AWSQS: Google App Engine Maintence scheduled for 2009.08.18 16:00 UTC for one hour

[C Sowa]

FYI, just received this notice:
http://groups.google.com/group/google-appengine-downtime-notify/browse_thread/thread/994ca7857dbcf246#

The impact on AWSQS will be variable.


Signing Requests:

Worst case is you will receive an XML document with an error message
and an HTTP 500 error code.

If, however, you have made a "recent" signing request and your AWS
Id / Key pair is still in memory at the time of the outage, AWSQS will
be able to sign your request and respond as usual, as long as GAE does
not flush the app from memory in the interim. The exact nature of
"recent", however, depends on many external factors.


Accumulated usage counts:

Counts of requests that are successful will not be accumulated for
this period and for up to twenty minutes before the outage.


Thanks for your patience !

[C Sowa]

Follow up:

Apparently there was little or no impact to AWSQS operations (no
errors logged), with the possible exception of some missing request
counts. Despite the original GAE downtime notice stating that both
database and memcache reads would be affected, either they weren't, or
things were handled in such a way as to minimize impact (e.g., perhaps
not having both APIs down at the same time).

However, GAE's default memcache failure handling (no exceptions
thrown, basically looks like cache misses) seems inadequate to me, so
I've added some custom exceptions to my cache wrapper class. Handlers
with error loggers were already present in most cases in expectation
of errors that never occurred. This will allow more detailed analysis
of application behavior during limited capability conditions in the
future. Changes to be rolled out tonight, but this should be entirely
transparent in normal production conditions.