[opencms-dev] Repeated (daily) crashes of OpenCms 7.0.5

[Christian Steinert]

oh well - reading helps. Since you wrote that the backups are not done 
around the time when things crash, then backups can probably not be the 
cause for this.
Concerning the 404 handler: this handler is not only used for delivering 
404 error pages - it also seems to be (and more importantly) used for 
static export. So if you have any static export active (including static 
export on demand, where the file system is used as sort of an additional 
cache), then the exported pager are generated like this (description is 
for export on demand):
- Publishing something clears out all files in the export folder
- request URLs for exportable resources are rewritten to point to the 
export folder
- when somebody requests a URL that was not yet exported, then the 404 
handler kicks in. It will check, whether the same resource that is 
missing in the export location does exist in opencms. If so, the 
resource is generated, delivered and written to the export folder
- when another request is done for the export location, opencms has 
already written the file there, so it can be served from the export 
folder by tomcat directly, without the 404 handler of opencms being 
invoked again to re-generate the resource.

This seems to be the mechanism as far as I understand.
So, if static export is active, then the 404 handler will ultimately be 
triggered to cause the resources to be exported. This does not explain 
though, why the crashes happen "only" once a day. Unless the crashes are 
happening not too long after having published something or clearing the 
export folder for some other reason.

Best Regards
Christian


>
>   
>> - There's some evidence that the threads are waiting for something to happen with MySQL.  We observe this behavior:  our sites remain up and running, but no one can log into the Workplace.  The stacktrace in opencms.log is shown below (much clipped to save space.)  Our IT people say there is nothing unusual in the MySQL logs that correspond to these exceptions.
>>     
>
> Maybe it's something entirely different, but you should take a look at when and how your backups are done. Usually, when mysql is backed then usually, the DB is locked for writes during that time to get a consistent state copied into the backup.
>
> A recommended way for doing backups with MySQL is, to do constant replication to a second db server instance and then take that replica offline for backups. When bringing the replica up again, it will automatically catch up again quickly.  In this way you get a consistent backup of your DB without blocking the main app.
>
> Regards
> Christian
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