path: root/lib/et/doc/src/et_selector.xml

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  <header>
    <copyright>
      <year>2002</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
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    </legalnotice>

    <title>et_selector</title>
    <prepared>H&aring;kan Mattsson</prepared>
    <responsible>H&aring;kan Mattsson</responsible>
    <docno></docno>
    <approved>H&aring;kan Mattsson</approved>
    <checked></checked>
    <date></date>
    <rev>%VSN%</rev>
    <file>et_selector.xml</file>
  </header>
  <module>et_selector</module>
  <modulesummary>Define event transforms and trace patterns</modulesummary>
  <description>
    <p></p>
  </description>
  
  <funcs>
    <func>
      <name>make_pattern(RawPattern) -> TracePattern</name>
      <fsummary>Makes a trace pattern suitable to feed change_pattern/1</fsummary>

      <type>
        <v>RawPattern = detail_level()</v>
        <v>TracePattern = erlang_trace_pattern_match_spec()</v>
        <v>detail_level() = min | max | integer(X) when X &gt;= 0, X =&lt; 100</v>
      </type>

      <desc>
        <p>Makes a trace pattern suitable to feed change_pattern/1</p>
        <p>Min detail level deactivates tracing of calls to <c>et:trace_me/4,5</c></p>
        <p>Max detail level activates tracing of all calls to <c>et:trace_me/4,5</c></p>
        <p>integer(X) detail level activates tracing of all calls to
        <c>et:trace_me/4,5</c> whose detail level argument is lesser than
        X.</p>
        <p>See also <c>erlang:trace_pattern/2</c> for more info about its <c>match_spec()</c></p>
      </desc>
    </func>

    <func>
      <name>change_pattern(Pattern) -> ok</name>

      <fsummary>Activates/deactivates tracing by changing the current trace pattern</fsummary>

      <type>
        <v>Pattern = detail_level() | empty_match_spec() | erlang_trace_pattern_match_spec()</v>
        <v>detail_level() = min | max | integer(X) when  X &gt;= 0, X =&lt; 100</v>
        <v>empty_match_spec() = [] </v>
      </type>

      <desc>
        <p>Activates/deactivates tracing by changing the current trace pattern.</p>
        <p><c>min</c> detail level deactivates tracing of calls to <c>et:trace_me/4,5</c></p>
        <p><c>max</c> detail level activates tracing of all calls to <c>et:trace_me/4,5</c></p>
        <p><c>integer(X)</c> detail level activates tracing of all
        calls to <c>et:trace_me/4,5</c> whose detail level argument is
        lesser than <c>X</c>.</p>
        <p>An empty match spec deactivates tracing of calls to <c>et:trace_me/4,5</c></p>
        <p>Other match specs activates tracing of calls to
        <c>et:trace_me/4,5</c> accordingly with
        <c>erlang:trace_pattern/2</c>.</p>
      </desc>
    </func>
    <func>
      <name>parse_event(Mod, ValidTraceData) -> false | true | {true, Event}</name>

      <fsummary>Transforms trace data and makes an event record out of it</fsummary>

      <type>
          <v>Mod = module_name() | undefined</v>
          <v>module_name() = atom()</v>
          <v>ValidTraceData = erlang_trace_data() | record(event)</v>
        <v>erlang_trace_data() = {trace, Pid, Label, Info} |  {trace, Pid, Label, Info, Extra} |  {trace_ts, Pid, Label, Info, ReportedTS} |  {trace_ts, Pid, Label, Info, Extra, ReportedTS} |  {seq_trace, Label, Info} |  {seq_trace, Label, Info, ReportedTS} |  {drop, NumberOfDroppedItems}</v>
      </type>

      <desc>
        <p>Transforms trace data and makes an event record out of it.</p>

        <p>See <c>erlang:trace/3</c> for more info about the semantics of the
        trace data.</p>

        <p>An event record consists of the following fields:</p>
	<taglist>
          <tag><em>detail_level</em></tag>
	  <item><p>Noise has a high level as opposed to essentials.</p></item>


          <tag><em>trace_ts</em></tag>
	  <item><p>Time when the trace was generated.  Same as
	  event_ts if omitted in trace data.</p></item>

          <tag><em>event_ts</em></tag>
	  <item><p>Time when the event record was created.</p></item>

          <tag><em>from</em></tag>
	  <item><p>From actor, such as sender of a message.</p></item>

          <tag><em>to</em></tag>
	  <item><p>To actor, such as receiver of message.</p></item>

          <tag><em>label</em></tag>
	  <item><p>Label intended to provide a brief event summary.</p></item>

          <tag><em>contents</em></tag>
	  <item><p>All nitty gritty details of the event.</p></item>
	</taglist>

        <p>See <c>et:trace_me/4</c>and <c>et:trace_me/5</c> for details.</p>

        <p>Returns:</p>
	<taglist>
          <tag><em>{true, Event}</em></tag>
	  <item><p>where Event is an #event{} record representing the
	  trace data</p></item>

          <tag><em>true</em></tag>
	  <item><p>means that the trace data already is an event
	  record and that it is valid as it is. No transformation is
	  needed.</p></item>

          <tag><em>false</em></tag>
	  <item><p>means that the trace data is uninteresting and
	  should be dropped</p></item>
	</taglist>
      </desc>
    </func>
  </funcs>
  
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