[jira] [Commented] (QPID-8484) [Broker-J] Reimplementation of the limit number of connections per user

["Alex Rudyy (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/QPID-8484?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17220574#comment-17220574 ] 

Alex Rudyy commented on QPID-8484:
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Hi [~lacam],

I agree that limiting connection number and frequency would be better to do as a resource restriction rather than ACL. Implementation of the special broker plugin for it seems like a good idea. Though, if it would be difficult to do, I do not mind adding the functionality into the broker-core. It would be beneficial, if you could share some design for the work or at least provide a bit more details on the implementation approach.

{quote}
ACL logic compares the actual counter value with the limit for every connection (the counter value at the moment of the acl rule check) and 2,3 … or all 7 connections can be denied. The ACL logic does not know which connection broke the limit.
{quote}

That is a defect. The intention was to deny only connections above the limit. I will try to fix the issue.

> [Broker-J] Reimplementation of the limit number of connections per user
> -----------------------------------------------------------------------
>
>                 Key: QPID-8484
>                 URL: https://issues.apache.org/jira/browse/QPID-8484
>             Project: Qpid
>          Issue Type: Improvement
>          Components: Broker-J
>    Affects Versions: qpid-java-broker-8.0.1, qpid-java-broker-8.0.2
>            Reporter: Marek Laca
>            Priority: Major
>              Labels: connection, limit, user
>
> If some user creates too much connections, he can prevent other users from connecting to amqp ports. [QPID-8369|https://issues.apache.org/jira/projects/QPID/issues/QPID-8369] added an ability to limit maximum open connections per user.
>  The user connection limit was implemented as ACL dynamic rule and it is part of the access control logic.
> But I have queries about the implementation:
>  * The connection count of the user is not checked properly.
>  For example 2 connections should be rejected when an user has limit 5 and tries to open 7 parallel connections. But what happens:
>  ## Every connection increments the counter then the counter will be 7.
>  ## ACL logic compares the actual counter value with the limit for every connection (the counter value at the moment of the acl rule check) and 2,3 … or all 7 connections can be denied. The ACL logic does not know which connection broke the limit.
>  ## The counter is decremented when connection is closed.
>  * ACL rules were static and so the result of the check did not vary in time and the Broker could cache the result ALLOWED or DENIED. From my point of view a dynamic check should not be part of the ACL logic because it makes ACL logic time dependent.
>  * The user connection limit should be checked as soon as possible.
> I suggest to introduce a new plugin (similar to the access control provider plugin) that will hold the user's counters of open connections.
>  It will provide following functionality:
>  * It registers new connections for given user and the connection will be rejected if the user breaks the limit. The registration and update of user's counters will be an atomic operation.
>  * It de-registers the connections for given user.
> If user breaks the limit then the connection will be closed with proper response "amqp:resource-limit-exceeded" instead of "amqp:not-allowed".



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