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mongos
¶
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
Options¶
-
mongos
¶
-
--help
,
-h
¶
Returns a basic help and usage text.
-
--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 “Configuration File Options” document for more information about these options.
Not all configuration options for
mongod
make sense in the context ofmongos
.
-
--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
.)
-
--port
<port>
¶ Specifies a TCP port for the
mongos
to listen for client connections. By defaultmongos
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 defaultmongos
listens for connections all interfaces. You may attachmongos
to any interface; however, when attachingmongos
to a publicly accessible interface ensure that you have implemented proper authentication and/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 setmaxConns
, 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
.
-
--pidfilepath
<path>
¶ Specify a file location to hold the “PID” or process ID of the
mongos
process. Useful for tracking themongos
process in combination with themongos --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.
-
--nounixsocket
¶
Disables listening on the UNIX socket.
mongos
always listens on the UNIX socket, unless--nounixsocket
is set,--bind_ip
is not set, or--bind_ip
specifies127.0.0.1
.
-
--unixSocketPrefix
<path>
¶ Specifies a path for the UNIX socket. Unless this option has a value
mongos
creates a socket with/tmp
as a prefix.MongoDB will always create and listen on a UNIX socket, unless
--nounixsocket
is set,--bind_ip
is not set, or--bind_ip
specifies127.0.0.1
.
-
--fork
¶
Enables a daemon mode for
mongos
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. Allmongos
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 yourmongos
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 “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 inmongod
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 thatmongos
uses when selecting replica set members to pass read operations to from clients. Specify a value to--localThreshold
in milliseconds. The default value is15
, which corresponds to the default value in all of the client drivers.When
mongos
receives a request that permits reads to secondary members, themongos
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 themongos
recalculates the average.See the Member Selection section of the read preference documentation for more information.
-
--noAutoSplit
¶
New in version 2.0.7.
--noAutoSplit
preventsmongos
from automatically inserting metadata splits in a sharded collection. If set on allmongos
, 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 allmongos
.Warning
With
--noAutoSplit
enabled, the data in your sharded cluster may become imbalanced over time. Enable with caution.