Cluster ordinal and ordinal should be consistent

[hannes-ucsc]

The cluster ordinal is assigned as instances enter the running state. The ordinal is determined by an ordering on the composite key (launch time, private IP and instance ID) which is not necessarily consistent with the cluster ordinal.

We should include cluster name and cluster ordinal as the dominant members in the composite key of the ordinal ordering. The problem is that these two are derived from instance tags, not attributes of the boto.ec2.instance.Instance objects which is what the key function currently is limited to accessing.

We could bind() the instances before sorting them. This might be expensive.

We could access the instance.tags dictionary in the key function. Some tags might not be populated.

[hannes-ucsc]

Thanks, @arkal for helping think this through.

[arkal]

:)