[[logging-settings]]
=== Logging settings in {kib}
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<titleabbrev>Logging settings</titleabbrev>
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You do not need to configure any additional settings to use the logging features in {kib}. Logging is enabled by default and will log at `info` level using the `pattern` layout, which outputs logs to `stdout`.

However, if you are planning to ingest your logs using Elasticsearch or another tool, we recommend using the `json` layout, which produces logs in ECS format. In general, `pattern` layout is recommended when raw logs will be read by a human, and `json` layout when logs will be read by a machine.

NOTE: The logging configuration is validated against the predefined schema and if there are any issues with it, {kib} will fail to start with the detailed error message.

{kib} relies on three high-level entities to set the logging service: appenders, loggers, and root. These can be configured in the `logging` namespace in `kibana.yml`.

- Appenders define where log messages are displayed (stdout or console) and their layout (`pattern` or `json`). They also allow you to specify if you want the logs stored and, if so, where (file on the disk).
- Loggers define what logging settings, such as the level of verbosity and the appenders, to apply to a particular context. Each log entry context provides information about the service or plugin that emits it and any of its sub-parts, for example, `metrics.ops` or `elasticsearch.query`.
- Root is a logger that applies to all the log entries in {kib}.

The following table serves as a quick reference for different logging configuration keys. Note that these are not stand-alone settings and may require additional logging configuration. See the <<logging-configuration, Configure Logging in {kib}>> guide and complete <<log-settings-examples, examples>> for common configuration use cases. 

[cols="2*<"]
|===
| `logging.appenders[].<appender-name>`
| Unique appender identifier.

| `logging.appenders[].console:`
| Appender to use for logging records to *stdout*. By default, uses the `[%date][%level][%logger] %message` **pattern** layout. To use a **json**, set the <<log-in-json-ECS-example,layout type to `json`>>.

| `logging.appenders[].file:`
| Allows you to specify a fileName to write log records to disk. To write <<log-to-file-example,all log records to file>>, add the file appender to `root.appenders`. If configured, you also need to specify <<log-to-file-example, `logging.appenders.file.pathName`>>.

| `logging.appenders[].rolling-file:`
| Similar to https://logging.apache.org/log4j/2.x/[Log4j's] `RollingFileAppender`, this appender will log to a file and rotate if following a rolling strategy when the configured policy triggers. There are currently two policies supported: <<size-limit-triggering-policy, `size-limit`>> and <<time-interval-triggering-policy, `time-interval`>>.

| `logging.appenders[].<appender-name>.type`
| The appender type determines where the log messages are sent. Options are `console`, `file`, `rewrite`, `rolling-file`. Required.

| `logging.appenders[].<appender-name>.fileName`
| Determines the filepath where the log messages are written to for file and rolling-file appender types. Required for appenders that write to file.

| `logging.appenders[].<appender-name>.policy.type`
| Specify the triggering policy for when a rollover should occur for the `rolling-file` type appender. 

| `logging.appenders[].<appender-name>.policy.interval`
| Specify the time interval for rotating a log file for a `time-interval` type `rolling-file` appender. *Default 24h*

| `logging.appenders[].<appender-name>.policy.size`
| Specify the size limit at which the policy should trigger a rollover for a `size-limit` type `rolling-file` appender. *Default 100mb*. 

| `logging.appenders[].<appender-name>.policy.interval`
| Specify the time interval at which the policy should trigger a rollover for a time-interval type `rolling-file` appender. 

| `logging.appenders[].<appender-name>.policy.modulate`
| Whether the interval should be adjusted to cause the next rollover to occur on the interval boundary. Boolean. Default `true`.

| `logging.appenders[].<appender-name>.strategy.type`
| Rolling file strategy type. Only `numeric` is currently supported.

| `logging.appenders[].<appender-name>.strategy.pattern`
| The suffix to append to the file path when rolling. Must include `%i`.

| `logging.appenders[].<appender-name>.strategy.max`
| The maximum number of files to keep. Optional. Default is `7` and the maximum is `100`.

| `logging.appenders[].<appender-name>.layout.type`
| Determines how the log messages are displayed. Options are `pattern`, which provides human-readable output, or `json`, which provides ECS-compliant output. Required.

| `logging.appenders[].<appender-name>.layout.highlight`
| Optional boolean to highlight log messages in color. Applies to `pattern` layout only. Default is `false`.

| `logging.appenders[].<appender-name>.layout.pattern`
| Optional <<pattern-layout, string pattern>> for placeholders that will be replaced with data from the actual log message. Applicable to pattern type layout only.

| `logging.root.appenders[]`
| List of specific appenders to apply to `root`. Defaults to `console` with `pattern` layout.

| `logging.root.level`
| Specify default verbosity for all log messages to fall back to if not specifically configured at the individual logger level. Options are `all`, `fatal`, `error`, `warn`, `info`, `debug`, `trace`, `off`. The `all` and `off` levels can be used only in configuration and are just handy shortcuts that allow you to log every log record or disable logging entirely or for a specific logger. Default is `info`.

| `logging.loggers[].<logger>.name:`
| Specific logger instance.

| `logging.loggers[].<logger>.level`
| Specify verbosity of log messages for <logger> context. Optional and inherits the verbosity of any ancestor logger, up to the `root` logger `level`.

| `logging.loggers[].<logger>.appenders`
| Determines the appender to apply to a specific logger context as an array. Optional and falls back to the appender(s) of the `root` logger if not specified.

|===