log4 KB
Structured Log — logfmt (log)
A structured application log in logfmt — space-separated key=value pairs (ts, level, msg, method, path, status, duration, request_id) as used by many Go and Heroku-style services. A fixture for testing logfmt parsers.
Preview — first 31 lineslog
ts=2026-01-15T14:00:02.959Z level=info msg="request completed" method=POST path=/api/orders status=200 duration_ms=856 request_id=req-51336
ts=2026-01-15T14:00:06.148Z level=info msg="request completed" method=GET path=/login status=200 duration_ms=294 request_id=req-57215
ts=2026-01-15T14:00:10.338Z level=error msg="request failed" method=GET path=/api/products status=500 duration_ms=568 request_id=req-58864
ts=2026-01-15T14:00:14.937Z level=info msg="request completed" method=GET path=/login status=200 duration_ms=745 request_id=req-59465
ts=2026-01-15T14:00:16.777Z level=error msg="request failed" method=POST path=/api/orders status=500 duration_ms=840 request_id=req-69699
ts=2026-01-15T14:00:18.158Z level=warn msg="slow or missing" method=GET path=/api/orders status=200 duration_ms=159 request_id=req-78904
ts=2026-01-15T14:00:21.740Z level=error msg="request failed" method=PUT path=/ status=500 duration_ms=90 request_id=req-48415
ts=2026-01-15T14:00:25.330Z level=info msg="request completed" method=PUT path=/health status=200 duration_ms=429 request_id=req-30520
ts=2026-01-15T14:00:25.627Z level=debug msg="handling request" method=POST path=/ status=200 duration_ms=356 request_id=req-95967
ts=2026-01-15T14:00:30.511Z level=info msg="request completed" method=POST path=/api/products status=200 duration_ms=364 request_id=req-62116
ts=2026-01-15T14:00:34.793Z level=warn msg="slow or missing" method=PUT path=/health status=404 duration_ms=668 request_id=req-53195
ts=2026-01-15T14:00:39.166Z level=error msg="request failed" method=PUT path=/login status=500 duration_ms=225 request_id=req-83851
ts=2026-01-15T14:00:42.311Z level=warn msg="slow or missing" method=GET path=/api/orders status=404 duration_ms=608 request_id=req-90519
ts=2026-01-15T14:00:45.390Z level=info msg="request completed" method=POST path=/health status=200 duration_ms=163 request_id=req-58677
ts=2026-01-15T14:00:46.139Z level=error msg="request failed" method=PUT path=/api/products status=500 duration_ms=747 request_id=req-62835
ts=2026-01-15T14:00:47.128Z level=info msg="request completed" method=PUT path=/api/products status=200 duration_ms=463 request_id=req-66377
ts=2026-01-15T14:00:51.924Z level=error msg="request failed" method=PUT path=/ status=500 duration_ms=485 request_id=req-46397
ts=2026-01-15T14:00:55.263Z level=debug msg="handling request" method=PUT path=/api/products status=200 duration_ms=460 request_id=req-24885
ts=2026-01-15T14:00:55.484Z level=info msg="request completed" method=GET path=/login status=200 duration_ms=134 request_id=req-26066
ts=2026-01-15T14:00:55.677Z level=info msg="request completed" method=DELETE path=/api/orders status=200 duration_ms=94 request_id=req-63192
ts=2026-01-15T14:01:00.420Z level=info msg="request completed" method=DELETE path=/health status=200 duration_ms=82 request_id=req-67789
ts=2026-01-15T14:01:02.483Z level=debug msg="handling request" method=POST path=/login status=200 duration_ms=348 request_id=req-11859
ts=2026-01-15T14:01:03.669Z level=info msg="request completed" method=PUT path=/ status=200 duration_ms=590 request_id=req-99915
ts=2026-01-15T14:01:03.999Z level=warn msg="slow or missing" method=POST path=/ status=404 duration_ms=476 request_id=req-20696
ts=2026-01-15T14:01:04.985Z level=debug msg="handling request" method=POST path=/checkout status=200 duration_ms=666 request_id=req-79614
ts=2026-01-15T14:01:05.290Z level=info msg="request completed" method=PUT path=/ status=200 duration_ms=188 request_id=req-30415
ts=2026-01-15T14:01:05.531Z level=debug msg="handling request" method=GET path=/api/orders status=200 duration_ms=506 request_id=req-60762
ts=2026-01-15T14:01:08.259Z level=info msg="request completed" method=PUT path=/api/products status=200 duration_ms=503 request_id=req-15565
ts=2026-01-15T14:01:08.298Z level=info msg="request completed" method=POST path=/api/orders status=200 duration_ms=884 request_id=req-46986
ts=2026-01-15T14:01:09.971Z level=info msg="request completed" method=GET path=/api/products status=200 duration_ms=447 request_id=req-94198
Specifications
- Lines
- 30
- Format
- logfmt
- Schema
- key=value pairs
- Seed
- 506
What is a .log file?
LOG files are plain-text records of events emitted by software, typically one entry per line with a timestamp, severity, and message. There is no single standard, so formats range from unstructured text to structured JSON lines. They are central to debugging, monitoring, and auditing.
How to use this file
Use an example LOG file to test log parsers, timestamp and severity extraction, line-oriented streaming, and ingestion into monitoring or analysis pipelines.
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Generated by generation/data_logs.py. Free for any use, no attribution required — license.