Master Envoy Proxy HTTP Routing: From Basic to Advanced URL Rewrites

Overview

Envoy Proxy implements HTTP routing through the Router Filter, which maps incoming HTTP requests to upstream clusters, enabling reverse‑proxy behavior or service‑mesh routing based on the Host/Authority header.

Basic Routing Example

The simplest configuration forwards all traffic received on port 10000 to three static backend services (172.139.20.170:8090, 172.139.20.3:8090, 172.139.20.92:8090).

static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address:
        address: 0.0.0.0
        port_value: 10000
    filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
          stat_prefix: ingress_http
          access_log:
          - name: envoy.access_loggers.stdout
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
          http_filters:
          - name: envoy.filters.http.router
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match:
                  prefix: "/"
                route:
                  cluster: simple_cluster
  clusters:
  - name: simple_cluster
    lb_policy: ROUND_ROBIN
    type: STATIC
    load_assignment:
      cluster_name: simple_cluster
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address: { address: 172.139.20.170, port_value: 8090 }
        - endpoint:
            address:
              socket_address: { address: 172.139.20.3, port_value: 8090 }
        - endpoint:
            address:
              socket_address: { address: 172.139.20.92, port_value: 8090 }

Adding URL Path Rewrite

When the request URL starts with /gray, the /gray prefix is stripped and the traffic is sent to who_cluster; all other traffic continues to the simple cluster.

static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address:
        address: 0.0.0.0
        port_value: 10000
    filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
          stat_prefix: ingress_http
          access_log:
          - name: envoy.access_loggers.stdout
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
          http_filters:
          - name: envoy.filters.http.router
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match:
                  prefix: "/gray"
                route:
                  cluster: who_cluster
                  regex_rewrite:
                    pattern:
                      regex: "^/gray(/|)(.*)"
                    substitution: "/\\2"
              - match:
                  prefix: "/"
                route:
                  cluster: simple_cluster
  clusters:
  - name: who_cluster
    lb_policy: ROUND_ROBIN
    type: STATIC
    load_assignment:
      cluster_name: simple_cluster
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address: { address: 172.139.20.170, port_value: 8090 }
  - name: simple_cluster
    lb_policy: ROUND_ROBIN
    type: STATIC
    load_assignment:
      cluster_name: simple_cluster
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address: { address: 172.139.20.3, port_value: 8090 }
        - endpoint:
            address:
              socket_address: { address: 172.139.20.92, port_value: 8090 }

Reducing URL Path Prefix

If the URL begins with /hostname, the prefix is rewritten to /who/hostname before forwarding to who_cluster; otherwise the request is routed to the simple cluster.

static_resources:
  listeners:
  - name: listener_0
    address:
      socket_address:
        address: 0.0.0.0
        port_value: 10000
    filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
          stat_prefix: ingress_http
          access_log:
          - name: envoy.access_loggers.stdout
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
          http_filters:
          - name: envoy.filters.http.router
            typed_config:
              "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
          route_config:
            name: local_route
            virtual_hosts:
            - name: local_service
              domains: ["*"]
              routes:
              - match:
                  prefix: "/hostname"
                route:
                  cluster: who_cluster
                  prefix_rewrite: "/who/hostname"
              - match:
                  prefix: "/"
                route:
                  cluster: simple_cluster
  clusters:
  - name: who_cluster
    lb_policy: ROUND_ROBIN
    type: STATIC
    load_assignment:
      cluster_name: simple_cluster
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address: { address: 172.139.20.170, port_value: 8090 }
  - name: simple_cluster
    lb_policy: ROUND_ROBIN
    type: STATIC
    load_assignment:
      cluster_name: simple_cluster
      endpoints:
      - lb_endpoints:
        - endpoint:
            address:
              socket_address: { address: 172.139.20.3, port_value: 8090 }
        - endpoint:
            address:
              socket_address: { address: 172.139.20.92, port_value: 8090 }

Conclusion

In the cloud‑native era, routing is no longer merely a technical configuration; it is a business‑level strategy that operations teams must design deliberately.