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2 SASL Error Logging

The SASL application introduces three types of reports:

  • Supervisor report
  • Progress report
  • Crash report

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 .app file of SASL. For details, see the sasl(6) application in the Reference Manual and the app(4) file in the Kernel Reference Manual.

2.1 Supervisor Report

A supervisor report is issued when a supervised child terminates unexpectedly. A supervisor report contains the following items:

Supervisor

Name of the reporting supervisor.

Context

Indicates in which phase the child terminated from the supervisor's point of view. This can be start_error, child_terminated, or shutdown_error.

Reason

Termination reason.

Offender

Start specification for the child.

2.2 Progress Report

A progress report is issued when a supervisor starts or restarts a child. A progress report contains the following items:

Supervisor

Name of the reporting supervisor.

Started

Start specification for the successfully started child.

2.3 Crash Report

Processes started with functions proc_lib:spawn or proc_lib:spawn_link are wrapped within a catch. A crash report is issued when such a process terminates with an unexpected reason, which is any reason other than normal, shutdown, or {shutdown,Term}. Processes using behaviors gen_server, gen_fsm or gen_statem are examples of such processes. A crash report contains the following items:

Crasher

Information about the crashing process, such as initial function call, exit reason, and message queue.

Neighbours

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.

Example

The following example shows the reports generated when a process crashes. The example process is a permanent process supervised by the test_sup 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 proc_lib:spawn/3. The supervisor generates a supervisor report showing the crashed process. A progress report is generated when the process is finally restarted.

=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}]

2.4 Multi-File Error Report Logging

Multi-file error report logging is used to store error messages received by error_logger. 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.

For more details, see the sasl(6) application in the Reference Manual.

2.5 Report Browser

The report browser is used to browse and format error reports written by the error logger handler log_mf_h defined in STDLIB.

The log_mf_h handler writes all reports to a report logging directory, which is specified when configuring the SASL application.

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 error_logger_mf_dir.

Starting Report Browser

Start the rb_server with function rb:start([Options]) as shown in the following example:

5> rb:start([{max, 20}]).
rb: reading report...done.
rb: reading report...done.
rb: reading report...done.
rb: reading report...done.
{ok,<0.199.0>}

Online Help

Enter command rb:help() to access the report browser online help system.

List Reports in Server

Use function rb:list() to list all loaded reports:

4> rb:list().
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

Show Reports

Use function rb:show(Number) to show details of a specific report:

7> rb:show(4).
        
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> rb:show(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

ok

Search Reports

All reports containing a common pattern can be shown. Suppose a process crashes because it tries to call a non-existing function release_handler:mbj_func/1. The reports can then be shown as follows:

12> rb:grep("mbj_func").
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

Stop Server

Use function rb:stop() to stop the rb_server:

13> rb:stop().
ok

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Licensed under the Apache License, Version 2.0.