Question

I’m working on an application that will run on Google App Engine. I would like it to respond gracefully to App Engine maintenance periods.

According to the documentation, memcache will simply not store or retrieve data during maintenance periods:

During a read-only maintenance period,
calls to the memcache API will not
throw exceptions but will instead
return False for set() calls and None
for get() calls (just like any other
cache miss). In addition, memcache API
calls will return immediately during
this period, without any additional
latency.

Does this apply to incr() calls as well? It seems like it should, but I cannot find any documentation to this effect and I want to be sure.

Answer 1

The documentation for incr() states:

The return value is a new long integer value, or None if key was not in the cache or could not be incremented for any other reason.

As the documentation also makes clear that you’re unable to set or get data during maintenance, and incr() is really just a helper function around set(), you should expect a return value of None during maintenance periods for the incr() function.