https://github.com/mbien/jfrlog

JFRLog - a SLF4J to JFR Bridge
https://github.com/mbien/jfrlog

flight-recorder java jfr jfr-bridge jvm logging openjdk slf4j

Last synced: about 1 month ago
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JFRLog - a SLF4J to JFR Bridge

• Host: GitHub
• URL: https://github.com/mbien/jfrlog
• Owner: mbien
• License: mit
• Created: 2020-08-22T09:22:44.000Z (about 4 years ago)
• Default Branch: master
• Last Pushed: 2023-09-25T03:23:32.000Z (about 1 year ago)
• Last Synced: 2024-10-04T10:15:53.548Z (about 1 month ago)
• Topics: flight-recorder, java, jfr, jfr-bridge, jvm, logging, openjdk, slf4j
• Language: Java
• Homepage: https://mbien.dev/blog/entry/jfrlog-logging-directly-to-the
• Size: 44.9 KB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# JFRLog - a SLF4J to JFR Bridge

This project implements a SLF4J logger which records all log messages as Java Flight Recorder events.

## quickstart

1. replace your SLF4J compatible logging impl with slf4j-jfr-bridge-x.x.x.jar

2. start the JVM with JFR enabled (e.g. -XX:StartFlightRecording:filename=logs/recording.jfr,dumponexit=true)

   or enable recording later

3. check the flight recorder repository or recording dump for log.* events:

```bash

$ jfr print --events "log.*" logs/recording.jfr

...

log.Info {

  startTime = 07:38:02.730

  message = "Started @5532ms"

  origin = "org.eclipse.jetty.server.Server"

  throwable = N/A

  eventThread = "main" (javaThreadId = 1)

}

...

```

note: JFRLog has currently no fallback, if no recording is active you won't see any logs.

## maven central coordinates

```xml

    dev.mbien.jfrlog

    slf4j-jfr-bridge

    0.1.0

```

## configuration

JFRLog can be configured in two ways: via JVM -D arguments or via a jfrlog.properties

file in the classpath. JVM -D properties are handled with higher priority and override

properties with the same key stored in the file.

(note: disabling specific log events in the JFR recording profile will filter the loggers too)

example:

```

java -Djfrlog.default=info -Djfrlog.dev.cool.app=error -Djfrlog.dev.cool.app.MyKlass=debug (...) app.jar

```

Sets MyKlass to debug, the rest of the package to error and the default log level

to info for everything else. The most specific rule wins (order does not matter).

other options:

```

jfrlog.recordOrigin=true

```

Records the origin (logger name) of the log message. Enabled by default.

```

jfrlog.loggerCache=false

```

This is off by default and should be kept off unless there is a good reason to enable

it. It is going to guarantee that the same logger instance is returned for a given

logger name.

## commandline tools

JFRLog also provides commandline tools for easy JFR record inspection.

Add the jbang catalog:

```bash

$ jbang catalog add jfrlog https://github.com/mbien/JFRLog/blob/master/cli/jbang-catalog.json

```

and use jfrprint to print JFR events (not only log message events).

```bash

$ MSG_PATTERN="{eventName,0d,C} {startTime,dt:yyyy-MM-dd HH:mm:ss.SSS} [{eventThread.javaName}]\

 {origin,1d}: {message} {throwable,o,n}"

$ jbang jfrprint 10h log.* "$MSG_PATTERN" dump.jfr

INFO 2020-09-30 16:12:42.458 [main] jfrlogtest.LogTest: Hello There!

WARN 2020-09-30 16:12:42.461 [main] jfrlogtest.LogTest: don’t panic

java.lang.IllegalArgumentException: test, please ignore

	at dev.mbien.jfrlogtest.LogTest.main(LogTest.java:12)

...

```

More info in this [blog entry](https://mbien.dev/blog/entry/jfrlog-commandline-tools)

## requirements

JFRLog requires Java 8+ to run, but Java 14+ to build/test since the junit tests rely on the JFR

streaming API (JEP 349).

## license

This project is distributed under the MIT License, see LICENSE file.