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https://issues.apache.org/jira/browse/DISPATCH-630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15853745#comment-15853745
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Rob Godfrey edited comment on DISPATCH-630 at 2/6/17 9:34 AM:
--------------------------------------------------------------
{quote}
I actually think it is defined. In particular, the existing mechanism already
in place for JMS isnt really effective unless that behaviour is defined. We
even incorporated it into the capability name.
{quote}
I disagree because what you have here is a "client" that is behaving in an
inconsistent manner. If the client is behaving per the JMS mapping spec, it
MUST set the desired capability, so there is no issue. The notion of a
container id is that it represents a single logical entity ... what you are
describing is an entity that is changing its desires/nature over time. I think
enforcing that a distributed network needs to look up every connection (and
remember every connection) just in case the client is behaving in an
inconsistent manner is too large a burden to place on the server side... and I
can see no use case for providing this support. In particular this would mean
that every connection establishment would need to utilize some sort of global
synchronization lock to guard against the case of two connections for the same
container-id being created "at the same time".
{quote}
I think it would probably be further required to define here that an existing
connection which requested sole of the container use but didnt use the property
to request prior connections be dropped, also cant then be dropped for a
connection that later does, since doing so would be violating the contract
agreed with the earlier connection.
{quote}
Again I disagree - The container-id represents a single entity... the
behaviour here should either be undefined or (since the client container has
clearly changed its mind) the server container should respect the most recent
wish of the client. Again, in practice this should never occur as the client
will have a fixed mode of operation (JMS-like, MQTT-like, or doesn't desire
sole connection behaviour).
{quote}
Some more details of the JMS mechanism for completeness, are: If the server
fails the connection attempt, we specified it should add a symbol keyed boolean
property of "amqp:connection-establishment-failed" as a hint that the Open has
failed and a Close will follow immediately with the reason (since the spec has
no way to convey that scenario, unlike with Attach/Detach where it does by
setting the appropriate source/target as a null). We also specified it should
add an entry to the Close error info map to hint that the container-id was the
cause, by adding an symbol key/value of "invalid-field"/"container-id",
allowing the client to specifically throw InvalidClientIDException as required.
{quote}
I'd like to define this behaviour somewhere in an AMQP specification too - I'm
not sure whether that should go in the same document as connection uniqueness,
or in a separate document dealing solely with "Connection establishment failure"
was (Author: rgodfrey):
{quote}
I actually think it is defined. In particular, the existing mechanism already
in place for JMS isnt really effective unless that behaviour is defined. We
even incorporated it into the capability name.
{quote}
I disagree because what you have here is a "client" that is behaving in an
inconsistent manner. If the client is behaving per the JMS mapping spec, it
MUST set the desired capability, so there is no issue. The notion of a
container id is that it represents a single logical entity ... what you are
describing is an entity that is changing its desires/nature over time. I think
enforcing that a distributed network needs to look up every connection (and
remember every connection) just in case the client is behaving in an
inconsistent manner is too large a burden to place on the server side... and I
can see no use case for providing this support.
{quote}
I think it would probably be further required to define here that an existing
connection which requested sole of the container use but didnt use the property
to request prior connections be dropped, also cant then be dropped for a
connection that later does, since doing so would be violating the contract
agreed with the earlier connection.
{quote}
Again I disagree - The container-id represents a single entity... the
behaviour here should either be undefined or (since the client container has
clearly changed its mind) the server container should respect the most recent
wish of the client. Again, in practice this should never occur as the client
will have a fixed mode of operation (JMS-like, MQTT-like, or doesn't desire
sole connection behaviour).
{quote}
Some more details of the JMS mechanism for completeness, are: If the server
fails the connection attempt, we specified it should add a symbol keyed boolean
property of "amqp:connection-establishment-failed" as a hint that the Open has
failed and a Close will follow immediately with the reason (since the spec has
no way to convey that scenario, unlike with Attach/Detach where it does by
setting the appropriate source/target as a null). We also specified it should
add an entry to the Close error info map to hint that the container-id was the
cause, by adding an symbol key/value of "invalid-field"/"container-id",
allowing the client to specifically throw InvalidClientIDException as required.
{quote}
I'd like to define this behaviour somewhere in an AMQP specification too - I'm
not sure whether that should go in the same document as connection uniqueness,
or in a separate document dealing solely with "Connection establishment failure"
> Detecting connections with the same container-id
> ------------------------------------------------
>
> Key: DISPATCH-630
> URL: https://issues.apache.org/jira/browse/DISPATCH-630
> Project: Qpid Dispatch
> Issue Type: Improvement
> Reporter: Paolo Patierno
> Priority: Minor
>
> Using the router in the EnMasse project and looking into the MQTT
> specification we have the following problem on the current EnMasse
> implemetation.
> The MQTT specification says the following ...
> Let's imagine that a client is connected to the broker with client id "1234"
> and that another client tries to connect with same client id. The broker will
> shut down the connection with first client opening the new one.
> Now with our MQTT support, the MQTT gateway can run as multiple instances
> (multiple pods) so this check can't be executed by the gateway locally
> because a client "1234" could connect to MQTT GW-1 and another client (always
> "1234") could connect to the MQTT GW-2 and the gateways don't know about each
> other. The common point they have is the router network inside EnMasse and
> the fact that for each MQTT client a new AMQP connection is created on the
> other side attaching a link with this name : $mqtt.to.<client-id>
> The following idea came ...
> If during the connection we use a container-id that is equals to the
> client-id, could the router have a feature for detecting connections with
> same container-id and providing a way to close the previous ones ?
> It should be an information shared (and cached ?) by routers in their
> inter-router protocol.
> If not at connection level, maybe at link attachment level ? (when two
> clients attach to the same $mqtt.to.<client-id> link)
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