I am trying to set up a high availability RabbitMQ cluster with mirrored queues.
Actually, I have set that up and that was the easy part. Now comes the part where my producers and consumers need to access the cluster, or specifically, the master node, whichever that might be at the time. I am trying to set up HAproxy for that but I have some questions pertaining to how it would work.
Specifically, HAproxy is not being used here as a balancer as it is to do health checks. Suppose the original master goes down and the oldest surviving slave is promoted to new master? How can HAproxy be set up the detect who this is and route all connections to the new master?
You can configure HAProxy to do this. Check out this complete guide from RabbitMQ.
If you want to achieve real load balancing with RabbitMQ in a HA-configuration, this might also interest you.
Related
Hoping someone might be able to give me some guidance on this. I have setup a RabbitMQ cluster on 3 nodes.
- Node1 (Master), Node2 and Node3
The part I can't figure out is I cannot find any information about what happens if Master goes down, what is the client pointing to?
If Node1 goes down, then surely the clients which are configured to point to Node1 will not be able to automatically fail-over to whatever becomes the new master?
My idea was to setup a load balancer which detects which node is master and only ever redirects requests to that node?
Any thoughts or ideas?
Thanks :)
Spring amqp helps in solving this easily. It provides the failover mechanism out of the box. You can just configure the address of the nodes with comma separated and pass it to addresses parameter while creating the connection factory.
For eg:
<rabbit:connection-factory id="rabbitConnectionFactory" addresses="192.168.1.2:5672,192.168.1.3:5672" username="${rabbitmq.username}"
connection-factory="clientConnectionFactory"
cache-mode="${rabbit.cacheMode}"
channel-cache-size="${rabbit.channelCacheSize}"
password="${rabbitmq.password}" virtual-host="${rabbitmq.vhost}"/>
This way, when the first node goes down, the connection will be made to the second node.
If clients are only capable of connecting to one node, and that node goes down, clients will lose connectivity. You need (as you surmise) some kind of setup whereby either:
you place a load-balancer in front of the nodes, and the clients connect only to the load-balancer; OR
the clients can connect to any of the available nodes, trying each in turn.
Whichever solution, there is no need to direct all client traffic to the master node. Clients nodes can connect to either a master or slave broker.
At CloudAMQP we have one single URL to the cluster that clients connect to and we recommend to always configure clients to automatically reconnect on connection loss.
We have fail over and load balancing between nodes, and it's done over DNS, with a low TTL (30s).
https://www.cloudamqp.com/blog/2015-12-29-cloudamqp-plan-setup-pause-minority-mirrored-nodes-and-the-cap-theorem.html
i have the following scenario which i want to fulfill:
rabbit mq must be loadbalanced (is it something which is provided by rabbitmq out of the box OR something like haproxy load balancer would work great. Which one is well loadbalanced.)
CAN haproxy directly push messages to rabbitmq (lets say a POST request coming to http://localhost:3333/redirectToRabbit gets redirected to rabbit and optionally either the ACK or RESPONSE goes back to client. Also note haproxy would load balance the request)
with HA; what the best configuration ( exchange with durable queue, durable queue or something else. NOTE: How would the messages gets redirected to some other rabbitmq instance if one of the rabbitmq instance goes down -- persisted and auto redirection to available rabbitmq )
Assuming you setup a two-node RabbitMQ cluster. Before talking about ha proxy, you need to understand the ha policies and the behavior of ha queues first. Different ha options might cause completely different behaviors of RabbitMQ message replication and node failover. RabbitMQ is so flexible, so don't expect a golden way of configuration which could meet all scenarios.
Then, since you have two nodes which could accept connections, your client could either use a loadbalancer (such as ha proxy) or to use a client driver which supports connecting to multiple nodes of a cluster. Either way will work.
When using haproxy, you have one load balancer ip. Client connects only to this load balancer ip, the load balancer forward you connection to the underlying nodes. But as long as a connection created, the client connection instance keeps talking to one of the node. When one of the node is down, if no "Health Checking" options are configured in your load balancer, client might get random connection failures. When you have "Health Checking" options configured correctly, the load balancer knows which nodes are down, so that clients will only connect to healthy nodes, which solves the issue.
When not using a load balancer and only base on client driver to connect to all the nodes, the client driver should be able to handle connection failure or health check internally and do failover/retry, etc, to ensure connections go to healthy nodes.
I have a Redis Cluster that clients are connecting to via HAPRoxy with a Virtual IP. The Redis cluster has three nodes (with each node sharing the same server with a running sentinel instance).
My question is, when i clients gets a "MOVED" error/message from a cluster node upon sending a request, does it bypass the HAProxy the second time when it connects since it has been provided with an IP:port when the MOVEd message was issued? If not, how does the HAProxy know the second time to send it to the correct node?
I just need to understand how this works under the hood.
If you want to use HAProxy in front of Redis Cluster nodes, you will need to either:
Set up an HAProxy for each master/slave pair, and wire up something to update HAProxy when a failure happens, as well as probably intercept the topology related commands to insert the virtual IPs rather than the IPs the nodes themselves have and report via the topology commands/responses.
Customize HAProxy to teach it how to be the cluster-aware Redis client so the actual client doesn't know about cluster at all. This means teaching it the Redis protocol, storing the cluster's topology information, and selecting the node to query based on the key(s) being accessed by the consumer code.
With Redis Cluster the client must be able to access every node in the cluster. Of the two options above Option 2 is the "easier" one, but at this point I wouldn't recommend either.
Conceivably you could use the VIP as a "first place to get the topology info" IP but I suspect you'd have serious issues develop as that original IP would not be one of the ones properly being reported as a nod handling data. For that you could simply use round-robin DNS and avoid that problem, or use the built-in "here is a list of cluster IPs (or names?)" to the initial connection configuration.
Your simplest, and least likely to be problematic, route is to go "full native" and simply give full and direct access to every node in the cluster to your clients and not use HAProxy at all.
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?
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