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       mongos - MongoDB Shard Utility


       mongos  for  "MongoDB  Shard,"  is a routing service for MongoDB shard configurations that
       processes queries from the application layer, and determines the location of this data  in
       the  sharded  cluster, in order to complete these operations.  From the perspective of the
       application, a mongos instance behaves identically to any other MongoDB instance.

       Note   Changed in version 2.1.

              Some aggregation operations using the aggregate  will  cause  mongos  instances  to
              require  more  CPU  resources  than in previous versions. This modified performance
              profile may dictate alternate architecture decisions if  you  use  the  aggregation
              framework extensively in a sharded environment.

       See also

              /sharding and /core/sharded-clusters.



       --help, -h
              Returns a basic help and usage text.

              Returns the version of the mongod daemon.

       --config <filename>, -f <filename>
              Specifies a configuration file, that you can use to specify runtime-configurations.
              While the options  are  equivalent  and  accessible  via  the  other  command  line
              arguments, the configuration file is the preferred method for runtime configuration
              of mongod. See the "/reference/configuration-options" document for more information
              about these options.

              Not all configuration options for mongod make sense in the context of mongos.

       --verbose, -v
              Increases  the  amount  of internal reporting returned on standard output or in the
              log file specified by --logpath. Use the -v form to control the level of  verbosity
              by including the option multiple times, (e.g. -vvvvv.)

              Runs  the  mongos  instance  in  a  quiet mode that attempts to limit the amount of

       --port <port>
              Specifies a TCP port for the mongos to listen for client  connections.  By  default
              mongos listens for connections on port 27017.

              UNIX-like systems require root access to access ports with numbers lower than 1024.

       --bind_ip <ip address>
              The  IP address that the mongos process will bind to and listen for connections. By
              default mongos listens for connections on the localhost (i.e.  address.)
              You may attach mongos to any interface; however, if you attach mongos to a publicly
              accessible  interface  you  must  implement  proper  authentication   or   firewall
              restrictions to protect the integrity of your database.

       --maxConns <number>
              Specifies  the  maximum number of simultaneous connections that mongos will accept.
              This setting will have no effect if the value of this setting is higher  than  your
              operating system's configured maximum connection tracking threshold.

              This  is  particularly useful for mongos if you have a client that creates a number
              of collections but allows them to timeout rather than close the  collections.  When
              you  set  maxConns,  ensure  the  value  is  slightly  higher  than the size of the
              connection pool or the total number of connections to prevent erroneous  connection
              spikes from propagating to the members of a shard cluster.

       Note   You cannot set maxConns to a value higher than 20000.

              Forces the mongos to validate all requests from clients upon receipt to ensure that
              invalid objects are never inserted into the database. This option has a performance
              impact, and is not enabled by default.

       --logpath <path>
              Specify a path for the log file that will hold all diagnostic logging information.

              Unless  specified,  mongos  will output all log information to the standard output.
              Additionally, unless you also specify --logappend, the logfile will be  overwritten
              when the process restarts.

              Specify  to  ensure  that  mongos appends additional logging data to the end of the
              logfile rather than overwriting the content of the log when the process restarts.

              New in version 2.1.0.

              Sends all logging output to the host's syslog system rather than to standard output
              or a log file as with --logpath.

              You cannot use --syslog with --logpath.

       --pidfilepath <path>
              Specify  a  file  location  to  hold the "PID" or process ID of the mongos process.
              Useful for tracking the mongos  process  in  combination  with  the  mongos  --fork

              Without a specified --pidfilepath option, mongos creates no PID file.

       --keyFile <file>
              Specify  the path to a key file to store authentication information. This option is
              only useful for the connection between  mongos  instances  and  components  of  the
              sharded cluster.

       See also


              Disables  listening  on  the UNIX socket. Without this option mongos creates a UNIX

       --unixSocketPrefix <path>
              Specifies a path for the UNIX socket. Unless specified, mongos creates a socket  in
              the /tmp path.

       --fork Enables  a  daemon mode for mongod which forces the process to the background. This
              is the normal mode of operation, in production  and  production-like  environments,
              but may not be desirable for testing.

       --configdb <config1>,<config2><:port>,<config3>
              Set  this option to specify a configuration database (i.e. config database) for the
              sharded cluster. You must specify either 1 configuration server or 3  configuration
              servers, in a comma separated list.

       Note   mongos instances read from the first config server in the list provided. All mongos
              instances must specify the hosts to the --configdb setting in the same order.

              If your configuration databases reside in more that  one  data  center,  order  the
              hosts in the --configdb argument so that the config database that is closest to the
              majority of your mongos instances is first servers in the list.

              Never remove a config server from the --configdb  parameter,  even  if  the  config
              server or servers are not available, or offline.

       --test This  option is for internal testing use only, and runs unit tests without starting
              a mongos instance.

              This option updates the meta data format used by the config database.

       --chunkSize <value>
              The value of the --chunkSize determines the size of each chunk,  in  megabytes,  of
              data  distributed  around  the  sharded cluster. The default value is 64 megabytes,
              which is the ideal size for chunks in most deployments: larger chunk size can  lead
              to uneven data distribution, smaller chunk size often leads to inefficient movement
              of chunks between nodes. However, in some circumstances it may be necessary to  set
              a different chunk size.

              This  option  only  sets the chunk size when initializing the cluster for the first
              time. If you modify the run-time option later, the new value will have  no  effect.
              See  the "sharding-balancing-modify-chunk-size" procedure if you need to change the
              chunk size on an existing sharded cluster.

       --ipv6 Enables IPv6 support to allow clients to connect to  mongos  using  IPv6  networks.
              MongoDB disables IPv6 support by default in mongod and all utilities.

              Permits  JSONP  access via an HTTP interface. Consider the security implications of
              allowing this activity before enabling this option.

              Disables the scripting engine.

              New in version 2.1.2.

              Disables the HTTP interface.

              New in version 2.2.

              --localThreshold affects the logic that mongos  uses  when  selecting  replica  set
              members   to   pass   read   operations   to  from  clients.  Specify  a  value  to
              --localThreshold in milliseconds. The default value is 15, which corresponds to the
              default value in all of the client drivers.

              When  mongos receives a request that permits reads to secondary members, the mongos

                 · find the member of the set with the lowest ping time.

                 · construct a list of replica set members that is  within  a  ping  time  of  15
                   milliseconds of the nearest suitable member of the set.

                   If you specify a value for --localThreshold, mongos will construct the list of
                   replica members that are within the latency allowed by this value.

                 · The mongos will select a member to read from at random from this list.

              The ping time used for a set member compared by the --localThreshold setting  is  a
              moving  average  of  recent ping times, calculated, at most, every 10 seconds. As a
              result, some queries may  reach  members  above  the  threshold  until  the  mongos
              recalculates the average.

              See  the  replica-set-read-preference-behavior-member-selection section of the read
              preference documentation for more information.

              New in version 2.0.7.

              --noAutoSplit prevents mongos from automatically inserting  metadata  splits  in  a
              sharded  collection.  If set on all mongos, this will prevent MongoDB from creating
              new chunks as the data in a collection grows.

              Because any mongos in a cluster can create a split, to totally disable splitting in
              a cluster you must set --noAutoSplit on all mongos.

              With  --noAutoSplit enabled, the data in your sharded cluster may become imbalanced
              over time. Enable with caution.

   SSL Options

              /administration/ssl for full documentation of MongoDB's support.

       --authenticationDatabase <dbname>
              New in version 2.4.

              Specifies the database that holds the user's (e.g --username) credentials.

              By default, mongos assumes that the database specified to the --db  argument  holds
              the user's credentials, unless you specify --authenticationDatabase.

              See  userSource,  /reference/privilege-documents and /reference/user-privileges for
              more information about delegated authentication in MongoDB.

       --authenticationMechanism <name>
              New in version 2.4.

              Specifies the authentication mechanism. By default, the authentication mechanism is
              MONGODB-CR,  which  is  the MongoDB challenge/response authentication mechanism. In
              the MongoDB Subscriber Edition, mongos also includes support for GSSAPI  to  handle
              Kerberos authentication.

              See   /tutorial/control-access-to-mongodb-with-kerberos-authentication   for   more
              information about Kerberos authentication.


       MongoDB Documentation Project


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