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Author Archives: Christian Posta

Christian Posta
Christian is a Principal Consultant at FuseSource specializing in developing enterprise software applications with an emphasis on software integration and messaging. His strengths include helping clients build software using industry best practices, Test Driven Design, ActiveMQ, Apache Camel, ServiceMix, Spring Framework, and most importantly, modeling complex domains so that they can be realized in software. He works primarily using Java and its many frameworks, but his favorite programming language is Python. He's in the midst of learning Scala and hopes to contribute to the Apache Apollo project.

Apache Apollo REST API

java-interview-questions-answers

Apache Apollo is a next-generation, high-performance, multi-protocol messaging broker built from the ground up to one day be a drop-in replacement of ActiveMQ 5.x. I have blogged about it in the past (Part I has already been published with part II on its way). Apollo’s non-blocking, asynchronous architecture allows it to be super fast and scale very well on multi-core ...

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ActiveMQ: Understanding Memory Usage

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As indicated by some recent mailing list emails and a lot of info returned from Google, ActiveMQ’s SystemUsage and particularly the MemoryUsage functionality has left some people confused. I’ll try to explain some details around MemoryUsage that might be helpful in understanding how it works. I won’t cover StoreUsage and TempUsage as my colleauges have covered those in some depth. ...

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Benchmarking JMS layer with JMSTester

java-interview-questions-answers

For most of the clients I’ve been to, scaling out a JMS messaging layer with ActiveMQ is a priority. There are a couple ways to achieve this, but without a doubt, creating benchmarks and analyzing an architecture on real hardware (or as my colleague Gary Tully says “asking the machine”) is step one. But what opensource options do you have ...

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Guaranteed messaging for topics, the JMS spec, and ActiveMQ

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Recently a customer asked me to look closer at ActiveMQ’s implementation of “persistent” messages, how it applies to topics, and what happens in failover scenarios when there are non-durable subscribers. I had understood that the JMS semantics specify that only durable subscribers to a topic are guaranteed message delivery for a persistent delivery mode, even in the face of message-broker ...

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Managing large deployments of MQ and ESB with Fuse Fabric, Part I

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FuseSource just recently released enterprise versions of their distributions of ActiveMQ and ServiceMix. Some of the top features include incremental patching, custom platform installers, and third party verification. One of the coolest features that comes part of the new enterprise editions is Fuse Fabric and some new tooling that allows you to leverage Fabric to manage your environment. Fabric allows ...

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ActiveMQ Network Connectors

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This post is more for me and any ActiveMQ contributors that may be interested in how the Network Connectors work for ActiveMQ. I recently spent some time looking at the code and thought that it would be good to draw up some quick diagrams to help me remember what I learned and help to identify where to debug in the ...

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Understanding how OSGI bundles get resolved

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I’d like to review how OSGI bundles get resolved and use Apache Karaf to demonstrate. Karaf is a full-featured OSGI container based on the Apache Felix kernel and is the corner stone for the Apache ServiceMix integration container. For part one, I will discuss how bundles are resolved by an OSGI framework. In part two, I’ll demonstrate each rule using ...

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Java static methods can be a code smell

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Definition of code smell (from Wikipedia): “any symptom in the source code of a program that possibly indicates a deeper problem.” In Java, static methods allow you to execute code at a “class scope” as opposed to an instance scope like member methods. This means, they rely on class-level variables (if any), parameters passed to the static method, or any ...

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Backing Spring Integration routes with ActiveMQ

spring-interview-questions-answers

As discussed in my previous post, Spring Integration (SI) is a routing framework built on top of the Spring Framework that allows you to use proven enterprise integration patterns to solve system integration problems via messaging. Once you’ve gotten SI configured and working to perform your routing and mediation logic, you may find that you’d like to take the next ...

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