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Diffstat (limited to 'lib/kernel/doc/src/logger_formatter.xml')
| -rw-r--r-- | lib/kernel/doc/src/logger_formatter.xml | 353 |
1 files changed, 255 insertions, 98 deletions
diff --git a/lib/kernel/doc/src/logger_formatter.xml b/lib/kernel/doc/src/logger_formatter.xml index 6a17e3641f..02f89b26be 100644 --- a/lib/kernel/doc/src/logger_formatter.xml +++ b/lib/kernel/doc/src/logger_formatter.xml @@ -33,123 +33,280 @@ <file>logger_formatter.xml</file> </header> <module>logger_formatter</module> - <modulesummary>Default formatter for the Logger application.</modulesummary> + <modulesummary>Default formatter for Logger.</modulesummary> <description> - <p>Default formatter for the Logger application.</p> + <p>Each log handler has a configured formatter specified as a + module and a configuration term. The purpose of the formatter is + to translate the log events to a final printable string + (<seealso marker="stdlib:unicode#type-chardata"><c>unicode:chardata()</c> + </seealso>) which can be written to the output + device of the handler.</p> + <p><c>logger_formatter</c> is the default formatter used by + Logger.</p> </description> + <datatypes> <datatype> + <name name="config"/> + <desc> + <p>The configuration term for <c>logger_formatter</c> is a + <seealso marker="stdlib:maps">map</seealso>, and the + following keys can be set as configuration parameters:</p> + <taglist> + <tag><c>chars_limit = pos_integer() | unlimited</c></tag> + <item> + <p>A positive integer representing the value of the option + with the same name to be used when calling + <seealso marker="stdlib:io_lib#format-3"> + <c>io_lib:format/3</c></seealso>. + This value limits the total number of characters printed + for each log event. Notice that this is a soft limit. For a + hard truncation limit, see option <c>max_size</c>.</p> + <p>Defaults to <c>unlimited</c>.</p> + <note> + <p><c>chars_limit</c> has no effect on log messages on + string form. These are expected to be short, but can + still be truncated by the <c>max_size</c> + parameter.</p> + </note> + </item> + <tag><marker id="depth"/><c>depth = pos_integer() | unlimited</c></tag> + <item> + <p>A positive integer representing the maximum depth to + which terms shall be printed by this formatter. Format + strings passed to this formatter are rewritten. The + format controls ~p and ~w are replaced with ~P and ~W, + respectively, and the value is used as the depth + parameter. For details, see + <seealso marker="stdlib:io#format-2">io:format/2,3</seealso> + in STDLIB.</p> + <p>Defaults to <c>unlimited</c>.</p> + <note> + <p><c>depth</c> has no effect on log messages on string + form. These are expected to be short, but can still be + truncated by the <c>max_size</c> parameter.</p> + </note> + </item> + <tag><c>legacy_header = boolean()</c></tag> + <item> + <p>If set to <c>true</c> a header field is added to + logger_formatter's part of <c>Metadata</c>. The value of + this field is a string similar to the header created by + the old <c>error_logger</c> event handlers. It can be + included in the log event by adding the + tuple <c>{logger_formatter,header}</c> to the + template. See the description of + the <seealso marker="#type-template"><c>template()</c></seealso> + type for more information.</p> + <p>Defaults to <c>false</c>.</p> + </item> + <tag><c>max_size = pos_integer() | unlimited</c></tag> + <item> + <p>A positive integer representing the absolute maximum size a + string returned from this formatter can have. If the + formatted string is longer, after possibly being limited + by <c>chars_limit</c> or <c>depth</c>, it is truncated.</p> + <p>Defaults to <c>unlimited</c>.</p> + </item> + <tag><c>report_cb = fun((</c><seealso marker="logger#type-report"><c>logger:report()</c></seealso><c>) -> {</c><seealso marker="stdlib:io#type-format"><c>io:format()</c></seealso><c>,[term()]})</c></tag> + <item> + <p>A report callback is used by the formatter to transform + log messages on report form to a format string and + arguments. The report callback can be specified in the + metadata for the log event. If no report callback exist + in metadata, <c>logger_formatter</c> will + use <seealso marker="logger#format_report-1"> + <c>logger:format_report/1</c></seealso> as default + callback.</p> + <p>If this configuration parameter is set, it replaces + both the default report callback, and any report + callback found in metadata. That is, all reports are + converted by this configured function.</p> + <p>The value must be a function with arity 1, + returning <c>{Format,Args}</c>, and it will be called + with a report as only argument.</p> + </item> + <tag><c>single_line = boolean()</c></tag> + <item> + <p>If set to <c>true</c>, all newlines in the message are + replaced with <c>", "</c>, and whitespaces following + directly after newlines are removed. Note that newlines + added by the <c>template</c> parameter are not replaced.</p> + <p>Defaults to <c>true</c>.</p> + </item> + <tag><c>template = </c><seealso marker="#type-template"><c>template()</c></seealso></tag> + <item> + <p>The template describes how the formatted string is + composed by combining different data values from the log + event. See the description of + the <seealso marker="#type-template"><c>template()</c></seealso> + type for more information about this.</p> + </item> + <tag><c>time_designator = byte()</c></tag> + <item> + <p>Timestamps are formatted according to RFC3339, and the + time designator is the character used as date and time + separator.</p> + <p>Defaults to <c>$T</c>.</p> + <p>The value of this parameter is used as + the <c>time_designator</c> option + to <seealso marker="stdlib:calendar#system_time_to_rfc3339-2"> + <c>calendar:system_time_to_rcf3339/2</c></seealso>.</p> + </item> + <tag><c>time_offset = integer() | [byte()]</c></tag> + <item> + <p>The time offset, either a string or an integer, to be + used when formatting the timestamp.</p> + <p>An empty string is interpreted as local time. The + values <c>"Z"</c>, <c>"z"</c> or <c>0</c> are + interpreted as Universal Coordinated Time (UTC).</p> + <p>Strings, other than <c>"Z"</c>, <c>"z"</c>, + or <c>""</c>, must be on the form <c>±[hh]:[mm]</c>, for + example <c>"-02:00"</c> or <c>"+00:00"</c>.</p> + <p>Integers must be in microseconds, meaning that the + offset <c>7200000000</c> is equivalent + to <c>"+02:00"</c>.</p> + <p>Defaults to an empty string, meaning that timestamps + are displayed in local time. However, for backwards + compatibility, if the SASL configuration + parameter <seealso marker="sasl:sasl_app#utc_log"> + <c>utc_log</c></seealso><c>=true</c>, the default is + changed to <c>"Z"</c>, meaning that timestamps are displayed + in UTC.</p> + <p>The value of this parameter is used as + the <c>offset</c> option + to <seealso marker="stdlib:calendar#system_time_to_rfc3339-2"> + <c>calendar:system_time_to_rcf3339/2</c></seealso>.</p> + </item> + </taglist> + </desc> + </datatype> + <datatype> <name name="template"/> <desc> + <p>The template is a list of atoms, tuples and strings. The + atoms <c>level</c> or <c>msg</c>, are treated as + placeholders for the severity level and the log message, + respectively. Other atoms or tuples are interpreted as + placeholders for metadata, where atoms are expected to match + top level keys, and tuples represent paths to sub keys when + the metadata is a nested map. For example the + tuple <c>{key1,key2}</c> is replaced by the value of + the <c>key2</c> field in the nested map below. The + atom <c>key1</c> on its own is replaced by the complete + value of the <c>key1</c> field. The values are converted to + strings.</p> + +<code> +#{key1=>#{key2=>my_value, + ...} + ...}</code> + + <p>Strings in the template are printed literally.</p> + <p>The default template differs depending on the values + of <c>legacy_header</c> + and <c>single_line</c>:</p> + + <p>The default value for the <c>template</c> configuration + parameter depends on the value of the <c>single_line</c> + and <c>legacy_header</c> configuration parameters as + follows.</p> + + <p>The log event used in the examples is:</p> + <code> +?LOG_ERROR("name: ~p~nexit_reason: ~p",[my_name,"It crashed"])</code> + + <taglist> + <tag><c>legacy_header=true, single_line=false</c></tag> + <item> + <p>Default + template: <c>[{logger_formatter,header},"\n",msg,"\n"]</c></p> + + <p>Example log entry:</p> + <code type="none"> +=ERROR REPORT==== 17-May-2018::18:30:19.453447 === +name: my_name +exit_reason: "It crashed"</code> + + <p>Notice that all eight levels can occur in the heading, + not only <c>ERROR</c>, <c>WARNING</c> or <c>INFO</c> as the + old <c>error_logger</c> produced. And microseconds are + added at the end of the timestamp.</p> + </item> + + <tag><c>legacy_header=true, single_line=true</c></tag> + <item> + <p>Default + template: <c>[{logger_formatter,header},"\n",msg,"\n"]</c></p> + + <p>Notice that the template is here the same as + for <c>single_line=false</c>, but the resulting log entry + differs in that there is only one line after the + heading:</p> + <code type="none"> +=ERROR REPORT==== 17-May-2018::18:31:06.952665 === +name: my_name, exit_reason: "It crashed"</code> + </item> + + <tag><c>legacy_header=false, single_line=true</c></tag> + <item> + <p>Default template: <c>[time," ",level,": ",msg,"\n"]</c></p> + + <p>Example log entry:</p> + <code type="none"> +2018-05-17T18:31:31.152864+02:00 error: name: my_name, exit_reason: "It crashed"</code> + </item> + + <tag><c>legacy_header=false, single_line=false</c></tag> + <item> + <p>Default template: <c>[time," ",level,":\n",msg,"\n"]</c></p> + + <p>Example log entry:</p> + <code type="none"> +2018-05-17T18:32:20.105422+02:00 error: +name: my_name +exit_reason: "It crashed"</code> + </item> + </taglist> </desc> </datatype> </datatypes> <funcs> <func> + <name name="check_config" arity="1"/> + <fsummary>Validates the given formatter configuration.</fsummary> + <desc> + <p>This callback function is called by Logger when the + formatter configuration for a handler is set or modified. It + returns <c>ok</c> if the configuration is valid, + and <c>{error,term()}</c> if it is faulty.</p> + </desc> + </func> + <func> <name name="format" arity="2"/> <fsummary>Formats the given message.</fsummary> <desc> - <p>Formats the given message.</p> - <p>The template is a list of atoms, tuples and strings. Atoms - can be <c>level</c> or <c>msg</c>, which are placeholders - for the severity level and the log message, - repectively. Tuples are interpreted as placeholders for - metadata. Each element in the tuple must be an atom which - matches a key in the nested metadata map, e.g. the - tuple <c>{key1,key2}</c> will be replaced by the value of - the key2 field in this nested map (the value vill be - converted to a string):</p> - -<code> -#{key1=>#{key2=>my_value, - ...}, - ...}</code> - - - <p> Strings are printed literally.</p> - - <p><c>depth</c> is a positive integer representing the maximum - depth to which terms shall be printed by this - formatter. Format strings passed to this formatter are - rewritten. The format controls ~p and ~w are replaced with - ~P and ~W, respectively, and the value is used as the depth - parameter. For details, see - <seealso marker="stdlib:io#format-2">io:format/2,3</seealso> - in STDLIB.</p> - - <p><c>chars_limit</c> is a positive integer representing the - value of the option with the same name to be used when calling - <seealso marker="stdlib:io#format-3">io:format/3</seealso>. This - value limits the total number of characters printed bu the - formatter. Notes that this is a soft limit. For a hard - truncation limit, see option <c>max_size</c>.</p> - - <p><c>max_size</c> is a positive integer representing the - maximum size a string returned from this formatter can - have. If the formatted string is longer, after possibly - being limited by <c>depth</c> and/or <c>chars_limit</c>, it - will be truncated.</p> - - <p><c>utc</c> is a boolean. If set to true, all dates are - displayed in Universal Coordinated Time. Default - is <c>false</c>.</p> - - <p><c>report_cb</c> must be a function with arity 1, - returning <c>{Format,Args}</c>. This function will replace - any <c>report_cb</c> found in metadata.</p> - - <p>If <c>single_line=true</c>, all newlines in the message are - replaced with <c>", "</c>, and whitespaces following directly - after newlines are removed. Note that newlines added by the - formatter template are not replaced.</p> - - <p>If <c>legacy_header=true</c> a header field is added to - logger_formatter's part of <c>Metadata</c>. The value of - this field is a string similar to the header created by the - old <c>error_logger</c> event handlers. It can be included - in the log event by adding the - tuple <c>{logger_formatter,header}</c> to the template.</p> - - <p>The default template when <c>legacy_header=true</c> is</p> - - <code>[{logger_formatter,header},"\n",msg,"\n"]</code> - - <p>which will cause log entries like this:</p> - - <code>=ERROR REPORT==== 29-Dec-2017::13:30:51.245123 === - process: <0.74.0> - exit_reason: "Something went wrong"</code> - - <p>Note that all eight levels might occur here, not - only <c>ERROR</c>, <c>WARNING</c> or <c>INFO</c>. And also - that micro seconds are added at the end of the - timestamp.</p> - - <p>The default template when <c>single_line=true</c> is</p> - - <code>[time," ",level,": ",msg,"\n"]</code> - - <p>which will cause log entries like this:</p> - - <code>2017-12-29 13:31:49.640317 error: process: <0.74.0>, exit_reason: "Something went wrong"</code> - - <p>The default template when both <c>legacy_header</c> and - <c>single_line</c> are set to false is:</p> - - <code>[time," ",level,":\n",msg,"\n"]</code> - - <p>which will cause log entries like this:</p> - - <code>2017-12-29 13:32:25.191925 error: - process: <0.74.0> - exit_reason: "Something went wrong"</code> - + <p>This the formatter callback function to be called from + handlers. The log event is processed as follows:</p> + <list> + <item>If the message is on report form, it is converted to + <c>{Format,Args}</c> by calling the report + callback.</item> + <item>The size is limited according to the values of + configuration parameters <c>chars_limit</c> + and <c>depth</c>. Notice that this does not apply to + messages on string form.</item> + <item>The full log entry is composed according to + the <c>template</c>.</item> + <item>If the final string is too long, it is truncated + according to the value of configuration + parameter <c>max_size</c>.</item> + </list> </desc> </func> - </funcs> </erlref> |