On 1 March 2017 at 16:08, Rob Godfrey <rob.j.godf...@gmail.com> wrote:
> On 1 March 2017 at 16:56, Gordon Sim <g...@redhat.com> wrote:
>
>> On 01/03/17 15:37, Gordon Sim wrote:
>>
>>> On 01/03/17 14:31, Kai Hudalla wrote:
>>>
>>>> Assuming that we have a link established between a Receiver (r) and a
>>>> Sender (s)
>>>> with a current link-credit of 4 and a delivery count of 20 on both sides.
>>>>
>>>> When invoking r.flow(6), the given credit (6) is _added_ to the
>>>> receiver's
>>>> current credit resulting in r.getCredit() returning 10.
>>>>
>>>> When the FLOW is then flushed to the sender, the sender seems to _add_
>>>> the link-
>>>> credit from the FLOW to its already existing credit. Analogously, this
>>>> results in
>>>> s.getCredit() now returning 10.
>>>>
>>>> With this approach, it doesn't seem to be possible to stop the sender
>>>> from
>>>> sending messages. The only thing a receiver can do is to wait until
>>>> the sender
>>>> has used up all its credit (which may be a lot given that with the
>>>> current
>>>> approach the sender's credit can pile up substantially).
>>>>
>>>> Or am I mistaken?
>>>>
>>>
>>> Can you specify a negative value to Receiver::flow()? I.e. would that
>>> subtract from the credit and send a corresponding flow to the sender?
>>>
>>
>> That seems to work for proton-c which has a similar API. (Not ideal, but a
>> workaround at least).
>>
>
> Adding a convenience "stop()" method in the API to perform the interaction
> as described in section 2.6.10 Stopping a link
> <http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html#doc-idp429232>
> would
> be a nice addition I think.
>
> -- Rob
>
Thats essentially what I've always had in mind. Theres probably more
to consider around waht people can do while the link is actually
stopping, e.g. what happens if flow() is called again before the peer
actually stops (if they reply at all..) etc.
>
>>
>> $ PN_TRACE_FRM=1 python revoke_credit.py
>>> [0x563feb999040]: -> SASL
>>> [0x563feb999040]: <- SASL
>>> [0x563feb999040]:0 <- @sasl-mechanisms(64)
>>> [sasl-server-mechanisms=@PN_SYMBOL[:ANONYMOUS,
>>> :PLAIN]]
>>> [0x563feb999040]:0 -> @sasl-init(65) [mechanism=:ANONYMOUS,
>>> initial-response=b"anonymous@localhost.localdomain"]
>>> [0x563feb999040]:0 <- @sasl-outcome(68) [code=0]
>>> [0x563feb999040]: -> AMQP
>>> [0x563feb999040]:0 -> @open(16)
>>> [container-id="023946f1-0197-4559-bd72-7fff5a687958",
>>> hostname="localhost", channel-max=32767]
>>> [0x563feb999040]:0 -> @begin(17) [next-outgoing-id=0,
>>> incoming-window=2147483647, outgoing-window=2147483647]
>>> [0x563feb999040]:0 -> @attach(18)
>>> [name="023946f1-0197-4559-bd72-7fff5a687958-examples",
>>> handle=0, role=true, snd-settle-mode=2, rcv-settle-mode=0,
>>> source=@source(40) [address="examples", durable=0, timeout=0,
>>> dynamic=false], target=@target(41) [durable=0, timeout=0, dynamic=false],
>>> initial-delivery-count=0, max-message-size=0]
>>> [0x563feb999040]: <- AMQP
>>> [0x563feb999040]:0 <- @open(16)
>>> [container-id="a6022696-2483-49f5-8ea6-a6f50db0e7ae",
>>> channel-max=32767, offered-capabilities=@PN_SYMBOL[:"ANONYMOUS-RELAY"],
>>> properties={:product="qpid-cpp", :version="1.36.0", :platform="Linux",
>>> :host="localhost.localdomain"}]
>>> [0x563feb999040]:0 <- @begin(17) [remote-channel=0, next-outgoing-id=0,
>>> incoming-window=2147483647, outgoing-window=2147483647]
>>> [0x563feb999040]:0 <- @attach(18)
>>> [name="023946f1-0197-4559-bd72-7fff5a687958-examples",
>>> handle=0, role=false, snd-settle-mode=2, rcv-settle-mode=0,
>>> source=@source(40) [address="examples", durable=0, timeout=0,
>>> dynamic=false, distribution-mode=:move], target=@target(41) [durable=0,
>>> timeout=0, dynamic=false], initial-delivery-count=0, max-message-size=0]
>>> [0x563feb999040]:0 -> @flow(19) [next-incoming-id=0,
>>> incoming-window=2147483647, next-outgoing-id=0, outgoing-window=2147483647,
>>> handle=0, delivery-count=0, link-credit=100, drain=false]
>>> [0x563feb999040]:0 <- @transfer(20) [handle=0, delivery-id=0,
>>> delivery-tag=b"\x00\x00\x00\x00", message-format=0, settled=false,
>>> more=false] (46) "\x00Sp\xc0\x08\x05BP\x00@@R\x
>>> 03\x00St\xc1\x14\x04\xa1\x02snR\x01\xa1\x02ts\x81\x14\xa7\
>>> xccS\x8fD\x99\x84\x00Sw\xa1\x03one"
>>> one
>>> [0x563feb999040]:0 -> @flow(19) [next-incoming-id=1,
>>> incoming-window=2147483647, next-outgoing-id=0, outgoing-window=2147483647,
>>> handle=0, delivery-count=1, link-credit=0, drain=false]
>>> [0x563feb999040]:0 -> @disposition(21) [role=true, first=0, last=0,
>>> settled=true, state=@accepted(36) []]
>>>
>>
>> If there are messages in flight when you revoke the credit, they will
>> still be delivered from my tests.
>>
>>
>>
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