> ## 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, i.e the environment variables in the SASL application specification, which is found in the `.app` file of SASL. See sasl(Application), and app(File) in the Kernel Reference Manual for the details.

> ### 2.1 Supervisor Report

> A supervisor report is issued when a supervised child terminates in an unexpected way. A supervisor report contains the following items:

> Supervisor.
>   The 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.
>   The termination reason.
> Offender.
>   The start specification for the child.

> ### 2.2 Progress Report

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

> Supervisor.
>   The name of the reporting supervisor.
> Started.
>   The start specification for the successfully started child.

> ### 2.3 Crash Report

> Processes started with the `proc_lib:spawn` or `proc_lib:spawn_link` functions are wrapped within a `catch`. A crash report is issued whenever such a process terminates with an unexpected reason, which is any reason other than `normal` or `shutdown`. Processes using the `gen_server` and `gen_fsm` behaviours are examples of such processes. A crash report contains the following items:

> Crasher.
>   Information about the crashing process is reported, such as initial function call, exit reason, and message queue.
> Neighbours.
>   Information about processes which are linked to the crashing process and do not trap exits. These processes are the neighbours which will terminate because of this process crash. The information gathered is the same as the information for Crasher, shown in the previous item.

> #### 2.3.1 An Example

> The following example shows the reports which are generated when a process crashes. The example process is an `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 the `proc_lib:spawn/3` function. The supervisor generates a supervisor report showing the process that has crashed, and then a progress report is generated when the process is finally re-started.

>             =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, which are received by the `error_logger`. The error messages are stored in several files and each file is smaller than a specified amount of kilobytes, and no more than a specified number of files exist at the same time. The logging is very fast because each error message is written as a binary term.

> Refer to `sasl` application in the Reference Manual for more details.

> ### 2.5 Report Browser

> The report browser is used to browse and format error reports written by the error logger handler `error_logger_mf_h`.

> The `error_logger_mf_h` handler writes all reports to a report logging directory. This directory is specified when configuring the SASL application.

> If the report browser is used off-line, the reports can be copied to another directory which is specified when starting the browser. If no such directory is specified, the browser reads reports from the SASL `error_logger_mf_dir`.

> #### 2.5.1 Starting the Report Browser

> Start the `rb_server` with the 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.

> #### 2.5.2 On-line Help

> Enter the command rb:help(). to access the report browser on-line help system.

> #### 2.5.3 List Reports in the Server

> The function `rb:list()` lists 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

> #### 2.5.4 Show Reports

> To show details of a specific report, use the function `rb:show(Number)`:

>     10> rb:show(1).
>     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

> #### 2.5.5 Search the Reports

> It is possible to show all reports which contain a common pattern. Suppose a process crashes because it tries to call a non-existing function `release_handler:mbj_func.` We could then show reports 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

> ##### 2.5.5.1 Stop the Server

> Stop the `rb_server` with the function `rb:stop()`:

>     13> rb:stop().
>     ok

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