The Advanced Message Queuing Protocol (AMQP) is an
open standard
An open standard is a standard that is openly accessible and usable by anyone. It is also a common prerequisite that open standards use an open license that provides for extensibility. Typically, anybody can participate in their development due to ...
application layer
An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Su ...
protocol for
message-oriented middleware
Message-oriented middleware (MOM) is software or hardware infrastructure supporting sending and receiving messages between distributed systems. Message-oriented middleware is in contrast to streaming-oriented middleware where data is communicate ...
. The defining features of AMQP are message orientation, queuing,
routing
Routing is the process of selecting a path for traffic in a Network theory, network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched ...
(including point-to-point and publish-and-subscribe), reliability and security.
AMQP mandates the behavior of the messaging provider and client to the extent that implementations from different vendors are
interoperable
Interoperability is a characteristic of a product or system to work with other products or systems. While the term was initially defined for information technology or systems engineering services to allow for information exchange, a broader de ...
, in the same way as
SMTP
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typi ...
,
HTTP
HTTP (Hypertext Transfer Protocol) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, wher ...
,
FTP
The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and dat ...
, etc. have created interoperable systems. Previous standardizations of
middleware
Middleware is a type of computer software program that provides services to software applications beyond those available from the operating system. It can be described as "software glue".
Middleware makes it easier for software developers to imple ...
have happened at the API level (e.g. JMS) and were focused on standardizing programmer interaction with different middleware implementations, rather than on providing interoperability between multiple implementations. Unlike JMS, which defines an API and a set of behaviors that a messaging implementation must provide, AMQP is a wire-level protocol. A wire-level protocol is a description of the format of the data that is sent across the network as a
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...
of
byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...
s. Consequently, any tool that can create and interpret messages that conform to this data format can interoperate with any other compliant tool irrespective of implementation language.
Overview
AMQP is a binary application layer protocol, designed to efficiently support a wide variety of messaging applications and communication patterns. It provides flow controlled, message-oriented communication with message-delivery guarantees such as ''at-most-once'' (where each message is delivered once or never), ''at-least-once'' (where each message is certain to be delivered, but may do so multiple times) and ''exactly-once'' (where the message will always certainly arrive and do so only once), and authentication and/or encryption based on SASL and/or TLS. It assumes an underlying reliable transport layer protocol such as
Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, th ...
(TCP).
The AMQP specification is defined in several layers: (i) a type system, (ii) a symmetric, asynchronous protocol for the transfer of messages from one process to another, (iii) a standard, extensible message format and (iv) a set of standardised but extensible 'messaging capabilities.'
History
AMQP was originated in 2003 by John O'Hara at
JPMorgan Chase
JPMorgan Chase & Co. (stylized as JPMorganChase) is an American multinational financial services, finance corporation headquartered in New York City and incorporated in Delaware. It is List of largest banks in the United States, the largest ba ...
in
London
London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
. AMQP was conceived as a co-operative open effort. The initial design was by JPMorgan Chase from mid-2004 to mid-2006 and it contracted iMatix Corporation to develop a C broker and protocol documentation. In 2005 JPMorgan Chase approached other firms to form a working group that included
Cisco Systems
Cisco Systems, Inc. (using the trademark Cisco) is an American multinational corporation, multinational digital communications technology conglomerate (company), conglomerate corporation headquartered in San Jose, California. Cisco develops, m ...
Red Hat
Red Hat, Inc. (formerly Red Hat Software, Inc.) is an American software company that provides open source software products to enterprises and is a subsidiary of IBM. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North ...
Microsoft
Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
and StormMQ implementations.
The working group grew to 23 companies including
Bank of America
The Bank of America Corporation (Bank of America) (often abbreviated BofA or BoA) is an American multinational investment banking, investment bank and financial services holding company headquartered at the Bank of America Corporate Center in ...
,
Barclays
Barclays PLC (, occasionally ) is a British multinational universal bank, headquartered in London, England. Barclays operates as two divisions, Barclays UK and Barclays International, supported by a service company, Barclays Execution Services ...
, Cisco Systems,
Credit Suisse
Credit Suisse Group AG (, ) was a global Investment banking, investment bank and financial services firm founded and based in Switzerland. According to UBS, eventually Credit Suisse was to be fully integrated into UBS. While the integration ...
,
Deutsche Börse
Deutsche Börse AG (), or the Deutsche Börse Group, is a German multinational corporation that offers a marketplace for organizing the trading of shares and other securities. It is also a transaction services provider, giving companies and inv ...
,
Goldman Sachs
The Goldman Sachs Group, Inc. ( ) is an American multinational investment bank and financial services company. Founded in 1869, Goldman Sachs is headquartered in Lower Manhattan in New York City, with regional headquarters in many internationa ...
Progress Software
Progress Software Corporation is an American public company that produces software for creating and deploying business applications. Founded in Burlington, Massachusetts with offices in 16 countries, the company posted revenues of $531.3 mill ...
Informatica
Informatica Inc. is an American software development company founded in 1993. It is headquartered in Redwood City, California. Its core products include enterprise cloud data management and data integration. It was co-founded by Gaurav Dhillon a ...
Novell
Novell, Inc. () was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as NetWare. Novell technolog ...
,
Red Hat
Red Hat, Inc. (formerly Red Hat Software, Inc.) is an American software company that provides open source software products to enterprises and is a subsidiary of IBM. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North ...
, Software AG, Solace Systems, StormMQ, Tervela Inc., TWIST Process Innovations ltd, VMware (which acquired Rabbit Technologies) and WSO2.
In 2008, Pieter Hintjens, CEO and chief software designer of iMatix, wrote an article called "What is wrong with AMQP (and how to fix it)" and distributed it to the working group to alert of imminent failure, identify problems seen by iMatix and propose ways to fix the AMQP specification. By then, iMatix had already started work on ZeroMQ. In 2010, Hintjens announced that iMatix would leave the AMQP workgroup and did not plan to support AMQP/1.0 in favor of the significantly simpler and faster ZeroMQ.
In August 2011, the AMQP working group announced its reorganization into an
OASIS
In ecology, an oasis (; : oases ) is a fertile area of a desert or semi-desert environmentVMware, Apache, INETCO and IIT Software demonstrated software running the protocol in an interoperability demonstration. The next day, on 1 November 2011, the formation of an
OASIS
In ecology, an oasis (; : oases ) is a fertile area of a desert or semi-desert environmentmiddleware
Middleware is a type of computer software program that provides services to software applications beyond those available from the operating system. It can be described as "software glue".
Middleware makes it easier for software developers to imple ...
problems.
Description of AMQP 1.0
Type system
AMQP defines a self-describing encoding scheme allowing interoperable representation of a wide range of commonly used types. It also allows typed data to be
annotated
An annotation is extra information associated with a particular point in a document or other piece of information. It can be a note that includes a comment or explanation. Annotations are sometimes presented in the margin of book pages. For anno ...
with additional meaning, for example a particular string value might be annotated so that it could be understood as a
URL
A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...
. Likewise a map value containing key-value pairs for 'name', 'address' etc., might be annotated as being a representation of a 'customer' type.
The type-system is used to define a message format allowing standard and extended meta-data to be expressed and understood by processing entities. It is also used to define the communication primitives through which messages are exchanged between such entities, i.e. the AMQP ''frame bodies''.
Performatives and the link protocol
The basic unit of data in AMQP is a ''frame''. There are nine AMQP frame bodies defined that are used to initiate, control and tear down the transfer of messages between two peers. These are:
* open (the ''connection'')
* begin (the ''session'')
* attach (the ''link'')
* transfer
* flow
* disposition
* detach (the ''link'')
* end (the ''session'')
* close (the ''connection'')
The ''link protocol'' is at the heart of AMQP.
An ''attach'' frame body is sent to initiate a new link; a ''detach'' to tear down a link. Links may be established in order to receive or send messages.
Messages are sent over an established ''link'' using the ''transfer'' frame. Messages on a link flow in only one direction.
Transfers are subject to a credit-based flow control scheme, managed using ''flow'' frames. This allows a process to protect itself from being overwhelmed by too large a volume of messages or more simply to allow a subscribing link to pull messages as and when desired.
Each transferred message must eventually be ''settled''. Settlement ensures that the sender and receiver agree on the state of the transfer, providing reliability guarantees. Changes in state and settlement for a transfer (or set of transfers) are communicated between the peers using the ''disposition'' frame. Various reliability guarantees can be enforced this way: at-most-once, at-least-once and exactly-once.
Multiple links, in both directions, can be grouped together in a ''session''. A session is a bidirectional, sequential conversation between two peers that is initiated with a ''begin'' frame and terminated with an ''end'' frame. A connection between two peers can have multiple sessions multiplexed over it, each logically independent. Connections are initiated with an ''open'' frame in which the sending peer's capabilities are expressed, and terminated with a ''close'' frame.
Message format
AMQP defines as the ''bare message'', that part of the message that is created by the sending application. This is considered immutable as the message is transferred between one or more processes.
Ensuring the message as sent by the application is immutable allows for end-to-end message signing and/or
encryption
In Cryptography law, cryptography, encryption (more specifically, Code, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the inf ...
and ensures that any integrity checks (e.g. hashes or digests) remain valid. The message can be annotated by intermediaries during transit, but any such annotations are kept distinct from the immutable ''bare message''. Annotations may be added before or after the bare message.
The ''header'' is a standard set of delivery-related annotations that can be requested or indicated for a message and includes time to live, durability, priority.
The bare message itself is structured as an optional list of standard properties (message id, user id, creation time, reply to, subject, correlation id, group id etc.), an optional list of
application-specific properties (i.e., extended properties) and a body, which AMQP refers to as application data.
Properties are specified in the AMQP type system, as are annotations. The application data can be of any form, and in any encoding the application chooses. One option is to use the AMQP type system to send structured, self-describing data.
Messaging capabilities
The link protocol transfers messages between two ''nodes'' but assumes very little as to what those nodes are or how they are implemented.
A key category is those nodes used as a ''rendezvous point'' between senders and receivers of messages (e.g. ''queues'' or ''topics''). The AMQP specification calls such nodes ''distribution nodes'' and codifies some common behaviors.
This includes:
* some standard outcomes for transfers, through which receivers of messages can for example accept or reject messages
* a mechanism for indicating or requesting one of the two basic distribution patterns, competing- and non-competing- consumers, through the ''distribution modes'' ''move'' and ''copy'' respectively
* the ability to create nodes on-demand, e.g. for temporary response queues
* the ability to refine the set of message of interest to a receiver through filters
Though AMQP can be used in simple peer-to-peer systems, defining this framework for messaging capabilities additionally enables interoperability with messaging intermediaries (brokers, bridges etc.)
in larger, richer messaging networks. The framework specified covers basic behaviors but allows for extensions to evolve that can be further codified and standardised.
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
project sponsored by VMware, supports AMQP 1.0 with release 4.0
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
AMQP protocol version 1.0 is the current specification version. It focuses on core features which are necessary for interoperability at Internet scale. It contains less explicit routing than previous versions because core functionality is the first to be rigorously standardized. AMQP 1.0 interoperability has been more extensively tested with more implementors than prior versions.
The AMQP website contains the .
Earlier versions of AMQP, published prior to the release of 1.0 (see History above) and significantly different from it, include:
AMQP 0-9-1 which has clients available "for many popular programming languages and platforms" AMQP 0-10
Comparable specifications
These open protocol specifications cover the same or a similar space as AMQP:
* Streaming Text Oriented Messaging Protocol (STOMP), a text-based protocol developed at Codehaus; uses the JMS-like semantics of 'destination'.
*
Extensible Messaging and Presence Protocol
Extensible Messaging and Presence Protocol (abbreviation XMPP, originally named Jabber) is an open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance. Based on XML (Extensible Marku ...
(XMPP), the Extensible Messaging and Presence Protocol.
* MQTT, a lightweight publish-subscribe protocol.
* OpenWire as used by ActiveMQ.
Java Message Service (JMS), is often compared to AMQP. However, JMS is an API specification (part of the
Java EE
Jakarta EE, formerly Java Platform, Enterprise Edition (Java EE) and Java 2 Platform, Enterprise Edition (J2EE), is a set of specifications, extending Java SE with specifications for enterprise features such as distributed computing and web serv ...
specification) that defines how message producers and consumers are implemented. JMS does not guarantee interoperability between implementations, and the JMS-compliant messaging system in use may need to be deployed on both client and server. On the other hand, AMQP is a wire-level protocol specification. In theory AMQP provides interoperability as different AMQP-compliant software can be deployed on the client and server sides.
See also
*
Peer-to-peer
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network, forming a peer-to-peer network of Node ...
*
Message queue
In computer science, message queues and mailboxes are software-engineering components typically used for inter-process communication (IPC), or for inter- thread communication within the same process. They use a queue for messaging – the ...