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<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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See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>SASL Error Logging</title>
<prepared>Magnus Fröberg</prepared>
<responsible>Bjarne Däcker</responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date>1999-04-13</date>
<rev>B</rev>
<file>error_logging.xml</file>
</header>
<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 handler that
formats and writes these reports, as specified in the configuration
parameters for SASL, that is, the environment variables
in the SASL application specification, which is found in the
<c>.app</c> file of SASL. 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 Kernel 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 ===
<0.63.0>: Divide by zero !
=CRASH REPORT==== 27-May-1996::13:38:56 ===
crasher:
pid: <0.63.0>
registered_name: []
error_info: {badarith,{test,s,[]}}
initial_call: {test,s,[]}
ancestors: [test_sup,<0.46.0>]
messages: []
links: [<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,<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,<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 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
<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,<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 <0.17.0> 1996-10-16 16:14:54
19 progress <0.14.0> 1996-10-16 16:14:55
18 error <0.15.0> 1996-10-16 16:15:02
17 progress <0.14.0> 1996-10-16 16:15:06
16 progress <0.38.0> 1996-10-16 16:15:12
15 progress <0.17.0> 1996-10-16 16:16:14
14 progress <0.17.0> 1996-10-16 16:16:14
13 progress <0.17.0> 1996-10-16 16:16:14
12 progress <0.14.0> 1996-10-16 16:16:14
11 error <0.17.0> 1996-10-16 16:16:21
10 error <0.17.0> 1996-10-16 16:16:21
9 crash_report release_handler 1996-10-16 16:16:21
8 supervisor_report <0.17.0> 1996-10-16 16:16:21
7 progress <0.17.0> 1996-10-16 16:16:21
6 progress <0.17.0> 1996-10-16 16:16:36
5 progress <0.17.0> 1996-10-16 16:16:36
4 progress <0.17.0> 1996-10-16 16:16:36
3 progress <0.14.0> 1996-10-16 16:16:36
2 error <0.15.0> 1996-10-16 16:17:04
1 progress <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 <0.20.0> 1996-10-16 16:16:36
===============================================================================
supervisor {local,sasl_sup}
started
[{pid,<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 <0.24.0> 1996-10-16 16:16:21
===============================================================================
Crashing process
pid <0.24.0>
registered_name release_handler
error_info {undef,{release_handler,mbj_func,[]}}
initial_call
{gen,init_it,
[gen_server,
<0.20.0>,
<0.20.0>,
{erlang,register},
release_handler,
release_handler,
[],
[]]}
ancestors [sasl_sup,<0.18.0>]
messages []
links [<0.23.0>,<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 <0.24.0> 1996-10-16 16:16:21
===============================================================================
** undefined function: release_handler:mbj_func[] **
Found match in report number 10
ERROR REPORT <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 <0.24.0> 1996-10-16 16:16:21
===============================================================================
Crashing process
pid <0.24.0>
registered_name release_handler
error_info {undef,{release_handler,mbj_func,[]}}
initial_call
{gen,init_it,
[gen_server,
<0.20.0>,
<0.20.0>,
{erlang,register},
release_handler,
release_handler,
[],
[]]}
ancestors [sasl_sup,<0.18.0>]
messages []
links [<0.23.0>,<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 <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 <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>