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https://issues.apache.org/jira/browse/PROTON-40?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466808#comment-13466808
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Ted Ross commented on PROTON-40:
--------------------------------
I've lowered the priority of this issue to minor.
There's a subtlety in the engine API that causes problems in the work sequence
for a receiver link. This is either a bug of a documentation issue.
Specifically, if an application is processing inbound messages on a link and it
invokes pn_settle before calling pn_advance, the queued count (on the link)
decrements twice and a delivery is lost.
The lack of batching of dispositions remains true but it is now an opportunity
for optimization rather than a data-loss issue.
Here's an updated trace:
[0x181da90:1] -> TRANSFER @20 [1, 0, b"\x00\x00\x00\x00\xff\x7f\x00\x00", 0,
false, false] (183) "..."
[0x181da90:1] -> TRANSFER @20 [1, 1, b"\x01\x00\x00\x00\xff\x7f\x00\x00", 0,
false, false] (183) "..."
[0x181da90:1] -> TRANSFER @20 [1, 2, b"\x02\x00\x00\x00\xff\x7f\x00\x00", 0,
false, false] (183) "..."
[0x181da90:1] <- FLOW @19 [3, 1021, 0, 1024, 1, 3, 8, null, false]
[0x181da90:1] <- DISPOSITION @21 [true, 0, 0, true, @36 []]
[0x181da90:1] <- DISPOSITION @21 [true, 1, 1, true, @36 []]
[0x181da90:1] <- DISPOSITION @21 [true, 2, 2, true, @36 []]
> Batching of message IDs in Disposition frames not supported
> -----------------------------------------------------------
>
> Key: PROTON-40
> URL: https://issues.apache.org/jira/browse/PROTON-40
> Project: Qpid Proton
> Issue Type: Bug
> Components: proton-c
> Reporter: Ted Ross
> Priority: Minor
>
> If a proton client calls pn_disposition on more than one received delivery
> between the sending of disposition frames, the next disposition frame will
> reference only the first message in the batch.
> Ref: This code fragment from pn_post_disp which uses the same value for
> first and last id:
> return pn_post_frame(transport->disp, ssn_state->local_channel,
> "DL[oIIo?DL[]]", DISPOSITION,
> link->endpoint.type == RECEIVER, state->id,
> state->id,
> delivery->local_settled,
> (bool)code, code);
> The result of this is that dispositions for messages are lost and senders
> hang if there are credit windows of greater than one. It would be ok, but
> inefficient, to send multiple singleton dispositions. In fact, proton simply
> skips one or more disposition so the settlement of messages is incomplete.
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