gRPC HTTP/1.1 reverse bridge

This is a filter that enables converting an incoming gRPC request into a HTTP/1.1 request to allow a server that does not understand HTTP/2 or gRPC semantics to handle the request.

The filter works by:

  • Checking the content type of the incoming request. If it’s a gRPC request, the filter is enabled.

  • The content type is modified to a configurable value. This can be a noop by configuring application/grpc.

  • The gRPC frame header is optionally stripped from the request body. The content length header will be adjusted if so.

  • On receiving a response, the content type of the response is validated and the status code is mapped to a grpc-status which is inserted into the response trailers.

  • The response body is optionally prefixed by the gRPC frame header, again adjusting the content length header if necessary.

Due to being mapped to HTTP/1.1, this filter will only work with unary gRPC calls.

gRPC frame header management

By setting the withhold_grpc_frame option, the filter will assume that the upstream does not understand any gRPC semantics and will convert the request body into a simple binary encoding of the request body and perform the reverse conversion on the response body. This ends up simplifying the server side handling of these requests, as they no longer need to be concerned with parsing and generating gRPC formatted data.

This works by stripping the gRPC frame header from the request body, while injecting a gRPC frame header in the response.

If this feature is not used, the upstream must be ready to receive HTTP/1.1 requests prefixed with the gRPC frame header and respond with gRPC formatted responses.

How to disable HTTP/1.1 reverse bridge filter per route

admin:
  access_log_path: /dev/stdout
  address:
    socket_address:
      address: 0.0.0.0
      port_value: 9901
static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address:
        address: 0.0.0.0
        port_value: 80
    filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager
          access_log:
          - name: envoy.access_loggers.file
            typed_config:
              "@type": type.googleapis.com/envoy.config.accesslog.v2.FileAccessLog
              path: /dev/stdout
          stat_prefix: ingress_http
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match:
                  prefix: "/route-with-filter-disabled"
                route:
                  host_rewrite: localhost
                  cluster: grpc
                  timeout: 5.00s
                # per_filter_config disables the filter for this route
                per_filter_config:
                  envoy.filters.http.grpc_http1_reverse_bridge:
                    disabled: true
              - match:
                  prefix: "/route-with-filter-enabled"
                route:
                  host_rewrite: localhost
                  cluster: other
                  timeout: 5.00s
          http_filters:
          - name: envoy.filters.http.grpc_http1_reverse_bridge
            typed_config:
              "@type": type.googleapis.com/envoy.config.filter.http.grpc_http1_reverse_bridge.v2alpha1.FilterConfig
              content_type: application/grpc+proto
              withhold_grpc_frames: true
          - name: envoy.router
            typed_config: {}
  clusters:
  - name: other
    connect_timeout: 5.00s
    type: LOGICAL_DNS
    dns_lookup_family: V4_ONLY
    lb_policy: ROUND_ROBIN
    hosts:
      - socket_address:
          address: localhost
          port_value: 4630
  - name: grpc
    connect_timeout: 5.00s
    type: strict_dns
    lb_policy: round_robin
    http2_protocol_options: {}
    load_assignment:
      cluster_name: grpc
      endpoints:
        - lb_endpoints:
            - endpoint:
                address:
                  socket_address:
                    address: localhost
                    port_value: 10005