From 6912c3db95b4ca0d78b5c388daae262321645624 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?=
The
The keys
The default values are 1 restart per 5 seconds. This was chosen to + be safe for most systems, even with deep supervision hierarchies, + but you will probably want to tune the settings for your particular + use case.
+First, the intensity decides how big bursts of restarts you want + to tolerate. For example, you might want to accept a burst of at + most 5 or 10 attempts, even within the same second, if it results + in a successful restart.
+Second, you need to consider the sustained failure rate, if + crashes keep happening but not often enough to make the supervisor + give up. If you set intensity to 10 and set the period as low as 1, + the supervisor will allow child processes to keep restarting up to + 10 times per second, forever, filling your logs with crash reports + until someone intervenes manually.
+You should therefore set the period to be long enough that you can + accept that the supervisor keeps going at that rate. For example, + if you have picked an intensity value of 5, then setting the period + to 30 seconds will give you at most one restart per 6 seconds for + any longer period of time, which means that your logs won't fill up + too quickly, and you will have a chance to observe the failures and + apply a fix.
+These choices depend a lot on your problem domain. If you don't + have real time monitoring and ability to fix problems quickly, for + example in an embedded system, you might want to accept at most + one restart per minute before the supervisor should give up and + escalate to the next level to try to clear the error automatically. + On the other hand, if it is more important that you keep trying + even at a high failure rate, you might want a sustained rate of as + much as 1-2 restarts per second.
+Avoiding common mistakes:
+ Do not forget to consider the burst rate. If you set intensity
+ to 1 and period to 6, it gives the same sustained error rate as
+ 5/30 or 10/60, but will not allow even 2 restart attempts in
+ quick succession. This is probably not what you wanted. Do not set the period to a very high value if you want to
+ tolerate bursts. If you set intensity to 5 and period to 3600
+ (one hour), the supervisor will allow a short burst of 5
+ restarts, but then gives up if it sees another single restart
+ almost an hour later. You probably want to regard those crashes
+ as separate incidents, so setting the period to 5 or 10 minutes
+ will be more reasonable. If your application has multiple levels of supervision, then
+ do not simply set the restart intensities to the same values on
+ all levels. Keep in mind that the total number of restarts
+ (before the top level supervisor gives up and terminates the
+ application) will be the product of the intensity values of all
+ the supervisors above the failing child process. For example, if the top level allows 10 restarts, and the next
+ level also allows 10, a crashing child below that level will be
+ restarted 100 times, which is probably excessive. Allowing at
+ most 3 restarts for the top level supervisor might be a better
+ choice in this case.
+
- Se section
+ See section
This type of time-out is useful to for example act on inactivity. - Let us start restart the code sequence + Let us restart the code sequence if no button is pressed for say 30 seconds:
Date: Tue, 14 Feb 2017 11:30:58 +0200
Subject: Fixed typos in system/doc
---
system/doc/efficiency_guide/bench.erl | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'system/doc')
diff --git a/system/doc/efficiency_guide/bench.erl b/system/doc/efficiency_guide/bench.erl
index 1f60e858f6..a1be24b051 100644
--- a/system/doc/efficiency_guide/bench.erl
+++ b/system/doc/efficiency_guide/bench.erl
@@ -355,7 +355,7 @@ create_html_report(ResultList) ->
{ok, OutputFile} = file:open("index.html", [write]),
- %% Create the begining of the result html-file.
+ %% Create the beginning of the result html-file.
Head = Title = "Benchmark Results",
io:put_chars(OutputFile, "\n"),
io:put_chars(OutputFile, "\n"),
--
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