Compression

The Java driver supports compression of messages to and from MongoDB servers. The driver implements the three algorithms that are supported by MongoDB servers:

• Snappy: Snappy compression can be used when connecting to MongoDB servers starting with the 3.4 release.
• Zlib: Zlib compression can be used when connecting to MongoDB servers starting with the 3.6 release.
• Zstandard: Zstandard compression can be used when connecting to MongoDB servers starting with the 4.2 release.

The driver will negotiate which, if any, compression algorithm is used based on capabilities advertised by the server in the hello command response.

Specify compression via ConnectionString

import com.mongodb.ConnectionString;
import com.mongodb.reactivestreams.client.MongoClients;
import com.mongodb.reactivestreams.client.MongoClient;

To specify compression with ConnectionString, specify compressors as part of the connection string, as in:

ConnectionString connectionString = new ConnectionString("mongodb://localhost/?compressors=snappy");
MongoClient mongoClient = MongoClients.create(connectionString);

for Snappy compression, or

ConnectionString connectionString = new ConnectionString("mongodb://localhost/?compressors=zlib");
MongoClient mongoClient = MongoClients.create(connectionString);

for zlib compression, or

ConnectionString connectionString = new ConnectionString("mongodb://localhost/?compressors=zstd");
MongoClient mongoClient = MongoClients.create(connectionString);

for Zstandard compression, or

ConnectionString connectionString = new ConnectionString("mongodb://localhost/?compressors=snappy,zlib,zstd");
MongoClient mongoClient = MongoClients.create(connectionString);

to configure multiple compressors.

In all cases the driver will use the first compressor in the list for which the server advertises support.

Specify compression via MongoClientSettings

import com.mongodb.MongoClientSettings;
import com.mongodb.MongoCompressor;
import java.util.Arrays;

To specify compression with MongoClientSettings, set the compressors property to a list of MongoCompressor instances:

MongoClientSettings settings = MongoClientSettings.builder()
        .compressorList(Arrays.asList(MongoCompressor.createSnappyCompressor()))
        .build();
MongoClient client = MongoClients.create(settings);

for Snappy compression, or

MongoClientSettings settings = MongoClientSettings.builder()
        .compressorList(Arrays.asList(MongoCompressor.createZlibCompressor()))
        .build();
MongoClient client = MongoClients.create(settings);

for zlib compression, or

MongoClientSettings settings = MongoClientSettings.builder()
        .compressorList(Arrays.asList(MongoCompressor.createZstdCompressor()))
        .build();
MongoClient client = MongoClients.create(settings);

for Zstandard compression, or

MongoClientSettings settings = MongoClientSettings.builder()
        .compressorList(Arrays.asList(MongoCompressor.createSnappyCompressor(),
                                      MongoCompressor.createZlibCompressor(),
                                      MongoCompressor.createZstdCompressor()))
        .build();
MongoClient client = MongoClients.create(settings);

to configure multiple compressors.

As with configuration with a URI, the driver will use the first compressor in the list for which the server advertises support.

Dependencies

As the JDK has no built-in support for Snappy or Zstandard, the driver takes a dependency on existing open-source Snappy and Zstandard implementations. See the snappy-java Github repository and the zstd-java Github repository for details.