Gearman is an open-source application framework designed to distribute appropriate computer tasks to multiple computers, so large tasks can be done more quickly. In some cases, load balancing rather than raw speed may be the main goal; a Web server, for instance, could use Gearman to send tasks for which it is not optimized to another computer (which may be running on a different

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...

, using another

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

, or loaded with a computer language better suited to a particular operation). It was originally written in

Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed ...

Brad Fitzpatrick Bradley Joseph Fitzpatrick (born February 5, 1980) is an American programmer. He is best known as the creator of LiveJournal and is the author of a variety of free software projects such as memcached, PubSubHubbub, OpenID, and Perkeep. Personal l ...

. Brian Aker and Eric Day rewrote the framework in C.

How Gearman Works

Gearman assigns each involved computer a role as client, job server, or worker. A worker machine can be assigned multiple instances of the worker role, which allows more powerful computers to complete more portions of a given task. Tasks originate on a client, are transmitted from the client to the job server, and performed on one or more workers. The completed task's output is then returned, again by way of the job server, to the client where the task originated. Gearman is conceptually related to

MapReduce MapReduce is a programming model and an associated implementation for processing and generating big data sets with a parallel and distributed algorithm on a cluster. A MapReduce program is composed of a ''map'' procedure, which performs filte ...

; Gearman handles MapReduce by allowing worker nodes to map out work to other workers, with the original worker acting as the reducer. Gearman performs coalescence on the work sent by a client. If two or more clients ask for work to be completed on the same body of work, either by seeing that the same blocks are being sent or by using the unique value sent by the client, it will coalesce the work so that only one worker is used. It does this specifically to avoid

thundering herd problem In computer science, the thundering herd problem occurs when a large number of processes or threads waiting for an event are awakened when that event occurs, but only one process is able to handle the event. When the processes wake up, they will ea ...

s which are common to cache hit failures. To mitigate the damage that would be done if a job server (or its network connection) were to fail, clients can be configured with more than one assigned job server; if the first assigned job server fails, another can be transparently substituted. Gearman implements a protocol that consists of binary packets containing requests and responses; this protocol defines the structure of messages passing between the three parts of a Gearman implementation. By default, the Gearman protocol uses TCP port 4730. It previously operated on port 7003, but this conflicted with the AFS port range and the new port (4730) was assigned by

IANA The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Internet P ...

. The name "Gearman" was chosen as an

anagram An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. For example, the word ''anagram'' itself can be rearranged into the phrase "nag a ram"; which ...

for "Manager", "since it dispatches jobs to be done, but does not do anything useful itself."

Features

* Job retries * Round robin scheduling * Coalescence * Persistence storage via: ** libmemcached ** libdrizzle ** SQLite **

MySQL MySQL () is an Open-source software, open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A rel ...

Postgres PostgreSQL ( ) also known as Postgres, is a free and open-source software, free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. PostgreSQL features transaction processing, transactions ...

** tokyocabinet **

Redis Redis (; Remote Dictionary Server) is an in-memory key–value database, used as a distributed cache and message broker, with optional durability. Because it holds all data in memory and because of its design, Redis offers low- latency reads ...

(unreleased - currently in development) **

MongoDB MongoDB is a source-available, cross-platform, document-oriented database program. Classified as a NoSQL database product, MongoDB uses JSON-like documents with optional database schema, schemas. Released in February 2009 by 10gen (now MongoDB ...

(unreleased - currently in development)

Implementations

Gearmand, up to version 1.1.12

Gearmand, from version 1.1.13

java-gearman-service

Gearman::Server

TclGearman

Clients

Currently there are client libraries for C, Perl, Node.js, Python, PHP, Ruby, Java, .NET, JMS, MySQL,

PostgreSQL PostgreSQL ( ) also known as Postgres, is a free and open-source software, free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. PostgreSQL features transaction processing, transactions ...

, and

Drizzle Drizzle is a light precipitation which consists of liquid water drops that are smaller than those of rain – generally smaller than in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation r ...

.Gearman page Client & Worker APIs
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External links

* http://danga.com/words/2007_06_usenix/usenix.pdf * http://gearman.org/documentation/ * http://gearman.org/download/ * http://lists.danga.com/pipermail/gearman/2008-April/000076.html * https://web.archive.org/web/20081209012837/http://krow.livejournal.com/628025.html
GearmanBundle for Symfony2 projects

Citations

Application programming interfaces Message-oriented middleware Software using the BSD license