feat: init dynamic modules work

.github/workflows/pr_style_check.yaml

@@ -87,6 +87,7 @@ jobs:
             refactor
             mcp
             aigw
+            dynamic_module
           subjectPattern: ^(?![A-Z]).+$
           subjectPatternError: |
             The subject "{subject}" found in the pull request title "{title}"

Makefile

@@ -270,6 +270,11 @@ build.%: ## Build a binary for the given command under the internal/cmd director
 build: ## Build all binaries under cmd/ directory.
 	@$(foreach COMMAND_NAME,$(COMMANDS),$(MAKE) build.$(COMMAND_NAME);)
 
+# This builds the dynamic module filter for Envoy. This is the shared library that can be loaded by Envoy to run the AI Gateway filter.
+.PHONE: build-dm
+build-dm: ## Build the dynamic module for Envoy.
+	CGO_ENABLED=1 go build -tags "envoy_1.36" -buildmode=c-shared -o $(OUTPUT_DIR)/libaigateway.so ./cmd/dynamic_module
+
 # This builds the docker images for the controller, extproc and testupstream for the e2e tests.
 .PHONY: build-e2e
 build-e2e: ## Build the docker images for the controller, extproc and testupstream for the e2e tests.

cmd/dynamic_module/main.go

@@ -0,0 +1,127 @@
+// Copyright Envoy AI Gateway Authors
+// SPDX-License-Identifier: Apache-2.0
+// The full text of the Apache license is available in the LICENSE file at
+// the root of the repo.
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"time"
+
+	"github.com/envoyproxy/ai-gateway/internal/tracing"
+	"github.com/prometheus/client_golang/prometheus"
+	otelprom "go.opentelemetry.io/otel/exporters/prometheus"
+
+	"github.com/envoyproxy/ai-gateway/internal/backendauth"
+	"github.com/envoyproxy/ai-gateway/internal/dynamicmodule"
+	"github.com/envoyproxy/ai-gateway/internal/dynamicmodule/sdk"
+	"github.com/envoyproxy/ai-gateway/internal/filterapi"
+	"github.com/envoyproxy/ai-gateway/internal/internalapi"
+	"github.com/envoyproxy/ai-gateway/internal/metrics"
+)
+
+func main() {} // This must be present to make a shared library.
+
+// Set the envoy.NewHTTPFilter function to create a new http filter.
+func init() {
+	g := &globalState{}
+	if err := g.initializeEnv(); err != nil {
+		panic("failed to create env config: " + err.Error())
+	}
+
+	// TODO: use a writer implemented with the Logger ABI of Envoy.
+	logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelDebug, // Adjust log level from environment variable if needed.
+	}))
+	if err := filterapi.StartConfigWatcher(context.Background(),
+		os.Getenv("AI_GATEWAY_DYNAMIC_MODULE_FILTER_CONFIG_PATH"), g, logger, time.Second*5); err != nil {
+		panic("failed to start filter config watcher: " + err.Error())
+	}
+	sdk.NewHTTPFilterConfig = g.newHTTPFilterConfig
+}
+
+// globalState implements [filterapi.ConfigReceiver] to load filter configuration.
+type globalState struct {
+	fc  *filterapi.RuntimeConfig
+	env *dynamicmodule.Env
+}
+
+// newHTTPFilterConfig creates a new http filter based on the config.
+//
+// `config` is the configuration string that is specified in the Envoy configuration.
+func (g *globalState) newHTTPFilterConfig(name string, _ []byte) sdk.HTTPFilterConfig {
+	switch name {
+	case "ai_gateway.router":
+		return dynamicmodule.NewRouterFilterConfig(g.env, &g.fc)
+	case "ai_gateway.upstream":
+		return dynamicmodule.NewUpstreamFilterConfig(g.env)
+	default:
+		panic("unknown filter: " + name)
+	}
+}
+
+// LoadConfig implements [filterapi.ConfigReceiver.LoadConfig].
+func (g *globalState) LoadConfig(ctx context.Context, config *filterapi.Config) error {
+	newConfig, err := filterapi.NewRuntimeConfig(ctx, config, backendauth.NewHandler)
+	if err != nil {
+		return fmt.Errorf("cannot create runtime filter config: %w", err)
+	}
+	g.fc = newConfig // This is racy but we don't care.
+	return nil
+}
+
+func (g *globalState) initializeEnv() error {
+	ctx := context.Background()
+	promRegistry := prometheus.NewRegistry()
+	promReader, err := otelprom.New(otelprom.WithRegisterer(promRegistry))
+	if err != nil {
+		return fmt.Errorf("failed to create prometheus reader: %w", err)
+	}
+
+	meter, _, err := metrics.NewMeterFromEnv(ctx, os.Stdout, promReader)
+	if err != nil {
+		return fmt.Errorf("failed to create metrics: %w", err)
+	}
+
+	endpointPrefixes, err := internalapi.ParseEndpointPrefixes(os.Getenv(
+		"AI_GATEWAY_DYNAMIC_MODULE_FILTER_ENDPOINT_PREFIXES",
+	))
+	if err != nil {
+		return fmt.Errorf("failed to parse endpoint prefixes: %w", err)
+	}
+
+	metricsRequestHeaderAttributes, err := internalapi.ParseRequestHeaderAttributeMapping(os.Getenv(
+		"AI_GATEWAY_DYNAMIC_MODULE_FILTER_METRICS_REQUEST_HEADER_ATTRIBUTES",
+	))
+	if err != nil {
+		return fmt.Errorf("failed to parse metrics header mapping: %w", err)
+	}
+	spanRequestHeaderAttributes, err := internalapi.ParseRequestHeaderAttributeMapping(os.Getenv(
+		"AI_GATEWAY_DYNAMIC_MODULE_FILTER_TRACING_REQUEST_HEADER_ATTRIBUTES",
+	))
+	if err != nil {
+		return fmt.Errorf("failed to parse tracing header mapping: %w", err)
+	}
+
+	tracing, err := tracing.NewTracingFromEnv(ctx, os.Stdout, spanRequestHeaderAttributes)
+	if err != nil {
+		return err
+	}
+
+	g.env = &dynamicmodule.Env{
+		RootPrefix:                    os.Getenv("AI_GATEWAY_DYNAMIC_MODULE_ROOT_PREFIX"),
+		EndpointPrefixes:              endpointPrefixes,
+		ChatCompletionMetricsFactory:  metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationChat),
+		MessagesMetricsFactory:        metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationMessages),
+		CompletionMetricsFactory:      metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationCompletion),
+		EmbeddingsMetricsFactory:      metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationEmbedding),
+		ImageGenerationMetricsFactory: metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationImageGeneration),
+		RerankMetricsFactory:          metrics.NewMetricsFactory(meter, metricsRequestHeaderAttributes, metrics.GenAIOperationRerank),
+		Tracing:                       tracing,
+	}
+	return nil
+}

internal/dynamicmodule/dynamic_module.go

@@ -0,0 +1,45 @@
+// Copyright Envoy AI Gateway Authors
+// SPDX-License-Identifier: Apache-2.0
+// The full text of the Apache license is available in the LICENSE file at
+// the root of the repo.
+
+package dynamicmodule
+
+import (
+	"github.com/envoyproxy/ai-gateway/internal/internalapi"
+	"github.com/envoyproxy/ai-gateway/internal/metrics"
+	tracing "github.com/envoyproxy/ai-gateway/internal/tracing/api"
+)
+
+// endpoint represents the type of the endpoint that the request is targeting.
+type endpoint int
+
+const (
+	// chatCompletionsEndpoint represents the /v1/chat/completions endpoint.
+	chatCompletionsEndpoint endpoint = iota
+	// completionsEndpoint represents the /v1/completions endpoint.
+	completionsEndpoint
+	// embeddingsEndpoint represents the /v1/embeddings endpoint.
+	embeddingsEndpoint
+	// imagesGenerationsEndpoint represents the /v1/images/generations endpoint.
+	imagesGenerationsEndpoint
+	// rerankEndpoint represents the /v2/rerank endpoint of cohere.
+	rerankEndpoint
+	// messagesEndpoint represents the /v1/messages endpoint of anthropic.
+	messagesEndpoint
+	// modelsEndpoint represents the /v1/models endpoint.
+	modelsEndpoint
+)
+
+// Env holds the environment configuration for the dynamic module that is process-wide.
+type Env struct {
+	RootPrefix       string
+	EndpointPrefixes internalapi.EndpointPrefixes
+	ChatCompletionMetricsFactory,
+	MessagesMetricsFactory,
+	CompletionMetricsFactory,
+	EmbeddingsMetricsFactory,
+	ImageGenerationMetricsFactory,
+	RerankMetricsFactory metrics.Factory
+	Tracing tracing.Tracing
+}