Longevity

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Longevity is the degree to which an ACP can support long-running conversations caused by long-running operations. The primary problem for conversation with long-running operations is that there could be huge span of times when processes are uncertain of each other’s states. Consider a simple request/reply conversation where some process A sends a request to B, but B takes a long time to execute the requested operation and sends back a reply. While waiting for the reply, process A doesn’t know if B received the request, has failed, or is just taking a long time. ACPs that support long-running operations include mechanisms for exchanging state information independent of results.

We rank the longevity for ACP patterns according to the following 3-point rubric:

Rank/Criteria

3. The problem (P) addressed by the pattern is primarily concerned with long-running conversations and the solution (S) can guarantee the following in successful conversations:

  • a. Participants made aware of each other’s states in periodically.
  • b. Each participant in the conversation can detect when other participants are no longer available or accessible.

2. P is concerned with long-running conversations and S provides for (a).

1. P is not concerned with long-running conversations and S doesn’t limit longevity.

Next: Adaptability for Scalable Distribution | Return to Qualities of Communication Protocols