Is it possible to use KahaDB based persistance with network of brokers in ActiveMQ. I need to setup network of broker to mitigate risk of single point of failure with single centralized broker (master/slave).
If you do mean "network of brokers", yes, you just need to config KahaDb for each brokers, no difference with single point.
But network of brokers is different with master/slave, it is used to allow many brokers to be connected together, to provide massive scalability.
If you mean master/slave, it does not support kahadb yet, but is under review, see http://activemq.apache.org/kahadb-master-slave.html
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Is i correct understand that best way provide reliability of queue it is network of master-slave brokers (for example master-slave by using ZooKeeper)?
In consumers and producers failover settings we set master's addresses and when one of the masters go offline another master-slave nodes of the brokers network get this master's messager from his slaves and we don't lose messages.
When broken master go online, its get new consumers and producers and get some messages.
I'm right?
There are two ways to provide high availability with ActiveMQ.
Master/slave setup using a shared store. For KahaDB (default store), that would be a shared disk somewhere. NFS/Windows file share or similar. There are many ways to create reliable shared disks. SAN and what not.
Replicated master/slave. That would be LevelDB with Zookeeper. If you can't get a high performance, reliable shared disk, this would be your best option.
You are correct the client should enter a failover address when they connect.
I am trying to set up cluster of brokers, which should have same feature like rabbitMQ cluster, but over WAN (my machines are in different locations), so rabbitMQ cluster does not work.
I am looking to alternatives, rabbitMQ federation is just backup the messages in the downstream, can not make sure they have exactly the same messages available at any time (downstream still keeps the old messages already consumed in the upstream)
how about ActiveMQ Master/Slave, I have found :
http://activemq.apache.org/how-do-distributed-queues-work.html
"queues and topics are all replicated between each broker in the cluster (so often to a master and maybe a single slave). So each broker in the cluster has exactly the same messages available at any time so if a master fails, clients failover to a slave and you don't loose a message."
My concern is that if it can automatically update to make sure Master/Slave always have the same messages, which means the consumed messages in Master will also disappear in Slaves.
Thanks :)
ActiveMQ has various clustering features.
First there is High Availability - "Master/Slave". The idea is that several physical servers act as a single logical ActiveMQ broker. If one goes down, another takes it place without losing data. You can do that by sharing the message store (shared file system or shared JDBC), or you could setup a replicated cluster, which replicates read/writes to the master down to all slaves (you need three+ servers). ActiveMQ is using LevelDB and Apache Zookeeper to achieve this.
The other format of cluster available in ActiveMQ is to be able to distribute load and separate security over several logical brokers. Brokers are then connected in a network of brokers. Messages are by default passed around to the broker with available consumers for that message. However, there is a rich toolbox of features in ActiveMQ to tweak a network of brokers to do things as always send a copy of a message to specific broker etc. It takes some messing with the more advanced features though (static network connectors and queue mirroring, maybe more).
Maybe there is a better way to solve your requirements, which is not really specified in the question?
There're 2 brokers which are configured as a cluster through network connector.
Allways, messages are sent by a producer to broker0, and consumed by a consumer of broker0. But we found that some duplicated messages are sent to broker1, even broker0 are working well.
That's say, this duplicated messages are contains in both broker0 and broker1. Could anyone tell me the reason ?
Thank you
Such kind of situation can occur, if you are trying to use two independent ActiveMQ instances in a cluster and client has been given access to both broker URLs.
The solution is to use the master-slave feature that is designed to provide high availability.
Why only can java provide support for failover protocol in activemq whereas not other languages.
My doubt is that in the failover protocol like failover://(tcp://host1:61616,tcp://host2:61616)?randomize=false also the client uses one of the the inner urls like tcp://host1:61616 and then how does the broker comes to know that the call was using some failover protocol or not and then how the broker decides that it needs to replicate the message ?
Please understand that failover protocol is meant for reconnect logic on client side only and AMQ broker isn't even aware if a client is using failover protocol or not.
From the official AMQ documentation:
The Failover transport layers reconnect logic on top of any of the
other transports.
The Failover configuration syntax allows you to specify any number of
composite uris. The Failover transport randomly chooses one of the
composite URI and attempts to establish a connection to it. If it does
not succeed or if it subsequently fails, a new connection is
established to one of the other uris in the list.
Not sure what you mean by replication here but as per the official doc
The Failover transport tracks transactions by default. The inflight
transactions are replayed on reconnection.
There are different scenarios to put up a HA solution with ActiveMQ.
If clients connect using the failover protocol to host1,host2, then the broker setup needs to be setup for HA as well.
One solution is to cluster host1 and host2 in an Active-Active solution. Then messages are always propagated when they are asked for - the queues are shared in the entire cluster among all amq brokers.
Otherwise, if the active-active solution is not prefered, then a master-slave solution can be setup where the two brokers, host1 and host2, share the data area (for instance using a Database for persistance or a shared SAN disk).
There are more combinations of setups, but the failover protocol assumes that the entire solution can handle that messages arrives to different brokers, if one goes down. As far as I know, there is no other magic in the failover protocol, from the broker perspective.
I'm trying to set up three brokers in a network for load balancing -- clients and producers can connect to any of these brokers.
Questions:
What is the recommended topology to use to network these brokers? More specifically, what is the networkConnector configuration to use on each of these brokers? should duplex setting be enabled? (I guess duplex setting depends on the topology we choose)
A->B->C->A or A<-->B<-->C<-->A
Client should use failover protocol to connect to these brokers, right? e.g. failover://(tcp://b1:6161, tcp://b2:6161, tcp://b3:6161)
Any duplicate message handling required on the client side in case of restarts? See http://forum.springsource.org/showthread.php?108461-Failover-issue-in-ActiveMQ -- not clear why duplicate message issue exists here
Ideally we want to set up topology as shown in this post http://edelsonmedia.com/?p=143 -- not clear how to set up networkConnector on masters and slaves.
1.) I can't actually recommend a topology. This choice depends on the number of hops (between the broker where the messages enters the cluster and the broker where the consumer conects to) you can accept. In a heave traffic scenario every hop adds to the network load.
In my company we use a hypercube network (every broker knows every other broaker) and it works great.
Generaly you should make sure that your node configurations are as similar as possible. Using duplex makes sure you have less connections to configure (since the connection from B to A is already part of the duplex connection from A to B) but it introduce a large number of differences into your config file.
Personaly i created my own start script for ActiveMQ that auto-generated the connection config based on the dns names of my cluster (mycluster-01 to 06).
2.) yes. You might want to add ?randomize=false if you want to make sure the client uses the first entry in the list.
3.) Duplicate entries can happen if there are failures during message transport or as race conditions during heavy load. In general one message only is owned by one broker.
4.) dont set up network connectors between masters and slaves (REALLY DONT). Use the pure Master Slave feature of activeMQ and configure the master for each slave (you don't have to configure anything on the masters). For the all Masters configure NetworkConnections to the other Masters with failover to their slaves)
http://activemq.apache.org/pure-master-slave.html