path: root/lib/sasl/doc/src/error_logging.xml

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<chapter>
  <header>
    <copyright>
      <year>1997</year><year>2016</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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      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>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>
  <p>The <c>SASL</c> 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 <c>SASL</c> application is started, it adds a handler that 
    formats and writes these reports, as specified in the configuration
    parameters for <c>SASL</c>, that is, the environment variables
    in the <c>SASL</c> application specification, which is found in the 
    <c>.app</c> file of <c>SASL</c>. For details, see the
    <seealso marker="sasl_app"><c>sasl(6)</c></seealso> application in the
    Reference Manual and the <seealso marker="kernel:app"><c>app(4)</c></seealso>
    file in the <c>Kernel</c> Reference Manual.</p>

  <section>
    <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>
    <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>
    <title>Crash Report</title>
    <p>Processes started with functions 
      <seealso marker="stdlib:proc_lib#spawn/1"><c>proc_lib:spawn</c></seealso> or
      <seealso marker="stdlib:proc_lib#spawn_link/1"><c>proc_lib:spawn_link</c></seealso> 
      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
      <seealso marker="stdlib:gen_server"><c>gen_server</c></seealso>,
      <seealso marker="stdlib:gen_fsm"><c>gen_fsm</c></seealso> or
      <seealso marker="stdlib:gen_statem"><c>gen_statem</c></seealso>
      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>
      <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
        <seealso marker="stdlib:proc_lib#spawn/3"><c>proc_lib:spawn/3</c></seealso>. 
	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>
    <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
      <seealso marker="sasl_app"><c>sasl(6)</c></seealso>
      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 
      <seealso marker="stdlib:log_mf_h"><c>log_mf_h</c></seealso> 
      defined in <c>STDLIB</c>.</p>
    <p>The <c>log_mf_h</c> handler writes all reports to a
      report logging directory, which is specified when
      configuring the <c>SASL</c> 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 <c>SASL</c>
      <c>error_logger_mf_dir</c>.</p>

    <section>
      <title>Starting Report Browser</title>
      <p>Start the <c>rb_server</c> with function
        <seealso marker="rb#start/1"><c>rb:start([Options])</c></seealso> 
	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 
      <seealso marker="rb#help/0"><c>rb:help()</c></seealso> 
      to access the report browser online help system.</p>
    </section>

    <section>
      <title>List Reports in Server</title>
      <p>Use function 
      <seealso marker="rb#list/0"><c>rb:list()</c></seealso> 
      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 
      <seealso marker="rb#show/1"><c>rb:show(Number)</c></seealso> 
      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 
      <seealso marker="rb#stop/0"><c>rb:stop()</c></seealso> 
      to stop the <c>rb_server</c>:</p>
      <pre>
13> <input>rb:stop().</input>
ok</pre>
    </section>
  </section>
</chapter>