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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..33f1919de0 --- /dev/null +++ b/lib/kernel/doc/src/logger.xml @@ -0,0 +1,1122 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>2017</year><year>2018</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 Logger, the standard logging facility + in Erlang/OTP.</modulesummary> + + <description> + <p>This module implements the main API for logging in + Erlang/OTP. To create a log event, use the + <seealso marker="#logging_API">API functions</seealso> or the + log + <seealso marker="#macros">macros</seealso>, for example:</p> + <code> +?LOG_ERROR("error happened because: ~p", [Reason]). % With macro +logger:error("error happened because: ~p", [Reason]). % Without macro + </code> + <p>To configure the Logger backend, + use <seealso marker="kernel_app#logger">Kernel configuration + parameters</seealso> + or <seealso marker="#configuration_API">configuration + functions</seealso> in the Logger API.</p> + + <p>By default, the Kernel application installs one log handler at + system start. This handler is named <c>default</c>. It receives + and processes standard log events produced by the Erlang runtime + system, standard behaviours and different Erlang/OTP + applications. The log events are by default printed to the + terminal.</p> + <p>If you want your systems logs to be printed to a file instead, + you must configure the default handler to do so. The simplest + way is to include the following in + your <seealso marker="config"><c>sys.config</c></seealso>:</p> + <code> +[{kernel, + [{logger, + [{handler, default, logger_std_h, + #{config => #{type => {file, "path/to/file.log"}}}}]}]}]. + </code> + <p> + For more information about: + </p> + <list type="bulleted"> + <item>the Logger facility in general, see + the <seealso marker="logger_chapter">User's + Guide</seealso>.</item> + <item>how to configure Logger, see + the <seealso marker="logger_chapter#configuration">Configuration</seealso> + section in the User's Guide.</item> + <item>the built-in handlers, + see <seealso marker="logger_std_h">logger_std_h</seealso> and + <seealso marker="logger_disk_log_h">logger_disk_log_h</seealso>.</item> + <item>the built-in formatter, + see <seealso marker="logger_formatter">logger_formatter</seealso>.</item> + <item>built-in filters, + see <seealso marker="logger_filters">logger_filters</seealso>.</item> + </list> + + <note> + <p>Since Logger is new in Erlang/OTP 21.0, we do reserve the right + to introduce changes to the Logger API and functionality in + patches following this release. These changes might or might not + be backwards compatible with the initial version.</p> + </note> + + </description> + + <datatypes> + <datatype> + <name name="primary_config"/> + <desc> + <p>Primary configuration data for Logger. 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> + </list> + </desc> + </datatype> + <datatype> + <name name="handler_config"/> + <desc> + <p>Handler configuration data for Logger. The following + default values apply:</p> + <list> + <item><c>level => all</c></item> + <item><c>filter_default => log</c></item> + <item><c>filters => []</c></item> + <item><c>formatter => {logger_formatter, DefaultFormatterConfig</c>}</item> + </list> + <p>In addition to these, the following fields are + automatically inserted by Logger, values taken from the + two first parameters + to <seealso marker="#add_handler-3"><c>add_handler/3</c></seealso>:</p> + <list> + <item><c>id => HandlerId</c></item> + <item><c>module => Module</c></item> + </list> + <p>Handler specific configuration data is inserted by the + handler callback itself, in a sub structure associated with + the field named <c>config</c>.</p> + <p>See the <seealso marker="logger_formatter#type-config"> + <c>logger_formatter(3)</c></seealso> manual page for + information about the default configuration for this + formatter.</p> + </desc> + </datatype> + <datatype> + <name name="filter"/> + <desc> + <p>A filter which can be installed as a handler filter, or as + a primary filter in Logger.</p> + </desc> + </datatype> + <datatype> + <name name="filter_arg"/> + <desc> + <p>The second argument to the filter fun.</p> + </desc> + </datatype> + <datatype> + <name name="filter_id"/> + <desc> + <p>A unique identifier for a filter.</p> + </desc> + </datatype> + <datatype> + <name name="filter_return"/> + <desc> + <p>The return value from the filter fun.</p> + </desc> + </datatype> + <datatype> + <name name="formatter_config"/> + <desc> + <p>Configuration data for the + formatter. See <seealso marker="logger_formatter"> + <c>logger_formatter(3)</c></seealso> + for an example of a formatter implementation.</p> + </desc> + </datatype> + <datatype> + <name name="handler_id"/> + <desc> + <p>A unique identifier for a handler instance.</p> + </desc> + </datatype> + <datatype> + <name name="level"/> + <desc> + <p>The severity level for the message to be logged.</p> + </desc> + </datatype> + <datatype> + <name name="log_event"/> + <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:system_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 overwrite process metadata, which in turn + overwrite values set by Logger.</p> + <p>The following custom metadata keys have special meaning:</p> + <taglist> + <tag><c>domain</c></tag> + <item> + <p>The value associated with this key is used by filters + for grouping log events originating from, for example, + specific functional + areas. See <seealso marker="logger_filters#domain-2"> + <c>logger_filters:domain/2</c></seealso> + for a description of how this field can be used.</p> + </item> + <tag><c>report_cb</c></tag> + <item> + <p>If the log message is specified as + a <seealso marker="#type-report"><c>report()</c></seealso>, + the <c>report_cb</c> key can be associated with a fun + (report callback) that converts the report to a format + string and arguments. See + section <seealso marker="logger_chapter#log_message">Log + Message</seealso> in the User's Guide for more + information about report callbacks.</p> + </item> + </taglist> + </desc> + </datatype> + <datatype> + <name name="msg_fun"/> + <desc> + <p></p> + </desc> + </datatype> + <datatype> + <name name="report"/> + <desc> + <p></p> + </desc> + </datatype> + <datatype> + <name name="timestamp"/> + <desc> + <p>A timestamp produced + with <seealso marker="erts:erlang#system_time-1"> + <c>erlang:system_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 to the + metadata. 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> + + <section> + <marker id="logging_API"/> + <title>Logging API functions</title> + </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> + </funcs> + + <section> + <marker id="configuration_API"/> + <title>Configuration API functions</title> + </section> + <funcs> + <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 referring to this + handler.</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_event()</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#filters">Filters</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_handlers" arity="1" clause_i="1"/> + <fsummary>Set up log handlers from the application's + configuration parameters.</fsummary> + <desc> + <p>Reads the application configuration parameter <c>logger</c> and + calls <c>add_handlers/1</c> with its contents.</p> + </desc> + </func> + + <func> + <name name="add_handlers" arity="1" clause_i="2"/> + <fsummary>Setup logger handlers.</fsummary> + <type name="config_handler"/> + <desc> + <p>This function should be used by custom Logger handlers to make + configuration consistent no matter which handler the system uses. + Normal usage is to add a call to <c>logger:add_handlers/1</c> + just after the processes that the handler needs are started, + and pass the application's <c>logger</c> configuration as the argument. + For example:</p> + <code> +-behaviour(application). +start(_, []) -> + case supervisor:start_link({local, my_sup}, my_sup, []) of + {ok, Pid} -> + ok = logger:add_handlers(my_app), + {ok, Pid, []}; + Error -> Error + end.</code> + <p>This reads the <c>logger</c> configuration parameter from + the <c>my_all</c> application and starts the configured + handlers. The contents of the configuration use the same + rules as the + <seealso marker="logger_chapter#handler-configuration">logger handler configuration</seealso>. + </p> + <p>If the handler is meant to replace the default handler, the Kernel's + default handler have to be disabled before the new handler is added. + A <c>sys.config</c> file that disables the Kernel handler and adds + a custom handler could look like this:</p> + <code> +[{kernel, + [{logger, + %% Disable the default Kernel handler + [{handler, default, undefined}]}]}, + {my_app, + [{logger, + %% Enable this handler as the default + [{handler, default, my_handler, #{}}]}]}]. + </code> + </desc> + </func> + + <func> + <name name="add_primary_filter" arity="2"/> + <fsummary>Add a primary filter to Logger.</fsummary> + <desc> + <p>Add a primary filter to 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_event()</c></tag> + <item> + <p>The filter <em>passed</em>. The next primary filter, if + any, is applied. If no more primary filters exist, the + log event is forwarded to the handler part of 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 + primary filter, if any, is applied. If no more primary + filters exist, the value of the + primary <c>filter_default</c> configuration parameter + specifies if the log event shall be discarded or + forwarded to the handler part.</p> + </item> + </taglist> + <p>See section <seealso marker="logger_chapter#filters"> + Filters</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="get_config" arity="0"/> + <fsummary>Look up the current Logger configuration</fsummary> + <desc> + <p>Look up all current Logger configuration, including primary + and handler configuration, and module level settings.</p> + </desc> + </func> + + <func> + <name name="get_handler_config" arity="0"/> + <fsummary>Look up the current configuration for all handlers.</fsummary> + <desc> + <p>Look up the current configuration for all handlers.</p> + </desc> + </func> + + <func> + <name name="get_handler_config" arity="1"/> + <fsummary>Look up the current configuration for the given + handler.</fsummary> + <desc> + <p>Look up the current configuration for the given handler.</p> + </desc> + </func> + + <func> + <name name="get_handler_ids" arity="0"/> + <fsummary>Look up the identities for all installed handlers.</fsummary> + <desc> + <p>Look up the identities for all installed handlers.</p> + </desc> + </func> + + <func> + <name name="get_primary_config" arity="0"/> + <fsummary>Look up the current primary configuration for Logger.</fsummary> + <desc> + <p>Look up the current primary configuration for Logger.</p> + </desc> + </func> + + <func> + <name name="get_module_level" arity="0"/> + <fsummary>Look up all current module levels.</fsummary> + <desc> + <p>Look up all current module levels. Returns a list + containing one <c>{Module,Level}</c> element for each module + for which the module level was previously set + with <seealso marker="#set_module_level-2"> + <c>set_module_level/2</c></seealso>.</p> + </desc> + </func> + + <func> + <name name="get_module_level" arity="1"/> + <fsummary>Look up the current level for the given modules.</fsummary> + <desc> + <p>Look up the current level for the given modules. Returns a + list containing one <c>{Module,Level}</c> element for each + of the given modules for which the module level was + previously set with <seealso marker="#set_module_level-2"> + <c>set_module_level/2</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="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="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="remove_primary_filter" arity="1"/> + <fsummary>Remove a primary filter from Logger.</fsummary> + <desc> + <p>Remove the primary filter identified + by <c><anno>FilterId</anno></c> from Logger.</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="#update_handler_config-2"> + <c>update_handler_config/2</c></seealso>, or, if a more + complex merge is needed, read the current configuration + with <seealso marker="#get_handler_config-1"><c>get_handler_config/1</c> + </seealso>, then do the merge before writing the new + configuration back with this function.</p> + <p>If a key is removed compared to the current configuration, + and the key is known 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 does not exist, it will + be added.</p> + </desc> + </func> + + <func> + <name name="set_primary_config" arity="1"/> + <fsummary>Set primary configuration data for Logger.</fsummary> + <desc> + <p>Set primary configuration data for Logger. This + overwrites the current configuration.</p> + <p>To modify the existing configuration, + use <seealso marker="#update_primary_config-1"> + <c>update_primary_config/1</c></seealso>, or, if a more + complex merge is needed, read the current configuration + with <seealso marker="#get_primary_config-0"><c>get_primary_config/0</c> + </seealso>, then do the merge before writing the new + configuration back with this function.</p> + <p>If a key is removed compared to the current configuration, + the default value is used.</p> + </desc> + </func> + + <func> + <name name="set_primary_config" arity="2"/> + <fsummary>Add or update primary configuration data for Logger.</fsummary> + <desc> + <p>Add or update primary configuration data for 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 + does not exist, it will be added.</p> + </desc> + </func> + + <func> + <name name="set_module_level" arity="2"/> + <fsummary>Set the log level for the specified modules.</fsummary> + <desc> + <p>Set the log level for the + specified modules.</p> + <p>The log level for a module overrides the primary log level + of Logger for log events 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 primary log level for 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 primary log level.</p> + <p>If the level for <c>mymodule</c> is 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 primary log level for Logger, use + <seealso marker="#set_primary_config/2"> + <c>set_primary_config(level, Level)</c></seealso>.</p> + <p>To change the log level for a handler, use + <seealso marker="#set_handler_config/3"> + <c>set_handler_config(HandlerId, level, Level)</c> + </seealso>.</p> + <note> + <p>The originating module for a log event is only detected + if the key <c>mfa</c> exists in the metadata, and is + associated with <c>{Module, Function, Arity}</c>. When log + macros are used, this association is automatically added + to all log events. If an API function is called directly, + without using a macro, the logging client must explicitly + add this information if module levels shall have any + effect.</p> + </note> + </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="unset_module_level" arity="0"/> + <fsummary>Remove module specific log settings for all modules.</fsummary> + <desc> + <p>Remove module specific log settings. After this, the + primary log level is used for all modules.</p> + </desc> + </func> + + <func> + <name name="unset_module_level" arity="1"/> + <fsummary>Remove module specific log settings for the given + modules.</fsummary> + <desc> + <p>Remove module specific log settings. After this, the + primary log level is used for the specified modules.</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="update_formatter_config" arity="2"/> + <fsummary>Update the formatter configuration for the specified handler.</fsummary> + <desc> + <p>Update the formatter configuration for the specified handler.</p> + <p>The new configuration is merged with the existing formatter + configuration.</p> + <p>To overwrite the existing configuration without any merge, + use</p> + <pre> +<seealso marker="#set_handler_config-3">set_handler_config(HandlerId, formatter, + {FormatterModule, FormatterConfig})</seealso>.</pre> + </desc> + </func> + + <func> + <name name="update_formatter_config" arity="3"/> + <fsummary>Update the formatter configuration for the specified handler.</fsummary> + <desc> + <p>Update the formatter configuration for the specified handler.</p> + <p>This is equivalent to</p> + <pre> +<seealso marker="#update_formatter_config-2">update_formatter_config(<anno>HandlerId</anno>, #{<anno>Key</anno> => <anno>Value</anno>})</seealso></pre> + </desc> + </func> + + <func> + <name name="update_handler_config" arity="2"/> + <fsummary>Update configuration data for the specified handler.</fsummary> + <desc> + <p>Update configuration data for the specified handler. This function + behaves as if it was implemented as follows:</p> + <code type="erl"> +{ok, {_, Old}} = logger:get_handler_config(HandlerId), +logger:set_handler_config(HandlerId, maps:merge(Old, Config)). + </code> + <p>To overwrite the existing configuration without any merge, + use <seealso marker="#set_handler_config-2"><c>set_handler_config/2</c> + </seealso>.</p> + </desc> + </func> + + <func> + <name name="update_primary_config" arity="1"/> + <fsummary>Update primary configuration data for Logger.</fsummary> + <desc> + <p>Update primary configuration data for Logger. This function + behaves as if it was implemented as follows:</p> + <code type="erl"> +Old = logger:get_primary_config(), +logger:set_primary_config(maps:merge(Old, Config)). + </code> + <p>To overwrite the existing configuration without any merge, + use <seealso marker="#set_primary_config-1"><c>set_primary_config/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> + </funcs> + + <section> + <marker id="misc_API"/> + <title>Miscellaneous API functions</title> + </section> + <funcs> + <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="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>. This is the default report callback used + by <seealso marker="logger_formatter"> + <c>logger_formatter</c></seealso> when no custom report + callback is found. See + section <seealso marker="logger_chapter#log_message">Log + Message</seealso> in the Kernel User's Guide for + information about report callbacks and valid forms of log + messages.</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 <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> + <marker id="handler_callback_functions"/> + <title>Handler Callback Functions</title> + <p>The following functions are to be exported from a handler + callback module.</p> + </section> + + <funcs> + <func> + <name>HModule:adding_handler(Config1) -> {ok, Config2} | {error, + Reason}</name> + <fsummary>An instance of this handler is about to be added.</fsummary> + <type> + <v>Config1 = Config2 = + <seealso marker="#type-handler_config">handler_config()</seealso></v> + <v>Reason = term()</v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called on a temporary process when an new + handler is about to be added. The purpose is to verify the + configuration and initiate all resources needed by the + handler.</p> + <p>The handler identity is associated with the <c>id</c> key + in <c>Config1</c>.</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>HModule:changing_config(Config1, Config2) -> {ok, Config3} | {error, Reason}</name> + <fsummary>The configuration for this handler is about to change.</fsummary> + <type> + <v>Config1 = Config2 = Config3 = + <seealso marker="#type-handler_config">handler_config()</seealso></v> + <v>Reason = term()</v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called on a temporary process when the + configuration for a handler is about to change. 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>The handler identity is associated with the <c>id</c> key + in <c>Config1</c>.</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> + + <func> + <name>HModule:log(LogEvent, Config) -> void()</name> + <fsummary>Log the given log event.</fsummary> + <type> + <v>LogEvent = + <seealso marker="#type-log_event">log_event()</seealso></v> + <v>Config = + <seealso marker="#type-handler_config">handler_config()</seealso></v> + </type> + <desc> + <p>This callback function is mandatory.</p> + <p>The function is called when all primary filters and all + handler filters for the handler in question have passed for + the given log event. It is called on the client process, that + is, the process that issued the log event.</p> + <p>The handler identity is associated with the <c>id</c> key + in <c>Config</c>.</p> + <p>The handler must log the event.</p> + <p>The return value from this function is ignored by + Logger.</p> + </desc> + </func> + + <func> + <name>HModule:removing_handler(Config) -> ok</name> + <fsummary>The given handler is about to be removed.</fsummary> + <type> + <v>Config = + <seealso marker="#type-handler_config">handler_config()</seealso></v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called on a temporary process when a + handler is about to be removed. The purpose is to release + all resources used by the handler.</p> + <p>The handler identity is associated with the <c>id</c> key + in <c>Config</c>.</p> + <p>The return value is ignored by Logger.</p> + </desc> + </func> + + </funcs> + + <section> + <marker id="formatter_callback_functions"/> + <title>Formatter Callback Functions</title> + <p>The following functions are to be exported from a formatter + callback module.</p> + </section> + + <funcs> + <func> + <name>FModule:check_config(FConfig) -> ok | {error, Reason}</name> + <fsummary>Validate the given formatter configuration.</fsummary> + <type> + <v>FConfig = + <seealso marker="#type-formatter_config">formatter_config()</seealso></v> + <v>Reason = term()</v> + </type> + <desc> + <p>This callback function is optional.</p> + <p>The function is called by a Logger when formatter + configuration is set or modified. The formatter must + validate the given configuration and return <c>ok</c> if it + is correct, and <c>{error,Reason}</c> if it is faulty.</p> + <p>The following Logger API functions can trigger this callback:</p> + <list> + <item><seealso marker="logger#add_handler-3"> + <c>logger:add_handler/3</c></seealso></item> + <item><seealso marker="logger#set_handler_config-2"> + <c>logger:set_handler_config/2,3</c></seealso></item> + <item><seealso marker="logger#update_handler_config-2"> + <c>logger:updata_handler_config/2</c></seealso></item> + <item><seealso marker="logger#update_formatter_config-2"> + <c>logger:update_formatter_config/2</c></seealso></item> + </list> + <p>See <seealso marker="logger_formatter"> + <c>logger_formatter(3)</c></seealso> + for an example implementation. <c>logger_formatter</c> is the + default formatter used by Logger.</p> + </desc> + </func> + <func> + <name>FModule:format(LogEvent, FConfig) -> FormattedLogEntry</name> + <fsummary>Format the given log event.</fsummary> + <type> + <v>LogEvent = + <seealso marker="#type-log_event">log_event()</seealso></v> + <v>FConfig = + <seealso marker="#type-formatter_config">formatter_config()</seealso></v> + <v>FormattedLogEntry = + <seealso marker="unicode#type-chardata">unicode:chardata()</seealso></v> + </type> + <desc> + <p>This callback function is mandatory.</p> + <p>The function can be called by a log handler to convert a + log event term to a printable string. The returned value + can, for example, be printed as a log entry to the console + or a file using <seealso marker="stdlib:io#put_chars-1"> + <c>io:put_chars/1,2</c></seealso>.</p> + <p>See <seealso marker="logger_formatter"> + <c>logger_formatter(3)</c></seealso> + for an example implementation. <c>logger_formatter</c> is the + default formatter used by Logger.</p> + </desc> + </func> + </funcs> + + <section> + <title>See Also</title> + <p> + <seealso marker="config"><c>config(4)</c></seealso>, + <seealso marker="erts:erlang"><c>erlang(3)</c></seealso>, + <seealso marker="stdlib:io"><c>io(3)</c></seealso>, + <seealso marker="logger_disk_log_h"><c>logger_disk_log_h(3)</c></seealso>, + <seealso marker="logger_filters"><c>logger_filters(3)</c></seealso>, + <seealso marker="logger_formatter"><c>logger_formatter(3)</c></seealso>, + <seealso marker="logger_std_h"><c>logger_std_h(3)</c></seealso>, + <seealso marker="stdlib:unicode"><c>unicode(3)</c></seealso> + </p> + </section> +</erlref> + + |