Logevents - a simple SLF4J implementation

Setting up and configuring logging should be easy, whether you want to do it with configuration files or in code. Log Events is a small (265kb, no dependencies) logging framework built on top of SLF4J - the logging lingua franka for Java.

For detailed instructions, see the manual.

Quick start

Add dependencies (for Maven)

<dependencies>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>2.0.7</version>
    </dependency>

    <dependency>
        <groupId>org.logevents</groupId>
        <artifactId>logevents</artifactId>
        <version>0.5.0</version>
        <scope>runtime</scope>
    </dependency>
</dependencies>

Simple configuration

root=WARN file,console
logger.org.example=INFO
logger.org.example.myapp=DEBUG,TRACE@marker=HTTP_REQUEST&mdc:user=admin
logevents.status=CONFIG

By default, the file observer will log to a file named logs/your-app-name-%date.log and console logs ANSI-colored logs to the console.

The default level for loggers with this configuration will be WARN, by org.example will log at INFO and org.example.myapp will log at DEBUG, or trace for HTTP_REQUEST when the user is admin. See LogEventFilter for details. Use level NONE to turn off logging.

Logevents will output configuration information to system err.

Configuration in a Twelve-Factor setting

Here is an example setup in a cloud environment. Logevents can be configured with environment variables and use stdout as the main channel for logging, outputting JSON logs for more powerful downstream parsing

# Output logevents configuration debug to stderr
LOGEVENTS_STATUS=CONFIG
# Skip sun.reflect packages in stack traces
LOGEVENTS_PACKAGEFILTER=sun.reflect

# By default only output to console at DEBUG
LOGEVENTS_ROOT=DEBUG console

# Console format should be JSON for easier log parsing
LOGEVENTS_OBSERVER_CONSOLE_FORMATTER=ConsoleJsonLogEventFormatter

# Install logging to Microsoft Teams for all ERROR messages
LOGEVENTS_ROOT_OBSERVER_TEAMS=ERROR
LOGEVENTS_OBSERVER_TEAMS=MicrosoftTeamsLogEventObserver
LOGEVENTS_OBSERVER_TEAMS_URL=https://example.webhook.office.com/webhookb2/...

# Turn down logging for selected packages
LOGEVENTS_LOGGER_ORG_ECLIPSE_JETTY=WARN
# Turn up logging to TRACE for com.example message for selected users are
LOGEVENTS_LOGGER_COM_EXAMPLE=DEBUG,TRACE@mdc:user=superuser|admin|tester

Features:

Console logging with good default colors (also on Windows). Use observer.console.format=ConsoleJsonLogEventFormatter to output single-line JSON logs, suitable for log parsing
File logging with reasonable defaults
JUnit support to easy assert on what is logged
Email logging, including throttling to reduce spamming when get lots of log messages
Slack to send log messages to you favorite chat channel
Microsoft Teams
Logging to database
Display logs on a web dashboard
Elasticsearch . Logging directly to Elastic search Index API avoids edge cases when writing and parsing log files
Humio . Logging directly to Humio via their Elastic search Bulk API.
Azure Application Insights ( requires optional com.microsoft.azure:applicationinsights-core dependency)
JMX integration to view the configuration and tweak log levels
Filter loggers on markers and MDC values (e.g. logger.org.example.app=INFO,DEBUG@mdc:user=superuser|admin)
Filter observers on markers and MDC values