November 17, 2021

Top 20 Apache ActiveMQ Interview Questions & Answers


Ques: 1). What exactly is ActiveMQ?


Apache Message-oriented middleware (MOM) is a type of software that transmits messages between applications, and ActiveMQ is one of them. ActiveMQ facilitates loose coupling of elements in an IT system using standards-based, asynchronous communication, which is frequently basic to business messaging and distributed applications. Messages are translated from sender to receiver using ActiveMQ. Instead of requiring both the client and the server to be online at the same time in order to interact, it can connect numerous clients and servers and allow messages to be queued.

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Ques: 2). In Apache ActiveMQ, what are clusters?


Load balancing of messages on a queue between consumers is supported by ActiveMQ in a stable and high-performance manner. This scenario is known as the competing consumers pattern in corporate integration. The principle is illustrated in the diagram below: Interview questions for Activemq

The burden is distributed in an extremely fluid manner. In high-load periods, more consumers might be provisioned and joined to the queue without changing any queue setup, as the new consumer would behave like any other competing consumer. Better availability than load-balanced systems. To determine whether real-servers are offline, load balancers often use a monitoring system. A failed consumer will not compete for messages if there are competing consumers, so messages will not be given to it even if it is not monitored.

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Ques: 3). What Is The Difference Between ActiveMQ And AmQP?


The Advanced Message Queue Protocol is a wire-level protocol for client-to-messaging-broker communication that serves as a specification for how messaging clients and brokers will interact.

AMQP is a message protocol rather than a messaging system like ActiveMQ.

Open wire protocols, such as OpenWire, a fast binary format, are supported by AMQP.

Stomp is a text-based protocol that is simple to implement.

MQTT is a little binary format designed for restricted devices over a shaky network.

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Ques: 4). What distinguishes ActiveMQ from other messaging systems?


  • It is a Java messaging service implementation, therefore it contains all of Java's features.
  • Extremely persistent
  • It has a high level of security and authentication.
  • Various brokers can form a cluster and collaborate with one another.
  • ActiveMQ offers a number of client APIs in a range of languages.

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Ques: 5). What are the most important advantages of ActiveMQ?


  • Allows users to combine many languages with various operating systems.
  • Allows for location transparency.
  • Communication that is both reliable and effective
  • It's simple to scale up and offers asynchronous communication.
  • Reduced coupling

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Ques: 6). What are ActiveMQ's biggest drawbacks?


It's a complicated mechanism that only allows one thread per connection.

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Ques: 7), In ActiveMQ, what is a topic?


Virtual Topics are a hybrid of Topics and Queues, with listeners consuming messages from the queues as messages to the topic.

ActiveMQ assists in replicating and duplicating every message from the topic to the actual consumers queues.

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Ques: 8). What is the difference between Activemq and Fuse Message Broker?


Multiple Protocol Messaging is a Java-based message broker that supports industry-standard protocols and allows users to choose from a wide range of client languages, including JavaScript, C, C++, and Python.

Fuse Message Broker is a distributor of FuseSource's Apache ActiveMQ, which it develops and updates as part of the Apache ActiveMQ community.

Bug fixes are more likely to come from the Fuse Broker release than from an official Apache ActiveMQ release.

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Ques: 9). What exactly is KahaDB?


KahaDB is a file-based persistence database that runs on the same machine as the message broker. It has been designed to be persistent in a short amount of time. Since ActiveMQ 5.4, it has been the default storage mechanism. Compared to its predecessor, the AMQ Message Store, KahaDB consumes fewer file descriptors and recovers faster.


Ques: 10). What exactly is LevelDB?


LevelDB is a somewhat faster index than KahaDB, with slightly better performance figures. The LevelDB store will allow replication in forthcoming ActiveMQ releases.


Ques: 11). What's the difference between RabbitMQ and ActiveMQ?


ActiveMQ is a Java-scripted open-source message broker that is built on the Java Message Service client. The RabbitMQ protocol is based on the Advanced Message Queuing protocol.


Ques: 12). What are the benefits of using a combination of topics and queues instead of traditional topics?


There will be no lost communications even if a customer is offline. All messages are copied to the queues that have been registered by ActiveMQ.

A dead letter queue will be set up if a customer is unable to process a message. Without affecting the other consumers, the consumer can be resolved and the message forwarded to his own dedicated queue.

To implement a load balancing mechanism we can register multiple instances of a consumer on a queue.


Ques: 13). If the ActiveMQ server is unavailable, what should I do?


This begins with ActiveMQ's storage mechanism. Non-persistent messages are stored in memory under typical conditions, while persistent messages are stored in files, with their maximum limitations set in the configuration file's node. When the number of non-persistent messages reaches a specific threshold and memory becomes scarce, ActiveMQ will write the non-persistent messages in memory to a temporary file to free up space Despite the fact that they are all saved in files, the distinction between persistent messages and non-persistent temporary files is that persistent messages will be restored from the file after restart, whereas non-persistent temporary files would be removed immediately.


Ques: 14). What happens if the file size exceeds the configuration's maximum limit?


Set a 2GB persistent file limit and mass-produce persistent messages until the file exceeds its limit. The producer is currently prohibited, but the consumer can connect and consume the message as usual. The producer can continue to transmit messages after a portion of the message has been eaten and the file has been erased to make room, and the service will automatically revert to normal.

Set a 2GB limit on temporary files, mass-produce non-persistent messages, and write temporary files. When the maximum limit is reached, the producer is blocked, and consumers can still connect but not consume messages, or consumers who were previously sluggish consumers suddenly consume Stop. The complete system is linked, but it is unable to give services, causing it to hang.


Ques: 15). What is message-oriented middleware, and how does it work?


Message-oriented middleware (MOM) is a software or hardware framework that allows distributed systems to send and receive messages. MOM simplifies the development of applications that span different operating systems and network protocols by allowing application modules to be distributed across heterogeneous platforms. The middleware establishes a distributed communications layer that hides the intricacies of the multiple operating systems and network interfaces from the application developer.


Ques: 16). What is the benefit of Activemq over other options such as databases?


Activemq is a messaging system that allows two distributed processes to communicate successfully. It can keep messages in a database to communicate between processes, but you'd have to erase them as soon as they were received. For each message, this means a row insert and remove. When you try to scale that up to hundreds of messages per second, databases start to break down.

Message-oriented middleware, such as ActiveMQ, is designed to handle these scenarios. They assume that messages will be erased promptly in a healthy system and can make optimizations to prevent the overhead. It can also push messages to consumers rather than requiring them to poll for fresh messages via SQL queries. This minimises the amount of time it takes for new messages to be processed into the system.


Ques: 17). What are some of the platforms supported by ActiveMQ?


Some of the common platforms supported by ActiveMQ include:

Any java platform that has an update of 5.0 or more.

J2EE 1.4 is another platform

JMS 1.1

JCA 1.5 resource adaptor


Ques: 18). Make a distinction between ActiveMQ and Mule.


ActiveMQ is a messaging service with a lot of options for both the broker and the client. Mule, on the other side, is an ESB that may provide executive functionality to merely the broker by exchanging messages between various software components.

Mule's architecture is such that it is designed to provide a programming configuration that is feasible for integrating applications between a database and an operating system. Mule, on the other hand, does not support any form of native messaging system, hence it is typically used in conjunction with ActiveMQ. the user is required to introduce different and unique frameworks to define various boundaries for connectivity.


Ques: 19). What is the process for dealing with an application server using JMS connections?


The server session is created with the help of an application server, which then stores them in a pool. An association buyer uses the server's session to place messages in JMS sessions. The JMS session is created by a server session. The messaging audience is created by an application produced by application software engineers.


Ques: 20). What distinguishes ActiveMQ from the spread toolkit?


Spread Toolkit is a C++ library for informing, with only rudimentary support for JMS. It does not support robust informing, exchanges, XA, or JMS 1.1 in its entirety. It's also depending on a locally installed version of Spread inspiration. Apache ActiveMQ, on the other hand, is the JMS provider used in Apache Geronimo. It is J2EE 1.4 certified in Geronimo and is a completely pure version of the Java programming language. ActiveMQ supports real-time and persistent messaging, exchanges, XA, J2EE 1.4, JMS 1.1, JCA 1.5, and a slew of other features like Message Groups and Clustering.

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