Tellier Benoit created JAMES-2794:
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Summary: RabbitMQ Mail Queue deleted elements are dequeued
Key: JAMES-2794
URL: https://issues.apache.org/jira/browse/JAMES-2794
Project: James Server
Issue Type: Bug
Components: Queue, rabbitmq
Affects Versions: master
Reporter: Tellier Benoit
Assignee: Tellier Benoit
We expect that deleted elements not to be dequeued, which RabbitMQ MailQueue
fails to do.
While working on this bug solving here
https://github.com/linagora/james-project/pull/2445 , I realized one of the
invariants we enforced on MailQueue does not hold.
The invariant is: "A single email is enqueued a single time in a given queue".
That invariant is broken for instance when:
- reprocessing an email: the name is not altered
- Recipient RewriteTable rewrites to a distant server
- RemoteDelivery bouncing configured with an SMTP gateway
RabbitMQ mail queue does need to leverage a Cassandra projection in order to
offer MailQueue manageable capabilities (clear, delete, browse, size amongst
others). We naturally chose the mail name, used everywhere to identify an email
in order to build this projection.
This results in a given mail being enqueued a single time in a single queue: on
the second enqueue, the mail will be referenced as already deleted from the
queue and will be discarded.
In https://github.com/linagora/james-project/pull/2445 I scratched the surface
by enforcing the aforementioned invariants where the right approach is to make
the RabbitMQ mail queue correctly handle multiple emails enqueue with the same
name. Which might involve table schema changes.
We need to assign email an EnQueueId that identifies them. This level of
indirection allows to enqueue several time the same email.
Migration strategy:
### The breaking way
- Stop exposing James to JMAP& SMTP traffic and waits for the queue to empty
- Deploy the newest version (will create new empty tables)
- Re-enable traffic
In case the upgrade isdone carelessly, some email might be lost.
I don't think we can really be smarter here...
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