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Diffstat (limited to 'lib/stdlib/doc/src/gen_event.xml')
| -rw-r--r-- | lib/stdlib/doc/src/gen_event.xml | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/lib/stdlib/doc/src/gen_event.xml b/lib/stdlib/doc/src/gen_event.xml index df09294de6..4f4931eed0 100644 --- a/lib/stdlib/doc/src/gen_event.xml +++ b/lib/stdlib/doc/src/gen_event.xml @@ -630,12 +630,66 @@ gen_event:stop -----> Module:terminate/2 <p>The function should return the updated internal state.</p> </desc> </func> + <func> + <name>Module:format_status(Opt, [PDict, State]) -> Status</name> + <fsummary>Optional function for providing a term describing the + current event handler state.</fsummary> + <type> + <v>Opt = normal | terminate</v> + <v>PDict = [{Key, Value}]</v> + <v>State = term()</v> + <v>Status = term()</v> + </type> + <desc> + <note> + <p>This callback is optional, so event handler modules need + not export it. If a handler does not export this function, + the gen_event module uses the handler state directly for + the purposes described below.</p> + </note> + <p>This function is called by a gen_event process when:</p> + <list typed="bulleted"> + <item>One + of <seealso marker="sys#get_status/1">sys:get_status/1,2</seealso> + is invoked to get the gen_event status. <c>Opt</c> is set + to the atom <c>normal</c> for this case.</item> + <item>The event handler terminates abnormally and gen_event + logs an error. <c>Opt</c> is set to the + atom <c>terminate</c> for this case.</item> + </list> + <p>This function is useful for customising the form and + appearance of the event handler state for these cases. An + event handler callback module wishing to customise + the <c>sys:get_status/1,2</c> return value as well as how + its state appears in termination error logs exports an + instance of <c>format_status/2</c> that returns a term + describing the current state of the event handler.</p> + <p><c>PDict</c> is the current value of the gen_event's + process dictionary.</p> + <p><c>State</c> is the internal state of the event + handler.</p> + <p>The function should return <c>Status</c>, a term that + customises the details of the current state of the event + handler. Any term is allowed for <c>Status</c>. The + gen_event module uses <c>Status</c> as follows:</p> + <list typed="bulleted"> + <item>When <c>sys:get_status/1,2</c> is called, gen_event + ensures that its return value contains <c>Status</c> in + place of the event handler's actual state term.</item> + <item>When an event handler terminates abnormally, gen_event + logs <c>Status</c> in place of the event handler's actual + state term.</item> + </list> + <p>One use for this function is to return compact alternative + state representations to avoid having large state terms + printed in logfiles.</p> + </desc> + </func> </funcs> <section> <title>SEE ALSO</title> - <p><seealso marker="supervisor">supervisor(3)</seealso>, + <p><seealso marker="supervisor">supervisor(3)</seealso>, <seealso marker="sys">sys(3)</seealso></p> </section> </erlref> - |