path: root/lib/kernel/doc/src/logger.xml

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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2017</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>logger</title>
    <prepared></prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev>A</rev>
    <file>logger.xml</file>
  </header>
  <module>logger</module>
  <modulesummary>API module for the logger application.</modulesummary>

  <description>

  </description>

  <datatypes>
    <datatype>
      <name name="level"/>
      <desc>
	<p>The severity level for the message to be logged.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="log"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="report"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="msg_fun"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="metadata"/>
      <desc>
	<p>Metadata associated with the message to be logged.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="config"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="handler_id"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="filter_id"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="filter"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
    <datatype>
      <name name="filter_return"/>
      <desc>
	<p></p>
      </desc>
    </datatype>
  </datatypes>

  <section>
    <title>Macros</title>
    <p>The following macros are defined:</p>

    <list>
      <item><c>?LOG_EMERGENCY(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_EMERGENCY(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_ALERT(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_ALERT(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_CRITICAL(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_CRITICAL(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_ERROR(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_ERROR(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_WARNING(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_WARNING(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_NOTICE(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_NOTICE(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_INFO(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_INFO(FunOrFormat,Args[,Metadata])</c></item>
      <item><c>?LOG_DEBUG(StringOrReport[,Metadata])</c></item>
      <item><c>?LOG_DEBUG(FunOrFormat,Args[,Metadata])</c></item>
    </list>

    <p>All macros expand to a call to logger, where <c>Level</c> is
      taken from the macro name, and the following metadata is added,
      or merged with the given <c>Metadata</c>:</p>

    <code>
#{mfa=>{?MODULE,?FUNCTION_NAME,?FUNCTION_ARITY},
  file=>?FILE,
  line=>?LINE}
    </code>

    <p>The call is wrapped in a case statement and will be evaluated
      only if <c>Level</c> is equal to or below the configured log
      level.</p>
  </section>

  <funcs>
    <func>
      <name>emergency(StringOrReport[,Metadata])</name>
      <name>emergency(Format,Args[,Metadata])</name>
      <name>emergency(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>emergency</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(emergency,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>alert(StringOrReport[,Metadata])</name>
      <name>alert(Format,Args[,Metadata])</name>
      <name>alert(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>alert</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(alert,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>critical(StringOrReport[,Metadata])</name>
      <name>critical(Format,Args[,Metadata])</name>
      <name>critical(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>critical</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(critical,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>error(StringOrReport[,Metadata])</name>
      <name>error(Format,Args[,Metadata])</name>
      <name>error(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>error</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(error,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>warning(StringOrReport[,Metadata])</name>
      <name>warning(Format,Args[,Metadata])</name>
      <name>warning(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>warning</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(warning,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>notice(StringOrReport[,Metadata])</name>
      <name>notice(Format,Args[,Metadata])</name>
      <name>notice(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>notice</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(notice,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>info(StringOrReport[,Metadata])</name>
      <name>info(Format,Args[,Metadata])</name>
      <name>info(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>info</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(info,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name>debug(StringOrReport[,Metadata])</name>
      <name>debug(Format,Args[,Metadata])</name>
      <name>debug(Fun,FunArgs[,Metadata])</name>
      <fsummary>Logs the given message as level <c>debug</c>.</fsummary>
      <desc>
        <p>Equivalent to
	<seealso marker="#log-2"><c>log(debug,...)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="log" arity="2"/>
      <name name="log" arity="3" clause_i="1"/>
      <name name="log" arity="3" clause_i="2"/>
      <name name="log" arity="3" clause_i="3"/>
      <name name="log" arity="4" clause_i="1"/>
      <name name="log" arity="4" clause_i="2"/>
      <fsummary>Logs the given message.</fsummary>
      <type variable="Level"/>
      <type variable="StringOrReport" name_i="1"/>
      <type variable="Format" name_i="3"/>
      <type variable="Args" name_i="3"/>
      <type variable="Fun" name_i="4"/>
      <type variable="FunArgs" name_i="4"/>
      <type variable="Metadata"/>
      <desc>
        <p>Log the given message.</p>
      </desc>
    </func>

    <func>
      <name name="get_logger_config" arity="0"/>
      <fsummary>Lookup the current configuration for logger.</fsummary>
      <desc>
        <p>Lookup the current configuration for logger.</p>
      </desc>
    </func>

    <func>
      <name name="get_handler_config" arity="1"/>
      <fsummary>Lookup the current configuration for the given handler.</fsummary>
      <desc>
        <p>Lookup the current configuration for the given handler.</p>
      </desc>
    </func>

    <func>
      <name name="i" arity="0"/>
      <fsummary>Get information about all logger configurations</fsummary>
      <desc>
        <p>Same as <seealso marker="#i/1"><c>logger:i(term)</c></seealso></p>
      </desc>
    </func>

    <func>
      <name name="i" arity="1" clause_i="1"/>
      <name name="i" arity="1" clause_i="2"/>
      <name name="i" arity="1" clause_i="3"/>
      <fsummary>Get information about all logger configurations</fsummary>
      <desc>
        <p>The <c>logger:i/1</c> function can be used to get all
          current logger configuration.  The way that the information
          is returned depends on the <c><anno>Action</anno></c></p>
        <taglist>
          <tag>string</tag>
          <item>Return the pretty printed current logger configuration
            as iodata.</item>
          <tag>term</tag>
          <item>Return the current logger configuration as a term. The
            format of this term may change inbetween releases. For a
            stable format use <seealso marker="#get_handler_config/1">
	      <c>logger:get_handler_config/1</c></seealso>
            and <seealso marker="#get_logger_config/0">
	      <c>logger:get_logger_config/0</c></seealso>.
            The same as calling <c>logger:i()</c>.</item>
	  <tag>print</tag>
          <item>Pretty print all the current logger configuration to
            standard out. Example:
            <code><![CDATA[1> logger:i(print).
Current logger configuration:
  Level: info
  FilterDefault: log
  Filters:
  Handlers:
    Id: logger_std_h
      Module:    logger_std_h
      Level:     info
      Formatter:
        Module: logger_formatter
        Config: #{template => [{logger_formatter,header},"\n",msg,"\n"],
                  legacy_header => true}
      Filter Default: stop
      Filters:
        Id: stop_progress
          Fun:    fun logger_filters:progress/2
          Config: stop
        Id: remote_gl
          Fun:    fun logger_filters:remote_gl/2
          Config: stop
        Id: domain
          Fun:    fun logger_filters:domain/2
          Config: {log,prefix_of,[beam,erlang,otp,sasl]}
        Id: no_domain
          Fun:    fun logger_filters:domain/2
          Config: {log,no_domain,[]}
      Handler Config:
        logger_std_h: #{type => standard_io}
  Level set per module:
    Module: my_module
      Level:    debug]]></code>
          </item>
        </taglist>
      </desc>
    </func>

    <func>
      <name name="add_logger_filter" arity="2"/>
      <fsummary>Add a filter to the logger.</fsummary>
      <desc>
        <p>Add a filter to the logger.</p>
      </desc>
    </func>

    <func>
      <name name="add_handler_filter" arity="3"/>
      <fsummary>Add a filter to the specified handler.</fsummary>
      <desc>
        <p>Add a filter to the specified handler.</p>
      </desc>
    </func>

    <func>
      <name name="remove_logger_filter" arity="1"/>
      <fsummary>Remove a filter from the logger.</fsummary>
      <desc>
        <p>Remove the filter with the specified identity from the logger.</p>
      </desc>
    </func>

    <func>
      <name name="remove_handler_filter" arity="2"/>
      <fsummary>Remove a filter from the specified handler.</fsummary>
      <desc>
        <p>Remove the filter with the specified identity from the given handler.</p>
      </desc>
    </func>

    <func>
      <name name="add_handler" arity="3"/>
      <fsummary>Add a handler with the given configuration.</fsummary>
      <desc>
        <p>Add a handler with the given configuration.</p>
      </desc>
    </func>

    <func>
      <name name="remove_handler" arity="1"/>
      <fsummary>Remove the handler with the specified identity.</fsummary>
      <desc>
        <p>Remove the handler with the specified identity.</p>
      </desc>
    </func>

    <func>
      <name name="set_module_level" arity="2"/>
      <fsummary>Set the log level for the specified module.</fsummary>
      <desc>
        <p>Set the log level for the specified module.</p>
        <p>To change the logging level globally, use
        <seealso marker="#set_logger_config/2"><c>logger:set_logger_config(level, Level)</c></seealso>.
        </p>
      </desc>
    </func>

    <func>
      <name name="reset_module_level" arity="1"/>
      <fsummary>Remove a module specific log setting.</fsummary>
      <desc>
        <p>Remove a module specific log setting. After this, the
          global log level is used for the specified module.</p>
      </desc>
    </func>

    <func>
      <name name="set_logger_config" arity="1"/>
      <fsummary>Set configuration data for the logger.</fsummary>
      <desc>
        <p>Set configuration data for the logger. This overwrites the
          current logger configuration.</p>
	<p>To modify the existing configuration,
	  use <seealso marker="#set_logger_config-2"><c>set_logger_config/2</c>
	  </seealso>, or read the current configuration
	  with <seealso marker="#get_logger_config-0"><c>get_logger_config/0</c>
	  </seealso>, then merge in your added or updated
	  associations before writing it back.</p>
      </desc>
    </func>

    <func>
      <name name="set_logger_config" arity="2"/>
      <fsummary>Add or update configuration data for the logger.</fsummary>
      <desc>
        <p>Add or update configuration data for the logger. If the
          given <c><anno>Key</anno></c> already exists, its associated
          value will be set to <c><anno>Value</anno></c>. If it
          doesn't exist, it will be added.</p>
      </desc>
    </func>

    <func>
      <name name="set_handler_config" arity="2"/>
      <fsummary>Set configuration data for the specified handler.</fsummary>
      <desc>
        <p>Set configuration data for the specified handler. This
          overwrites the current handler configuration.</p>
	<p>To modify the existing configuration,
	  use <seealso marker="#set_handler_config-3"><c>set_handler_config/3</c>
	  </seealso>, or read the current configuration
	  with <seealso marker="#get_handler_config-1"><c>get_handler_config/1</c>
	  </seealso>, then merge in your added or updated
	  associations before writing it back.</p>
      </desc>
    </func>

    <func>
      <name name="set_handler_config" arity="3"/>
      <fsummary>Add or update configuration data for the specified
        handler.</fsummary>
      <desc>
        <p>Add or update configuration data for the specified
          handler. If the
          given <c><anno>Key</anno></c> already exists, its associated
          value will be set to <c><anno>Value</anno></c>. If it
          doesn't exist, it will be added.</p>
      </desc>
    </func>

    <func>
      <name name="compare_levels" arity="2"/>
      <fsummary>Compare the severity of two log levels.</fsummary>
      <desc>
        <p>Compare the severity of two log levels. Returns <c>gt</c>
          if <c>Level1</c> is more severe than
          <c>Level2</c>, <c>lt</c> if <c>Level1</c> is less severe,
          and <c>eq</c> if the levels are equal.</p>
      </desc>
    </func>

    <func>
      <name name="set_process_metadata" arity="1"/>
      <fsummary>Set metadata to use when logging from current process.</fsummary>
      <desc>
        <p>Set metadata which <c>logger</c> automatically inserts in
          all log events produced on the current process. Subsequent
          calls will overwrite previous data set by this function.</p>
	<p>When logging, location data produced by the log macros,
	  and/or metadata given as argument to the log call (API
	  function or macro), will be merged with the process
	  metadata. If the same keys occur, values from the metadata
	  argument to the log call will overwrite values in the
	  process metadata, which in turn will overwrite values from
	  the location data.</p>
      </desc>
    </func>

    <func>
      <name name="update_process_metadata" arity="1"/>
      <fsummary>Update metadata to use when logging from current process.</fsummary>
      <desc>
	<p>Update metadata to use when logging from current process</p>
	<p>This function behaves as if it was implemented as follows:</p>
	<code type="erl">
logger:set_process_metadata(maps:merge(logger:get_process_metadata(),Meta))
	</code>
	<p>If no process metadata exists, the function behaves as
	  <seealso marker="#set_process_metadata-1"><c>set_process_metadata/1</c>
	  </seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="get_process_metadata" arity="0"/>
      <fsummary>Retrieve data set with set_process_metadata/1.</fsummary>
      <desc>
        <p>Retrieve data set
          with <seealso marker="#set_process_metadata-1">
	    <c>set_process_metadata/1</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="unset_process_metadata" arity="0"/>
      <fsummary>Delete data set with set_process_metadata/1.</fsummary>
      <desc>
        <p>Delete data set
          with <seealso marker="#set_process_metadata-1">
	    <c>set_process_metadata/1</c></seealso>.</p>
      </desc>
    </func>

  </funcs>

</erlref>