MemoryLimiter extension as an http/grpc middleware (#14071)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
This PR augments the memorylimiter extension to be an HTTP/GRPC
middleware. The extension can be used as an HTTP/GRPC middleware once
this is merged.
Example: 

```
receivers:
  otlp:
    protocols:
      grpc:
        middlewares:
          - id: memory_limiter
      http:
        middlewares:
          - id: memory_limiter

extensions:
  memory_limiter:
    check_interval: 1s
    limit_percentage: 1
    spike_limit_percentage: 0.05

..........
```

<!-- Issue number if applicable -->
#### Link to tracking issue
Fixes #9591 
Fixes #14081

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Setup a minimal collector to test that the middleware is indeed
ratelimiting while the memory usage is closer to limit.
```
receivers:
  otlp:
    protocols:
      grpc:
        middlewares:
          - id: memory_limiter
      http:
        middlewares:
          - id: memory_limiter
processors:
exporters:
  debug:
    verbosity: detailed
    sampling_initial: 5
    sampling_thereafter: 200
    use_internal_logger: false

extensions:
  memory_limiter:
    check_interval: 1s
    limit_percentage: 1 # this is the minimum possible, since it's an integer. 
    spike_limit_percentage: 0.05

service:
  extensions:
    - memory_limiter
  pipelines:
    metrics:
      receivers: [otlp]
      processors: []
      exporters: [debug]
    traces:
      receivers: [otlp]
      processors: []
      exporters: [debug]
    logs:
      receivers: [otlp]
      processors: []
      exporters: [debug]
  telemetry:
    logs:
      level: debug
      development: false
      disable_caller: false
      disable_stacktrace: false

```

#### Documentation
Updated the readme for memory limiter extension.

---------

Co-authored-by: Bogdan Drutu <[email protected]>
Co-authored-by: Joshua MacDonald <[email protected]>

Author: 3 people

.chloggen/memorylimiter_middleware.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: extension/memory_limiter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: The memorylimiter extension can be used as an HTTP/GRPC middleware. 
+
+# One or more tracking issues or pull requests related to the change
+issues: [14081]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

cmd/otelcorecol/go.mod

@@ -112,7 +112,7 @@ require (
 	go.opentelemetry.io/collector/exporter/xexporter v0.141.0 // indirect
 	go.opentelemetry.io/collector/extension/extensionauth v1.47.0 // indirect
 	go.opentelemetry.io/collector/extension/extensioncapabilities v0.141.0 // indirect
-	go.opentelemetry.io/collector/extension/extensionmiddleware v0.141.0 // indirect
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.45.0 // indirect
 	go.opentelemetry.io/collector/extension/extensiontest v0.141.0 // indirect
 	go.opentelemetry.io/collector/extension/xextension v0.141.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.47.0 // indirect

extension/memorylimiterextension/README.md

@@ -14,6 +14,29 @@ The memory limiter extension is used to prevent out of memory situations on
 the collector. The extension will potentially replace the Memory Limiter Processor. 
 It provides better guarantees from running out of memory as it will be used by the 
 receivers to reject requests before converting them into OTLP. All the configurations 
-are the same as Memory Limiter Processor. The extension is under development and does nothing.
+are the same as Memory Limiter Processor. 
+
+
+This extension can be used as an extension for all HTTP and gRPC receivers that
+are configured through the standard `confighttp` and `configgrpc` libraries. For
+example, to configure this extension in the OTLP receiver:
+
+```
+receivers:
+  otlp:
+    protocols:
+      grpc:
+        middlewares:
+          - id: memory_limiter
+      http:
+        middlewares:
+          - id: memory_limiter
+
+extensions:
+  memory_limiter:
+    check_interval: 1s
+    limit_percentage: 1
+    spike_limit_percentage: 0.05
+```
 
 see [memorylimiterprocessor](../../processor/memorylimiterprocessor/README.md) for additional details

extension/memorylimiterextension/go.mod

@@ -8,10 +8,12 @@ require (
 	go.opentelemetry.io/collector/component/componenttest v0.141.0
 	go.opentelemetry.io/collector/confmap v1.47.0
 	go.opentelemetry.io/collector/extension v1.47.0
+	go.opentelemetry.io/collector/extension/extensionmiddleware v1.45.0
 	go.opentelemetry.io/collector/extension/extensiontest v0.141.0
 	go.opentelemetry.io/collector/internal/memorylimiter v0.141.0
 	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.1
+	google.golang.org/grpc v1.77.0
 )
 
 require (
@@ -50,7 +52,11 @@ require (
 	go.opentelemetry.io/otel/trace v1.39.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
+	golang.org/x/net v0.46.1-0.20251013234738-63d1a5100f82 // indirect
 	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/text v0.30.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20251022142026-3a174f9686a8 // indirect
+	google.golang.org/protobuf v1.36.10 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 
@@ -71,3 +77,5 @@ replace go.opentelemetry.io/collector/extension/extensiontest => ../../extension
 replace go.opentelemetry.io/collector/featuregate => ../../featuregate
 
 replace go.opentelemetry.io/collector/internal/testutil => ../../internal/testutil
+
+replace go.opentelemetry.io/collector/extension/extensionmiddleware => ../../extension/extensionmiddleware

extension/memorylimiterextension/go.sum

@@ -5,13 +5,23 @@ package memorylimiterextension // import "go.opentelemetry.io/collector/extensio
 
 import (
 	"context"
+	"net/http"
 
 	"go.uber.org/zap"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension/extensionmiddleware"
 	"go.opentelemetry.io/collector/internal/memorylimiter"
 )
 
+var (
+	_ extensionmiddleware.GRPCServer = (*memoryLimiterExtension)(nil)
+	_ extensionmiddleware.HTTPServer = (*memoryLimiterExtension)(nil)
+)
+
 type memoryLimiterExtension struct {
 	memLimiter *memorylimiter.MemoryLimiter
 }
@@ -38,3 +48,24 @@ func (ml *memoryLimiterExtension) Shutdown(ctx context.Context) error {
 func (ml *memoryLimiterExtension) MustRefuse() bool {
 	return ml.memLimiter.MustRefuse()
 }
+
+func (ml *memoryLimiterExtension) GetHTTPHandler(base http.Handler) (http.Handler, error) {
+	return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
+		if ml.MustRefuse() {
+			http.Error(resp, http.StatusText(http.StatusTooManyRequests), http.StatusTooManyRequests)
+			return
+		}
+		base.ServeHTTP(resp, req)
+	}), nil
+}
+
+func (ml *memoryLimiterExtension) GetGRPCServerOptions() ([]grpc.ServerOption, error) {
+	return []grpc.ServerOption{grpc.UnaryInterceptor(
+		func(ctx context.Context, req any, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp any, err error) {
+			if ml.MustRefuse() {
+				return nil, status.Errorf(codes.ResourceExhausted, "RESOURCE_EXHAUSTED")
+			}
+			return handler(ctx, req)
+		},
+	)}, nil
+}