Not sure if it is related, but I was getting some interesting memcache
errors that I had to work around:
javax.servlet.ServletContext log: Exception while dispatching incoming
RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method
'public abstract java.lang.String
com.WikiHop.client.SearchPath.find(java.lang.String,java.lang.String)
throws java.lang.IllegalArgumentException' threw an unexpected
exception: com.google.appengine.api.memcache.InvalidValueException: IO
exception parsing value of '3434143'
at
com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:
378)
...
Caused by: com.google.appengine.api.memcache.InvalidValueException: IO
exception parsing value of '3434143'
at
com.google.appengine.api.memcache.MemcacheServiceImpl.get(MemcacheServiceImpl.java:
289)
at
com.google.appengine.api.memcache.jsr107cache.GCache.get(GCache.java:
166)
On Dec 16, 2:53 pm, Tom Phillips <[email protected]> wrote:
> Certainly Ikai,
>
> Firstly, some of my logs (url and classes slightly modified to hide
> some app details) that show how only the same instance picks up the
> entry. I'm determining and logging the instance using a UUID that I
> assign to a static class variable. The key for the cache lookup is
> passed in as a request query parameter to the followup requests.
>
> Here are two runs of the code to follow. In each, the bottom log is
> the cache entry being added. The next two are subsequent requests that
> both look for the entry. The entry is only found when then instance
> matches, regardless of which follow-up request.
>
> This first run shows how the bottom instance is different from the one
> that services both followup requests. So they don't find the entry:
>
> 50.16.21.20 - - [16/Dec/2010:11:19:40 -0800] "GET /processg?key=619001
> W 12-16 11:19AM 40.373 com.mycode.CallProcessGatherServlet doGet:
> LOOKING IN CACHE on Instance: b7c866f2-d74b-45df-9993-1d2c4705d3d1
> W 12-16 11:19AM 40.373 com.mycode.CallProcessGatherServlet doGet:
> Message NOT found in cache for 619001 - building
>
> 50.16.21.20 - - [16/Dec/2010:11:19:35 -0800] "POST /startreminder?
> key=619001&pname=Optimal+Physio+Dev&atime=Friday+December+17%2C
> +2%3A18+PM&rlang=en&rvoice=woman
> W 12-16 11:19AM 33.173 com.mycode.CallMLServlet doGet: LOOKING IN
> CACHE on Instance: b7c866f2-d74b-45df-9993-1d2c4705d3d1
> W 12-16 11:19AM 33.173 com.mycode.CallMLServlet doGet: Message NOT
> found in cache for 619001 - building
>
> 0.1.0.2 - - [16/Dec/2010:11:19:08 -0800] "POST /tasks/voicereminder
> HTTP/1.1" 200 105 "http://cliniconexdev.appspot.com/cron/
> processreminders?state=new"
> W 12-16 11:19AM 08.581 com.mycode.CallPhoneAdapter doSend: CACHING
> message from instance: e4d5452e-c744-4333-b1d4-38eb55f97445
> W 12-16 11:19AM 08.585 com.mycode.CallPhoneAdapter doSend: Adding to
> cache with key:619001
> W 12-16 11:19AM 08.604 com.mycode.CallPhoneAdapter doSend:
> Successfully cached reminder 619001
>
> In this second run, the first followup request hits the same instance
> that added it, and finds it. The second isn't so lucky, hitting a
> different instance
>
> 184.73.13.122 - - [16/Dec/2010:11:22:39 -0800] "GET /processg?
> key=620001
> W 12-16 11:22AM 38.782 com.mycode.CallProcessGatherServlet doGet:
> LOOKING IN CACHE on Instance: ff6ef71c-a017-4316-aa81-e77db741702b
> W 12-16 11:22AM 38.782 com.mycode.CallProcessGatherServlet doGet:
> Message NOT found in cache for 620001 - building
>
> 204.236.222.67 - - [16/Dec/2010:11:22:28 -0800] "POST /startreminder?
> key=620001&pname=Optimal+Physio+Dev&atime=Friday+December+17%2C
> +2%3A18+PM&rlang=en&rvoice=woman HTTP/1.1" 200 683 -
> "CallProxy/0.7,gzip(gfe)" "cliniconexdev.appspot.com" ms=24 cpu_ms=23
> api_cpu_ms=0 cpm_usd=0.000805
> W 12-16 11:22AM 28.127 com.mycode.CallMLServlet doGet: LOOKING IN
> CACHE on Instance: b7c866f2-d74b-45df-9993-1d2c4705d3d1
> W 12-16 11:22AM 28.134 com.mycode.CallMLServlet doGet: Message for
> entry 620001 FOUND in cache - using
>
> 0.1.0.2 - - [16/Dec/2010:11:22:06 -0800] "POST /tasks/voicereminder
> HTTP/1.1" 200 105 "http://cliniconexdev.appspot.com/cron/
> processreminders?state=new" "AppEngine-Google;
> (+http://code.google.com/appengine)" "cliniconexdev.appspot.com"
> ms=506 cpu_ms=1664 api_cpu_ms=941 cpm_usd=0.046287 queue_name=reminder-
> queue task_name=17196018701084092971
> W 12-16 11:22AM 05.964 com.mycode.CallPhoneAdapter doSend: CACHING
> message from instance: b7c866f2-d74b-45df-9993-1d2c4705d3d1
> W 12-16 11:22AM 05.965 com.mycode.CallPhoneAdapter doSend: Adding to
> cache with key:620001
> W 12-16 11:22AM 05.984 com.mycode.CallPhoneAdapter doSend:
> Successfully cached reminder 620001
>
> Here is the code that creates the cache (if required) and adds the
> entry in the first request:
> Cache cache = null;
>
> log.warning("CACHING message from instance: " + jvmId);
>
> try {
> cache = CacheManager.getInstance().getCache("cache_reminderVoice");
> } catch (final Exception e) {
> log.fine("Cache cache_reminderVoice not yet created");
>
> }
>
> if (cache == null) {
> try {
> cache = CacheManager.getInstance().getCacheFactory()
> .createCache(Collections.emptyMap());
> CacheManager.getInstance().registerCache("cache_reminderVoice",
> cache);
> } catch (final CacheException e) {
> log.warning("Could not create/register cache
> cache_reminderVoice: "
> + e.getMessage());
> }
>
> }
>
> try {
> // Put the value into the cache.
> log.warning("Adding to cache with key:" +
> reminder.getKeyId().toString());
> if (parts == null) {
> log.warning("Hmmmm..parts was null");
> }
> cache.put(reminder.getKeyId().toString(), parts);
>
> // Get the value from the cache just to test it is there
> final CacheEntry entry = cache.getCacheEntry(reminder.getKeyId()
> .toString());
> if (entry != null) {
> log.warning("Successfully cached reminder " +
> reminder.getKeyId());
> } else {
> log.warning("Could not get cached voice message parts");
> }
> } catch (final Exception e) {
> log.warning("FAILED to cache voice message parts: " +
> e.getMessage());
> }
>
> Here is the code (same in both request handlers) that retrieves the
> entry from the cache:
>
> Cache cache = null;
>
> log.warning("LOOKING IN CACHE on Instance: " +
> TwilioPhoneAdapter.jvmId);
>
> try {
> cache =
> CacheManager.getInstance().getCache("cache_reminderVoice");
> if (cache != null) {
> parts = (VoiceParts) cache.get(key);
> }
> if (parts != null) {
> log.warning("Message for entry " + key + " FOUND in cache -
> using");
> }
> } catch (final Exception e) {
> log.warning("Cache cache_reminderVoice not yet created");
> }
>
> if (parts == null) {
> log.warning("Message NOT found in cache for " + key + " -
> building");
> parts = ...//Builds the parts up from scratch
> }
>
> Thanks for checking it out Ikai.
> Tom
>
> On Dec 16, 1:32 pm, "Ikai Lan (Google)" <[email protected]>
> wrote:
>
> > This is definitely not a design intent. Can you post any code or
> > reproduction steps?
>
> > --
> > Ikai Lan
> > Developer Programs Engineer, Google App Engine
> > Blogger:http://googleappengine.blogspot.com
> > Reddit:http://www.reddit.com/r/appengine
> > Twitter:http://twitter.com/app_engine
>
> > On Wed, Dec 15, 2010 at 7:42 PM, Tom Phillips <[email protected]> wrote:
> > > I posted on this this in the java forum, but no traction there and I
> > > suspect it's not java specific.
>
> > > Memcache entries seem to be being scoped to an instance, not global.
> > > After a cache entry is made, it can be retrieved fine for any request
> > > that goes to that same instance. Any request to one of the other
> > > instances never finds the entry in the cache.
>
> > > Bug in Always On? Bug in 1.4.0? Design intent?
>
> > > Thanks,
> > > Tom
>
> > > --
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