Configuring Logging

Red Hat JBoss EAP 8 Logging Subsystem

Logging is vital for application servers like Red Hat JBoss EAP 8.
Red Hat JBoss EAP 8’s logging subsystem, consistent with its modular design, is managed by a subsystem and configured in domain.xml for managed domain mode and standalone.xml for standalone servers.
The subsystem comprises of three key components:
1. Handlers:
  1. These dictate where and how server events are logged.
  2. JBoss EAP offers various built-in handlers for logging application messages.
2. Loggers:
  1. Also known as log categories, these organize events into logical groups based on package namespaces within the Java Virtual Machine.
  2. They specify which handlers process and log messages.
3. Root Logger:
  1. Positioned atop the logger hierarchy, the root logger captures all log messages of a specified level not handled by specific log categories.

Default Log File Locations

Standalone Mode:
1. Log files reside in the standalone/log directory within the base directory.
2. This directory contains two key log files:
  1. gc.log.0.current: Managed by settings in BASE_DIR/bin/standalone.sh, exclusively logs JVM flags and memory management events from the latest server startup.
  2. server.log: Containing server log events, with ongoing additions, this file’s configurations are specified within the logging subsystem section of standalone.xml.
Domain Mode:
1. Logging spans several locations relative to the base directory.
  1. domain/log/host-controller.log: Documents host controller startup events, including connection issues, debug messages, and runtime errors.
  2. domain/log/process-controller.log: Records process startup and shutdown events on the host, including those of the host controller and individual servers.
  3. domain/servers/<server-name>/log/server.log: Houses log events specific to each server on the host.
2. Each server on a host possesses its own log directory. For instance, if a host includes a server named dev-server-one, its log file resides in domain/servers/dev-server-one/log/server.log.

It’s advisable to regularly rotate server.log files, typically on an hourly or daily basis, or when file size thresholds are met.

Built-in Log Handlers

Red Hat JBoss EAP 8 features built-in handlers, including:
1. Console handler: Writes to the console. Configured using the <console-handler> element.
2. File handler: Writes to a file. Configured using the <file-handler> element.
3. Periodic-rotating file handler: Rotates logs based on time intervals. Configured using the <periodic-rotating-file-handler> element.
4. Size-rotating file handler: Rotates logs based on file size. Configured using the <size-rotating-file-handler> element.
5. Asynchronous handler: Writes logs asynchronously to sub-handlers. Configured using the <async-handler> element.
6. Syslog handler: Sends events to a remote syslog server. configured using the <syslog-handler> element.
Handlers are configured within the logging subsystem section of the server configuration file.

For example, the standalone.xml file and most of the profiles in the domain.xml file come preconfigured with a <console-handler> definition.

[standalone@localhost:9990 /] /subsystem=logging/console-handler=CONSOLE:read-resource
{
    "outcome" => "success",
    "result" => {
        "autoflush" => true,
        "enabled" => true,
        "encoding" => undefined,
        "filter" => undefined,
        "filter-spec" => undefined,
        "formatter" => "%d{HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n",
        "level" => "DEBUG",
        "name" => "CONSOLE",
        "named-formatter" => "COLOR-PATTERN",
        "target" => "System.out"
    }
}

Lab 1: Change log level using JBoss CLI

Outcome: In this lab, you check the current log level and change it to "DEBUG" using JBoss EAP CLI.

Start the standalone Red Hat JBoss EAP 8 server.

[vagrant@server ~]$ cd /opt/EAP-8.0.0/bin/
[vagrant@server bin]$ sudo -u jboss ./standalone.sh

Open another terminal and connect to the JBoss EAP CLI.
```
[vagrant@server bin]$ sudo -u jboss ./jboss-cli.sh -c
```

Confirm the current log level is "INFO" by executing command shown below.

[standalone@localhost:9990 /]  /subsystem=logging/root-logger=ROOT:read-resource
{
    "outcome" => "success",
    "result" => {
        "filter" => undefined,
        "filter-spec" => undefined,
        "handlers" => [
            "CONSOLE",
            "FILE"
        ],
        "level" => "INFO"
    }
}

Change the log level to "DEBUG" using the command shown below.

[standalone@localhost:9990 /] /subsystem=logging/root-logger=ROOT:write-attribute(name="level", value="DEBUG")
{"outcome" => "success"}

Confirm the log level is updated to "DEBUG".

[standalone@localhost:9990 /]  /subsystem=logging/root-logger=ROOT:read-resource
{
    "outcome" => "success",
    "result" => {
        "filter" => undefined,
        "filter-spec" => undefined,
        "handlers" => [
            "CONSOLE",
            "FILE"
        ],
        "level" => "DEBUG"
    }
}

Notice the logs in the first terminal shows "DEBUG" logs:

...output_omitted...
07:34:51,304 DEBUG [org.jboss.as.repository] (ServerService Thread Pool -- 77) Current content hash references are {f9418ea27525e0f3c02ea099405265246b22b55a=[ContentReference{contentIdentifier=/deployment=kitchensink.war, hexHash=f9418ea27525e0f3c02ea099405265246b22b55a}], 555df23b973ed9f76f7c817deec3bab6a13a7ea3=[ContentReference{contentIdentifier=/deployment=temperature-converter.war, hexHash=555df23b973ed9f76f7c817deec3bab6a13a7ea3}]}
07:39:51,306 DEBUG [org.jboss.as.repository] (ServerService Thread Pool -- 77) Current content hash references are {f9418ea27525e0f3c02ea099405265246b22b55a=[ContentReference{contentIdentifier=/deployment=kitchensink.war, hexHash=f9418ea27525e0f3c02ea099405265246b22b55a}], 555df23b973ed9f76f7c817deec3bab6a13a7ea3=[ContentReference{contentIdentifier=/deployment=temperature-converter.war, hexHash=555df23b973ed9f76f7c817deec3bab6a13a7ea3}]}
...output_omitted...

Stop the standalone server and JBoss CLI by pressing Ctrl+C.

Lab 2: Configuring Logging Handlers

Outcome: In this lab, you create a size rotating file handler and verify that it’s created successfully.

Start the standalone Red Hat JBoss EAP 8 server.

[vagrant@server ~]$ cd /opt/EAP-8.0.0/bin/
[vagrant@server bin]$ sudo -u jboss ./standalone.sh

Open another terminal and connect to the JBoss EAP CLI.
```
[vagrant@server bin]$ sudo -u jboss ./jboss-cli.sh -c
```

Create custom handler named 'CUSTOM_HANDLER' that would capture all of the logs generated by the category com.example.www in a file called /opt/EAP-8.0.0/standalone/log/logtest.log, after the log file reaches 1 MB in size, the logging subsystem should rotates the log file to a new log file with a numbered suffix.

[standalone@localhost:9990 /] /subsystem=logging/size-rotating-file-handler=CUSTOM_HANDLER/:add\
> (file={"path"=>"logtest.log",\
> "relative-to"=>"jboss.server.log.dir"},\
> formatter="%d{HH:mm:ss,SSS} %-5p [%c] (%t) %s%E%n",\
> level=DEBUG,max-backup-index=3,name=CUSTOM_HANDLER,\
> rotate-size=1m)
{"outcome" => "success"}

[standalone@localhost:9990 /] /subsystem=logging/logger=com.example.www:add\
(category=com.example.www,handlers=["CUSTOM_HANDLER"])

Verify that the handler was added successfully.

[standalone@localhost:9990 /] /subsystem=logging/size-rotating-file-handler=CUSTOM_HANDLER:read-resource
{
    "outcome" => "success",
    "result" => {
        "append" => true,
        "autoflush" => true,
        "enabled" => true,
        "encoding" => undefined,
        "file" => {
            "path" => "logtest.log",
            "relative-to" => "jboss.server.log.dir"
        },
        "filter" => undefined,
        "filter-spec" => undefined,
        "formatter" => "%d{HH:mm:ss,SSS} %-5p [%c] (%t) %s%E%n",
        "level" => "DEBUG",
        "max-backup-index" => 3,
        "name" => "CUSTOM_HANDLER",
        "named-formatter" => undefined,
        "rotate-on-boot" => false,
        "rotate-size" => "1m",
        "suffix" => undefined
    }
}

Open a new terminal and confirm the respective log file is create.

[vagrant@server ~]$ ls -ld /opt/EAP-8.0.0/standalone/log/logtest.log
-rw-r--r--. 1 jboss jboss 0 Apr 30 08:59 /opt/EAP-8.0.0/standalone/log/logtest.log

Stop the standalone server and JBoss CLI by pressing Ctrl+C.