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Configuration with JSON

Klogging can be configured from JSON files. This example is exactly equivalent to the first DSL example:

"sinks": {
"stdout": {
"renderWith": "RENDER_SIMPLE",
"sendTo": "STDOUT"
"seq": {
"seqServer": "http://localhost:5341"
"logging": [
"fromLoggerBase": "com.example",
"levelRanges": [
"fromMinLevel": "INFO",
"toSinks": [

Locating configuration files

Klogging looks for configuration files as follows:

  1. If the environment variable KLOGGING_CONFIG_PATH exists, load the file at that absolute path if it exists.
  2. Search the classpath for the file klogging.json first, and klogging.conf.

If a configuration file is found it is read as JSON or HOCON.


JSON file names must end with .json and HOCON files must end with .conf.

Configuration object names


Equivalent to the sinks DSL function. Object keyed by sink name with keys:

  • renderWith: name of a built-in renderer. Current values are RENDER_SIMPLE, RENDER_ISO8601, RENDER_ANSI, RENDER_CLEF and RENDER_GELF.

  • sendTo: name of a built-in sender. Current values are STDOUT and STDERR.

  • seqServer: URL of a Seq server where events are to be dispatched. By default, the RENDER_CLEF renderer is used.

  • apiKey: a Seq API key. It is a secret that should be passed in via an environment variable, for example: "apiKey": "${SEQ_API_KEY}"

  • checkCertificate: a boolean value (default true) that specifies if the TLS certificate used by a secure seqServer URL should be checked.

  • splunkServer: connection details for a Splunk HEC endpoint:

    • hecUrl specifies the URL of the Splunk server’s HEC endpoint. It uses HTTPS by default.
    • hecToken is the HEC token used by Splunk for these logging events. It is a secret that should be passed in via the execution environment.
    • index is the Splunk index for the events (optional). If set, it must be a value configured in Splunk. If not set, Splunk will use the default index configured for the HEC token.
    • sourceType is the Splunk sourcetype value (optional). If not set, Splunk will use httpevent or a value configured for the HEC token.
    • source is the Splunk source value, typically the name of an application (optional). If not set, Splunk will use a name configured with the HEC token.
    • checkCertificate indicates whether Klogging should check the TLS certificate used by the Splunk server (string: default "true").

An example of a Splunk sink called splunk is:

"splunk": {
"splunkServer": {
"hecUrl": "https://localhost:8088",
"hecToken": "${SPLUNK_HEC_TOKEN}",
"source": "MyApplication",
"checkCertificate": "false"

You should have only one of splunkServer, seqServer or sendTo in a sink. If you have more than one, splunkServer takes precedence over seqServer, which takes precedence over sendTo.

You can create a custom renderer or sender and include its fully-qualified class name in a sink definition.


Equivalent to the logging DSL function. Array of objects, each with optional keys:

  • fromLoggerBase: base name to match logger names.

  • exactLogger: exact name of logger to match.

  • matchLogger: a Kotlin regular expression pattern used to match logger names.


You should specify only one of these in a logging object. If more are specified, matchLogger takes precedence over exactLogger, which takes precedence over fromLoggerBase.


If you specify no key, all loggers will match. This configuration is the equivalent of the root logger in Log4j or Logback.


Array of objects, each with keys:

  • fromMinLevel: Name of the minimum level for log events to be emitted. For example, if the value is INFO then events at severity INFO, ERROR and FATAL will be emitted. Equivalent to the fromMinLevel DSL function.

  • toMaxLevel: Name of the maximum level for log events to be emitted. For example, if the value is INFO then events at severity TRACE, DEBUG and INFO will be emitted. Equivalent to the toMaxLevel DSL function.

  • You can combine fromMinLevel and toMaxLevel values to set an inclusive range of levels. Equivalent to the inLevelRange DSL function.

  • atLevel: Name of the exact level at which log events will be emitted. Equivalent to the atLevel DSL function.

  • toSinks: Array of sink names where events will be sent. If it does not match a key of the sinks object, a warning is written to the console and the configuration is ignored.


You must specify at least one levelRange object with at least one matching sink name or no logs will be emitted.

Other options

"kloggingMinLogLevel": "DEBUG",
"minDirectLogLevel": "INFO",
"baseContext": {
"appName": "analysis-service",
"buildNumber": "${BUILD_NUMBER}"


Set the minimum level of the Klogging internal logger.


Set the minimum level for sending log events directly to sinks.


Specify context items to add to every log event.