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Compression

  • concept
    +
    In response to increasing volumes of data being sent over the wire, Couchbase Data Platform provides data compression between the SDK and Couchbase Server.

    From version 3.5.2, the .NET SDK enables compression by default using Snappier, a performance-focused C# port of Snappy. This was previously opt-in only via installing the corresponding Couchbase.Extensions package.

    Overview

    Documents may already be stored compressed with Snappy on the server. New documents may be passed from client applications to the server in compressed form, saving around 40% in bandwidth (depending on the document content and size), and also transmission time. These operations take place automatically, after the SDK negotiates the capability with the server, and do not require any changes on the client side.

    For SDKs with Snappy compression enabled, documents will be automatically compressed if compression is not turned Off in Couchbase Server (see below). Instructions to disable compression can be found at the bottom of the page.

    Usage and customization

    Starting with .NET SDK v3.5.2, Snappier compression is enabled by default in the ClusterOptions. You can disable compression or customize certain settings, both via ClusterOptions or Connection String parameters:

    // ConnectionString parameters
var connectionString = "couchbase://localhost:8091?compression=true&compression_min_size=512&compression_min_ratio=0.82";

// ClusterOptions parameters
var clusterOptions = new ClusterOptions
{
    Compression = true,
    CompressionMinRatio = 0.82f, // Float value between 1 and 0.
    CompressionMinSize = 512 // Integer value represented in bytes.
};

// Connect
clusterOptions.WithConnectionString(connectionString);
clusterOptions.WithCredentials("Administrator", "password");

var cluster = await Cluster.ConnectAsync(clusterOptions).ConfigureAwait(false);

    Please refer to the API Documentation for details on CompressionMinRatio and CompressionMinSize.

    Advanced: Bring Your Own Compression

    You can provide the SDK with your own implementation of Snappy compression/decompression by implementing the ICompressionAlgorithm interface, and passing it through your ClusterOptions with:

    clusterOptions.WithCompressionAlgorithm(myCompressionImplementation);

// See Couchbase.Compression.Snappier.Internal.SnappierCompression for details on how Snappier implements the interface.

    Even when compression is turned Off server-side, Couchbase Server will decompress documents in memory, and store them recompressed on disk (using Snappy) see server compression docs.

    It is therefore not recommended to implement a different compression algorithm than Snappy as this may very well cause data corruption.

    Limits

    The document must be below 20MiB in size in both compressed and uncompressed form. Compression is only available in the Enterprise Edition of Couchbase Data Platform.

    This size limit is enforced by Couchbase Server; in practice it will affect very few users, as most JSON documents are considerably smaller. A compressed doument of just under 20MB, which is greater than 20,971,520 bytes (20 MiB) when uncompressed, will be rejected by the server as follows:

    • Couchbase Server decompresses the document to check that it is valid JSON, and is correctly compressed with Snappy, and at this point measures it against max data size (20 MiB).

    • If the decompressed value’s size exceeds this limit, the mutation is failed with a "too big" error code (E2BIG code 3).

    Therefore, where necessary, enforce document size limits in your application on uncompressed documents.

    Operating Modes (Server-side)

    The three modes in which compression can be used, "off", "passive" and "active", are configured per bucket in the configuration settings on the cluster.

    Table 1. Compression Operating Modes
    OFF PASSIVE ACTIVE

    Negotiating SNAPPY

    ignore

    acknowledge

    acknowledge

    Sending compressed data when SNAPPY feature enabled

    -

    accept

    accept

    Sending compressed data when SNAPPY feature disabled

    reject as invalid

    reject as invalid

    reject as invalid

    Receiving data which were previously compressed on the server

    server inflates and sends plain data

    server sends compressed data

    server sends compressed data

    Receiving data which were not previously compressed on the server

    server sends plain data

    server sends plain data

    server might send compressed data (the compression is done in the background on the server)

    Compression for .NET SDK 3.4.10 to 3.5.1

    Snappier is integrated with the .NET Couchbase.Extensions Library. Since .NET SDK 3.4.10, the .NET SDK has been able to work with external Snappy libraries as the setting for the Server flag SnappyEverywhere is now supported.

    Install Snappier with the .NET Couchbase.Extensions Library,