On 13/08/15 10:38 +0200, Ulrich Windl wrote: >>>> Miloš Kozák <milos.ko...@lejmr.com> schrieb am 13.08.2015 um 09:56 in >>> Nachricht <55cc4daa.4020...@lejmr.com>: > >> >> Dne 13.8.2015 v 09:26 Andrei Borzenkov napsal(a): >>> On Thu, Aug 13, 2015 at 10:01 AM, Miloš Kozák <milos.ko...@lejmr.com> >>> wrote: >>>> However, this does not make sense at all. Presumably, the >>>> pacemaker should get along with lsb scripts which comes from >>>> system repository, right? >>>> >>> Let's forget about pacemaker for a moment. You have system startup >>> where service B needs service A. initscript for service A completes >>> and script for service B is started but service A is not yet ready to >>> be used. >>> >>> This is a bug in startup script. Irrespectively of whether you use it >>> with pacemaker or not. >> >> I am sorry, but I didnt get the point.. >> >> If service A is not ready then service B should not be started. > > As you seem to be ignorant for advice: > Yes, you are right: Service B should check whether service A is up before > starzing itself. > The easy change for the start script of B is to find aout what command was run > before it to check whether the command before did everything OK by checking > again itself. > > [...]
The harder task for the sketched, relaxed (not strictly serialized, at least per prerequisite-ordering) environment is for service B aware of its prerequisite-ordered predecessor A to (also) decide if A is not by any chance just proceeding with a startup sequence -- something requiring a very detailed knowledge of its internals and being prone to race-conditions anyway. Hence reasonable, high-level, init systems require such startup sequences to be completely finished by the time they acknowledge service at hand as "started" and allow prerequisite-ordered successor to join the game too. Consequently, the responsibility for such "is finished with startup (successfully or not)?" is deferred to the lower-level dedicated startup recipes that should then signal this back to the init system (e.g., by finishing only when the startup is over) credibly to prevent mess ups. Going full circle, if such assumption is broken in httpd initscript, it should be fixed. -- Jan (Poki)
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