NAME

       mongos - MongoDB Shard Utility

SYNOPSIS

       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.

OPTIONS

       mongos

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

       --version
              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.)

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

       --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. 127.0.0.1 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.

       --objcheck
              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.

       --logappend
              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.

       --syslog
              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.

       Warning
              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 option.

              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

              sharding-security

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

       --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.

       Warning
              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.

       --upgrade
              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.

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

       --noscripting
              Disables the scripting engine.

       --nohttpinterface
              New in version 2.1.2.

              Disables the HTTP interface.

       --localThreshold
              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 will:

                 • 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.

       --noAutoSplit
              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.

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

   SSL Options
       See

              /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.

AUTHOR

       MongoDB Documentation Project

COPYRIGHT

       2011-2013, 10gen, Inc.