25P04

At a glance

25P04 is a FATAL condition emitted by transaction_timeout, which covers both an explicit BEGIN transaction and an implicitly started single-statement transaction. The selected 18.6 case uses 300 ms; PG10 is a source/version preflight skip because the setting is unavailable there, so it does not probe an unknown setting. A separate PG16.15/PG17.11 boundary comparison records unavailable-setting 42704 on PG16 and natural FATAL 25P04 on PG17; it is separate from the selected base case.

Meaning

transaction_timeout limits the lifetime of an explicit or implicit transaction, including time spent executing or waiting while that transaction is open. When it fires, PostgreSQL emits terminating connection due to transaction timeout and terminates the session. It is different from statement_timeout, which aborts one statement, and from idle_in_transaction_session_timeout, which covers only client-idle time inside an open transaction. If transaction_timeout is shorter than or equal to either of those settings, the longer timeout is ignored; prepared transactions are not subject to it.

Diagnosis

On a supported server, capture the effective SHOW transaction_timeout, SHOW statement_timeout, and SHOW idle_in_transaction_session_timeout values on the timed session itself. A control connection's SHOW or pg_settings describes the observer backend and cannot establish another session's effective SET values. From the control connection inspect pg_stat_activity fields such as pid, application_name, state, xact_start, state_change, query_start, and query to identify the owning application or pool and whether the transaction is active or idle. Match the collector record by backend PID, SQLSTATE 25P04, error_severity = FATAL, and the exact message. In the selected 18.6 run the driver also exposed 25P04 and the original connection was closed; a fresh owner connection successfully ran SELECT 1. PG10 is skipped by the minimum-version preflight before SET transaction_timeout is sent.

Response

Discard the terminated session and reconnect. Keep legitimate transactions within the chosen budget by shortening work, splitting a long unit of work, or raising the effective timeout; do not lower it to hide the error. Set it to 0 only when the deployment deliberately accepts the absence of this guard. When the server closes the terminated session, it rolls back the open incomplete transaction before exiting; the dead connection cannot accept a later ROLLBACK. A known transaction that had not committed on that session cannot be recovered through that connection. If a separate network failure left it uncertain whether COMMIT reached the server, reconcile the business result from a fresh connection before retrying; the selected case sent no commit and does not establish that uncertainty. PG10 has no compatible setting in this batch.

FATAL message

The server source emits terminating connection due to transaction timeout at FATAL severity; the original connection is terminated.

Observed diagnostics

18.6 (Homebrew) / latest: FATAL SQLSTATE 25P04; primary terminating connection due to transaction timeout; backend PID 30576; original connection closed True; collector CSV 25P04; collector JSON 25P04; fresh probe 1. 10.21 (Debian 10.21-1.pgdg90+1) / pg10: case not_applicable (minimum-version preflight; the unsupported setting was not probed).

Separate boundary comparison: 16.15 / pg16 returned 42704 for unavailable transaction_timeout and remained IDLE, so it is not 25P04 coverage. 17.11 / pg17 produced FATAL 25P04 after 300 ms with backend PID 73; CSV and JSON both recorded FATAL 25P04, the original connection closed, and a fresh connection was IDLE. These records are outside the selected base case.

Representative case

The SQL excerpt below is not a paste-all script: run the setting, PID, and BEGIN on a test connection, then stop sending it queries while a separate observer or log collector waits for FATAL; after the old connection is terminated, open a fresh owner connection for the final probe. The runner reads these statements from the shared registry; complete assertions, collector correlation, environment, and cleanup are in case export.

-- set_timeout
SET transaction_timeout = '300ms';
-- backend_pid
SELECT pg_backend_pid();
-- begin
BEGIN;
-- probe
SELECT 1;

The SQLSTATE, diagnostics, states, and repair assertions for this excerpt come from the shared registry (SHA-256 d05a26e56716c5c8c178f741843e6b14be87423ec9d1eb1a026ff67a57ce4658); structured evidence.

Authored evidence IDs: identity, timeout-path, runtime, runtime.version-boundary. Selected base runtime record: runtime.25P04-batch2c-latest-20260909.latest. Separate boundary records: runtime.25P04-boundary-pg16-20260909.pg16 and runtime.25P04-boundary-pg17-20260909.pg17.

The separate boundary comparison has already recorded the availability check: PG16 returned 42704 and PG17 continued to a natural FATAL 25P04. This boundary block is branched, not a paste-all script. On PG16, run SHOW transaction_timeout; after the expected 42704, use the same still-healthy connection for SELECT 1 if you need to prove recovery, then stop and skip SET transaction_timeout, BEGIN, and the timeout wait. On PG17 or later, after SHOW succeeds, run SET transaction_timeout, capture the PID, and run BEGIN; then stop sending queries and let the observer or collector wait for the old connection's FATAL and closure. Open a fresh connection only for the final probe. The boundary records are diagnostic comparisons and do not add to the selected base case count.

-- availability_probe
SHOW transaction_timeout;
-- set_timeout
SET transaction_timeout = '300ms';
-- backend_pid
SELECT pg_backend_pid();
-- begin
BEGIN;
-- probe
SELECT 1;

Versions and limits

The locked catalogue first observes transaction_timeout in 17.0. The selected 18.6 case passes with CSV/JSON collector evidence and a fresh-connection probe. The separate PG17.11 boundary case independently records natural FATAL 25P04, while PG16.15 records unavailable-setting 42704; neither replaces the selected base run. The PG10 case is a real not_applicable minimum-version preflight skip: the handler does not send or probe the unknown setting, so this is not evidence of an earlier boundary.

Related

25P03 idle-in-transaction timeout, 40001 serialization failure, 57014 query canceled.

Sources

• src.errcodes.18.6 (SHA-256 6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba)
• src.calls.REL_18_6 — raw/calls/REL_18_6.jsonl (SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf)
• src.postgres.18.6 (SHA-256 9fb62275b1badf94d01ab351337b60410cd9b3ab1fe63fa9f23d6d2185a21061)
• src.config.18.6 (SHA-256 ffca322c15315ba670733d6b320f23cbba7374db0d18937298ffc07b58799ef6) · official documentation
• doc.monitoring.18.6 (SHA-256 06b147f8d966fe46821871703ffcee8a3449cc3f7de5b64b9177f48569fe96f6) · official monitoring documentation
• src.system_views.18.6 (SHA-256 418f4ae7472fe0742e6fbdc7a055581602c5131e082aa6f17e2c7269bf711972) · official pg_settings documentation
• doc.protocol.18.6 (SHA-256 745339e07ebbc2bb67d98b258e25772ada644ef26011e3cd6b3fcbb435235f89) · official protocol documentation

Source evidence

Evidence belongs to the frozen source and runtime versions listed here. It is not a runtime verification of the selected manual version.

• src/backend/utils/errcodes.txt · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• raw/calls/REL_18_6.jsonl · ·
• src/backend/tcop/postgres.c · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• doc/src/sgml/config.sgml · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• doc/src/sgml/monitoring.sgml · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/catalog/system_views.sql · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• doc/src/sgml/protocol.sgml · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7

Message templates

terminating connection due to transaction timeout

Reproduction & repair cases

Recorded runtime evidence

{
  "primary": "terminating connection due to transaction timeout",
  "severity": "FATAL",
  "sqlstate": "25P04",
  "backend_pid": 30576,
  "status_before_timeout": "INTRANS",
  "collector_csv_sqlstate": "25P04",
  "fresh_connection_probe": 1,
  "collector_json_sqlstate": "25P04",
  "fresh_connection_status": "IDLE",
  "original_connection_closed": true,
  "collector_csv_error_severity": "FATAL",
  "collector_json_error_severity": "FATAL",
  "recovery_requires_new_connection": true
}

{
  "setting": "transaction_timeout",
  "preflight": "minimum_version",
  "case_status": "not_applicable",
  "minimum_version": 170000,
  "server_version_num": 100021,
  "setting_probe_skipped": true
}

{
  "setting": "transaction_timeout",
  "status_after_probe": "IDLE",
  "availability_primary": "unrecognized configuration parameter \"transaction_timeout\"",
  "availability_severity": "ERROR",
  "availability_sqlstate": "42704",
  "fresh_connection_probe": 1,
  "natural_25P04_observed": false
}

{
  "primary": "terminating connection due to transaction timeout",
  "setting": "transaction_timeout",
  "sqlstate": "25P04",
  "timeout_ms": 300,
  "backend_pid": 73,
  "driver_severity": "FATAL",
  "status_before_timeout": "INTRANS",
  "collector_csv_severity": "FATAL",
  "collector_csv_sqlstate": "25P04",
  "fresh_connection_probe": 1,
  "natural_25P04_observed": true,
  "collector_json_severity": "FATAL",
  "collector_json_sqlstate": "25P04",
  "fresh_connection_status": "IDLE",
  "original_connection_closed": true
}