diff options
Diffstat (limited to 'lib/kernel/doc/src/logger_chapter.xml')
| -rw-r--r-- | lib/kernel/doc/src/logger_chapter.xml | 130 |
1 files changed, 108 insertions, 22 deletions
diff --git a/lib/kernel/doc/src/logger_chapter.xml b/lib/kernel/doc/src/logger_chapter.xml index f4a752bde9..bfd0acf634 100644 --- a/lib/kernel/doc/src/logger_chapter.xml +++ b/lib/kernel/doc/src/logger_chapter.xml @@ -69,6 +69,8 @@ figure shows two log handlers, but any number of handlers can be installed.</p> + <!-- The image is edited with dia in logger_arch.dia file, + and .png file generated with make target 'png'. --> <image file="logger_arch.png"> <icaption>Conceptual Overview</icaption> </image> @@ -111,7 +113,10 @@ of functions on the form <c>logger:Level/1,2,3</c>, which are all shortcuts for <seealso marker="logger#log-2"> - <c>logger:log(Level,Arg1[,Arg2[,Arg3]])</c></seealso>.</p> + <c>logger:log(Level,Arg1[,Arg2[,Arg3]])</c></seealso>.</p> + <p>The macros are defined in <c>logger.hrl</c>, which is included + in a module with the directive</p> + <code>-include_lib("kernel/include/logger.hrl").</code> <p>The difference between using the macros and the exported functions is that macros add location (originator) information to the metadata, and performs lazy evaluation by wrapping the @@ -192,10 +197,28 @@ the log event's <seealso marker="#metadata">metadata</seealso>. The report callback is a convenience function that the <seealso marker="#formatters">formatter</seealso> can use - to convert the report to a format string and arguments. The + to convert the report to a format string and arguments, or + directly to a string. The formatter can also use its own conversion function, if no callback is provided, or if a customized formatting is desired.</p> + <p>The report callback must be a fun with one or two + arguments. If it takes one argument, this is the report + itself, and the fun returns a format string and arguments:</p> + <pre>fun((<seealso marker="logger#type-report"><c>logger:report()</c></seealso>) -> {<seealso marker="stdlib:io#type-format"><c>io:format()</c></seealso>,[term()]})</pre> + <p>If it takes two arguments, the first is the report, and the + second is a map containing extra data that allows direct + coversion to a string:</p> + <pre>fun((<seealso marker="logger#type-report"><c>logger:report()</c></seealso>,<seealso marker="logger#type-report_cb_config"><c>logger:report_cb_config()</c></seealso>) -> <seealso marker="stdlib:unicode#type-chardata"><c>unicode:chardata()</c></seealso>) + </pre> + <p>The fun must obey the <c>depth</c> and <c>chars_limit</c> + parameters provided in the second argument, as the formatter can + not do anything useful of these parameters with the returned + string. The extra data also contains a field named + <c>single_line</c>, indicating if the printed log message may + contain line breaks or not. This variant is used when the + formatting of the report depends on the size or single line + parameters.</p> <p>Example, format string and arguments:</p> <code>logger:error("The file does not exist: ~ts",[Filename])</code> <p>Example, string:</p> @@ -222,7 +245,7 @@ logger:debug(#{got => connection_request, id => Id, state => State}, with <seealso marker="logger#set_process_metadata-1"> <c>logger:set_process_metadata/1</c></seealso> and <seealso marker="logger#update_process_metadata-1"> - <c>logger:update_process metadata/1</c></seealso>, + <c>logger:update_process_metadata/1</c></seealso>, respectively. This metadata applies to the process on which these calls are made, and Logger adds the metadata to all log events issued on that process.</p> @@ -364,8 +387,8 @@ logger:debug(#{got => connection_request, id => Id, state => State}, <p>In addition to the mandatory callback function <c>log/2</c>, a handler module can export the optional callback - functions <c>adding_handler/1</c>, <c>changing_config/2</c> - and <c>removing_handler/1</c>. See + functions <c>adding_handler/1</c>, <c>changing_config/3</c>, + <c>filter_config/1</c>, and <c>removing_handler/1</c>. See section <seealso marker="logger#handler_callback_functions">Handler Callback Functions</seealso> in the logger(3) manual page for more information about these function.</p> @@ -489,7 +512,7 @@ logger:debug(#{got => connection_request, id => Id, state => State}, <c>logger_level</c></seealso>. It is changed during runtime with <seealso marker="logger#set_primary_config-2"> <c>logger:set_primary_config(level,Level)</c></seealso>.</p> - <p>Defaults to <c>info</c>.</p> + <p>Defaults to <c>notice</c>.</p> </item> <tag><c>filters = [{FilterId,Filter}]</c></tag> <item> @@ -535,7 +558,7 @@ logger:debug(#{got => connection_request, id => Id, state => State}, <item><seealso marker="logger#set_handler_config-2"> <c>set_handler_config/2,3</c></seealso></item> <item><seealso marker="logger#update_handler_config-2"> - <c>update_handler_config/2</c></seealso></item> + <c>update_handler_config/2,3</c></seealso></item> <item><seealso marker="logger#add_handler_filter-3"> <c>add_handler_filter/3</c></seealso></item> <item><seealso marker="logger#remove_handler_filter-2"> @@ -670,8 +693,10 @@ logger:debug(#{got => connection_request, id => Id, state => State}, with <seealso marker="#logger_sasl_compatible"> <c>logger_sasl_compatible</c></seealso>.</p> <p>With this parameter, you can modify or disable the default - handler, add custom handlers and primary logger filters, and - set log levels per module.</p> + handler, add custom handlers and primary logger filters, set + log levels per module, and modify + the <seealso marker="#proxy">proxy</seealso> + configuration.</p> <p><c>Config</c> is any (zero or more) of the following:</p> <taglist> <tag><c>{handler, default, undefined}</c></tag> @@ -684,9 +709,13 @@ logger:debug(#{got => connection_request, id => Id, state => State}, <item> <p>If <c>HandlerId</c> is <c>default</c>, then this entry modifies the default handler, equivalent to calling</p> - <pre><seealso marker="logger#set_handler_config-2"> - logger:set_handler_config(default, Module, HandlerConfig) - </seealso></pre> + <pre><seealso marker="logger#remove_handler-1"> + logger:remove_handler(default) + </seealso></pre> + <p>followed by</p> + <pre><seealso marker="logger#add_handler-3"> + logger:add_handler(default, Module, HandlerConfig) + </seealso></pre> <p>For all other values of <c>HandlerId</c>, this entry adds a new handler, equivalent to calling</p> <pre><seealso marker="logger:add_handler/3"> @@ -719,6 +748,14 @@ logger:debug(#{got => connection_request, id => Id, state => State}, <p>for each <c>Module</c>.</p> <p>Multiple entries of this type are allowed.</p> </item> + <tag><c>{proxy, ProxyConfig}</c></tag> + <item> + <p>Sets the proxy configuration, equivalent to calling</p> + <pre><seealso marker="logger#set_proxy_config/1"> + logger:set_proxy_config(ProxyConfig) + </seealso></pre> + <p>Only one entry of this type is allowed.</p> + </item> </taglist> <p>See section <seealso marker="#config_examples">Configuration @@ -764,7 +801,7 @@ logger:debug(#{got => connection_request, id => Id, state => State}, [{kernel, [{logger, [{handler, default, logger_std_h, % {handler, HandlerId, Module, - #{config => #{type => {file,"log/erlang.log"}}}} % Config} + #{config => #{file => "log/erlang.log"}}} % Config} ]}]}]. </code> <p>Modify the default handler to print each log event as a @@ -794,10 +831,10 @@ logger:debug(#{got => connection_request, id => Id, state => State}, [{logger, [{handler, default, logger_std_h, #{level => error, - config => #{type => {file, "log/erlang.log"}}}}, + config => #{file => "log/erlang.log"}}}, {handler, info, logger_std_h, #{level => debug, - config => #{type => {file, "log/debug.log"}}}} + config => #{file => "log/debug.log"}}} ]}]}]. </code> </section> @@ -967,10 +1004,10 @@ ok</pre> <p>Then, add a new handler which prints to file. You can use the handler module <seealso marker="logger_std_h"><c>logger_std_h</c></seealso>, - and specify type <c>{file,File}</c>.:</p> + and configure it to log to file:</p> <pre> -4> <input>Config = #{config => #{type => {file,"./info.log"}}, level => info}.</input> -#{config => #{type => {file,"./info.log"}},level => info} +4> <input>Config = #{config => #{file => "./info.log"}, level => info}.</input> +#{config => #{file => "./info.log"},level => info} 5> <input>logger:add_handler(myhandler, logger_std_h, Config).</input> ok</pre> <p>Since <c>filter_default</c> defaults to <c>log</c>, this @@ -1004,7 +1041,8 @@ ok</pre> <list> <item><c>adding_handler(Config)</c></item> <item><c>removing_handler(Config)</c></item> - <item><c>changing_config(OldConfig, NewConfig)</c></item> + <item><c>changing_config(SetOrUpdate, OldConfig, NewConfig)</c></item> + <item><c>filter_config(Config)</c></item> </list> <p>When a handler is added, by for example a call to <seealso marker="logger#add_handler-3"> @@ -1023,11 +1061,18 @@ ok</pre> <p>When <seealso marker="logger#set_handler_config-2"> <c>logger:set_handler_config/2,3</c></seealso> or <seealso marker="logger#update_handler_config/2"> - <c>logger:update_handler_config/2</c></seealso> is called, + <c>logger:update_handler_config/2,3</c></seealso> is called, Logger - calls <c>HModule:changing_config(OldConfig, NewConfig)</c>. If + calls <c>HModule:changing_config(SetOrUpdate, OldConfig, NewConfig)</c>. If this function returns <c>{ok,NewConfig1}</c>, Logger writes <c>NewConfig1</c> to the configuration database.</p> + <p>When <seealso marker="logger#get_config-0"> + <c>logger:get_config/0</c></seealso> or + <seealso marker="logger#get_handler_config-0"> + <c>logger:get_handler_config/0,1</c></seealso> is called, + Logger calls <c>HModule:filter_config(Config)</c>. This function + must return the handler configuration where internal data is + removed.</p> <p>A simple handler that prints to the terminal can be implemented as follows:</p> @@ -1201,7 +1246,7 @@ do_log(Fd, LogEvent, #{formatter := {FModule, FConfig}}) -> <p>A configuration example:</p> <code type="none"> logger:add_handler(my_standard_h, logger_std_h, - #{config => #{type => {file,"./system_info.log"}, + #{config => #{file => "./system_info.log", sync_mode_qlen => 100, drop_mode_qlen => 1000, flush_qlen => 2000}}). @@ -1299,9 +1344,50 @@ logger:add_handler(my_disk_log_h, logger_disk_log_h, </section> <section> + <marker id="proxy"/> + <title>Logger Proxy</title> + <p>The Logger proxy is an Erlang process which is part of the + Kernel application's supervision tree. During startup, the proxy + process registers itself as the <c>system_logger</c>, meaning + that log events produced by the emulator are sent to this + process.</p> + <p>When a log event is issued on a process which has its group + leader on a remote node, Logger automatically forwards the log + event to the group leader's node. To achieve this, it first + sends the log event as an Erlang message from the original + client process to the proxy on the local node, and the proxy in + turn forwards the event to the proxy on the remote node.</p> + <p>When receiving a log event, either from the emulator or from a + remote node, the proxy calls the Logger API to log the event.</p> + <p>The proxy process is overload protected in the same way as + described in + section <seealso marker="#overload_protection">Protecting the + Handler from Overload</seealso>, but with the following default + values:</p> + <code> + #{sync_mode_qlen => 500, + drop_mode_qlen => 1000, + flush_qlen => 5000, + burst_limit_enable => false, + overload_kill_enable => false}</code> + <p>For log events from the emulator, synchronous message passing + mode is not applicable, since all messages are passed + asynchronously by the emulator. Drop mode is achieved by setting + the <c>system_logger</c> to <c>undefined</c>, forcing the + emulator to drop events until it is set back to the proxy pid + again.</p> + <p>The proxy uses <seealso marker="erts:erlang#send_nosuspend/2"> + <c>erlang:send_nosuspend/2</c></seealso> when sending log + events to a remote node. If the message could not be sent + without suspending the sender, it is dropped. This is to avoid + blocking the proxy process.</p> + </section> + + <section> <title>See Also</title> <p> <seealso marker="disk_log"><c>disk_log(3)</c></seealso>, + <seealso marker="erts:erlang"><c>erlang(3)</c></seealso>, <seealso marker="error_logger"><c>error_logger(3)</c></seealso>, <seealso marker="logger"><c>logger(3)</c></seealso>, <seealso marker="logger_disk_log_h"><c>logger_disk_log_h(3)</c></seealso>, |