardless of config value

Requirement: Semaphore-based concurrency control

The system SHALL use a global threading.Semaphore to limit the number of concurrent read_sql_df_slow executions. The limit SHALL be configurable via DB_SLOW_MAX_CONCURRENT with a default of 3.

Scenario: Concurrent queries within limit

  • WHEN 2 slow queries are running and a 3rd is submitted (limit=3)
  • THEN the 3rd query proceeds immediately

Scenario: Concurrent queries exceed limit

  • WHEN 3 slow queries are running and a 4th is submitted (limit=3)
  • THEN the 4th query waits up to 60 seconds for a slot
  • AND if no slot becomes available, raises RuntimeError with message indicating all slots are busy

Scenario: Semaphore release on query failure

  • WHEN a slow query raises an exception during execution
  • THEN the semaphore slot is released in the finally block

Requirement: Slow query active count diagnostic

The system SHALL expose the current number of active slow queries via get_slow_query_active_count() and include it in get_pool_status() as slow_query_active.

Scenario: Active count in pool status

  • WHEN 2 slow queries are running
  • THEN get_pool_status() returns slow_query_active: 2

Requirement: Gunicorn timeout accommodates slow queries

The Gunicorn worker timeout SHALL be at least 360 seconds to accommodate the maximum slow query duration (300s) plus overhead.

Scenario: Long query does not kill worker

  • WHEN a slow query takes 280 seconds to complete
  • THEN the Gunicorn worker does not timeout and the response is delivered

Requirement: Config settings in all environments

All environment configs (Config, DevelopmentConfig, ProductionConfig, TestingConfig) SHALL define DB_SLOW_CALL_TIMEOUT_MS and DB_SLOW_MAX_CONCURRENT.

Scenario: Testing config uses short timeout

  • WHEN running in testing environment
  • THEN DB_SLOW_CALL_TIMEOUT_MS defaults to 10000 and DB_SLOW_MAX_CONCURRENT defaults to 1