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diff --git a/lib/kernel/doc/src/logger.xml b/lib/kernel/doc/src/logger.xml new file mode 100644 index 0000000000..d901454e62 --- /dev/null +++ b/lib/kernel/doc/src/logger.xml @@ -0,0 +1,779 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!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 for the log event.</p> + <p>Logger adds the following metadata to each log event:</p> + <list> + <item><c>pid => self()</c></item> + <item><c>gl => group_leader()</c></item> + <item><c>time => erlang:monotonic_time(microsecond)</c></item> + </list> + <p>When a log macro is used, Logger also inserts location + information:</p> + <list> + <item><c>mfa => {?MODULE,?FUNCTION_NAME,?FUNCTION_ARITY}</c></item> + <item><c>file => ?FILE</c></item> + <item><c>line => ?LINE</c></item> + </list> + <p>You can add custom metadata, either by specifying a map as + the last parameter to any of the log macros or the API + functions, or by setting process metadata + with <seealso marker="#set_process_metadata-1"> + <c>set_process_metadata/1</c></seealso> + or <seealso marker="#update_process_metadata-1"> + <c>update_process_metadata/1</c></seealso>.</p> + <p>Logger merges all the metadata maps before forwarding the + log event to the handlers. If the same keys occur, values + from the log call overwrites process metadata, which in turn + overwrites values set by Logger.</p> + </desc> + </datatype> + <datatype> + <name name="config"/> + <desc> + <p>Configuration data for the logger part of Logger, or for a handler.</p> + <p>The following default values apply:</p> + <list> + <item><c>level => info</c></item> + <item><c>filter_default => log</c></item> + <item><c>filters => []</c></item> + <item><c>formatter => {logger_formatter,DefaultFormatterConfig</c>}</item> + </list> + <p>See the <seealso marker="logger_formatter#configuration"> + <c>logger_formatter(3)</c></seealso> manual page for + information about the default configuration for this + formatter.</p> + </desc> + </datatype> + <datatype> + <name name="handler_id"/> + <desc> + <p>A unique identifier for a handler instance.</p> + </desc> + </datatype> + <datatype> + <name name="filter_id"/> + <desc> + <p>A unique identifier for a filter.</p> + </desc> + </datatype> + <datatype> + <name name="filter"/> + <desc> + <p>A filter which can be installed for logger or for a handler.</p> + </desc> + </datatype> + <datatype> + <name name="filter_arg"/> + <desc> + <p>The second argument to the filter fun.</p> + </desc> + </datatype> + <datatype> + <name name="filter_return"/> + <desc> + <p>The return value from the filter fun.</p> + </desc> + </datatype> + <datatype> + <name name="timestamp"/> + <desc> + <p>A timestamp produced + with <seealso marker="erts:erlang#monotonic_time-1"> + <c>erlang:monotonic_time(microsecond)</c></seealso>.</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 location data is added. See the + description of + the <seealso marker="#type-metadata"><c>metadata()</c></seealso> + type for more information about the location data.</p> + + <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 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 all logger configurations</fsummary> + <desc> + <p>Display or return all current logger configuration.</p> + <taglist> + <tag><c><anno>Action</anno> = string</c></tag> + <item> + <p>Return the pretty printed current logger configuration + as iodata.</p> + </item> + <tag><c><anno>Action</anno> = term</c></tag> + <item> + <p>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>.</p> + </item> + <tag><c><anno>Action</anno> = print</c></tag> + <item> + <p>Pretty print all the current logger configuration to + standard out. Example:</p> + <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> + <p>The filter fun is called with the log event as the first + parameter, and the specified <c>filter_args()</c> as the + second parameter.</p> + <p>The return value of the fun specifies if a log event is to + be discarded or forwarded to the handlers:</p> + <taglist> + <tag><c>log()</c></tag> + <item> + <p>The filter <em>passed</em>. The next logger filter, if + any, is applied. If no more logger filters exist, the + log event is forwarded to the handler part of the + logger, where handler filters are applied.</p> + </item> + <tag><c>stop</c></tag> + <item> + <p>The filter <em>did not pass</em>, and the log event is + immediately discarded.</p> + </item> + <tag><c>ignore</c></tag> + <item> + <p>The filter has no knowledge of the log event. The next + logger filter, if any, is applied. If no more logger + filters exist, the value of the <c>filter_default</c> + configuration parameter for the logger specifies if the + log event shall be discarded or forwarded to the handler + part.</p> + </item> + </taglist> + <p>See section <seealso marker="logger_chapter#Filter"> + Filter</seealso> in the User's Guide for more information + about filters.</p> + <p>Some built-in filters exist. These are defined + in <seealso marker="logger_filters"><c>logger_filters</c></seealso>.</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> + <p>The filter fun is called with the log event as the first + parameter, and the specified <c>filter_args()</c> as the + second parameter.</p> + <p>The return value of the fun specifies if a log event is to + be discarded or forwarded to the handler callback:</p> + <taglist> + <tag><c>log()</c></tag> + <item> + <p>The filter <em>passed</em>. The next handler filter, if + any, is applied. If no more filters exist for this + handler, the log event is forwarded to the handler + callback.</p> + </item> + <tag><c>stop</c></tag> + <item> + <p>The filter <em>did not pass</em>, and the log event is + immediately discarded.</p> + </item> + <tag><c>ignore</c></tag> + <item> + <p>The filter has no knowledge of the log event. The next + handler filter, if any, is applied. If no more filters + exist for this handler, the value of + the <c>filter_default</c> configuration parameter for + the handler specifies if the log event shall be + discarded or forwarded to the handler callback.</p> + </item> + </taglist> + <p>See + section <seealso marker="logger_chapter#Filter">Filter</seealso> + in the User's Guide for more information about filters.</p> + <p>Some built-in filters exist. These are defined in + <seealso marker="logger_filters"><c>logger_filters</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="remove_logger_filter" arity="1"/> + <fsummary>Remove a filter from the logger.</fsummary> + <desc> + <p>Remove the filter identified + by <c><anno>FilterId</anno></c> 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 identified + by <c><anno>FilterId</anno></c> from the handler identified + by <c><anno>HandlerId</anno></c>.</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> + <p><c><anno>HandlerId</anno></c> is a unique identifier which + must be used in all subsequent calls reffering to this + handler.</p> + </desc> + </func> + + <func> + <name name="remove_handler" arity="1"/> + <fsummary>Remove the handler with the specified identity.</fsummary> + <desc> + <p>Remove the handler identified by <c><anno>HandlerId</anno></c>.</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 <c><anno>Module</anno></c>.</p> + <p>The log level for a module overrides the global log level + of the logger for log event originating from the module in + question. Notice, however, that it does not override the + level configuration for any handler.</p> + <p>For example: Assume that the global log level for the + logger is <c>info</c>, and there is one handler, <c>h1</c>, + with level <c>info</c> and one handler, <c>h2</c>, with + level <c>debug</c>.</p> + <p>With this configuration, no debug messages will be logged, + since they are all stopped by the global log level.</p> + <p>If the level for <c>mymodule</c> is set now set + to <c>debug</c>, then debug events from this module will be + logged by the handler <c>h2</c>, but not by + handler <c>h1</c>.</p> + <p>Debug events from other modules are still not logged.</p> + <p>To change the global log level for the logger, use + <seealso marker="#set_logger_config/2"> + <c>logger:set_logger_config(level,Level)</c></seealso>.</p> + <p>To change the log level for a handler, use + <seealso marker="#set_handler_config/3"> + <c>logger:set_handler_config(HandlerId,level,Level)</c></seealso>.</p> + <note> + <p>The originating module for a log event is only detected + if <c>mfa=>{Module,Function,Arity}</c> exists in the + metadata. When log macros are used, this association is + automatically added to all log events. If the logger API + is called directly, without using a macro, the logging + client must explicitly add this information.</p> + </note> + </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> + <p>If a key is removed compared to the current configuration, + the default value is used.</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 changed 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> + <p>If a key is removed compared to the current configuration, + and the key is know by Logger, the default value is used. If + it is a custom key, then it is up to the handler + implementation if the value is removed or a default value is + inserted.</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 changed + 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 Logger shall automatically insert in + all log events produced on the current process.</p> + <p>Location data produced by the log macros, and/or metadata + given as argument to the log call (API function or macro), + are merged with the process metadata. If the same keys + occur, values from the metadata argument to the log call + overwrite values from the process metadata, which in turn + overwrite values from the location data.</p> + <p>Subsequent calls to this function overwrites previous data + set. To update existing data instead of overwriting it, + see <seealso marker="#update_process_metadata-1"> + <c>update_process_metadata/1</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="update_process_metadata" arity="1"/> + <fsummary>Set or update metadata to use when logging from + current process.</fsummary> + <desc> + <p>Set or update metadata to use when logging from current + process</p> + <p>If process metadata exists for the current process, 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> or + <seealso marker="#update_process_metadata-1"> + <c>update_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> or + <seealso marker="#update_process_metadata-1"> + <c>update_process_metadata/1</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="format_report" arity="1"/> + <fsummary>Convert a log message on report form to {Format,Args}.</fsummary> + <desc> + <p>Convert a log message on report form to <c>{Format,Args}</c>.</p> + <p>This is the default report callback used + by <seealso marker="logger_formatter"> + <c>logger_formatter</c></seealso> when no custom report + callback is found.</p> + <p>The function produces lines of <c>Key: Value</c> from + key-value lists. Strings are printed with <c>~ts</c> and + other terms with <c>~tp</c>.</p> + <p>If the <c><anno>Report</anno></c> is a map, it is + converted to a key-value list before formatting as such.</p> + </desc> + </func> + + </funcs> + + <section> + <title>Callback Functions</title> + <p>The following functions are to be exported from a handler + callback module.</p> + </section> + + <funcs> + <func> + <name>Module:adding_handler(HandlerId,Config1) -> {ok,Config2} | {error,Reason}</name> + <fsummary>An instance of this handler is about to be added.</fsummary> + <type> + <v>HandlerId = + <seealso marker="#type-handler_id">handler_id()</seealso></v> + <v>Config1 = Config2 = + <seealso marker="#type-config">config()</seealso></v> + <v>Reason = term()</v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called when an new handler is about to be + added, and the purpose is to verify the configuration and + initiate all resourced needed by the handler.</p> + <p>If everything succeeds, the callback function can add + possible default values or internal state values to the + configuration, and return the adjusted map + in <c>{ok,Config2}</c>.</p> + <p>If the configuration is faulty, or if the initiation fails, + the callback function must return <c>{error,Reason}</c>.</p> + </desc> + </func> + + <func> + <name>Module:removing_handler(HandlerId,Config) -> ok</name> + <fsummary>The given handler is about to be removed.</fsummary> + <type> + <v>HandlerId = + <seealso marker="#type-handler_id">handler_id()</seealso></v> + <v>Config = + <seealso marker="#type-config">config()</seealso></v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called when a handler is about to be + removed, and the purpose is to release all resources used by + the handler. The return value is ignored by Logger.</p> + </desc> + </func> + + <func> + <name>Module:changing_config(HandlerId,Config1,Config2) -> {ok,Config3} | {error,Reason}</name> + <fsummary>The configuration for this handler is about to change.</fsummary> + <type> + <v>HandlerId = + <seealso marker="#type-handler_id">handler_id()</seealso></v> + <v>Config1 = Config2 = Config3 = + <seealso marker="#type-config">config()</seealso></v> + <v>Reason = term()</v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called when the configuration for a handler + is about to change, and the purpose is to verify and act on + the new configuration.</p> + <p><c>Config1</c> is the existing configuration + and <c>Config2</c> is the new configuration.</p> + <p>If everything succeeds, the callback function must return a + possibly adjusted configuration in <c>{ok,Config3}</c>.</p> + <p>If the configuration is faulty, the callback function must + return <c>{error,Reason}</c>.</p> + </desc> + </func> + </funcs> +</erlref> + + |