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<#import "/templates/links.adoc" as links>
<#import "/templates/profile.adoc" as profile>
<#import "/templates/options.adoc" as opts>

<@tmpl.guide
title="Configuring logging"
summary="Configure logging for {project_name}.">

{project_name} uses the JBoss Logging framework.
The following is a high-level overview for the available log handlers with the common parent log handler `root`:

<@opts.expectedValues option="log"/>

== Logging configuration

Logging is done on a per-category basis in {project_name}.
You can configure logging for the root log level or for more specific categories such as `org.hibernate` or `org.keycloak`.
It is also possible to tailor log levels for each particular log handler.

This {section} describes how to configure logging.

=== Log levels

The following table defines the available log levels.

[%autowidth]
|===
|Level|Description

|FATAL|Critical failures with complete inability to serve any kind of request.
|ERROR|A significant error or problem leading to the inability to process requests.
|WARN|A non-critical error or problem that might not require immediate correction.
|INFO|{project_name} lifecycle events or important information. Low frequency.
|DEBUG|More detailed information for debugging purposes, such as database logs. Higher frequency.
|TRACE|Most detailed debugging information. Very high frequency.
|ALL|Special level for all log messages.
|OFF|Special level to turn logging off entirely (not recommended).
|===

=== Configuring the root log level
When no log level configuration exists for a more specific category logger, the enclosing category is used instead. When there is no enclosing category, the root logger level is used.

To set the root log level, enter the following command:

<@kc.start parameters="--log-level=<root-level>"/>

Use these guidelines for this command:

* For `_<root-level>_`, supply a level defined in the preceding table.
* The log level is case-insensitive. For example, you could either use `DEBUG` or `debug`.
* If you were to accidentally set the log level twice, the last occurrence in the list becomes the log level. For example, if you included the syntax `--log-level="info,...,DEBUG,..."`, the root logger would be `DEBUG`.

=== Configuring category-specific log levels
You can set different log levels for specific areas in {project_name}. Use this command to provide a comma-separated list of categories for which you want a different log level:

<@kc.start parameters="--log-level=\"<root-level>,<org.category1>:<org.category1-level>\""/>

A configuration that applies to a category also applies to its sub-categories unless you include a more specific matching sub-category.

.Example
<@kc.start parameters="--log-level=\"INFO,org.hibernate:debug,org.hibernate.hql.internal.ast:info\""/>

This example sets the following log levels:

* Root log level for all loggers is set to INFO.
* The hibernate log level in general is set to debug.
* To keep SQL abstract syntax trees from creating verbose log output, the specific subcategory `org.hibernate.hql.internal.ast` is set to info. As a result, the SQL abstract syntax trees are omitted instead of appearing at the `debug` level.

==== Configuring levels as individual options
When configuring category-specific log levels, you can also set the log levels as individual `log-level-<category>` options instead of using the `log-level` option for that.
This is useful when you want to set the log levels for selected categories without overwriting the previously set `log-level` option.

.Example
If you start the server as:

<@kc.start parameters="--log-level=\"INFO,org.hibernate:debug\""/>

you can then set an environmental variable `KC_LOG_LEVEL_ORG_KEYCLOAK=trace` to change the log level for the `org.keycloak` category.

The `log-level-<category>` options take precedence over `log-level`. This allows you to override what was set in the `log-level` option.
For instance if you set `KC_LOG_LEVEL_ORG_HIBERNATE=trace` for the CLI example above, the  `org.hibernate` category will use the `trace` level instead of `debug`.

Bear in mind that when using the environmental variables, the category name must be in uppercase and the dots must be replaced with underscores.
When using other config sources, the category name must be specified "as is", for example:

<@kc.start parameters="--log-level=\"INFO,org.hibernate:debug\" --log-level-org.keycloak=trace"/>

== Enabling log handlers
To enable log handlers, enter the following command:

<@kc.start parameters="--log=\"<handler1>,<handler2>\""/>

The available handlers are:

<@opts.expectedValues option="log"/>

The more specific handler configuration mentioned below will only take effect when the handler is added to this comma-separated list.

=== Specify log level for each handler

The `log-level` property specifies the global root log level and levels for selected categories.
However, a more fine-grained approach for log levels is necessary to comply with the modern application requirements.

To set log levels for particular handlers, properties in format `log-<handler>-level` (where `<handler>` is available log handler) were introduced.

It means properties for log level settings look like this:

* `log-console-level` - Console log handler
* `log-file-level` - File log handler
* `log-syslog-level` - Syslog log handler

NOTE: The `log-<handler>-level` properties are available only when the particular log handlers are enabled.
More information in log handlers settings below.

Only log levels specified in <<Log levels>> section are accepted, and *must be in lowercase*.
There is no support for specifying particular categories for log handlers yet.

==== General principle

It is necessary to understand that setting the log levels for each particular handler *does not override the root level* specified in the `log-level` property.
Log handlers respect the root log level, which represents the maximal verbosity for the whole logging system.
It means individual log handlers can be configured to be less verbose than the root logger, but not more.

Specifically, when an arbitrary log level is defined for the handler, it does not mean the log records with the log level will be present in the output.
In that case, the root `log-level` must also be assessed.
Log handler levels provide the *restriction for the root log level*, and the default log level for log handlers is `all` - without any restriction.

==== Examples

.Example: `debug` for file handler, but `info` for console handler:
<@kc.start parameters="--log=console,file --log-level=debug --log-console-level=info"/>

The root log level is set to `debug`, so every log handler inherits the value - so does the file log handler.
To hide `debug` records in the console, we need to set the minimal (least severe) level to `info` for the console handler.

.Example: `warn` for all handlers, but `debug` for file handler:
<@kc.start parameters="--log=console,file,syslog --log-level=debug --log-console-level=warn --log-syslog-level=warn"/>

The root level must be set to the most verbose required level (`debug` in this case), and other log handlers must be amended accordingly.

.Example: `info` for all handlers, but `debug`+`org.keycloak.events:trace` for Syslog handler:
<@kc.start parameters="--log=console,file,syslog --log-level=debug,org.keycloak.events:trace, --log-syslog-level=trace --log-console-level=info --log-file-level=info"/>

In order to see the `org.keycloak.events:trace`, the `trace` level must be set for the Syslog handler.

=== Use different JSON format for log handlers
Every log handler provides the ability to have structured log output in JSON format.
It can be enabled by properties in the format `log-<handler>-output=json` (where `<handler>` is a log handler).

If you need a different format of the produced JSON, you can leverage the following JSON output formats:

* `default` (default)
* `ecs`

The `ecs` value refers to the https://www.elastic.co/guide/en/ecs-logging/overview/current/intro.html[ECS] (Elastic Common Schema).

ECS is an open-source, community-driven specification that defines a common set of fields to be used with Elastic solutions.
The ECS specification is being converged with https://opentelemetry.io/docs/concepts/semantic-conventions/[OpenTelemetry Semantic Conventions] with the goal of creating a single standard maintained by OpenTelemetry.

In order to change the JSON output format, properties in the format `log-<handler>-json-format` (where `<handler>` is a log handler) were introduced:

* `log-console-json-format` - Console log handler
* `log-file-json-format` - File log handler
* `log-syslog-json-format` - Syslog log handler

==== Example
If you want to have JSON logs in *ECS* (Elastic Common Schema) format for the console log handler, you can enter the following command:

<@kc.start parameters="--log-console-output=json --log-console-json-format=ecs"/>

.Example Log Message
[source,json]
----
{"@timestamp":"2025-02-03T14:53:22.539484211+01:00","event.sequence":9608,"log.logger":"io.quarkus","log.level":"INFO","message":"Keycloak 999.0.0-SNAPSHOT on JVM (powered by Quarkus 3.17.8) started in 4.615s. Listening on: http://0.0.0.0:8080","process.thread.name":"main","process.thread.id":1,"mdc":{},"ndc":"","host.hostname":"host-name","process.name":"/usr/lib/jvm/jdk-21.0.3+9/bin/java","process.pid":77561,"data_stream.type":"logs","ecs.version":"1.12.2","service.environment":"prod","service.name":"Keycloak","service.version":"999.0.0-SNAPSHOT"}
----

=== Asynchronous logging
{project_name} supports asynchronous logging, which might be useful for deployments requiring **high throughput** and **low latency**.
Asynchronous logging uses a separate thread to take care of processing all log records.
The logging handlers are invoked in exactly the same way as with synchronous logging, only done in separate threads.
You can enable asynchronous logging for all {project_name} log handlers.
A dedicated thread will be created for every log handler with enabled asynchronous logging.

The underlying mechanism for asynchronous logging uses a queue for processing log records.
Every new log record is added to the queue and then published to the particular log handler with enabled asynchronous logging.
Every log handler has a different queue.

If the queue is already full, it blocks the main thread and waits for free space in the queue.

==== When to use asynchronous logging

* You need **lower latencies** for incoming requests
* You need **higher throughput**
* You have **small worker thread pool** and want to offload logging to separate threads
* You want to reduce the impact of **I/O-heavy log handlers**
* You are logging to **remote destinations** (e.g., network syslog servers) and want to avoid blocking worker threads

WARNING: Be aware that enabling asynchronous logging might bring some **additional memory overhead** due to the additional separate thread and the inner queue.
In that case, it is not recommended to use it for resource-constrained environments.
Additionally, unexpected server shutdowns create a risk of **losing log records**.

==== Enable asynchronous logging
You can enable asynchronous logging globally for all log handlers by using `log-async` property as follows:

<@kc.start parameters="--log-async=true"/>

Or you can enable the asynchronous logging for every specific handler by using properties in the format `log-<handler>-async` (where `<handler>` is a log handler).
If the property for a specific handler is not set, the value from the parent `log-async` property is used.

You can use these properties as follows:

<@kc.start parameters="--log-console-async=true --log-file-async=true --log-syslog-async=true"/>

* `log-console-async` - Console log handler
* `log-file-async` - File log handler
* `log-syslog-async` - Syslog log handler

==== Change queue length
You can change the size of the queue used for the asynchronous logging.
The default size is **512** log records in the queue.

You can change the queue length as follows:

<@kc.start parameters="--log-console-async-queue-length=512 --log-file-async-queue-length=512 --log-syslog-async-queue-length=512"/>

These properties are available only when asynchronous logging is enabled for these specific log handlers.

== Console log handler
The console log handler is enabled by default, providing unstructured log messages for the console.

=== Configuring the console log format
{project_name} uses a pattern-based logging formatter that generates human-readable text logs by default.

The logging format template for these lines can be applied at the root level. The default format template is:

* `%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n`

The format string supports the symbols in the following table:

[%autowidth]
|===
|Symbol|Summary|Description

|%%|%|Renders a simple % character.
|%c|Category|Renders the log category name.
|++%d{xxx}++|Date|Renders a date with the given date format string.String syntax defined by `java.text.SimpleDateFormat`
|%e|Exception|Renders a thrown exception.
|%h|Hostname|Renders the simple host name.
|%H|Qualified host name|Renders the fully qualified hostname, which may be the same as the simple host name, depending on the OS configuration.
|%i|Process ID|Renders the current process PID.
|%m|Full Message|Renders the log message and an exception, if thrown.
|%n |Newline|Renders the platform-specific line separator string.
|%N|Process name|Renders the name of the current process.
|%p|Level|Renders the log level of the message.
|%r|Relative time|Render the time in milliseconds since the start of the application log.
|%s|Simple message|Renders only the log message without exception trace.
|%t|Thread name|Renders the thread name.
|%t++{id}++|Thread ID|Render the thread ID.
|%z{<zone name>}|Timezone|Set the time zone of log output to <zone name>.
|%L|Line number|Render the line number of the log message.
|===

=== Setting the logging format
To set the logging format for a logged line, perform these steps:

. Build your desired format template using the preceding table.
. Enter the following command:
+
<@kc.start parameters="--log-console-format=\"\'<format>\'\""/>

Note that you need to escape characters when invoking commands containing special shell characters such as `;` using the CLI. Therefore, consider setting it in the configuration file instead.

.Example: Abbreviate the fully qualified category name
<@kc.start parameters="--log-console-format=\"\'%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p [%c{3.}] (%t) %s%e%n\'\""/>

This example abbreviates the category name to three characters by setting `[%c{3.}]` in the template instead of the default `[%c]`.

=== Configuring JSON or plain console logging
By default, the console log handler logs plain unstructured data to the console. To use structured JSON log output instead, enter the following command:

<@kc.start parameters="--log-console-output=json"/>

.Example Log Message
[source, json]
----
{"timestamp":"2025-02-03T14:52:20.290353085+01:00","sequence":9605,"loggerClassName":"org.jboss.logging.Logger","loggerName":"io.quarkus","level":"INFO","message":"Keycloak 999.0.0-SNAPSHOT on JVM (powered by Quarkus 3.17.8) started in 4.440s. Listening on: http://0.0.0.0:8080","threadName":"main","threadId":1,"mdc":{},"ndc":"","hostName":"host-name","processName":"/usr/lib/jvm/jdk-21.0.3+9/bin/java","processId":76944}
----

When using JSON output, colors are disabled and the format settings set by `--log-console-format` will not apply.

To use unstructured logging, enter the following command:

<@kc.start parameters="--log-console-output=default"/>

.Example Log Message
[source]
----
2025-02-03 14:53:56,653 INFO  [io.quarkus] (main) Keycloak 999.0.0-SNAPSHOT on JVM (powered by Quarkus 3.17.8) started in 4.795s. Listening on: http://0.0.0.0:8080
----

=== Colors
Colored console log output for unstructured logs is disabled by default. Colors may improve readability, but they can cause problems when shipping logs to external log aggregation systems. To enable or disable color-coded console log output, enter following command:

<@kc.start parameters="--log-console-color=<false|true>"/>

=== Configuring the console log level
Log level for console log handler can be specified by `--log-console-level` property as follows:

<@kc.start parameters="--log-console-level=warn"/>

For more information, see the section <<Specify log level for each handler>> above.

== File logging
As an alternative to logging to the console, you can use unstructured logging to a file.

=== Enable file logging
Logging to a file is disabled by default. To enable it, enter the following command:

<@kc.start parameters="--log=\"console,file\""/>

A log file named `keycloak.log` is created inside the `data/log` directory of your {project_name} installation.

=== Configuring the location and name of the log file

To change where the log file is created and the file name, perform these steps:

. Create a writable directory to store the log file.
+
If the directory is not writable, {project_name} will start correctly, but it will issue an error and no log file will be created.

. Enter this command:
+
<@kc.start parameters="--log=\"console,file\" --log-file=<path-to>/<your-file.log>"/>

=== Configuring the file handler format
To configure a different logging format for the file log handler, enter the following command:

<@kc.start parameters="--log-file-format=\"<pattern>\""/>

See <<Configuring the console log format>> for more information and a table of the available pattern configuration.

=== Configuring the file log level
Log level for file log handler can be specified by `--log-file-level` property as follows:

<@kc.start parameters="--log-file-level=warn"/>

For more information, see the section <<Specify log level for each handler>> above.

== Centralized logging using Syslog

{project_name} provides the ability to send logs to a remote Syslog server.
It utilizes the protocol defined in https://datatracker.ietf.org/doc/html/rfc5424[RFC 5424].

=== Enable the Syslog handler
To enable logging using Syslog, add it to the list of activated log handlers as follows:

<@kc.start parameters="--log=\"console,syslog\""/>

=== Configuring the Syslog Application Name
To set a different application name, add the `--log-syslog-app-name` option as follows:

<@kc.start parameters="--log=\"console,syslog\" --log-syslog-app-name=kc-p-itadmins"/>

If not set, the application name defaults to `keycloak`.

=== Configuring the Syslog endpoint

To configure the endpoint(_host:port_) of your centralized logging system, enter the following command and substitute the values with your specific values:

<@kc.start parameters="--log=\"console,syslog\" --log-syslog-endpoint=myhost:12345"/>

When the Syslog handler is enabled, the host is using `localhost` as host value.
The Default port is `514`.

=== Configuring the Syslog log level
Log level for Syslog log handler can be specified by `--log-syslog-level` property as follows:

<@kc.start parameters="--log-syslog-level=warn"/>

For more information, see the section <<Specify log level for each handler>> above.

=== Configuring the Syslog protocol
Syslog uses TCP as the default protocol for communication.
To use UDP instead of TCP, add the `--log-syslog-protocol` option as follows:

<@kc.start parameters="--log=\"console,syslog\" --log-syslog-protocol=udp"/>

The available protocols are: `tpc`, `udp`, and `ssl-tcp`.

=== Configuring the Syslog counting framing

By default, Syslog messages sent over TCP or SSL-TCP are prefixed with the message size, as required by certain Syslog receivers.
This behavior is controlled by the `--log-syslog-counting-framing` option.

To explicitly enable or disable this feature, use the following command:

<@kc.start parameters="--log-syslog-counting-framing=true"/>

You can set the value to one of the following:

* `protocol-dependent` (default) – Enable counting framing only when the `log-syslog-protocol` is `tcp` or `ssl-tcp`.
* `true` – Always enable counting framing by prefixing messages with their size.
* `false` – Never use counting framing.

Note that using `protocol-dependent` ensures compatibility with most Syslog servers by enabling the prefix only when required by the protocol.

=== Configuring the Syslog log format
To set the logging format for a logged line, perform these steps:

. Build your desired format template using the preceding table.
. Enter the following command:
+
<@kc.start parameters="--log-syslog-format=\"\'<format>\'\""/>

Note that you need to escape characters when invoking commands containing special shell characters such as `;` using the CLI. Therefore, consider setting it in the configuration file instead.

.Example: Abbreviate the fully qualified category name
<@kc.start parameters="--log-syslog-format=\"\'%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p [%c{3.}] (%t) %s%e%n\'\""/>

This example abbreviates the category name to three characters by setting `[%c{3.}]` in the template instead of the default `[%c]`.

=== Configuring the Syslog type

Syslog uses different message formats based on particular RFC specifications.
To change the Syslog type with a different message format, use the `--log-syslog-type` option as follows:

<@kc.start parameters="--log-syslog-type=rfc3164"/>

Possible values for the `--log-syslog-type` option are:

<@opts.expectedValues option="log-syslog-type"/>

The preferred Syslog type is https://datatracker.ietf.org/doc/html/rfc5424[RFC 5424], which obsoletes https://datatracker.ietf.org/doc/html/rfc3164[RFC 3164], known as BSD Syslog protocol.

=== Configuring the Syslog maximum message length

To set the maximum length of the message allowed to be sent (in bytes), use the `--log-syslog-max-length` option as follows:

<@kc.start parameters="--log-syslog-max-length=1536"/>

The length can be specified in memory size format with the appropriate suffix, like `1k` or `1K`.
The length includes the header and the message.

If the length is not explicitly set, the default values are set based on the `--log-syslog-type` option as follows:

* `2048B` - for RFC 5424
* `1024B` - for RFC 3164

=== Configuring the Syslog structured output
By default, the Syslog log handler sends plain unstructured data to the Syslog server.
To use structured JSON log output instead, enter the following command:

<@kc.start parameters="--log-syslog-output=json"/>

.Example Log Message
[source, bash]
----
2024-04-05T12:32:20.616+02:00 host keycloak 2788276 io.quarkus - {"timestamp":"2024-04-05T12:32:20.616208533+02:00","sequence":9948,"loggerClassName":"org.jboss.logging.Logger","loggerName":"io.quarkus","level":"INFO","message":"Profile prod activated. ","threadName":"main","threadId":1,"mdc":{},"ndc":"","hostName":"host","processName":"QuarkusEntryPoint","processId":2788276}
----

When using JSON output, colors are disabled and the format settings set by `--log-syslog-format` will not apply.

To use unstructured logging, enter the following command:

<@kc.start parameters="--log-syslog-output=default"/>

.Example Log Message
[source, bash]
----
2024-04-05T12:31:38.473+02:00 host keycloak 2787568 io.quarkus - 2024-04-05 12:31:38,473 INFO  [io.quarkus] (main) Profile prod activated.
----

As you can see, the timestamp is present twice, so you can amend it correspondingly via the `--log-syslog-format` property.

<@opts.printRelevantOptions includedOptions="log log-*" excludedOptions="log-console-* log-file log-file-* log-syslog-*">

=== Console
<@opts.includeOptions includedOptions="log-console-*"/>

=== File
<@opts.includeOptions includedOptions="log-file log-file-*"/>

=== Syslog
<@opts.includeOptions includedOptions="log-syslog-*"/>

</@opts.printRelevantOptions>

</@tmpl.guide>
