So I've spent some time digging around the internet and experimenting with our setup, trying to determine the best configuration for a network of brokers. There are a variety of things which seem to conspire against me: the multitude of configuration options present in activemq, options which seem to have no "optimal" setting (each choice has different pros and cons), and behavior/features which change over time such that old recommendations may now be irrelevant or no longer correct. For reference, we are using a mesh network of brokers, where consumers may arrive at any broker in the network. We use topics, queues, and virtual queues. We use explicit receive() calls as well as listeners. We also utilize the "exclusive consumer" feature for some of our clustered consumers. All messaging is currently durable. Some relevant configuration bits (changes from the defaults).
* using activemq 5.9.1 * advisory support is enabled * PolicyEntry ** optimizedDispatch: true * Using ConditionalNetworkBridgeFilterFactory ** replayWhenNoConsumers: true ** replayDelay: 1000 * NetworkConnector ** prefetchSize: 1 ** duplex: false ** messageTTL: 9999 Alright, now that we got through all the context, here's the meat of the question. There are a bunch of configuration parameters (mostly focused in the NetworkConnector), and it's not at all clear to me if my current configuration is optimal. For instance, although we had been using a configuration similar to the above for about a year now (same as above except that messageTTL was 1), we only recently discovered that our exclusive consumers can sometimes stop processing messages. In certain cases, the consumer would end up bouncing around and the messages would end up getting stuck on one node. Adding the messageTTL setting seems to fix the problem (is it the right fix...?). * NetworkConnector ** "dynamicOnly" - i've seen a couple of places mention enabling this and some indication that it helps with scaling in a network of brokers (e.g. [3]). The description in [1] also makes it sound like something i would want to enable. However, the value defaults to false, which seems to indicate that there is a down-side to enabling it. Why wouldn't i want to enable this? ** "decreaseNetworkConsumerPriority", "suppressDuplicateQueueSubscriptions" - these params both seem like "damned if you do, damned if you don't" type parameters. The first comment in [2] seems to imply that in order to scale, you really want to enable these features so that producers prefer pushing messages to local consumers (makes sense). Yet, at the same time, it seems that enabling this feature will _decrease_ scalability in that it won't evenly distribute messages in the case when there are multiple active consumers (we use clusters of consumers in some scenarios). Also in [2], there are some allusions to stuck messages if you don't enable this feature. Should i enable these parameters? ** "networkTTL", "messageTTL", "consumerTTL" - until recently, we kept these at the defaults (1). However, we recently realized that we can end up with stuck messages with these settings. I've seen a couple of places which recommend setting "networkTTL" to the number of brokers in the network (e.g. [2]), or at least something > 1. However, the recommendation for "consumerTTL" on [1] is that this value should be 1 in a mesh network (and setting the "networkTTL" will set the "consumerTTL" as well). Additionally, [2] seems to imply that enabling "suppressDuplicateQueueSubscriptions" acts like "networkTTL" is 1 for proxy messages (unsure what this means?). We ended up setting only the "messageTTL" and this seemed to solve our immediate problem. Unsure if it will cause other problems...? ** "prefetchSize" - defaults to 1000, but I see recommendations that it should be 1 for network connectors (e.g. [3]). I think that in our initial testing i saw bad things happen with this setting and got more even load balancing by lowering it to 1. I think that about summarizes my questions and confusion. Any help would be appreciated! [1] http://activemq.apache.org/networks-of-brokers.html [2] https://issues.jboss.org/browse/MB-471 [3] http://www.javabeat.net/deploying-activemq-for-large-numbers-of-concurrent-applications/ -- View this message in context: http://activemq.2283324.n4.nabble.com/Correctly-configuring-a-network-of-brokers-tp4703715.html Sent from the ActiveMQ - User mailing list archive at Nabble.com.
