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https://issues.apache.org/jira/browse/UIMA-3713?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jerry Cwiklik updated UIMA-3713:
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Fix Version/s: 1.1.0-Ducc
> Modify DUCC to deal with out of order messages
> ----------------------------------------------
>
> Key: UIMA-3713
> URL: https://issues.apache.org/jira/browse/UIMA-3713
> Project: UIMA
> Issue Type: Bug
> Components: DUCC
> Affects Versions: 1.0.0-Ducc
> Reporter: Jerry Cwiklik
> Assignee: Jerry Cwiklik
> Fix For: 1.1.0-Ducc
>
>
> Its been observed that an Agent killed a JD immediately after starting it.
> This happens rarely but does occur.Looking through the Agent log I see that
> multiple OR state updates arrive almost instantly. In one of the states the
> OR requests a new process to be started while in the second state the process
> doesnt even exist. So the agent first launches the process and then
> subsequently kills it as this indicates a ghost process. A ghost process is
> one that exists in the agent's inventory but is not present in the OR state
> update.
> This is happening due to out of order messages. The OR generates its state
> updates at regular intervals (every 20 secs) and sends them to a jms topic.
> In this case, the PM fetches the update, trims it and sends it to agents. Not
> 100% sure, but it looks like there is some kind of a delay in a broker which
> causes messages to be held and than subsequently delivered in rapid
> succession.
> The agent should be able to cope with this. The OR should add a sequence
> number to each state it publishes. The PM should forward this sequence when
> it sends a trimmed state to the agents. The agent should compare received
> sequence against what it received on the previous update.If the new sequence
> is larger than the previous one, processing should be allowed. If the new
> sequence is smaller then previous, the message should be discarded.
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