Treat DB save errors as fetch retries

In the hub right now when the DB times out on content fetch, we'll rely on
the task queue to do the retries. This causes back-off, which is bad for
throughput. Instead, we should reschedule the task (possibly with the same
ETA) on the retry queue.

Traceback (most recent call last):
  File
"/base/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line
509, in __call__
    handler.post(*groups)
  File
"/base/data/home/apps/pubsubhubbub/feed-ids.336557603768777282/main.py",
line 319, in decorated
    return func(myself, *args, **kwargs)
  File
"/base/data/home/apps/pubsubhubbub/feed-ids.336557603768777282/main.py",
line 2294, in post
    if parse_feed(feed_record, headers, content):
  File
"/base/data/home/apps/pubsubhubbub/feed-ids.336557603768777282/main.py",
line 2211, in parse_feed
    db.run_in_transaction(txn)
  File "/base/python_lib/versions/1/google/appengine/api/datastore.py",
line 1819, in RunInTransaction
    DEFAULT_TRANSACTION_RETRIES, function, *args, **kwargs)
  File "/base/python_lib/versions/1/google/appengine/api/datastore.py",
line 1948, in RunInTransactionCustomRetries
    raise _ToDatastoreError(err)
Timeout

Original issue reported on code.google.com by bslatkin on 24 Sep 2009 at 4:57

ankurpiyush26 / pubsubhubbub

Treat DB save errors as fetch retries #77