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diff --git a/lib/kernel/doc/src/logger_disk_log_h.xml b/lib/kernel/doc/src/logger_disk_log_h.xml new file mode 100644 index 0000000000..90cc4fec30 --- /dev/null +++ b/lib/kernel/doc/src/logger_disk_log_h.xml @@ -0,0 +1,146 @@ +<?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_disk_log_h</title> + <prepared></prepared> + <responsible></responsible> + <docno></docno> + <approved></approved> + <checked></checked> + <date></date> + <rev>A</rev> + <file>logger_disk_log_h.xml</file> + </header> + <module>logger_disk_log_h</module> + <modulesummary>A disk_log based handler for the Logger + application.</modulesummary> + + <description> + <p>This is a handler for the Logger application that offers circular + (wrapped) logs by using the disk_log application. Multiple instances + of this handler can be added to logger, and each instance will print to + its own disk_log file, created with the name and settings specified in + the handler configuration.</p> + <p>The default standard handler, + <seealso marker="logger_std_h"><c>logger_std_h</c></seealso>, can be + replaced by a disk_log handler at startup of the kernel application. + See an example of this below.</p> + <p>The handler has an overload protection mechanism that will keep the handler + process and the kernel application alive during a high load of log + requests. How this feature works, and how to modify the configuration, + is described in the + <seealso marker="logger_chapter#overload_protection"><c>User's Guide</c> + </seealso>.</p> + <p>To add a new instance of the disk_log handler, use + <seealso marker="logger#add_handler-3"><c>logger:add_handler/3</c> + </seealso>. The handler configuration argument is a map which may contain + general configuration parameters, as documented in the + <seealso marker="logger_chapter#handler_configuration"><c>User's Guide</c> + </seealso>, as well as handler specific parameters.</p> + <p>The settings for the disk_log log file should be specified with the + key <c>disk_log_opts</c>. These settings are a subset of the disk_log + datatype + <seealso marker="disk_log#open-1"><c>dlog_option()</c></seealso>.</p> + <p>Parameters in the <c>disk_log_opts</c> map:</p> + <taglist> + <tag><c>file</c></tag> + <item>This is the full name of the disk_log log file.</item> + <tag><c>type</c></tag> + <item>This is the disk_log type, <c>wrap</c> or <c>halt</c>. The + default value is <c>wrap</c>.</item> + <tag><c>max_no_files</c></tag> + <item>This is the maximum number of files that disk_log will use + for its circular logging. The default value is <c>10</c>. (The setting + has no effect on a halt log).</item> + <tag><c>max_no_bytes</c></tag> + <item>This is the maximum number of bytes that will be written to + a log file before disk_log proceeds with the next file in order (or + generates an error in case of a full halt log). The default value for + a wrap log is <c>1048576</c> bytes, and <c>infinity</c> for a halt + log.</item> + </taglist> + <p>Specific configuration for the handler (represented as a sub map) + is specified with the key <c>logger_disk_log_h</c>. It may contain the + following parameter:</p> + <taglist> + <tag><c>filesync_repeat_interval</c></tag> + <item> + <p>This value (in milliseconds) specifies how often the handler will + do a disk_log sync operation in order to make sure that buffered data + gets written to disk. The handler will repeatedly attempt this + operation, but only perform it if something has actually been logged + since the last sync. The default value is <c>5000</c> milliseconds. + If <c>no_repeat</c> is set as value, the repeated sync operation is + disabled. The user can also call the + <seealso marker="logger_disk_log_h#disk_log_sync-1"><c>disk_log_sync/1</c> + </seealso> function to perform a disk_log sync.</p></item> + </taglist> + <p>There are a number of other configuration parameters available, that are + to be used for customizing the overload protection behaviour. The same + parameters are used both in the standard handler and the disk_log handler, + and are documented in the + <seealso marker="logger_chapter#overload_protection"><c>User's Guide</c> + </seealso>.</p> + <p>Note that when changing the configuration of the handler in runtime, by + calling + <seealso marker="logger#set_handler_config-2"><c>logger:set_handler_config/2 + or logger:set_handler_config/3</c></seealso>, the <c>disk_log_opts</c> + settings may not be modified.</p> + <p>Example of adding a disk_log handler:</p> + <code type="none"> +logger:add_handler(my_disk_log_h, logger_disk_log_h, + #{level => error, + filter_default => log, + disk_log_opts => + #{file => "./my_disk_log", + type => wrap, + max_no_files => 4, + max_no_bytes => 10000}, + logger_disk_log_h => + #{filesync_repeat_interval => 1000}}). + </code> + <p>In order to use the disk_log handler instead of the default standard + handler when starting en Erlang node, use the kernel configuration parameter + <seealso marker="kernel_app#configuration"><c>logger_dest</c></seealso> with + value <c>{disk_log,FileName}</c>. Example:</p> + <code type="none"> +erl -kernel logger_dest '{disk_log,"./system_disk_log"}' + </code> + </description> + + <funcs> + + <func> + <name name="disk_log_sync" arity="1" clause_i="1"/> + <fsummary>Writes buffered data to disk.</fsummary> + <desc> + <p>Write buffered data to disk.</p> + </desc> + </func> + + </funcs> + +</erlref> + + |