You get a Timeout error on a get() operation. I solved it by doing a retry when I get an exception. If the retry also failed I re-raise the exception to get it logged
2009/4/22 Morten Bek Ditlevsen <morten....@gmail.com>: > > Hi there, > I'm in the process of moving the database part of a social networking > site to GAE. > Each client sends a request to the server every 5 minutes with > location information. From the location I calculate a list of geoboxes > to store with the client's profile if the location is significantly > different from the last request. > > If I get requests more often than every 5 minutes, I send back an > empty response (clients send unique id, so a 5 minute memcache object > will tell me if I receive too many requests) so as not to burden the > server too much. > > > I already have a server up and running (apache, php, postgres) - and I > am experimenting with forwarding requests to GAE to measure load and > performance. > > In general everything looks good, but I am getting the occational > error on the server: > > One error I get is the datastore timeout. I am quite certain that I > write a record at max. every 5 minutes. For that record I only have > one composite index, and that index only has one list entry - so I > don't have 'exploding indexes'. Although the list may have 30-40 > entries, so 30-40 index entries must be created. > > The second error I get - less frequently - is data contention. The > record I update (still at max every 5 mins) is unique to each user, so > I don't understand where the contention comes from. > > The last error is actually the one that puzzles me the most. Timeout > while doing datastore fetches. Traceback is similar to: > > Traceback (most recent call last): > File "/base/python_lib/versions/1/google/appengine/ext/webapp/ > __init__.py", line 501, in __call__ > handler.get(*groups) > File "/base/data/home/apps/grindrservr/3.332855696947742792/ > main.py", line 870, in get > user = User.get_by_key_name(key_name) > File "/base/python_lib/versions/1/google/appengine/ext/db/ > __init__.py", line 849, in get_by_key_name > return get(*keys) > File "/base/python_lib/versions/1/google/appengine/ext/db/ > __init__.py", line 1044, in get > entities = datastore.Get(keys) > File "/base/python_lib/versions/1/google/appengine/api/ > datastore.py", line 221, in Get > raise _ToDatastoreError(err) > File "/base/python_lib/versions/1/google/appengine/api/ > datastore.py", line 1965, in _ToDatastoreError > raise errors[err.application_error](err.error_detail) > Timeout > > As far as I can tell the get_by_key_name should be so fast that it's > basically instant, so I don't understand the timeout here. > > I should state that out of maybe 300.000 requests only about 30 fail, > so that may actually be quite ok. But I would like to understand the > errors and if possible program my way around them. > > Any comments greatly appreciated. > > Sincerely, > /morten > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
