Enabling GZIP compression with Istio

Although Istio documentation does not specify how to enable GZIP compression, it is in fact possible to enable it via the built-in Compressor filter.

Assuming that you want to enable GZIP compression on specific applications, the following EnvoyFilter manifest will do the trick:

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: gzip
spec:
  workloadSelector:
    labels:
      # Put same labels that will identify your application
      app.kubernetes.io/instance: my-application
  configPatches:
    - applyTo: HTTP_FILTER
      match:
        context: SIDECAR_INBOUND
        listener:
          filterChain:
            filter:
              name: envoy.http_connection_manager
              subFilter:
                name: envoy.router
      patch:
        operation: INSERT_BEFORE
        value:
          name: envoy.filters.http.compressor
          typed_config:
            # See https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/compressor_filter for full options
            '@type': type.googleapis.com/envoy.extensions.filters.http.compressor.v3.Compressor
            compressor_library:
              name: text_optimized
              typed_config:
                '@type': type.googleapis.com/envoy.extensions.compression.gzip.compressor.v3.Gzip
            remove_accept_encoding_header: true

It is also possible to enable the compression globally at Istio gateway level. For that, you can replace “context” with “GATEWAY” and switch workloadSelector to a selector that will match to Istio gateways. (e.g. app: istio-ingressgateway)

typed_config is an important field where you can configure the filter. There are quite some configuration options you can check at the filter documentation. I am enabling remove_accept_encoding_header to make sure that the sidecar proxy strips away the Accept-Encoding header, so my application, if it accepts this header, does not attempt to compress the response.