envoy-filter-example：使用Envoy并添加自定义过滤器的示例

# Envoy filter example This project demonstrates the linking of additional HTTP filters with the Envoy binary. A new filter `sample` which adds a HTTP header is introduced. Integration tests demonstrating the filter's end-to-end behavior are also provided. ## Building To build the Envoy static binary: 1. `git submodule update --init` 2. `bazel build //http-filter-example:envoy` ## Testing To run the `sample` integration test: `bazel test //http-filter-example:http_filter_integration_test` ## How it works See the [network filter example](../README.md#how-it-works). ## How to write and use an HTTP filter - The main task is to write a class that implements the interface [`Envoy::Http::StreamDecoderFilter`][StreamDecoderFilter] as in [`http_filter.h`](http_filter.h) and [`http_filter.cc`](http_filter.cc), which contains functions that handle http headers, data, and trailers. Note that this is an example of decoder filters, and to write encoder filters or decoder/encoder filters you need to implement [`Envoy::Http::StreamEncoderFilter`][StreamEncoderFilter] or [`Envoy::Http::StreamFilter`][StreamFilter] instead. - You also need a class that implements `Envoy::Server::Configuration::NamedHttpFilterConfigFactory` to enable the Envoy binary to find your filter, as in [`http_filter_config.cc`](http_filter_config.cc). It should be linked to the Envoy binary by modifying [`BUILD`][BUILD] file. - Finally, you need to modify the Envoy config file to add your filter to the filter chain for a particular HTTP route configuration. For instance, if you wanted to change [the front-proxy example][front-envoy.yaml] to chain our `sample` filter, you'd need to modify its config to look like ```yaml http_filters: - name: sample # before envoy.router because order matters! typed_config: "@type": type.googleapis.com/sample.Decoder key: via val: sample-filter - name: envoy.router typed_config: {} ``` [StreamDecoderFilter]: https://github.com/envoyproxy/envoy/blob/b2610c84aeb1f75c804d67effcb40592d790e0f1/include/envoy/http/filter.h#L300 [StreamEncoderFilter]: https://github.com/envoyproxy/envoy/blob/b2610c84aeb1f75c804d67effcb40592d790e0f1/include/envoy/http/filter.h#L413 [StreamFilter]: https://github.com/envoyproxy/envoy/blob/b2610c84aeb1f75c804d67effcb40592d790e0f1/include/envoy/http/filter.h#L462 [BUILD]: https://github.com/envoyproxy/envoy-filter-example/blob/d76d3096c4cbd647d26b44b3f801c3afbc81d3e2/http-filter-example/BUILD#L15-L18 [front-envoy.yaml]: https://github.com/envoyproxy/envoy/blob/b2610c84aeb1f75c804d67effcb40592d790e0f1/examples/front-proxy/front-envoy.yaml#L28