Hi Joakim,
replacing the session with a cookie is unfortunately not an option for us,
our web framework stores a lot of stuff in the session.
I don't even want to use memcache at all, the session ends up in the
datastore anyway, so if I had a choice, I would disable memcache here. It's
just built that way in GAE. I'd do anything to stop our users from
getting 500-errors, and I'd like a way to ignore memcache errors here.
I read that the sessions get stored into memcache namespace "_ahs", so I
tried to register a LogAndContinue-Errorhandler for that namespace, but
unfortunately that doesn't work either, at least not this way:
MemcacheServiceFactory.getMemcacheService("_ahs").setErrorHandler(new
LogAndContinueErrorHandler(Level.INFO) {
@Override
public void handleDeserializationError(InvalidValueException
thrown) {
log.error("gotcha!",thrown);
super.handleDeserializationError(thrown);
}
@Override
public void handleServiceError(MemcacheServiceException thrown)
{
log.error("gotcha!",thrown);
super.handleServiceError(thrown);
}
});
Any idea how else to register a handler to prevent this from killing our
requests?
Cheers,
Per
On Friday, July 6, 2012 7:24:26 PM UTC+2, Joakim wrote:
>
> If silent failure on write is to be acceptable, we need a way to make sure
> following requests do not read session from memcache, as it could return an
> old value. I am unaware of any way to accomplish this reliably without
> hitting the datastore, at which point you might as well not have the
> session in memcache at all.
>
> One possible alternative is to replace the entire session with storing
> encrypted data in a cookie, though this only works for smaller amounts of
> data as the maximum size for an entire cookie is generally said to be 4095
> bytes.
>
> Just my 2 cents.
> Joakim
>
> On Wednesday, July 4, 2012 11:38:34 PM UTC+2, Per wrote:
>>
>>
>> When using sessions, these are (also) stored in memcache by GAE.
>> Unfortunately, it seems like any memcache hiccup can crash the process,
>> turning an otherwise fine page into a 500 page on the way out.
>>
>> To me that looks like a design flaw. After all, Memcache is optional, and
>> its expected to be unavailable or breaking every now and then. As of 1.6
>> you can even provide a policy to silently ignore memcache errors inside
>> your application. We're using
>> setErrorHandler(ErrorHandlers.getConsistentLogAndContinue(Level.SEVERE))
>> with Objectify just fine, but it doesn't seem to have any effect on the
>> Session-Save process. This seems to be entirely outside our control.
>>
>> These errors are really annoying some of our clients. Is there maybe some
>> kind of other error handler I'm missing?
>>
>> Here's the stracktrace for reference:
>>
>>
>> com.google.appengine.api.memcache.MemcacheServiceException: Memcache put:
>> Error setting single item (_ahsOH7nik8bCRTbIXblKurKQQ)
>> at
>> com.google.appengine.api.memcache.AsyncMemcacheServiceImpl$7.transform(AsyncMemcacheServiceImpl.java:426)
>> at
>> com.google.appengine.api.memcache.AsyncMemcacheServiceImpl$7.transform(AsyncMemcacheServiceImpl.java:418)
>> at
>> com.google.appengine.api.memcache.MemcacheServiceApiHelper$RpcResponseHandler.convertResponse(MemcacheServiceApiHelper.java:60)
>> at
>> com.google.appengine.api.memcache.MemcacheServiceApiHelper$1.wrap(MemcacheServiceApiHelper.java:112)
>> at
>> com.google.appengine.api.memcache.MemcacheServiceApiHelper$1.wrap(MemcacheServiceApiHelper.java:105)
>> at
>> com.google.appengine.api.utils.FutureWrapper.wrapAndCache(FutureWrapper.java:57)
>> at
>> com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:98)
>> at
>> com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:90)
>> at
>> com.google.appengine.api.memcache.MemcacheServiceImpl.quietGet(MemcacheServiceImpl.java:28)
>> at
>> com.google.appengine.api.memcache.MemcacheServiceImpl.put(MemcacheServiceImpl.java:81)
>> at
>> com.google.apphosting.runtime.jetty.MemcacheSessionStore.saveSession(MemcacheSessionStore.java:39)
>> at
>> com.google.apphosting.runtime.jetty.SessionManager$AppEngineSession.save(SessionManager.java:164)
>> at
>> com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:41)
>> at
>> org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
>> at
>> com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
>> at
>> org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
>> at
>> org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
>> at
>> org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
>> at
>> org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
>> at
>> org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
>> at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
>> at
>> com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
>> at
>> org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
>> at org.mortbay.jetty.Server.handle(Server.java:326)
>> at
>> org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
>> at
>> org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
>> at
>> com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
>> at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
>> at
>> com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
>> at
>> com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:477)
>> at
>> com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
>> at
>> com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
>> at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
>> at
>> com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
>> at
>> com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
>> at
>> com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
>> at
>> com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
>> at java.lang.Thread.run(Thread.java:679)
>>
>>
>> And here's the code I tried, but which didn't help:
>>
>> MemcacheService service =
>> MemcacheServiceFactory.getMemcacheService();
>> service.setErrorHandler(new
>> LogAndContinueErrorHandler(Level.SEVERE));
>>
>> Any help would be appreciated!
>>
>> Kind regards,
>> Per
>
>
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