mongoc_uri_t - Man Page


typedef struct _mongoc_uri_t mongoc_uri_t;


mongoc_uri_t provides an abstraction on top of the MongoDB connection URI format. It provides standardized parsing as well as convenience methods for extracting useful information such as replica hosts or authorization information.

See Connection String URI Reference on the MongoDB website for more information.


mongodb[+srv]://                             <1>
   [username:password@]                      <2>
   host1                                     <3>
   [:port1]                                  <4>
   [,host2[:port2],...[,hostN[:portN]]]      <5>
   [/[database]                              <6>
   [?options]]                               <7>

"mongodb" is the specifier of the MongoDB protocol. Use "mongodb+srv" with a single service name in place of "host1" to specify the initial list of servers with an SRV record.


An optional username and password.


The only required part of the uri.  This specifies either a hostname, IPv4 address, IPv6 address enclosed in "[" and "]", or UNIX domain socket.


An optional port number.  Defaults to :27017.


Extra optional hosts and ports.  You would specify multiple hosts, for example, for connections to replica sets.


The name of the database to authenticate if the connection string includes authentication credentials.  If /database is not specified and the connection string includes credentials, defaults to the 'admin' database.


Connection specific options.


Option names are case-insensitive. Do not repeat the same option (e.g. "mongodb://localhost/db?opt=value1&OPT=value2") since this may have unexpected results.

The MongoDB C Driver exposes constants for each supported connection option. These constants make it easier to discover connection options, but their string values can be used as well.

For example, the following calls are equal.

uri = mongoc_uri_new ("mongodb://localhost/?" MONGOC_URI_APPNAME "=applicationName");
uri = mongoc_uri_new ("mongodb://localhost/?appname=applicationName");
uri = mongoc_uri_new ("mongodb://localhost/?appName=applicationName");

Replica Set Example

To describe a connection to a replica set named 'test' with the following mongod hosts:

You would use a connection string that resembles the following.


SRV Example

If you have configured an SRV record with a name like "" whose records are a list of one or more MongoDB server hostnames, use a connection string like this:

uri = mongoc_uri_new ("mongodb+srv://");

The driver prefixes the service name with "_mongodb._tcp.", then performs a DNS SRV query to resolve the service name to one or more hostnames. If this query succeeds, the driver performs a DNS TXT query on the service name (without the "_mongodb._tcp" prefix) for additional URI options configured as TXT records.

On Unix, the MongoDB C Driver relies on libresolv to look up SRV and TXT records. If libresolv is unavailable, then using a "mongodb+srv" URI will cause an error. If your libresolv lacks res_nsearch then the driver will fall back to res_search, which is not thread-safe.

IPv4 and IPv6

If connecting to a hostname that has both IPv4 and IPv6 DNS records, the behavior follows RFC-6555. A connection to the IPv6 address is attempted first. If IPv6 fails, then a connection is attempted to the IPv4 address. If the connection attempt to IPv6 does not complete within 250ms, then IPv4 is tried in parallel. Whichever succeeds connection first cancels the other. The successful DNS result is cached for 10 minutes.

As a consequence, attempts to connect to a mongod only listening on IPv4 may be delayed if there are both A (IPv4) and AAAA (IPv6) DNS records associated with the host.

To avoid a delay, configure hostnames to match the MongoDB configuration. That is, only create an A record if the mongod is only listening on IPv4.

Connection Options

MONGOC_URI_RETRYREADSretryreadstrueIf "true" and the server is a MongoDB 3.6+ standalone, replica set, or sharded cluster, the driver safely retries a read that failed due to a network error or replica set failover.
MONGOC_URI_RETRYWRITESretrywritestrue if driver built w/ TLSIf "true" and the server is a MongoDB 3.6+ replica set or sharded cluster, the driver safely retries a write that failed due to a network error or replica set failover. Only inserts, updates of single documents, or deletes of single documents are retried.
MONGOC_URI_APPNAMEappnameEmpty (no appname)The client application name. This value is used by MongoDB when it logs connection information and profile information, such as slow queries.
MONGOC_URI_TLStlsEmpty (not set, same as false){true|false}, indicating if TLS must be used. (See also mongoc_client_set_ssl_opts() and mongoc_client_pool_set_ssl_opts().)
MONGOC_URI_COMPRESSORScompressorsEmpty (no compressors)Comma separated list of compressors, if any, to use to compress the wire protocol messages. Snappy, zlib, and zstd are optional build time dependencies, and enable the "snappy", "zlib", and "zstd" values respectively.
MONGOC_URI_CONNECTTIMEOUTMSconnecttimeoutms10,000 ms (10 seconds)This setting applies to new server connections. It is also used as the socket timeout for server discovery and monitoring operations.
MONGOC_URI_SOCKETTIMEOUTMSsockettimeoutms300,000 ms (5 minutes)The time in milliseconds to attempt to send or receive on a socket before the attempt times out.
MONGOC_URI_REPLICASETreplicasetEmpty (no replicaset)The name of the Replica Set that the driver should connect to.
MONGOC_URI_ZLIBCOMPRESSIONLEVELzlibcompressionlevel-1When the MONGOC_URI_COMPRESSORS includes "zlib" this options configures the zlib compression level, when the zlib compressor is used to compress client data.
MONGOC_URI_LOADBALANCEDloadbalancedfalseIf true, this indicates the driver is connecting to a MongoDB cluster behind a load balancer.
MONGOC_URI_SRVMAXHOSTSsrvmaxhosts0If zero, the number of hosts in DNS results is unlimited. If greater than zero, the number of hosts in DNS results is limited to being less than or equal to the given value.

Setting any of the *timeoutMS options above to either 0 or a negative value is discouraged due to unspecified and inconsistent behavior. The "default value" historically specified as a fallback for 0 or a negative value is NOT related to the default values for the *timeoutMS options documented above. The meaning of a timeout of 0 or a negative value may vary depending on the operation being executed, even when specified by the same URI option. To specify the documented default value for a *timeoutMS option, use the MONGOC_DEFAULT_* constants defined in mongoc-client.h instead.

Authentication Options

MONGOC_URI_AUTHMECHANISMauthmechanismSpecifies the mechanism to use when authenticating as the provided user. See Authentication for supported values.
MONGOC_URI_AUTHMECHANISMPROPERTIESauthmechanismpropertiesCertain authentication mechanisms have additional options that can be configured. These options should be provided as comma separated option_key:option_value pair and provided as authMechanismProperties. Specifying the same option_key multiple times has undefined behavior.
MONGOC_URI_AUTHSOURCEauthsourceThe authSource defines the database that should be used to authenticate to. It is unnecessary to provide this option the database name is the same as the database used in the URI.

Mechanism Properties

MONGOC_URI_CANONICALIZEHOSTNAMEcanonicalizehostnameUse the canonical hostname of the service, rather than its configured alias, when authenticating with Cyrus-SASL Kerberos.
MONGOC_URI_GSSAPISERVICENAMEgssapiservicenameUse alternative service name. The default is mongodb.

TLS Options

MONGOC_URI_TLStls{true|false}, indicating if TLS must be used.
MONGOC_URI_TLSCERTIFICATEKEYFILEtlscertificatekeyfilePath to PEM formatted Private Key, with its Public Certificate concatenated at the end.
MONGOC_URI_TLSCERTIFICATEKEYFILEPASSWORDtlscertificatekeypasswordThe password, if any, to use to unlock encrypted Private Key.
MONGOC_URI_TLSCAFILEtlscafileOne, or a bundle of, Certificate Authorities whom should be considered to be trusted.
MONGOC_URI_TLSALLOWINVALIDCERTIFICATEStlsallowinvalidcertificatesAccept and ignore certificate verification errors (e.g. untrusted issuer, expired, etc.)
MONGOC_URI_TLSALLOWINVALIDHOSTNAMEStlsallowinvalidhostnamesIgnore hostname verification of the certificate (e.g. Man In The Middle, using valid certificate, but issued for another hostname)
MONGOC_URI_TLSINSECUREtlsinsecure{true|false}, indicating if insecure TLS options should be used. Currently this implies MONGOC_URI_TLSALLOWINVALIDCERTIFICATES and MONGOC_URI_TLSALLOWINVALIDHOSTNAMES.
MONGOC_URI_TLSDISABLECERTIFICATEREVOCATIONCHECKtlsdisablecertificaterevocationcheck{true|false}, indicates if revocation checking (CRL / OCSP) should be disabled.
MONGOC_URI_TLSDISABLEOCSPENDPOINTCHECKtlsdisableocspendpointcheck{true|false}, indicates if OCSP responder endpoints should not be requested when an OCSP response is not stapled.

See Configuring TLS for details about these options and about building libmongoc with TLS support.

Deprecated SSL Options

The following options have been deprecated and may be removed from future releases of libmongoc.

ConstantKeyDeprecated ForKey

Server Discovery, Monitoring, and Selection Options

Clients in a mongoc_client_pool_t share a topology scanner that runs on a background thread. The thread wakes every heartbeatFrequencyMS (default 10 seconds) to scan all MongoDB servers in parallel. Whenever an application operation requires a server that is not known--for example, if there is no known primary and your application attempts an insert--the thread rescans all servers every half-second. In this situation the pooled client waits up to serverSelectionTimeoutMS (default 30 seconds) for the thread to find a server suitable for the operation, then returns an error with domain MONGOC_ERROR_SERVER_SELECTION.

Technically, the total time an operation may wait while a pooled client scans the topology is controlled both by serverSelectionTimeoutMS and connectTimeoutMS. The longest wait occurs if the last scan begins just at the end of the selection timeout, and a slow or down server requires the full connection timeout before the client gives up.

A non-pooled client is single-threaded. Every heartbeatFrequencyMS, it blocks the next application operation while it does a parallel scan. This scan takes as long as needed to check the slowest server: roughly connectTimeoutMS. Therefore the default heartbeatFrequencyMS for single-threaded clients is greater than for pooled clients: 60 seconds.

By default, single-threaded (non-pooled) clients scan only once when an operation requires a server that is not known. If you attempt an insert and there is no known primary, the client checks all servers once trying to find it, then succeeds or returns an error with domain MONGOC_ERROR_SERVER_SELECTION. But if you set serverSelectionTryOnce to "false", the single-threaded client loops, checking all servers every half-second, until serverSelectionTimeoutMS.

The total time an operation may wait for a single-threaded client to scan the topology is determined by connectTimeoutMS in the try-once case, or serverSelectionTimeoutMS and connectTimeoutMS if serverSelectionTryOnce is set "false".

MONGOC_URI_HEARTBEATFREQUENCYMSheartbeatfrequencymsThe interval between server monitoring checks. Defaults to 10,000ms (10 seconds) in pooled (multi-threaded) mode, 60,000ms (60 seconds) in non-pooled mode (single-threaded).
MONGOC_URI_SERVERSELECTIONTIMEOUTMSserverselectiontimeoutmsA timeout in milliseconds to block for server selection before throwing an exception. The default is 30,0000ms (30 seconds).
MONGOC_URI_SERVERSELECTIONTRYONCEserverselectiontryonceIf "true", the driver scans the topology exactly once after server selection fails, then either selects a server or returns an error. If it is false, then the driver repeatedly searches for a suitable server for up to serverSelectionTimeoutMS milliseconds (pausing a half second between attempts). The default for serverSelectionTryOnce is "false" for pooled clients, otherwise "true". Pooled clients ignore serverSelectionTryOnce; they signal the thread to rescan the topology every half-second until serverSelectionTimeoutMS expires.
MONGOC_URI_SOCKETCHECKINTERVALMSsocketcheckintervalmsOnly applies to single threaded clients. If a socket has not been used within this time, its connection is checked with a quick "hello" call before it is used again. Defaults to 5,000ms (5 seconds).
MONGOC_URI_DIRECTCONNECTIONdirectconnectionIf "true", the driver connects to a single server directly and will not monitor additional servers.  If "false", the driver connects based on the presence and value of the replicaSet option.

Setting any of the *TimeoutMS options above to 0 will be interpreted as "use the default value".

Connection Pool Options

These options govern the behavior of a mongoc_client_pool_t. They are ignored by a non-pooled mongoc_client_t.

MONGOC_URI_MAXPOOLSIZEmaxpoolsizeThe maximum number of clients created by a mongoc_client_pool_t total (both in the pool and checked out). The default value is 100. Once it is reached, mongoc_client_pool_pop() blocks until another thread pushes a client.
MONGOC_URI_MINPOOLSIZEminpoolsizeDeprecated. This option's behavior does not match its name, and its actual behavior will likely hurt performance.
MONGOC_URI_MAXIDLETIMEMSmaxidletimemsNot implemented.
MONGOC_URI_WAITQUEUEMULTIPLEwaitqueuemultipleNot implemented.
MONGOC_URI_WAITQUEUETIMEOUTMSwaitqueuetimeoutmsThe maximum time to wait for a client to become available from the pool.

Write Concern Options

MONGOC_URI_WwDetermines the write concern (guarantee). Valid values:
  • 0 = The driver will not acknowledge write operations but will pass or handle any network and socket errors that it receives to the client. If you disable write concern but enable the getLastError command’s w option, w overrides the w option.
  • 1 = Provides basic acknowledgement of write operations. By specifying 1, you require that a standalone mongod instance, or the primary for replica sets, acknowledge all write operations. For drivers released after the default write concern change, this is the default write concern setting.
  • majority = For replica sets, if you specify the special majority value to w option, write operations will only return successfully after a majority of the configured replica set members have acknowledged the write operation.
  • n = For replica sets, if you specify a number n greater than 1, operations with this write concern return only after n members of the set have acknowledged the write. If you set n to a number that is greater than the number of available set members or members that hold data, MongoDB will wait, potentially indefinitely, for these members to become available.
  • tags = For replica sets, you can specify a tag set to require that all members of the set that have these tags configured return confirmation of the write operation.
MONGOC_URI_WTIMEOUTMSwtimeoutmsThe time in milliseconds to wait for replication to succeed, as specified in the w option, before timing out. When wtimeoutMS is 0, write operations will never time out.
MONGOC_URI_JOURNALjournalControls whether write operations will wait until the mongod acknowledges the write operations and commits the data to the on disk journal.
  • true  = Enables journal commit acknowledgement write concern. Equivalent to specifying the getLastError command with the j option enabled.
  • false = Does not require that mongod commit write operations to the journal before acknowledging the write operation. This is the default option for the journal parameter.

Read Concern Options

MONGOC_URI_READCONCERNLEVELreadconcernlevelThe level of isolation for read operations. If the level is left unspecified, the server default will be used. See readConcern in the MongoDB Manual for details.

Read Preference Options

When connected to a replica set, the driver chooses which member to query using the read preference:

  1. Choose members whose type matches "readPreference".
  2. From these, if there are any tags sets configured, choose members matching the first tag set. If there are none, fall back to the next tag set and so on, until some members are chosen or the tag sets are exhausted.
  3. From the chosen servers, distribute queries randomly among the server with the fastest round-trip times. These include the server with the fastest time and any whose round-trip time is no more than "localThresholdMS" slower.
MONGOC_URI_READPREFERENCEreadpreferenceSpecifies the replica set read preference for this connection. This setting overrides any secondaryOk value. The read preference values are the following:
  • primary (default)
  • primaryPreferred
  • secondary
  • secondaryPreferred
  • nearest
MONGOC_URI_READPREFERENCETAGSreadpreferencetagsA representation of a tag set. See also Tag Sets.
MONGOC_URI_LOCALTHRESHOLDMSlocalthresholdmsHow far to distribute queries, beyond the server with the fastest round-trip time. By default, only servers within 15ms of the fastest round-trip time receive queries.
MONGOC_URI_MAXSTALENESSSECONDSmaxstalenesssecondsThe maximum replication lag, in wall clock time, that a secondary can suffer and still be eligible. The smallest allowed value for maxStalenessSeconds is 90 seconds.

When connecting to more than one mongos, libmongoc's localThresholdMS applies only to the selection of mongos servers. The threshold for selecting among replica set members in shards is controlled by the mongos's localThreshold command line option.

Legacy Options

For historical reasons, the following options are available. They should however not be used.

MONGOC_URI_SAFEsafe{true|false} Same as w={1|0}


MongoDB, Inc


Apr 03, 2024 1.26.2 libmongoc