Safer usage of memcache service in Google App Engine

gistfile1.groovy

// when doing the following...

if (ms.containsKey(key)) {
   return ms.get(key);
} else {
   // ... fetch and cache
}

// you run the risk that between the existence check in the if statement
// and the moment you actually call the get,
// memcache might have actually expired that key/value

// instead, in Gaelyk, we tend to do:

def result = ms.get(key)
if (ms == null) {
     // ... fetch and cache
}
return result