Hi Nick,
Thank you very much for your reply.
The contention is identified in the log:
1.
198.66.245.68 - - [22/Apr/2009:10:19:43 -0700] "GET
/setlocation?ll=40.064929,-75.242851&uid=e5b25e2d512b10fc913c2f8c290f55114550135a&c=28
HTTP/1.1" 500 916 - "gzip(gfe)"
2. E 04-22 10:19AM 43.004
too much contention on these datastore entities. please try again.
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 921, in get
user.put()
File "/base/python_lib/versions/1/google/appengine/ext/db/__init__.py",
line 669, in put
return datastore.Put(self._entity)
File "/base/python_lib/versions/1/google/appengine/api/datastore.py",
line 166, in Put
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)
TransactionFailedError: too much contention on these datastore
entities. please try again.
But I must admit that although this request can only cause a put() on that
specific record once every five minutes there could also come a put() from
another request. But my guess is that at most two puts on the same record
can happen within a short period of time.
Can the contention be caused by just two puts? I guess it could...
Would it be an idea to catch this exception and try the put again?
Sincerely,
/morten
On Thu, Apr 23, 2009 at 10:46 AM, Nick Johnson <nick.john...@google.com>wrote:
>
> Hi Morten,
>
> The likelihood you'll see a datastore timeout bears a relation to how
> expensive your operation is, but external factors - such as transient
> issues on our Bigtable Tabletservers - can have a much larger impact.
> As such, you'll occasionally (hopefully only very occasionally) see
> timeouts even on 'simple' operations like retrieving an entity by its
> key. The best approach is generally to retry the operation in
> circumstances like these.
>
> Regarding contention, how are you identifying it as such? Are you
> using explicit transactions, and getting TransactionFailedError? This
> is usually due to contention, but could also be caused by multiple
> timeouts.
>
> -Nick Johnson
>
> >
>
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