[jboss-jira] [JBoss JIRA] (JGRP-1648) FRAG/FRAG2: message batching can lead to incorrect ordering

[Bela Ban (JIRA)]

Bela Ban created JGRP-1648:
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             Summary: FRAG/FRAG2: message batching can lead to incorrect ordering
                 Key: JGRP-1648
                 URL: https://issues.jboss.org/browse/JGRP-1648
             Project: JGroups
          Issue Type: Feature Request
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 3.4


The implementation of up(MessageBatch) in FRAG and FRAG2 is incorrect because messages reassmbled from fragments are re-inserted into the batch at the end rather than in the place of the fragments.
Example: when we receive P1 P2 P3:1 P3:2 P3:3 and P4 (P3 was split into 3 fragments by sender P), then the resulting batch (see the code below) will be P1 P2 P4 P3, as the re-assembled message P3 is added to the *end* of the batch rather than re-inserted in-place.


{code}
    public void up(MessageBatch batch) {
        for(Message msg: batch) {
            FragHeader hdr=(FragHeader)msg.getHeader(this.id);
            if(hdr != null) { // needs to be defragmented
                batch.remove(msg);
                Message assembled_msg=unfragment(msg,hdr);
                if(assembled_msg != null)
                    batch.add(assembled_msg); // the newly added message will not get iterated over by the current iterator !
            }
        }
        if(!batch.isEmpty())
            up_prot.up(batch);
    }
{code}

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