• Резкое накопление сотен активных соединений со статусом ожидания WaitEventType: Lock.
• Ошибки в приложениях: ERROR: deadlock detected или canceling statement due to lock timeout.
• DDL-миграции (ALTER TABLE, CREATE INDEX) блокируют обычные SELECT/UPDATE операции.

1. Запрос для выявления блокировщиков и ожидающих сессий

SELECT 
    blocked_locks.pid     AS blocked_pid,
    blocked_activity.usename  AS blocked_user,
    blocking_locks.pid    AS blocking_pid,
    blocking_activity.usename AS blocking_user,
    blocked_activity.query    AS blocked_statement,
    blocking_activity.query   AS blocking_statement,
    now() - blocked_activity.query_start AS blocked_duration
FROM  pg_catalog.pg_locks blocked_locks
JOIN pg_catalog.pg_stat_activity blocked_activity ON blocked_activity.pid = blocked_locks.pid
JOIN pg_catalog.pg_locks blocking_locks 
    ON blocking_locks.locktype = blocked_locks.locktype
    AND blocking_locks.database IS NOT DISTINCT FROM blocked_locks.database
    AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation
    AND blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page
    AND blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple
    AND blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid
    AND blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid
    AND blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid
    AND blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid
    AND blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid
    AND blocking_locks.pid != blocked_locks.pid
JOIN pg_catalog.pg_stat_activity blocking_activity ON blocking_activity.pid = blocking_locks.pid
WHERE NOT blocked_locks.granted;

2. Принудительное завершение блокирующего процесса

-- Мягкая отмена выполняемого запроса
SELECT pg_cancel_backend(blocking_pid);

-- Жесткий разрыв соединения процесса
SELECT pg_terminate_backend(blocking_pid);

3. Превентивная настройка таймаутов в postgresql.conf

# Максимальное время ожидания захвата блокировки (например, 5 секунд)
lock_timeout = 5s

# Максимальное время выполнения запроса
statement_timeout = 30s

# Авторазрыв транзакций, зависших в состоянии «idle in transaction»
idle_in_transaction_session_timeout = 10s

# Задержка перед проверкой взаимной блокировки (дедлока)
deadlock_timeout = 1s

SELECT pg_reload_conf();