Writes using the GCS stream wrapper should be non-blocking (though you should be able to control the behavior using stream_set_blocking <http://php.net/manual/en/function.stream-set-blocking.php>). Reads are cached, so latency should not be an issue.
On Tuesday, January 26, 2016 at 8:15:49 PM UTC-5, Alex Kerr wrote: > > Thanks very much Adam. What's the latency like on Cloud Storage - would it > still be usable as a session store? > > Also I thought I read somewhere that file writes to GCS (e.g. via the PHP > wrapper) return immediately so don't hold up script execution (and thus > response to the client) - is that correct? > > Alex > > On Wednesday, January 27, 2016 at 12:30:20 AM UTC, Adam (Cloud Platform > Support) wrote: >> >> The frequency of cache clearances reported on the Stack Overflow is >> definitely not normal. The reason Memcache was chosen as the default >> session store is because it is cleared infrequently enough so as not to be >> noticed during the course of a single session, and session data is >> typically transient. >> >> On PHP the Cloud Storage stream wrapper >> <https://cloud.google.com/appengine/docs/php/googlestorage/> is probably >> the best choice actually, and it does cache file reads to Memcache. >> <https://cloud.google.com/appengine/docs/php/googlestorage/advanced> This >> is specific to PHP though as on the other runtimes Memcache caching is >> paired with Datastore (as is the case with NDB >> <https://cloud.google.com/appengine/docs/python/ndb/> on Python and >> Objectify <https://github.com/objectify/objectify> on Java), just some >> extra info. >> >> On Tuesday, January 26, 2016 at 11:26:42 AM UTC-5, Alex Kerr wrote: >>> >>> Actually further to my reply above, I found this old post recommending >>> using Cloud Storage instead: >>> https://groups.google.com/d/msg/google-appengine/ziMU2sXQg7c/5uat0Lxly2sJ >>> - is this a good idea? Seems like it at first glance for the reasons >>> mentioned (esp caching in memcache anyway). And adapting the example >>> session handler in the PHP docs should be easy I think: >>> http://php.net/manual/en/class.sessionhandlerinterface.php >>> >>> This would also be cheap given storage pricing and no data transfer >>> costs either way (in the same region). >>> >>> Can anyone see any drawbacks here? I'm assuming latency would be low >>> enough to be feasible...? What about if there are a large number of users >>> using my simultaneously - is there a limit to the number of simultaneous >>> streams to/from Cloud storage via the "gs://" file interface? >>> >>> I don't fully understand how cache would work here though (behind the >>> scenes via the gs:// interface - for a read, how is it known whether a >>> session file needs to be read from the cache or not, and if it's in the >>> cache, what happens if an updated session file was previously written to >>> Cloud Storage by the session handler? >>> >>> Thanks! >>> Alex >>> >>> >>> On Tuesday, January 26, 2016 at 1:23:51 AM UTC, Adam (Cloud Platform >>> Support) wrote: >>>> >>>> I don't have a code sample, but you would need to create a custom >>>> session handler with session_set_save_handler() >>>> <http://php.net/manual/en/function.session-set-save-handler.php> as >>>> per the suggestion provided in this post >>>> <http://stackoverflow.com/questions/20272634/storing-session-data-in-database-and-memcache> >>>> on >>>> Stack Overflow. >>>> >>>> On Monday, January 25, 2016 at 3:36:59 PM UTC-5, Alex Kerr wrote: >>>>> >>>>> Hi, >>>>> I'm using standard PHP session stuff for my web app, which means >>>>> session data is stored in App Engine's shared memcache. Google's docs >>>>> state >>>>> that this can get flushed so any logged in user sessions would fail. How >>>>> exactly do I add use of Datastore (or Cloud Storage?) into this process >>>>> so >>>>> that memcache is still used unless it gets flushed in which case >>>>> Datastore >>>>> is referred to? Is there a way to do this that minimises Datastore reads >>>>> & >>>>> writes and thus minimises cost and latency? I'm ideally after code (or >>>>> even >>>>> pseudocode) or even better a drop-in library or class :) >>>>> >>>>> Or, is a flush of the shared memcache so unlikely that it doesn't >>>>> really matter? >>>>> >>>>> Many thanks. >>>>> >>>> -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/6a6c2360-c3e5-4a6a-9626-06f5dae7532f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
