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<chapter>
  <header>
    <copyright>
      <year>1997</year><year>2021</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.
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      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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    </legalnotice>

    <title>SASL Error Logging</title>
    <prepared>Magnus Fr&ouml;berg</prepared>
    <responsible>Bjarne D&auml;cker</responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>1999-04-13</date>
    <rev>B</rev>
    <file>error_logging.xml</file>
    </header>
  <note>
    <p>The SASL error logging concept described in this section is
      deprecated since Erlang/OTP 21.0, when the
      new <seeguide marker="kernel:logger_chapter">logging
      API</seeguide> was introduced.</p>
    <p>The new default behaviour is that the SASL application no
      longer affects which log events that are logged.
      <seeguide marker="#supervisor_report">Supervisor
      reports</seeguide> and <seeguide marker="#crash_report">crash
      reports</seeguide> are logged via the default logger handler
      which is setup by
      Kernel. <seeguide marker="#progress_report">Progress
      reports</seeguide> are by default not logged, but can be enabled
      by setting the primary log level to <c>info</c>, for example by
      using the Kernel configuration
      parameter <seeapp marker="kernel:kernel_app#logger_level">
	<c>logger_level</c></seeapp>.</p>
    <p>The old SASL error logging behaviour can be re-enabled by setting the
      Kernel configuration
      parameter <seeapp marker="kernel:kernel_app#logger_sasl_compatible">
	<c>logger_sasl_compatible</c></seeapp> to <c>true</c>.</p>
    <p>The mechanism
      for <seeguide marker="#multi_file_logging">multi-file error report
      logging</seeguide> as described in this section is also kept for
      backwards compatibility. However, the new logging API also
      introduces <seeerl marker="kernel:logger_disk_log_h">
	<c>logger_disk_log_h(3)</c></seeerl>, which is a logger
      handler that can print to multiple files
      using <seeerl marker="kernel:disk_log"><c>disk_log(3)</c></seeerl>.</p>
  </note>

  <section>
    <title>SASL reports</title>
  <p>The SASL application introduces three types of reports:</p>
  <list type="bulleted">
    <item>Supervisor report</item>
    <item>Progress report</item>
    <item>Crash report</item>
  </list>
  <p>When the SASL application is started, it adds a Logger handler
    that formats and writes these reports, as specified in
    the <seeapp marker="sasl_app#deprecated_error_logger_config">configuration
    parameters for SASL</seeapp>.</p>

  <section>
    <marker id="supervisor_report"/>
    <title>Supervisor Report</title>
    <p>A supervisor report is issued when a supervised child terminates
      unexpectedly. A supervisor report contains the following
      items:</p>
    <taglist>
      <tag><c>Supervisor</c></tag>
      <item><p>Name of the reporting supervisor.</p></item>
      <tag><c>Context</c></tag>
      <item><p>Indicates in which phase the child terminated
       from the supervisor's point of view. This can be
       <c>start_error</c>, <c>child_terminated</c>, or
       <c>shutdown_error</c>.</p></item>
      <tag><c>Reason</c></tag>
      <item><p>Termination reason.</p></item>
      <tag><c>Offender</c></tag>
      <item><p>Start specification for the child.</p></item>
    </taglist>
  </section>

  <section>
    <marker id="progress_report"/>
    <title>Progress Report</title>
    <p>A progress report is issued when a supervisor starts or
      restarts a child. A progress report contains the following items:</p>
    <taglist>
      <tag><c>Supervisor</c></tag>
      <item><p>Name of the reporting supervisor.</p></item>
      <tag><c>Started</c></tag>
      <item><p>Start specification for the successfully
       started child.</p></item>
    </taglist>
    <marker id="CRASH"></marker>
  </section>

  <section>
    <marker id="crash_report"/>
    <title>Crash Report</title>
    <p>Processes started with functions 
      <seemfa marker="stdlib:proc_lib#spawn/1"><c>proc_lib:spawn</c></seemfa> or
      <seemfa marker="stdlib:proc_lib#spawn_link/1"><c>proc_lib:spawn_link</c></seemfa> 
      are wrapped within a <c>catch</c>. A crash report is issued when such 
      a process terminates with an unexpected reason, which is any reason 
      other than <c>normal</c>, <c>shutdown</c>, or <c>{shutdown,Term}</c>.
      Processes using behaviors
      <seeerl marker="stdlib:gen_server"><c>gen_server</c></seeerl>,
      <seeerl marker="stdlib:gen_fsm"><c>gen_fsm</c></seeerl> or
      <seeerl marker="stdlib:gen_statem"><c>gen_statem</c></seeerl>
      are examples of such processes. A crash report contains the following items:</p>
    <taglist>
      <tag><c>Crasher</c></tag>
      <item><p>Information about the crashing process, such
       as initial function call, exit reason, and message queue.</p></item>
      <tag><c>Neighbours</c></tag>
      <item><p>Information about processes that are linked to the crashing
       process and do not trap exits. These processes are the
       neighbours that terminate because of this process
       crash. The information gathered is the same as the information
       for Crasher, described in the previous item.</p></item>
    </taglist>
    </section>

    <section>
      <title>Example</title>
      <p>The following example shows the reports generated
        when a process crashes. The example process is a
        <c>permanent</c> process supervised by the <c>test_sup</c>
        supervisor. A division by zero is executed and the error is
        first reported by the faulty process. A crash report is
        generated, as the process was started using function
        <seemfa marker="stdlib:proc_lib#spawn/3"><c>proc_lib:spawn/3</c></seemfa>. 
	The supervisor generates a
        supervisor report showing the crashed process. A
        progress report is generated when the process is finally
        restarted.</p>
      <pre>
        =ERROR REPORT==== 27-May-1996::13:38:56 ===
        &lt;0.63.0>: Divide by zero !
        
        =CRASH REPORT==== 27-May-1996::13:38:56 ===
        crasher:
        pid: &lt;0.63.0>
        registered_name: []
        error_info: {badarith,{test,s,[]}}
        initial_call: {test,s,[]}
        ancestors: [test_sup,&lt;0.46.0>]
        messages: []
        links: [&lt;0.47.0>]
        dictionary: []
        trap_exit: false
        status: running
        heap_size: 128
        stack_size: 128
        reductions: 348
        neighbours:
        
        =SUPERVISOR REPORT==== 27-May-1996::13:38:56 ===
        Supervisor: {local,test_sup}
        Context:    child_terminated
        Reason:     {badarith,{test,s,[]}}
        Offender:   [{pid,&lt;0.63.0>},
        {name,test},
        {mfa,{test,t,[]}},
        {restart_type,permanent},
        {shutdown,200},
        {child_type,worker}]
        
        =PROGRESS REPORT==== 27-May-1996::13:38:56 ===
        Supervisor: {local,test_sup}
        Started:  [{pid,&lt;0.64.0>},
        {name,test},
        {mfa,{test,t,[]}},
        {restart_type,permanent},
        {shutdown,200},
        {child_type,worker}]</pre>
    </section>
  </section>

  <section>
    <marker id="multi_file_logging"/>
    <title>Multi-File Error Report Logging</title>
    <p>Multi-file error report logging is used to store error messages
      received by <c>error_logger</c>. The error messages
      are stored in several files and each file is smaller than a
      specified number of kilobytes. No more than a specified number
      of files exist at the same time. The logging is very fast, as
      each error message is written as a binary term.</p>
    <p>For more details, see the
      <seeapp marker="sasl_app#deprecated_error_logger_config">
	<c>sasl(6)</c></seeapp>
      application in the Reference Manual.</p>
  </section>

  <section>
    <title>Report Browser</title>
    <p>The report browser is used to browse and format error reports
      written by the error logger handler 
      <seeerl marker="stdlib:log_mf_h"><c>log_mf_h</c></seeerl> 
      defined in STDLIB.</p>
    <p>The <c>log_mf_h</c> handler writes all reports to a
      report logging directory, which is specified when
      configuring the SASL application.</p>
    <p>If the report browser is
      used offline, the reports can be copied to another directory
      specified when starting the browser. If no such directory
      is specified, the browser reads reports from the SASL
      <c>error_logger_mf_dir</c>.</p>

    <section>
      <title>Starting Report Browser</title>
      <p>Start the <c>rb_server</c> with function
        <seemfa marker="rb#start/1"><c>rb:start([Options])</c></seemfa> 
	as shown in the following example:</p>
      <pre>
        5> <input>rb:start([{max, 20}]).</input>
        rb: reading report...done.
        rb: reading report...done.
        rb: reading report...done.
        rb: reading report...done.
        {ok,&lt;0.199.0>}</pre>
    </section>

    <section>
      <title>Online Help</title>
      <p>Enter command 
      <seemfa marker="rb#help/0"><c>rb:help()</c></seemfa> 
      to access the report browser online help system.</p>
    </section>

    <section>
      <title>List Reports in Server</title>
      <p>Use function 
      <seemfa marker="rb#list/0"><c>rb:list()</c></seemfa> 
      to list all loaded reports:</p>
      <pre>
        4> <input>rb:list().</input>
        No                Type          Process       Date     Time
        ==                ====          =======       ====     ====
        20            progress         &lt;0.17.0> 1996-10-16 16:14:54
        19            progress         &lt;0.14.0> 1996-10-16 16:14:55
        18               error         &lt;0.15.0> 1996-10-16 16:15:02
        17            progress         &lt;0.14.0> 1996-10-16 16:15:06
        16            progress         &lt;0.38.0> 1996-10-16 16:15:12
        15            progress         &lt;0.17.0> 1996-10-16 16:16:14
        14            progress         &lt;0.17.0> 1996-10-16 16:16:14
        13            progress         &lt;0.17.0> 1996-10-16 16:16:14
        12            progress         &lt;0.14.0> 1996-10-16 16:16:14
        11               error         &lt;0.17.0> 1996-10-16 16:16:21
        10               error         &lt;0.17.0> 1996-10-16 16:16:21
        9        crash_report  release_handler 1996-10-16 16:16:21
        8   supervisor_report         &lt;0.17.0> 1996-10-16 16:16:21
        7            progress         &lt;0.17.0> 1996-10-16 16:16:21
        6            progress         &lt;0.17.0> 1996-10-16 16:16:36
        5            progress         &lt;0.17.0> 1996-10-16 16:16:36
        4            progress         &lt;0.17.0> 1996-10-16 16:16:36
        3            progress         &lt;0.14.0> 1996-10-16 16:16:36
        2               error         &lt;0.15.0> 1996-10-16 16:17:04
        1            progress         &lt;0.14.0> 1996-10-16 16:17:09
        ok</pre>
    </section>

    <section>
      <title>Show Reports</title>
      <p>Use function 
      <seemfa marker="rb#show/1"><c>rb:show(Number)</c></seemfa> 
      to show details of a specific report:</p>
      <pre>
7> <input>rb:show(4).</input>
        
PROGRESS REPORT  &lt;0.20.0>                                   1996-10-16 16:16:36
===============================================================================
supervisor                                                     {local,sasl_sup}
started
[{pid,&lt;0.24.0>},
{name,release_handler},
{mfa,{release_handler,start_link,[]}},
{restart_type,permanent},
{shutdown,2000},
{child_type,worker}]
        
ok
8> <input>rb:show(9).</input>
        
CRASH REPORT  &lt;0.24.0>                                      1996-10-16 16:16:21
===============================================================================
Crashing process                                                               
pid                                                                 &lt;0.24.0>
registered_name                                              release_handler
error_info                             {undef,{release_handler,mbj_func,[]}}
initial_call
{gen,init_it,
[gen_server,
&lt;0.20.0>,
&lt;0.20.0>,
{erlang,register},
release_handler,
release_handler,
[],
[]]}
ancestors                                                [sasl_sup,&lt;0.18.0>]
messages                                                                  []
links                                                    [&lt;0.23.0>,&lt;0.20.0>]
dictionary                                                                []
trap_exit                                                              false
status                                                               running
heap_size                                                                610
stack_size                                                               142
reductions                                                                54

ok</pre>
    </section>

    <section>
      <title>Search Reports</title>
      <p>All reports containing a common pattern can be shown.
        Suppose a process crashes because it tries to call a
        non-existing function <c>release_handler:mbj_func/1</c>.
        The reports can then be shown as follows:</p>
      <pre>
12> <input>rb:grep("mbj_func").</input>
Found match in report number 11
        
ERROR REPORT  &lt;0.24.0>                                      1996-10-16 16:16:21
===============================================================================
        
** undefined function: release_handler:mbj_func[] **
Found match in report number 10

ERROR REPORT  &lt;0.24.0>                                      1996-10-16 16:16:21
===============================================================================
        
** Generic server release_handler terminating 
** Last message in was {unpack_release,hej}
** When Server state == {state,[],
"/home/dup/otp2/otp_beam_sunos5_p1g_7",
[{release,
"OTP  APN 181 01",
"P1G",
undefined,
[],
permanent}],
undefined}
** Reason for termination == 
** {undef,{release_handler,mbj_func,[]}}
Found match in report number 9
        
CRASH REPORT  &lt;0.24.0>                                      1996-10-16 16:16:21
===============================================================================
Crashing process                                                               
pid                                                                 &lt;0.24.0>
registered_name                                              release_handler
error_info                             {undef,{release_handler,mbj_func,[]}}
initial_call
{gen,init_it,
[gen_server,
&lt;0.20.0>,
&lt;0.20.0>,
{erlang,register},
release_handler,
release_handler,
[],
[]]}
ancestors                                                [sasl_sup,&lt;0.18.0>]
messages                                                                  []
links                                                    [&lt;0.23.0>,&lt;0.20.0>]
dictionary                                                                []
trap_exit                                                              false
status                                                               running
heap_size                                                                610
stack_size                                                               142
reductions                                                                54
        
Found match in report number 8
        
SUPERVISOR REPORT  &lt;0.20.0>                                 1996-10-16 16:16:21
===============================================================================
Reporting supervisor                                           {local,sasl_sup}
        
Child process                                                                  
errorContext                                                child_terminated
reason                                 {undef,{release_handler,mbj_func,[]}}
pid                                                                 &lt;0.24.0>
name                                                         release_handler
start_function                               {release_handler,start_link,[]}
restart_type                                                       permanent
shutdown                                                                2000
child_type                                                            worker
        
ok</pre>
    </section>

    <section>
      <title>Stop Server</title>
      <p>Use function 
      <seemfa marker="rb#stop/0"><c>rb:stop()</c></seemfa> 
      to stop the <c>rb_server</c>:</p>
      <pre>
13> <input>rb:stop().</input>
ok</pre>
    </section>
  </section>
</chapter>

