An Active message (in

computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...

) is a messaging object capable of performing processing on its own. It is a lightweight messaging protocol used to optimize network communications with an emphasis on reducing latency by removing software overheads associated with buffering and providing applications with direct user-level access to the network hardware. This contrasts with traditional computer-based

messaging system In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categori ...

s in which messages are passive entities with no processing power.

Distributed Memory Programming

Active messages are communications primitive for exploiting the full

performance A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Management science In the work place ...

and flexibility of modern computer interconnects. They are often classified as one of the three main types of distributed memory programming, the other two being

data parallel Data parallelism is parallelization across multiple processors in parallel computing environments. It focuses on distributing the data across different nodes, which operate on the data in parallel. It can be applied on regular data structures like ...

and

message passing In computer science, message passing is a technique for invoking behavior (i.e., running a program) on a computer. The invoking program sends a message to a process (which may be an actor or object) and relies on that process and its supporting i ...

. The view is that Active Messages are actually a lower-level mechanism that can be used to implement data parallel or message passing efficiently. The basic idea is that each message has a header containing the address or index of a

userspace handler A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel ...

to be executed upon message arrival, with the contents of the message passed as an argument to the handler. Early active message systems passed the actual remote code address across the network, however this approach required the initiator to know the address of the remote handler function when composing a message, which can be quite limiting even within the context of a

SPMD In computing, single program, multiple data (SPMD) is a technique employed to achieve parallelism; it is a subcategory of MIMD. Tasks are split up and run simultaneously on multiple processors with different input in order to obtain results fast ...

programming model (and generally relies upon address space uniformity which is absent in many modern systems). Newer active message interfaces require the client to register a table with the software at initialization time that maps an integer index to the local address of a handler function; in these systems the sender of an active message provides an index into the remote handler table, and upon arrival of the active message the table is used to map this index to the handler address that is invoked to handle the message. Dan Bonachea and Paul H. Hargrove
"GASNet specification, v1.8.1"
Lawrence Berkeley National Laboratory Technical Repor
LBNL-2001064
August 2017. Other variations of active messages carry the actual code itself, not a pointer to the code. The message typically carries some data. On arrival at the receiving end, more data is acquired, and the computation in the active message is performed, making use of data in the message as well as data in the receiving node. This form of active messaging is not restricted to

, although originator and receiver must share some notions as to what data can be accessed at the receiving node.

Integration, usage for micro-services, orchestration, ESB architecture

A higher level implementation for active messages is also named

Swarm communication Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or migrating in some direction. ...

in the SwarmESB project. The basic model of the active messages is extend with new concepts and Java Script is used to express the code of the active messages.

References

Sources and external links

* https://web.archive.org/web/20070610055547/http://www.tc.cornell.edu/Services/Education/Topics/Parallel/Distributed/%2B6.3%2BActive%2BMessages.htm * https://github.com/salboaie/SwarmESB/
GASNet
- A communications middleware layer that includes Active Messages and Remote Memory Access (RMA), implemented over a wide variety of network hardware
AMUDP
- Active Messages (AM-2) over UDP (a standard component of the TCP/IP protocol stack)
AMMPI
- Active Messages (AM-2) over

MPI MPI or Mpi may refer to: Science and technology Biology and medicine * Magnetic particle imaging, an emerging non-invasive tomographic technique * Myocardial perfusion imaging, a nuclear medicine procedure that illustrates the function of the hear ...

Inter-process communication {{soft-eng-stub