Alog

• JDK 1.5+
• Javadoc

Overview

An asynchronous log handler for JUL (Java Util Logging). It prints log messages on separate threads for low latency logging.

• Minimal application interference.
• Small code / jar size.
• Files will be zipped after they reach a configurable size and the number of zip backups will be trimmed to a configurable maximum.

There are two ways to use Alog: programmatically and with configuration files.

Dependency Management

• Repository : JCenter
• groupId : com.comfortanalytics
• artifactId : alog

Programmatic Usage

Initially acquire logs with Alog.getLogger(). It will add a log handler only if one has not already been added.

import com.comfortanalytics.alog.*;

public static void main(String[] args) {
    Logger log = Alog.getLogger("myLog", new File("myLog.log")));
    AsyncLogHandler handler = Alog.getHandler(log);
    handler.setThrottle(100);
}

Multiple logs can share the same file. A single FileLogHandler will be maintained for each absolute file path. Be aware that once closed, none of the other logs can use the same handler.

import com.comfortanalytics.alog.*;

public static void main(String[] args) {
    Logger log = Alog.getLogger("myLog", new File("myLog.log")));
    Logger another = Alog.getLogger("anotherLog", new File("myLog.log")));
    if (log.getHandlers()[0] == another.getHandlers()[0]) {
        System.out.println("This will print.");
    }
}

The root log handler that prints to System.out should be replaced as well.

import com.comfortanalytics.alog.*;

public static void main(String[] args) {
    Alog.replaceRootHandler();
}

Configuration Files

Alog uses configuration as specified by Java Util Logging. See javadoc for java.util.logging.LogManager for details.

There are two handlers:

• com.comfortanalytics.alog.FileLogHandler
• com.comfortanalytics.alog.PrintStreamLogHandler

The following keys can be used with both:

• com.comfortanalytics.alog.filter is the name of a Filter class to use (defaults to no Filter).
• com.comfortanalytics.alog.formatter is the name of a Formatter class to use (defaults to null and uses an optimized Alog format) .
• com.comfortanalytics.alog.inferCaller is a boolean that determines whether or not to infer the source class and method name before submitting the log record for async processing (expensive, so the default is false).
• com.comfortanalytics.alog.level is the default level for the Handler (defaults to INFO).
• com.comfortanalytics.alog.maxQueue is the max async queue size above which records are ignored (defaults to 25000, use 0 for infinite).
• com.comfortanalytics.alog.throttle is the percentage (0-100) of the maxQueue after which log records less than INFO are ignored (defaults to 90%). A value of 100 effectively disables the throttle.

The following keys can also be used with the FileLogHandler:

• com.comfortanalytics.alog.backupThreshold is the approximate file size in bytes to zip up the log file and store it with a timestamp appended to the file name (default is 10000000 bytes).
• com.comfortanalytics.alog.encoding is the charset for encoding log files (default is "UTF-8").
• com.comfortanalytics.alog.filename is the pattern for generating the output file name. See below for details. (default is "java.log").
• com.comfortanalytics.alog.maxBackups is the number of zip backups to maintain (default is 10).

The filename pattern uses the following tokens:

• "/" represents the local pathname separator.
• "%t" is the system temporary directory.
• "%h" is the value of the "user.home" system property.
• "%%" translates to a single percent sign "%".

Example configuration for an async file handler:

myLog.handlers=com.comfortanalytics.alog.FileLogHandler
com.comfortanalytics.alog.level=CONFIG
com.comfortanalytics.alog.maxQueue=50000
com.comfortanalytics.alog.backupThreshold=100000000
com.comfortanalytics.alog.filename=%halog.log
com.comfortanalytics.alog.maxBackups=5

To replace the root handler that prints to the console with one that does it ansynchronously:

handlers=com.comfortanalytics.alog.PrintStreamLogHandler
com.comfortanalytics.alog.level=FINE
com.comfortanalytics.alog.maxQueue=5000
com.comfortanalytics.alog.throttle=95