Decompressor

Decompressor is an HTTP filter which enables Envoy to bidirectionally decompress data.

Configuration

How it works

When the decompressor filter is enabled, headers are inspected to determine whether or not the content should be decompressed. The content is decompressed and passed on to the rest of the filter chain. Note that decompression happens independently for request and responses based on the rules described below.

Currently the filter supports gzip compression only. Other compression libraries can be supported as extensions.

An example configuration of the filter may look like the following:

http_filters:
- name: decompressor
  typed_config:
    "@type": type.googleapis.com/envoy.extensions.filters.http.decompressor.v3.Decompressor
    decompressor_library:
      name: basic
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.compression.gzip.decompressor.v3.Gzip
        window_bits: 10

By default decompression will be skipped when:

  • A request/response does NOT contain content-encoding header.

  • A request/response includes content-encoding header, but it does not contain the configured decompressor’s content-encoding.

  • A request/response contains a cache-control header whose value includes “no-transform”.

When decompression is applied:

  • The content-length is removed from headers.

    Note

    If an updated content-length header is desired, the buffer filter can be installed as part of the filter chain to buffer decompressed frames, and ultimately update the header. Due to filter ordering a buffer filter needs to be installed after the decompressor for requests and prior to the decompressor for responses.

  • The content-encoding header is modified to remove the decompression that was applied.

Using different decompressors for requests and responses

If different compression libraries are desired for requests and responses, it is possible to install multiple decompressor filters enabled only for requests or responses. For instance:

http_filters:
# This filter is only enabled for requests.
- name: envoy.filters.http.decompressor
  typed_config:
    "@type": type.googleapis.com/envoy.extensions.filters.http.decompressor.v3.Decompressor
    decompressor_library:
      name: small
      typed_config:
        "@type": "type.googleapis.com/envoy.extensions.compression.gzip.decompressor.v3.Gzip"
        window_bits: 9
        chunk_size: 8192
    response_direction_config:
      common_config:
        enabled:
          default_value: false
          runtime_key: response_decompressor_enabled
# This filter is only enabled for responses.
- name: envoy.filters.http.decompressor
  typed_config:
    "@type": type.googleapis.com/envoy.extensions.filters.http.decompressor.v3.Decompressor
    decompressor_library:
      name: large
      typed_config:
        "@type": "type.googleapis.com/envoy.extensions.compression.gzip.decompressor.v3.Gzip"
        window_bits: 12
        chunk_size: 16384
    request_direction_config:
      common_config:
        enabled:
          default_value: false
          runtime_key: request_decompressor_enabled

Statistics

Every configured Deompressor filter has statistics rooted at <stat_prefix>.decompressor.<decompressor_library.name>.<decompressor_library_stat_prefix>.<request/response>* with the following:

Name

Type

Description

decompressed

Counter

Number of request/responses compressed.

not_decompressed

Counter

Number of request/responses not compressed.

total_uncompressed_bytes

Counter

The total uncompressed bytes of all the request/responses that were marked for decompression.

total_compressed_bytes

Counter

The total compressed bytes of all the request/responses that were marked for decompression.

Additional stats for the decompressor library are rooted at <stat_prefix>.decompressor.<decompressor_library.name>.<decompressor_library_stat_prefix>.decompressor_library.