Simple filter build+link example.

Duplicated the Echo network filter in Envoy, renamed Echo2, and
linked/configured in an Envoy static binary.

.gitignore

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+bazel-*

.gitmodules

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+[submodule "envoy"]
+	path = envoy
+	url = https://github.com/lyft/envoy.git

BUILD

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+package(default_visibility = ["//visibility:public"])
+
+load(
+    "@envoy//bazel:envoy_build_system.bzl",
+    "envoy_cc_binary",
+    "envoy_cc_library",
+    "envoy_cc_test",
+)
+
+envoy_cc_binary(
+    name = "envoy",
+    repository = "@envoy",
+    deps = [
+        ":echo2_config",
+        "@envoy//source/exe:envoy_main_lib",
+    ],
+)
+
+envoy_cc_library(
+    name = "echo2_lib",
+    srcs = ["echo2.cc"],
+    hdrs = ["echo2.h"],
+    repository = "@envoy",
+    deps = [
+        "@envoy//include/envoy/buffer:buffer_interface",
+        "@envoy//include/envoy/network:connection_interface",
+        "@envoy//include/envoy/network:filter_interface",
+        "@envoy//source/common/common:assert_lib",
+        "@envoy//source/common/common:logger_lib",
+    ],
+)
+
+envoy_cc_library(
+    name = "echo2_config",
+    srcs = ["echo2_config.cc"],
+    repository = "@envoy",
+    deps = [
+        ":echo2_lib",
+        "@envoy//include/envoy/network:connection_interface",
+        "@envoy//source/server:configuration_lib",
+    ],
+)
+
+envoy_cc_test(
+    name = "echo2_integration_test",
+    srcs = ["echo2_integration_test.cc"],
+    data =  ["echo2_server.json"],
+    repository = "@envoy",
+    deps = [
+        ":echo2_config",
+        "@envoy//test/integration:integration_lib"
+    ],
+)

README.md

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-# envoy-consumer
-Example project consuming Envoy and injecting additional filters/tests
+# Envoy filter example
+
+This project demonstrates the linking of additional filters with the Envoy binary.
+A new filter `echo2` is introduced, identical modulo renaming to the existing
+[`echo`](https://github.com/lyft/envoy/blob/master/source/common/filter/echo.h)
+filter. 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 //:envoy`
+
+## Testing
+
+To run the `echo2` integration test:
+
+`bazel test //:echo2_integration_test`
+
+To run the regular Envoy tests from this project:
+
+`bazel test @envoy//...`
+
+## How it works
+
+The [Envoy repository](https://github.com/lyft/envoy/) is provided as a submodule.
+The [`WORKSPACE`](WORKSPACE) file maps the `@envoy` repository to this local path.
+
+The [`BUILD`](BUILD) file introduces a new Envoy static binary target, `envoy`,
+that links together the new filter and `@envoy//source/exe:envoy_main_lib`. The
+`echo2` filter registers itself during the static initialization phase of the
+Envoy binary as a new filter.

WORKSPACE

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+workspace(name = "envoy")
+
+local_repository(
+    name = "envoy",
+    path = "envoy",
+)
+
+load("@envoy//bazel:repositories.bzl", "envoy_dependencies")
+load("@envoy//bazel:cc_configure.bzl", "cc_configure")
+
+envoy_dependencies()
+cc_configure()

bazel/get_workspace_status

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+../envoy/bazel/get_workspace_status

echo2.cc

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+#include "echo2.h"
+
+#include "envoy/buffer/buffer.h"
+#include "envoy/network/connection.h"
+
+#include "common/common/assert.h"
+
+namespace Filter {
+
+Network::FilterStatus Echo2::onData(Buffer::Instance& data) {
+  conn_log_trace("echo: got {} bytes", read_callbacks_->connection(), data.length());
+  read_callbacks_->connection().write(data);
+  ASSERT(0 == data.length());
+  return Network::FilterStatus::StopIteration;
+}
+
+} // Filter

echo2.h

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+#pragma once
+
+#include "envoy/network/filter.h"
+
+#include "common/common/logger.h"
+
+namespace Filter {
+
+/**
+ * Implementation of a basic echo filter.
+ */
+class Echo2 : public Network::ReadFilter, Logger::Loggable<Logger::Id::filter> {
+public:
+  // Network::ReadFilter
+  Network::FilterStatus onData(Buffer::Instance& data) override;
+  Network::FilterStatus onNewConnection() override { return Network::FilterStatus::Continue; }
+  void initializeReadFilterCallbacks(Network::ReadFilterCallbacks& callbacks) override {
+    read_callbacks_ = &callbacks;
+  }
+
+private:
+  Network::ReadFilterCallbacks* read_callbacks_{};
+};
+
+} // Filter

echo2_config.cc

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+#include "envoy/network/connection.h"
+
+#include "echo2.h"
+#include "server/configuration_impl.h"
+
+namespace Server {
+namespace Configuration {
+
+/**
+ * Config registration for the echo filter. @see NetworkFilterConfigFactory.
+ */
+class Echo2ConfigFactory : public NetworkFilterConfigFactory {
+public:
+  // NetworkFilterConfigFactory
+  NetworkFilterFactoryCb tryCreateFilterFactory(NetworkFilterType type, const std::string& name,
+                                                const Json::Object&, Server::Instance&) {
+    if (type != NetworkFilterType::Read || name != "echo2") {
+      return nullptr;
+    }
+
+    return [](Network::FilterManager& filter_manager)
+        -> void { filter_manager.addReadFilter(Network::ReadFilterSharedPtr{new Filter::Echo2()}); };
+  }
+};
+
+/**
+ * Static registration for the echo filter. @see RegisterNetworkFilterConfigFactory.
+ */
+static RegisterNetworkFilterConfigFactory<Echo2ConfigFactory> registered_;
+
+} // Configuration
+} // Server

echo2_integration_test.cc

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+#include "test/integration/integration.h"
+#include "test/integration/utility.h"
+
+class Echo2IntegrationTest : public BaseIntegrationTest, public testing::Test {
+public:
+  /**
+   * Global initializer for all integration tests.
+   */
+  static void SetUpTestCase() {
+    createTestServer("echo2_server.json", {"echo"});
+  }
+
+  /**
+   * Global destructor for all integration tests.
+   */
+  static void TearDownTestCase() {
+    test_server_.reset();
+  }
+};
+
+TEST_F(Echo2IntegrationTest, Echo) {
+  Buffer::OwnedImpl buffer("hello");
+  std::string response;
+  RawConnectionDriver connection(lookupPort("echo"), buffer,
+                                 [&](Network::ClientConnection&, const Buffer::Instance& data)
+                                     -> void {
+                                       response.append(TestUtility::bufferToString(data));
+                                       connection.close();
+                                     });
+
+  connection.run();
+  EXPECT_EQ("hello", response);
+}

echo2_server.json

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+{
+  "listeners": [
+  {
+    "address": "tcp://127.0.0.1:0",
+    "use_original_dst": true,
+    "filters": [
+      { "type": "read", "name": "ratelimit",
+        "config": {
+          "domain": "foo",
+          "descriptors": [[{"key": "foo", "value": "bar"}]],
+          "stat_prefix": "name"
+        }
+      },
+      { "type": "read", "name": "echo2", "config": {} }
+    ]
+  }],
+
+  "admin": { "access_log_path": "/dev/null", "profile_path": "{{ test_tmpdir }}/envoy.prof", "address": "tcp://127.0.0.1:0" },
+
+  "cluster_manager": {
+      "clusters": []
+  }
+}

tools/bazel.rc

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+../envoy/tools/bazel.rc