Provided by: gearman-job-server_1.0.6-5.1build2_amd64 bug

NAME

       gearmand - Gearmand Documentation, http://gearman.info/

SYNOPSIS

       General options

       -b [ --backlog ] arg (=32)
              Number of backlog connections for listen.

       --check-args
              Check command line and configuration file argments and then exit.

       -d [ --daemon ]
              Daemon, detach and run in the background.

       -f [ --file-descriptors ] arg
              Number  of  file  descriptors  to  allow for the process (total connections will be
              slightly less). Default is max allowed for user.

       -h [ --help ]
              Print this help menu.

       -j [ --job-retries ] arg (=0)
              Number of attempts to run the job before the job server removes it. This is helpful
              to ensure a bad job does not crash all available workers. Default is no limit.

       -l [ --log-file ] arg
              Log  file  to  write errors and information to.  Turning this option on also forces
              the first verbose level to be enabled.

       -L [ --listen ] arg
              Address the server should listen on. Default is INADDR_ANY.

       -p [ --port ] arg (=4730)
              Port the server should listen on.

       -P [ --pid-file ] arg
              File to write process ID out to.

       -r [ --protocol ] arg
              Load protocol module.

       -R [ --round-robin ]
              Assign work in round-robin order per worker connection. The default  is  to  assign
              work in the order of functions added by the worker.

       -q [ --queue-type ] arg
              Persistent queue type to use.

       -t [ --threads ] arg (=4)
              Number of I/O threads to use. Default=4.

       -u [ --user ] arg
              Switch to given user after startup.

       -v [ --verbose ] arg (=v)
              Increase verbosity level by one.

       -V [ --version ]
              Display the version of gearmand and exit.

       -w [ --worker-wakeup ] arg (=0)
              Number  of  workers  to  wakeup for each job received. The default is to wakeup all
              available workers.

       HTTP:

       --http-port arg (=8080)
              Port to listen on.

       sqlite

       --libsqlite3-db arg
              Database file to use.

       --libsqlite3-table arg (=gearman_queue)
              Table to use.

       Memcached(libmemcached)

       --libmemcached-servers arg
              List of Memcached servers to use.

       Drizzle/MySQL(libdrizzle)

       -host arg
              Host of server.

       -port arg
              Port of server. (by default Drizzle)

       -uds arg
              Unix domain socket for server.

       -user arg
              User name for authentication.

       -password arg
              Password for authentication.

       -db arg
              Schema/Database to use.

       -table arg
              Table to use.

       -mysql arg
              Use MySQL protocol.

       Postgres

       --libpq-conninfo arg
              PostgreSQL connection information string.

       --libpq-table arg (=queue)
              Table to use.

       tokyocabinet

       --libtokyocabinet-file arg
              File name of the database. [see: man tcadb, tcadbopen() for name guidelines]

       --libtokyocabinet-optimize
              Optimize database on open. [default=true]

DESCRIPTION

       Gearman provides a generic application framework to farm out work  to  other  machines  or
       processes  that are better suited to do the work. It allows you to do work in parallel, to
       load balance processing, and to call functions between languages. It  can  be  used  in  a
       variety  of  applications,  from  high-availability web sites to the transport of database
       replication events. In  other  words,  it  is  the  nervous  system  for  how  distributed
       processing communicates. A few strong points about Gearman:

       · Open  Source  -  It's  free!  (in  both meanings of the word) Gearman has an active open
         source community that is easy to  get  involved  with  if  you  need  help  or  want  to
         contribute.

       · Multi-language  -  There  are  interfaces  for  a  number of languages, and this list is
         growing. You also have the option  to  write  heterogeneous  applications  with  clients
         submitting work in one language and workers performing that work in another.

       · Flexible - You are not tied to any specific design pattern. You can quickly put together
         distributed applications using  any  model  you  choose,  one  of  those  options  being
         Map/Reduce.

       · Fast  -  Gearman has a simple protocol and interface with a new optimized server in C to
         minimize your application overhead.

       · Embeddable - Since Gearman is fast and lightweight, it is great for applications of  all
         sizes. It is also easy to introduce into existing applications with minimal overhead.

       · No single point of failure - Gearman can not only help scale systems, but can do it in a
         fault tolerant way.

   Thread Model
       The -t option to gearmand allows you to specify multiple I/O threads, this is  enabled  by
       default. There are currently three types of threads in the job server:

       Listening  and management thread - only one I/O thread - can have many Processing thread -
       only one

       When no -t option is given or -t 0 is given, all of three thread  types  happen  within  a
       single thread. When -t 1 is given, there is a thread for listening/management and a thread
       for I/O and processing. When -t 2 is given, there is a thread  for  each  type  of  thread
       above. For all -t option values above 2, more I/O threads are created.

       The  listening  and  management thread is mainly responsible for accepting new connections
       and assigning those connections to an I/O thread (if there are many). It also  coordinates
       startup  and shutdown within the server. This thread will have an instance of libevent for
       managing socket events and signals on an internal pipe. This pipe is used  to  wakeup  the
       thread or to coordinate shutdown.

       The I/O thread is responsible for doing the read and write system calls on the sockets and
       initial packet parsing. Once the packet has been parsed it it  put  into  an  asynchronous
       queue  for  the  processing thread (each thread has it's own queue so there is very little
       contention). Each I/O thread has it's own instance of libevent for managing socket  events
       and signals on an internal pipe like the listening thread.

       The  processing  thread  should  have no system calls within it (except for the occasional
       brk() for more memory), and manages the various lists and hash tables  used  for  tracking
       unique keys, job handles, functions, and job queues. All packets that need to be sent back
       to connections are put into an asynchronous queue for the I/O thread. The I/O thread  will
       pick  these  up and send them back over the connected socket. All packets flow through the
       processing thread since it contains the information needed to process the packets. This is
       due  to  the complex nature of the various lists and hash tables. If multiple threads were
       modifying them the locking overhead would most likely cause worse performance than  having
       it in a single thread (and would also complicate the code). In the future more work may be
       pushed to the I/O threads, and the processing thread can retain minimal  functionality  to
       manage  those  tables  and  lists. So far this has not been a significant bottleneck, a 16
       core Intel machine is able to process upwards of 50k jobs per second.

       For thread safety to work when UUID are generated, you must be running the uuidd daemon.

   Persistent Queues
       Inside the Gearman job server, all job queues are stored in memory. This means if a server
       restarts  or  crashes  with pending jobs, they will be lost and are never run by a worker.
       Persistent queues were added to allow background jobs to be stored in an external  durable
       queue  so  they may live between server restarts and crashes. The persistent queue is only
       enabled for background jobs because foreground jobs have an  attached  client.  If  a  job
       server goes away, the client can detect this and restart the foreground job somewhere else
       (or report an error back to the original caller). Background jobs on the other  hand  have
       no attached client and are simply expected to be run when submitted.

       The  persistent  queue  works by calling a module callback function right before putting a
       new job in the internal queue for pending jobs to be run. This allows the module to  store
       the  job  about to be run in some persistent way so that it can later be replayed during a
       restart. Once it is stored through the module, the job is put  onto  the  active  runnable
       queue, waking up available workers if needed. Once the job has been successfully completed
       by a worker, another module callback function is called to notify the module  the  job  is
       done  and  can be removed. If a job server crashes or is restarted between these two calls
       for a job, the jobs are reloaded during the next job server start.  When  the  job  server
       starts  up, it will call a replay callback function in the module to provide a list of all
       jobs that were not complete. This is used to populate the internal memory queue of jobs to
       be  run.  Once this replay is complete, the job server finishes its initialization and the
       jobs are now runnable once workers connect (the queue should be in the same state as  when
       it  crashed).  These  jobs are removed from the persistent queue when completed as normal.
       NOTE: Deleting jobs from the persistent queue  storage  will  not  remove  them  from  the
       in-memory queue while the server is running.

       The  queues are implemented using a modular interface so it is easy to add new data stores
       for the persistent queue.

       A persistent queue module is enabled by passing the -q or –queue-type option to  gearmand.
       Run  gearmand  –help  to  see which queue modules are supported on your system. If you are
       missing options for one you would like to use, you will need to install  any  dependencies
       and then recompile the gearmand package.

   Extended Protocols
       The  protocol  plugin  interface  allows  you  to  take  over  the packet send and receive
       functions, allowing you to pack the buffers as required by the protocol. The core read and
       write functions can (and should) be used by the protocol plugin.

   HTTP
       This  protocol  plugin  allows  you to map HTTP requests to Gearman jobs. It only provides
       client job submission currently, but it may be extended to support other request types  in
       the  future. The plugin can handle both GET and POST data, the latter being used to send a
       workload to the job server. The URL being requested is translated into the function  being
       called.

       For example, the request:

          POST /reverse HTTP/1.1
          Content-Length: 12

          Hello world!

       Is translated into a job submission request for the function “reverse” and workload “Hello
       world!”. This will respond with:

          HTTP/1.0 200 OK
          X-Gearman-Job-Handle: H:lap:4
          Content-Length: 12
          Server: Gearman/0.8

          !dlrow olleH

       The following headers can be passed to change the behavior of the job:

          * X-Gearman-Unique: <unique key>
          * X-Gearman-Background: true
          * X-Gearman-Priority: <high|low>

       For example, to run a low priority background job, the following request can be sent:

          POST /reverse HTTP/1.1
          Content-Length: 12
          X-Gearman-Background: true
          X-Gearman-Priority: low

          Hello world!

       The response for this request will not have any data associated with it  since  it  was  a
       background job:

          HTTP/1.0 200 OK
          X-Gearman-Job-Handle: H:lap:6
          Content-Length: 0
          Server: Gearman/0.8

       The HTTP protocol should be considered experimental.

HOME

       To find out more information please check: http://gearman.info/

SEE ALSO

       gearman(1) gearadmin(1) libgearmand(3)

AUTHOR

       Data Differential http://www.datadifferential.com/

COPYRIGHT

       2011-2013, Data Differential, http://www.datadifferential.com/