Broker/Cluster Message Replication
I am trying to determine if messages sent to a Broker within a Cluster are replicated to different Brokers and as such the different Brokers' persistence message stores?
I what a HA solution that has no single point of failure within a site (and ultimately across sites, but let's focus on a single site to start with). I need the replication to ensure that if Broker-A goes down the message is still available and can be consumed via Broker-B; and not relying on Broker-A being restarted.
There is a statement within the Technical Overview document thatmight suggest that what I am looking for is not possible. It says...
"Note that broker clusters provide service availability but not data availability. If one broker in a cluster fails, clients connected to that broker can reconnect to another broker in the cluster but may lose some data while they are reconnected to the alternate broker."
If I am not asking to much already any cases studies, blue prints etc. would be nice. But simple answers to this question will also get my deep thanks.
Regards
Paul
# 1
No - messages are not replicated.
In the pre-4.1 releases of MQ, messages are persisted on the local broker and are just forwarded to other brokers (they are not persistently store on other brokers) - MQ provides service but not data availability.
In 4.1, a JDBC database can be used as a centralized store which allows messages to be taken over by another running broker (data availability)
You can get HA with older versions of Message queue (that store messages on the local broker) by using SunCluster (or a similar product) which makes use of a highly available store and starts a backup broker (using the same messages) if a failure occurs.
We will be provided a replicated filebased data store in a future major release.
# 2
Thank you for the response. I think you have confirmed my fears, but I will ask some more questions, just to make sure I am 100% clear...
Can 2 brokers share the exact same JDBC message store? From what you are saying we could do that but Broker-B would have to be passive. But to be clear could both Brokers be active and using the same store at the same time?
I am baffled as to how guaranteed message order can be provided if a Broker and its store is unavailable. Is it that new messages are processed out of order? ie, new messages are processed ignoring the failed broker's messages? Are there known issues with guaranteed message order when a Broker fails?
Thank you again for the response.
Regards
Paul.
Message was edited by:
paularmstrong
