= Vert.x MongoDB Client

A Vert.x client allowing applications to interact with a MongoDB instance, whether that's
saving, retrieving, searching, or deleting documents.

Mongo is a great match for persisting data in a Vert.x application
as it natively handles JSON (BSON) documents.

*Features*

* Completely non-blocking
* Custom codec to support fast serialization to/from Vert.x JSON
* Supports a majority of the configuration options from the MongoDB Java Driver

This client is based on the
http://mongodb.github.io/mongo-java-driver/3.2/driver-async/getting-started[MongoDB Async Driver].

== Using Vert.x MongoDB Client

To use this project, add the following dependency to the _dependencies_ section of your build descriptor:

* Maven (in your `pom.xml`):

[source,xml,subs="+attributes"]
----
<dependency>
  <groupId>io.vertx</groupId>
  <artifactId>vertx-mongo-client</artifactId>
  <version>3.5.3</version>
</dependency>
----

* Gradle (in your `build.gradle` file):

[source,groovy,subs="+attributes"]
----
compile 'io.vertx:vertx-mongo-client:3.5.3'
----


== Creating a client

You can create a client in several ways:

=== Using the default shared pool

In most cases you will want to share a pool between different client instances.

E.g. you scale your application by deploying multiple instances of your verticle and you want each verticle instance
to share the same pool so you don't end up with multiple pools

The simplest way to do this is as follows:

[source,js]
----
var MongoClient = require("vertx-mongo-js/mongo_client");
var client = MongoClient.createShared(vertx, config);

----

The first call to `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#createShared[MongoClient.createShared]`
will actually create the pool, and the specified config will be used.

Subsequent calls will return a new client instance that uses the same pool, so the configuration won't be used.

=== Specifying a pool source name

You can create a client specifying a pool source name as follows

[source,js]
----
var MongoClient = require("vertx-mongo-js/mongo_client");
var client = MongoClient.createShared(vertx, config, "MyPoolName");

----

If different clients are created using the same Vert.x instance and specifying the same pool name, they will
share the same pool.

The first call to `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#createShared[MongoClient.createShared]`
will actually create the pool, and the specified config will be used.

Subsequent calls will return a new client instance that uses the same pool, so the configuration won't be used.

Use this way of creating if you wish different groups of clients to have different pools, e.g. they're
interacting with different databases.

=== Creating a client with a non shared data pool

In most cases you will want to share a pool between different client instances.
However, it's possible you want to create a client instance that doesn't share its pool with any other client.

In that case you can use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#createNonShared[MongoClient.createNonShared]`.

[source,js]
----
var MongoClient = require("vertx-mongo-js/mongo_client");
var client = MongoClient.createNonShared(vertx, config);

----

This is equivalent to calling `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#createShared[MongoClient.createShared]`
with a unique pool name each time.


== Using the API

The client API is represented by `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html[MongoClient]`.

=== Saving documents

To save a document you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#save[save]`.

If the document has no `\_id` field, it is inserted, otherwise, it is __upserted__.
Upserted means it is inserted if it doesn't already exist, otherwise it is updated.

If the document is inserted and has no id, then the id field generated will be returned to the result handler.

Here's an example of saving a document and getting the id back

[source,js]
----
// Document has no id
var document = {
  "title" : "The Hobbit"
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    var id = res;
    console.log("Saved book with id " + id);
  } else {
    res_err.printStackTrace();
  }
});

----

And here's an example of saving a document which already has an id.

[source,js]
----
// Document has an id already
var document = {
  "title" : "The Hobbit",
  "_id" : "123244"
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    // ...
  } else {
    res_err.printStackTrace();
  }
});

----

=== Inserting documents

To insert a document you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#insert[insert]`.

If the document is inserted and has no id, then the id field generated will be returned to the result handler.

[source,js]
----
// Document has an id already
var document = {
  "title" : "The Hobbit"
};
mongoClient.insert("books", document, function (res, res_err) {
  if (res_err == null) {
    var id = res;
    console.log("Inserted book with id " + id);
  } else {
    res_err.printStackTrace();
  }
});

----

If a document is inserted with an id, and a document with that id already exists, the insert will fail:

[source,js]
----
// Document has an id already
var document = {
  "title" : "The Hobbit",
  "_id" : "123244"
};
mongoClient.insert("books", document, function (res, res_err) {
  if (res_err == null) {
    //...
  } else {
    // Will fail if the book with that id already exists.
  }
});

----

=== Updating documents

To update a documents you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#updateCollection[updateCollection]`.

This updates one or multiple documents in a collection.
The json object that is passed in the `updateCollection` parameter must contain
http://docs.mongodb.org/manual/reference/operator/update-field/[Update Operators]
and determines how the object is updated.

The json object specified in the query parameter determines which documents in the collection will be updated.

Here's an example of updating a document in the books collection:

[source,js]
----
// Match any documents with title=The Hobbit
var query = {
  "title" : "The Hobbit"
};
// Set the author field
var update = {
  "$set" : {
    "author" : "J. R. R. Tolkien"
  }
};
mongoClient.updateCollection("books", query, update, function (res, res_err) {
  if (res_err == null) {
    console.log("Book updated !");
  } else {
    res_err.printStackTrace();
  }
});

----

To specify if the update should upsert or update multiple documents, use
`link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#updateCollectionWithOptions[updateCollectionWithOptions]`
and pass in an instance of `link:../dataobjects.html#UpdateOptions[UpdateOptions]`.

This has the following fields:

`multi`:: set to true to update multiple documents
`upsert`:: set to true to insert the document if the query doesn't match
`writeConcern`:: the write concern for this operation

[source,js]
----
// Match any documents with title=The Hobbit
var query = {
  "title" : "The Hobbit"
};
// Set the author field
var update = {
  "$set" : {
    "author" : "J. R. R. Tolkien"
  }
};
var options = {
  "multi" : true
};
mongoClient.updateCollectionWithOptions("books", query, update, options, function (res, res_err) {
  if (res_err == null) {
    console.log("Book updated !");
  } else {
    res_err.printStackTrace();
  }
});

----

=== Replacing documents

To replace documents you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#replaceDocuments[replaceDocuments]`.

This is similar to the update operation, however it does not take any operator.
Instead it replaces the entire document with the one provided.

Here's an example of replacing a document in the books collection

[source,js]
----
var query = {
  "title" : "The Hobbit"
};
var replace = {
  "title" : "The Lord of the Rings",
  "author" : "J. R. R. Tolkien"
};
mongoClient.replaceDocuments("books", query, replace, function (res, res_err) {
  if (res_err == null) {
    console.log("Book replaced !");
  } else {
    res_err.printStackTrace();
  }
});

----

=== Bulk operations

To execute multiple insert, update, replace, or delete operations at once, use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#bulkWrite[bulkWrite]`.

You can pass a list of `link:../dataobjects.html#BulkOperation[BulkOperations]`, with each working similar to the matching single operation.
You can pass as many operations, even of the same type, as you wish.

To specify if the bulk operation should be executed in order, and with what write option, use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#bulkWriteWithOptions[bulkWriteWithOptions]`
and pass an instance of `link:../dataobjects.html#BulkWriteOptions[BulkWriteOptions]`.
For more explanation what ordered means, see
https://docs.mongodb.com/manual/reference/method/db.collection.bulkWrite/#execution-of-operations[Execution of Operations].

=== Finding documents

To find documents you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#find[find]`.

The `query` parameter is used to match the documents in the collection.

Here's a simple example with an empty query that will match all books:

[source,js]
----
// empty query = match any
var query = {
};
mongoClient.find("books", query, function (res, res_err) {
  if (res_err == null) {
    Array.prototype.forEach.call(res, function(json) {
      console.log(JSON.stringify(json));
    });
  } else {
    res_err.printStackTrace();
  }
});

----

Here's another example that will match all books by Tolkien:

[source,js]
----
// will match all Tolkien books
var query = {
  "author" : "J. R. R. Tolkien"
};
mongoClient.find("books", query, function (res, res_err) {
  if (res_err == null) {
    Array.prototype.forEach.call(res, function(json) {
      console.log(JSON.stringify(json));
    });
  } else {
    res_err.printStackTrace();
  }
});

----

The matching documents are returned as a list of json objects in the result handler.

To specify things like what fields to return, how many results to return, etc use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#findWithOptions[findWithOptions]`
and pass in the an instance of `link:../dataobjects.html#FindOptions[FindOptions]`.

This has the following fields:

`fields`:: The fields to return in the results. Defaults to `null`, meaning all fields will be returned
`sort`:: The fields to sort by. Defaults to `null`.
`limit`:: The limit of the number of results to return. Default to `-1`, meaning all results will be returned.
`skip`:: The number of documents to skip before returning the results. Defaults to `0`.

=== Finding documents in batches

When dealing with large data sets, it is not advised to use the
`link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#find[find]` and
`link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#findWithOptions[findWithOptions]` methods.
In order to avoid inflating the whole response into memory, use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#findBatch[findBatch]`:

[source,js]
----
// will match all Tolkien books
var query = {
  "author" : "J. R. R. Tolkien"
};
mongoClient.findBatch("book", query).exceptionHandler(function (throwable) {
  throwable.printStackTrace();
}).endHandler(function (v) {
  console.log("End of research");
}).handler(function (doc) {
  console.log("Found doc: " + JSON.stringify(doc));
});

----

The matching documents are emitted one by one by the `link:../../jsdoc/module-vertx-js_read_stream-ReadStream.html[ReadStream]` handler.

`link:../dataobjects.html#FindOptions[FindOptions]` has an extra parameter `batchSize` which you can use to set the number of documents to load at once:

[source,js]
----
// will match all Tolkien books
var query = {
  "author" : "J. R. R. Tolkien"
};
var options = {
  "batchSize" : 100
};
mongoClient.findBatchWithOptions("book", query, options).exceptionHandler(function (throwable) {
  throwable.printStackTrace();
}).endHandler(function (v) {
  console.log("End of research");
}).handler(function (doc) {
  console.log("Found doc: " + JSON.stringify(doc));
});

----

By default, `batchSize` is set to 20.

=== Finding a single document

To find a single document you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#findOne[findOne]`.

This works just like `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#find[find]` but it returns just the first matching document.

=== Removing documents

To remove documents use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#removeDocuments[removeDocuments]`.

The `query` parameter is used to match the documents in the collection to determine which ones to remove.

Here's an example of removing all Tolkien books:

[source,js]
----
var query = {
  "author" : "J. R. R. Tolkien"
};
mongoClient.removeDocuments("books", query, function (res, res_err) {
  if (res_err == null) {
    console.log("Never much liked Tolkien stuff!");
  } else {
    res_err.printStackTrace();
  }
});

----

=== Removing a single document

To remove a single document you use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#removeDocument[removeDocument]`.

This works just like `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#removeDocuments[removeDocuments]` but it removes just the first matching document.

=== Counting documents

To count documents use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#count[count]`.

Here's an example that counts the number of Tolkien books. The number is passed to the result handler.

[source,js]
----
var query = {
  "author" : "J. R. R. Tolkien"
};
mongoClient.count("books", query, function (res, res_err) {
  if (res_err == null) {
    var num = res;
  } else {
    res_err.printStackTrace();
  }
});

----

=== Managing MongoDB collections

All MongoDB documents are stored in collections.

To get a list of all collections you can use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#getCollections[getCollections]`

[source,js]
----
mongoClient.getCollections(function (res, res_err) {
  if (res_err == null) {
    var collections = res;
  } else {
    res_err.printStackTrace();
  }
});

----

To create a new collection you can use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#createCollection[createCollection]`

[source,js]
----
mongoClient.createCollection("mynewcollectionr", function (res, res_err) {
  if (res_err == null) {
    // Created ok!
  } else {
    res_err.printStackTrace();
  }
});

----

To drop a collection you can use `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#dropCollection[dropCollection]`

NOTE: Dropping a collection will delete all documents within it!

[source,js]
----
mongoClient.dropCollection("mynewcollectionr", function (res, res_err) {
  if (res_err == null) {
    // Dropped ok!
  } else {
    res_err.printStackTrace();
  }
});

----


=== Running other MongoDB commands

You can run arbitrary MongoDB commands with `link:../../jsdoc/module-vertx-mongo-js_mongo_client-MongoClient.html#runCommand[runCommand]`.

Commands can be used to run more advanced MongoDB features, such as using MapReduce.
For more information see the mongo docs for supported http://docs.mongodb.org/manual/reference/command[Commands].

Here's an example of running an aggregate command. Note that the command name must be specified as a parameter
and also be contained in the JSON that represents the command. This is because JSON is not ordered but BSON is
ordered and MongoDB expects the first BSON entry to be the name of the command. In order for us to know which
of the entries in the JSON is the command name it must be specified as a parameter.

[source,js]
----
var command = {
  "aggregate" : "collection_name",
  "pipeline" : [
  ]
};
mongoClient.runCommand("aggregate", command, function (res, res_err) {
  if (res_err == null) {
    var resArr = res.result;
    // etc
  } else {
    res_err.printStackTrace();
  }
});

----

=== MongoDB Extended JSON support

For now, only `date`, `oid` and `binary` types are supported
(see http://docs.mongodb.org/manual/reference/mongodb-extended-json[MongoDB Extended JSON]).

Here's an example of inserting a document with a `date` field:

[source,js]
----
var document = {
  "title" : "The Hobbit",
  "publicationDate" : {
    "$date" : "1937-09-21T00:00:00+00:00"
  }
};
mongoService.save("publishedBooks", document, function (res, res_err) {
  if (res_err == null) {
    var id = res;
    mongoService.findOne("publishedBooks", {
      "_id" : id
    }, null, function (res2, res2_err) {
      if (res2_err == null) {
        console.log("To retrieve ISO-8601 date : " + res2.publicationDate.$date);
      } else {
        res2_err.printStackTrace();
      }
    });
  } else {
    res_err.printStackTrace();
  }
});

----

Here's an example (in Java) of inserting a document with a binary field and reading it back

[source,js]
----
byte[] binaryObject = new byte[40];
JsonObject document = new JsonObject()
  .put("name", "Alan Turing")
  .put("binaryStuff", new JsonObject().put("$binary", binaryObject));
mongoService.save("smartPeople", document, res -> {
  if (res.succeeded()) {
    String id = res.result();
    mongoService.findOne("smartPeople", new JsonObject().put("_id", id), null, res2 -> {
      if (res2.succeeded()) {
        byte[] reconstitutedBinaryObject = res2.result().getJsonObject("binaryStuff").getBinary("$binary");
        //This could now be de-serialized into an object in real life
      } else {
        res2.cause().printStackTrace();
      }
    });
  } else {
    res.cause().printStackTrace();
  }
});
----

Here's an example of inserting a base 64 encoded string, typing it as binary a binary field, and reading it back

[source,js]
----
//This could be a the byte contents of a pdf file, etc converted to base 64
var base64EncodedString = "a2FpbHVhIGlzIHRoZSAjMSBiZWFjaCBpbiB0aGUgd29ybGQ=";
var document = {
  "name" : "Alan Turing",
  "binaryStuff" : {
    "$binary" : base64EncodedString
  }
};
mongoService.save("smartPeople", document, function (res, res_err) {
  if (res_err == null) {
    var id = res;
    mongoService.findOne("smartPeople", {
      "_id" : id
    }, null, function (res2, res2_err) {
      if (res2_err == null) {
        var reconstitutedBase64EncodedString = res2.binaryStuff.$binary;
        //This could now converted back to bytes from the base 64 string
      } else {
        res2_err.printStackTrace();
      }
    });
  } else {
    res_err.printStackTrace();
  }
});

----
Here's an example of inserting an object ID and reading it back

[source,js]
----
var individualId = new (Java.type("org.bson.types.ObjectId"))().toHexString();
var document = {
  "name" : "Stephen Hawking",
  "individualId" : {
    "$oid" : individualId
  }
};
mongoService.save("smartPeople", document, function (res, res_err) {
  if (res_err == null) {
    var id = res;
    var query = {
      "_id" : id
    };
    mongoService.findOne("smartPeople", query, null, function (res2, res2_err) {
      if (res2_err == null) {
        var reconstitutedIndividualId = res2.individualId.$oid;
      } else {
        res2_err.printStackTrace();
      }
    });
  } else {
    res_err.printStackTrace();
  }
});

----

=== Getting distinct values

Here's an example of getting distinct value

[source,js]
----
var document = {
  "title" : "The Hobbit"
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    mongoClient.distinct("books", "title", Java.type("java.lang.String").class.getName(), function (res2, res2_err) {
      console.log("Title is : " + res2[0]);
    });
  } else {
    res_err.printStackTrace();
  }
});

----
Here's an example of getting distinct value in batch mode

[source,js]
----
var document = {
  "title" : "The Hobbit"
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    mongoClient.distinctBatch("books", "title", Java.type("java.lang.String").class.getName()).handler(function (book) {
      console.log("Title is : " + book.title);
    });
  } else {
    res_err.printStackTrace();
  }
});

----
* Here's an example of getting distinct value with query

[source,js]
----
var document = {
  "title" : "The Hobbit",
  "publicationDate" : {
    "$date" : "1937-09-21T00:00:00+00:00"
  }
};
var query = {
  "publicationDate" : {
    "$gte" : {
      "$date" : "1937-09-21T00:00:00+00:00"
    }
  }
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    mongoClient.distinctWithQuery("books", "title", Java.type("java.lang.String").class.getName(), query, function (res2, res2_err) {
      console.log("Title is : " + res2[0]);
    });
  }
});

----
Here's an example of getting distinct value in batch mode with query

[source,js]
----
var document = {
  "title" : "The Hobbit",
  "publicationDate" : {
    "$date" : "1937-09-21T00:00:00+00:00"
  }
};
var query = {
  "publicationDate" : {
    "$gte" : {
      "$date" : "1937-09-21T00:00:00+00:00"
    }
  }
};
mongoClient.save("books", document, function (res, res_err) {
  if (res_err == null) {
    mongoClient.distinctBatchWithQuery("books", "title", Java.type("java.lang.String").class.getName(), query).handler(function (book) {
      console.log("Title is : " + book.title);
    });
  }
});

----

== Configuring the client

The client is configured with a json object.

The following configuration is supported by the mongo client:


`db_name`:: Name of the database in the MongoDB instance to use. Defaults to `default_db`
`useObjectId`:: Toggle this option to support persisting and retrieving ObjectId's as strings. If `true`, hex-strings will
be saved as native Mongodb ObjectId types in the document collection. This will allow the sorting of documents based on creation
time. You can also derive the creation time from the hex-string using ObjectId::getDate(). Set to `false` for other types of your choosing.
If set to false, or left to default, hex strings will be generated as the document _id if the _id is omitted from the document.
Defaults to `false`.

The mongo client tries to support most options that are allowed by the driver. There are two ways to configure mongo
for use by the driver, either by a connection string or by separate configuration options.

NOTE: If the connection string is used the mongo client will ignore any driver configuration options.

`connection_string`:: The connection string the driver uses to create the client. E.g. `mongodb://localhost:27017`.
For more information on the format of the connection string please consult the driver documentation.

*Specific driver configuration options*

[source,js]
----
{
  // Single Cluster Settings
  "host" : "127.0.0.1", // string
  "port" : 27017,      // int

  // Multiple Cluster Settings
  "hosts" : [
    {
      "host" : "cluster1", // string
      "port" : 27000       // int
    },
    {
      "host" : "cluster2", // string
      "port" : 28000       // int
    },
    ...
  ],
  "replicaSet" :  "foo",    // string
  "serverSelectionTimeoutMS" : 30000, // long

  // Connection Pool Settings
  "maxPoolSize" : 50,                // int
  "minPoolSize" : 25,                // int
  "maxIdleTimeMS" : 300000,          // long
  "maxLifeTimeMS" : 3600000,         // long
  "waitQueueMultiple"  : 10,         // int
  "waitQueueTimeoutMS" : 10000,      // long
  "maintenanceFrequencyMS" : 2000,   // long
  "maintenanceInitialDelayMS" : 500, // long

  // Credentials / Auth
  "username"   : "john",     // string
  "password"   : "passw0rd", // string
  "authSource" : "some.db"   // string
  // Auth mechanism
  "authMechanism"     : "GSSAPI",        // string
  "gssapiServiceName" : "myservicename", // string

  // Socket Settings
  "connectTimeoutMS" : 300000, // int
  "socketTimeoutMS"  : 100000, // int
  "sendBufferSize"    : 8192,  // int
  "receiveBufferSize" : 8192,  // int
  "keepAlive" : true           // boolean

  // Heartbeat socket settings
  "heartbeat.socket" : {
  "connectTimeoutMS" : 300000, // int
  "socketTimeoutMS"  : 100000, // int
  "sendBufferSize"    : 8192,  // int
  "receiveBufferSize" : 8192,  // int
  "keepAlive" : true           // boolean
  }

  // Server Settings
  "heartbeatFrequencyMS" :    1000 // long
  "minHeartbeatFrequencyMS" : 500 // long
}
----

*Driver option descriptions*

`host`:: The host the MongoDB instance is running. Defaults to `127.0.0.1`. This is ignored if `hosts` is specified
`port`:: The port the MongoDB instance is listening on. Defaults to `27017`. This is ignored if `hosts` is specified
`hosts`:: An array representing the hosts and ports to support a MongoDB cluster (sharding / replication)
`host`:: A host in the cluster
`port`:: The port a host in the cluster is listening on
`replicaSet`:: The name of the replica set, if the MongoDB instance is a member of a replica set
`serverSelectionTimeoutMS`:: The time in milliseconds that the mongo driver will wait to select a server for an operation before raising an error.
`maxPoolSize`:: The maximum number of connections in the connection pool. The default value is `100`
`minPoolSize`:: The minimum number of connections in the connection pool. The default value is `0`
`maxIdleTimeMS`:: The maximum idle time of a pooled connection. The default value is `0` which means there is no limit
`maxLifeTimeMS`:: The maximum time a pooled connection can live for. The default value is `0` which means there is no limit
`waitQueueMultiple`:: The maximum number of waiters for a connection to become available from the pool. Default value is `500`
`waitQueueTimeoutMS`:: The maximum time that a thread may wait for a connection to become available. Default value is `120000` (2 minutes)
`maintenanceFrequencyMS`:: The time period between runs of the maintenance job. Default is `0`.
`maintenanceInitialDelayMS`:: The period of time to wait before running the first maintenance job on the connection pool. Default is `0`.
`username`:: The username to authenticate. Default is `null` (meaning no authentication required)
`password`:: The password to use to authenticate.
`authSource`:: The database name associated with the user's credentials. Default value is the `db_name` value.
`authMechanism`:: The authentication mechanism to use. See [Authentication](http://docs.mongodb.org/manual/core/authentication/) for more details.
`gssapiServiceName`:: The Kerberos service name if `GSSAPI` is specified as the `authMechanism`.
`connectTimeoutMS`:: The time in milliseconds to attempt a connection before timing out. Default is `10000` (10 seconds)
`socketTimeoutMS`:: The time in milliseconds to attempt a send or receive on a socket before the attempt times out. Default is `0` meaning there is no timeout
`sendBufferSize`:: Sets the send buffer size (SO_SNDBUF) for the socket. Default is `0`, meaning it will use the OS default for this option.
`receiveBufferSize`:: Sets the receive buffer size (SO_RCVBUF) for the socket. Default is `0`, meaning it will use the OS default for this option.
`keepAlive`:: Sets the keep alive (SO_KEEPALIVE) for the socket. Default is `false`
`heartbeat.socket`:: Configures the socket settings for the cluster monitor of the MongoDB java driver.
`heartbeatFrequencyMS`:: The frequency that the cluster monitor attempts to reach each server. Default is `5000` (5 seconds)
`minHeartbeatFrequencyMS`:: The minimum heartbeat frequency. The default value is `1000` (1 second)

NOTE: Most of the default values listed above use the default values of the MongoDB Java Driver.
Please consult the driver documentation for up to date information.