chore: add metadata example

Signed-off-by: Martijn Swaagman <[email protected]>

Author: Swaagie

examples/filter_metadata/Cargo.toml

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+[package]
+publish = false
+name = "proxy-wasm-example-filter-metadata"
+version = "0.0.1"
+authors = ["Martijn Swaagma <[email protected]>"]
+description = "Proxy-Wasm plugin example: Filter metadata"
+license = "Apache-2.0"
+edition = "2018"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+proxy-wasm = { path = "../../" }
+
+[profile.release]
+lto = true
+opt-level = 3
+codegen-units = 1
+panic = "abort"
+strip = "debuginfo"

examples/filter_metadata/README.md

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+## Proxy-Wasm plugin example: Metadata
+
+Proxy-Wasm plugin that demonstrates reading metadata set by other filters
+
+### Building
+
+```sh
+$ cargo build --target wasm32-wasip1 --release
+```
+
+### Using in Envoy
+
+This example can be run with [`docker compose`](https://docs.docker.com/compose/install/)
+and has a matching Envoy configuration.
+
+```sh
+$ docker compose up
+```
+
+Send HTTP request to `localhost:10000/` with a `x-custom-metadata` header value.
+
+> Not setting the header will return the configured welcome message.
+
+```sh
+$ curl localhost:10000/ -H "x-custom-metadata: some-value"
+Custom response with `x-custom-metadata` value "some-value"
+```

examples/filter_metadata/docker-compose.yaml

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+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+services:
+  envoy:
+    image: envoyproxy/envoy:v1.31-latest
+    hostname: envoy
+    ports:
+      - "10000:10000"
+    volumes:
+      - ./envoy.yaml:/etc/envoy/envoy.yaml
+      - ./target/wasm32-wasip1/release:/etc/envoy/proxy-wasm-plugins
+    networks:
+      - envoymesh
+networks:
+  envoymesh: {}

examples/filter_metadata/envoy.yaml

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+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+static_resources:
+  listeners:
+    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
+              codec_type: AUTO
+              route_config:
+                name: local_routes
+                virtual_hosts:
+                  - name: local_service
+                    domains:
+                      - "*"
+                    routes:
+                      - match:
+                          prefix: "/"
+                        direct_response:
+                          status: 200
+                          body:
+                            inline_string: "Welcome, set the `x-custom-metadata` header to change the response!\n"
+              http_filters:
+                # Set metadata
+                - name: envoy.filters.http.lua
+                  typed_config:
+                    "@type": type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua
+                    default_source_code:
+                      inline_string: |
+                        function envoy_on_request(request_handle)
+                          local headers = request_handle:headers()
+                          local data = headers:get("x-custom-metadata")
+
+                          if data then
+                            request_handle:streamInfo():dynamicMetadata():set("envoy.filters.http.lua", "x-custom-metadata", data)
+                          end
+
+                          request_handle:logInfo("Metadata set by lua filter")
+                        end
+                # Read it from a WASM filter
+                - name: envoy.filters.http.wasm
+                  typed_config:
+                    "@type": type.googleapis.com/udpa.type.v1.TypedStruct
+                    type_url: type.googleapis.com/envoy.extensions.filters.http.wasm.v3.Wasm
+                    value:
+                      config:
+                        name: "metadata_filter"
+                        vm_config:
+                          runtime: "envoy.wasm.runtime.v8"
+                          code:
+                            local:
+                              filename: "/etc/envoy/proxy-wasm-plugins/proxy_wasm_example_filter_metadata.wasm"
+                - name: envoy.filters.http.router
+                  typed_config:
+                    "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router

examples/filter_metadata/src/lib.rs

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+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use proxy_wasm::traits::*;
+use proxy_wasm::types::*;
+
+proxy_wasm::main! {{
+    proxy_wasm::set_log_level(LogLevel::Trace);
+    proxy_wasm::set_http_context(|_, _| -> Box<dyn HttpContext> { Box::new(MetadataHttp {}) });
+}}
+
+struct MetadataHttp {}
+
+impl Context for MetadataHttp {}
+
+impl HttpContext for MetadataHttp {
+    fn on_http_request_headers(&mut self, _: usize, _: bool) -> Action {
+        // Read data set by the lua filter
+        match self.get_property(vec![
+            "metadata",
+            "filter_metadata",
+            "envoy.filters.http.lua",
+            "x-custom-metadata",
+        ]) {
+            Some(metadata) => match String::from_utf8(metadata) {
+                Ok(data) => {
+                    self.send_http_response(
+                        200,
+                        vec![("Powered-By", "proxy-wasm")],
+                        Some(
+                            format!(
+                                "Custom response with `x-custom-metadata` value {:?}!\n",
+                                data
+                            )
+                            .as_bytes(),
+                        ),
+                    );
+                    Action::Pause
+                }
+                _ => Action::Continue,
+            },
+            _ => Action::Continue,
+        }
+    }
+}