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Diffstat (limited to 'lib/kernel/doc/src/logger_formatter.xml')
| -rw-r--r-- | lib/kernel/doc/src/logger_formatter.xml | 290 |
1 files changed, 193 insertions, 97 deletions
diff --git a/lib/kernel/doc/src/logger_formatter.xml b/lib/kernel/doc/src/logger_formatter.xml index 6a17e3641f..7df4c88f40 100644 --- a/lib/kernel/doc/src/logger_formatter.xml +++ b/lib/kernel/doc/src/logger_formatter.xml @@ -33,12 +33,187 @@ <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 + (<c>unicode:chardata()</c>) 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> + <section> + <title>Configuration</title> + <p>The configuration term for <c>logger_formatter</c> is a map, + 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">io_lib:format/3</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>Default is <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><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>Default is <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>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>Default is <c>unlimited</c>.</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>Default is <c>true</c>.</p> + </item> + <tag><c>legacy_header = boolen()</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 + section <seealso marker="#default_templates">Default + Templates</seealso> for more information.</p> + <p>Default is <c>false</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>template = </c><seealso marker="#type-template"><c>template()</c></seealso></tag> + <item> + <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, + repectively. 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>. See <seealso marker="#default_templates">Default + Templates</seealso> for more information</p> + </item> + <tag><c>utc = boolean()</c></tag> + <item> + <p>If set to <c>true</c>, all dates are displayed in Universal + Coordinated Time.</p> + <p>Default is <c>false</c>.</p> + </item> + </taglist> + </section> + + <section> + <marker id="default_templates"/> + <title>Default templates</title> + + <p>The default value for the <c>template</c> configuration + parameter depends on the value of <c>single_line</c> + and <c>legacy_header</c> as follows.</p> + + <p>The log event used in the examples is:</p> + <code> +?LOG_ERROR("name: ~p~nexit_reason: ~p",[my_reg_name,"It crashed"])</code> + + <taglist> + <tag><c>legacy_header=true</c></tag> + <item> + <p>Default template: <c>[{logger_formatter,header},"\n",msg,"\n"]</c></p> + + <p>Example log entry:</p> + <code> +=ERROR REPORT==== 29-Dec-2017::13:30:51.245123 === +name: my_reg_name +exit_reason: "It crashed"</code> + + <p>Notice that all eight levels might 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>single_line=true</c></tag> + <item> + <p>Default template: <c>[time," ",level,": ",msg,"\n"]</c></p> + + <p>Example log entry:</p> + <code>2017-12-29 13:31:49.640317 error: name: my_reg_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> +2017-12-29 13:32:25.191925 error: +name: my_reg_name +exit_reason: "It crashed"</code> + </item> + </taglist> + </section> + <datatypes> <datatype> <name name="template"/> @@ -52,101 +227,22 @@ <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> |