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Connections

Connection Options

On this page

  • Overview
  • Options
  • Single Timeout Setting
  • Timeout Examples

Overview

This guide explains several common MongoDB connection and authentication options. You can pass the connection options as parameters in the connection URI to specify the behavior of the client.

Options

The following table describes the connection options that you can set in your connection URI. Each entry provides the option name, value type, default value, and a description of the option.

Option Name
Type
Default Value
Description
timeoutMS
integer
null
Specifies the number of milliseconds that a single operation run on the Client can take before returning a timeout error. Operations honor this setting only if there is no deadline on the operation Context.
connectTimeoutMS
integer
30000
Specifies the time in milliseconds to attempt a connection before timing out.
maxPoolSize
integer
100
Specifies the maximum number of connections that a connection pool may have at a given time.
replicaSet
string
null
Specifies the replica set name for the cluster. All nodes in the replica set must have the same replica set name, or the Client will not consider them as part of the set.
maxIdleTimeMS
integer
0
Specifies the maximum amount of time a connection can remain idle in the connection pool before being removed and closed. The default is 0, meaning a connection can remain unused indefinitely.
minPoolSize
integer
0
Specifies the minimum number of connections that the driver maintains in a single connection pool.
serverSelectionTimeoutMS
integer
30000
Specifies the number of milliseconds to wait to find an available, suitable server to execute an operation.
heartbeatFrequencyMS
integer
10000
Specifies the number of milliseconds to wait between periodic background server checks.
tls
boolean
false
Specifies whether to establish a Transport Layer Security (TLS) connection with the instance. This is automatically set to true when using a DNS seedlist (SRV) in the connection string. You can override this behavior by setting the value to false.
w
string or integer
null
Specifies the write concern. To learn more about values, see the server documentation on Write Concern options.
directConnection
boolean
false
Specifies whether to force dispatch all operations to the host specified in the connection URI.

For a full list of connection options, see the ClientOptions API documentation.

Single Timeout Setting

You can set a single Timeout option on your Client instance to specify the maximum amount of time that a single operation can take to execute.

Set a client-level timeout by calling the SetTimeout() method when specifying options for your Client instance or by specifying the timeoutMS option in your connection URI. By default, all Database, Collection, Session, ChangeStream, and Bucket instances elsewhere in your application inherit the Timeout option from Client if you do not set a different timeout on specific operations in the operation's Context.

If you set a timeout on a Context passed into an operation, the driver uses that value for the operation. If you do not specify a Context timeout, the operation Context derives the timeout from the Client instance.

Note

Retries under Timeout Specification

If you set a timeout on your Client or in an operation-level Context and the server returns a retryable error, the driver retries the operation as many times as possible before the timeout expires.

Once the timeout expires, the driver returns a timeout error. See the Server manual for more information about retryable reads and retryable writes.

Timeout Examples

This section provides examples that demonstrate different ways to set a timeout in your application.

Client Option

The following code shows how to set the Timeout option on a Client by using the SetTimeout() method:

opts := options.Client().SetTimeout(5 * time.Second)
client, err := mongo.Connect(opts)

Connection String Option

The following example shows how to set a single timeout by using the timeoutMS URI option. Then, the code executes an insert operation that inherits the timeout:

uri := "mongodb://user:pass@sample.host:27017/?timeoutMS=5000"
client, err := mongo.Connect(options.Client().ApplyURI(uri))
...
coll.InsertOne(context.Background(), doc)

Operation Timeout

The following example shows how to set an operation-level timeout in a Context, which takes priority over a client-level timeout you might have set:

ctx, cancel := context.WithTimeout(context.TODO(), time.Second)
defer cancel()
res, err := coll.InsertOne(ctx, bson.D{{"x", 2}})

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