Add lookup processor skeleton

- introduce pkg/lookup with functional Source/LookupExtension constructors and a placeholder BaseSource/cache to be shared by upcoming extensions
- scaffold the lookup processor (config, factory, processor stub, tests) and sample config/README showing how to bind an external lookup extension
- add a noop lookup extension module plus factory/tests to demonstrate extension-based sources

Author: jsvd

.checkapi.yaml

@@ -6,6 +6,7 @@ ignored_paths:
   - extension/observer
   - extension/encoding
   - extension/opampcustommessages
+  - extension/lookup/nooplookupextension
   - pkg/batchperresourceattr
   - pkg/batchpersignal
   - pkg/core/xidutils
@@ -19,6 +20,7 @@ ignored_paths:
   - pkg/resourcetotelemetry
   - pkg/sampling
   - pkg/status
+  - pkg/lookup
   - pkg/translator/azure
   - pkg/translator/azurelogs
   - pkg/translator/faro
@@ -31,6 +33,7 @@ ignored_paths:
   - pkg/translator/skywalking
   - pkg/winperfcounters
   - pkg/xk8stest
+  - processor/lookupprocessor
   - processor/tailsamplingprocessor
   - receiver/hostmetricsreceiver # issue with the parser not identifying Config as a config struct
   - receiver/pulsarreceiver # 38930

.chloggen/feat_lookup_processor.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: lookupprocessor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adds lookup processor skeleton, shared lookup package, and noop lookup extension to define the new lookup interface surface.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [41816]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# 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]

.codecov.yml

@@ -348,6 +348,10 @@ component_management:
     name: extension_k8sleaderelector
     paths:
     - extension/k8sleaderelector/**
+  - component_id: extension_lookup_nooplookup
+    name: extension_lookup_nooplookup
+    paths:
+    - extension/lookup/nooplookupextension/**
   - component_id: extension_oauth2clientauth
     name: extension_oauth2clientauth
     paths:
@@ -496,6 +500,10 @@ component_management:
     name: processor_logstransform
     paths:
     - processor/logstransformprocessor/**
+  - component_id: processor_lookup
+    name: processor_lookup
+    paths:
+    - processor/lookupprocessor/**
   - component_id: processor_metricsgeneration
     name: processor_metricsgeneration
     paths:

extension/lookup/nooplookupextension/Makefile

@@ -0,0 +1 @@
+include ../../../Makefile.Common

extension/lookup/nooplookupextension/doc.go

@@ -0,0 +1,7 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package nooplookupextension exposes a minimal lookup extension that always
+// reports no results. It demonstrates the functional composition RFC for
+// extension implementations.
+package nooplookupextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/lookup/nooplookupextension"

extension/lookup/nooplookupextension/extension.go

@@ -0,0 +1,61 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package nooplookupextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/lookup/nooplookupextension"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/lookup"
+)
+
+const typeStr = "nooplookup"
+
+var Type = component.MustNewType(typeStr)
+
+type Config struct{}
+
+var _ component.Config = (*Config)(nil)
+
+func (*Config) Validate() error { return nil }
+
+func NewFactory() extension.Factory {
+	return extension.NewFactory(
+		Type,
+		createDefaultConfig,
+		createExtension,
+		component.StabilityLevelDevelopment,
+	)
+}
+
+func NewLookupExtensionFactory() extension.Factory {
+	return NewFactory()
+}
+
+func createDefaultConfig() component.Config {
+	return &Config{}
+}
+
+func createExtension(_ context.Context, set extension.Settings, _ component.Config) (extension.Extension, error) {
+	return NewLookupExtension(set.TelemetrySettings)
+}
+
+// NewLookupExtension creates the noop lookup extension using functional composition.
+func NewLookupExtension(settings component.TelemetrySettings) (lookup.LookupExtension, error) {
+	base, err := lookup.NewBaseSource(typeStr, settings, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return lookup.NewLookupExtension(
+		base.WrapLookup(func(context.Context, string) (any, bool, error) {
+			return nil, false, nil
+		}),
+		base.TypeFunc(),
+		lookup.StartFunc(base.Start),
+		lookup.ShutdownFunc(base.Shutdown),
+	), nil
+}

extension/lookup/nooplookupextension/extension_test.go

@@ -0,0 +1,43 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package nooplookupextension
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/extension/extensiontest"
+	"go.opentelemetry.io/otel/metric/noop"
+)
+
+func TestFactoryCreatesExtension(t *testing.T) {
+	factory := NewFactory()
+
+	cfg := factory.CreateDefaultConfig()
+	require.IsType(t, &Config{}, cfg)
+
+	settings := extensiontest.NewNopSettings(Type)
+
+	ext, err := factory.Create(t.Context(), settings, cfg)
+	require.NoError(t, err)
+	require.NoError(t, ext.Start(t.Context(), componenttest.NewNopHost()))
+	require.NoError(t, ext.Shutdown(t.Context()))
+}
+
+func TestNewLookupExtensionBehaviour(t *testing.T) {
+	settings := componenttest.NewNopTelemetrySettings()
+	settings.MeterProvider = noop.NewMeterProvider()
+
+	ext, err := NewLookupExtension(settings)
+	require.NoError(t, err)
+
+	ctx := t.Context()
+	require.NoError(t, ext.Start(ctx, componenttest.NewNopHost()))
+	val, found, err := ext.Lookup(ctx, "missing")
+	require.NoError(t, err)
+	require.False(t, found)
+	require.Nil(t, val)
+	require.NoError(t, ext.Shutdown(ctx))
+}

extension/lookup/nooplookupextension/go.mod

@@ -0,0 +1,47 @@
+module github.com/open-telemetry/opentelemetry-collector-contrib/extension/lookup/nooplookupextension
+
+go 1.24.0
+
+require (
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/lookup v0.118.0
+	github.com/stretchr/testify v1.11.1
+	go.opentelemetry.io/collector/component v1.42.1-0.20251002223229-5ec1466578ef
+	go.opentelemetry.io/collector/component/componenttest v0.136.1-0.20251002223229-5ec1466578ef
+	go.opentelemetry.io/collector/extension v1.42.1-0.20251002223229-5ec1466578ef
+	go.opentelemetry.io/collector/extension/extensiontest v0.136.1-0.20251002223229-5ec1466578ef
+	go.opentelemetry.io/otel/metric v1.38.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/hashicorp/go-version v1.7.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/featuregate v1.42.1-0.20251002223229-5ec1466578ef // indirect
+	go.opentelemetry.io/collector/internal/telemetry v0.136.1-0.20251002223229-5ec1466578ef // indirect
+	go.opentelemetry.io/collector/pdata v1.42.1-0.20251002223229-5ec1466578ef // indirect
+	go.opentelemetry.io/contrib/bridges/otelzap v0.13.0 // indirect
+	go.opentelemetry.io/otel v1.38.0 // indirect
+	go.opentelemetry.io/otel/log v0.14.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.38.0 // indirect
+	go.opentelemetry.io/otel/sdk/metric v1.38.0 // indirect
+	go.opentelemetry.io/otel/trace v1.38.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.27.0 // indirect
+	golang.org/x/net v0.41.0 // indirect
+	golang.org/x/sys v0.35.0 // indirect
+	golang.org/x/text v0.26.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250707201910-8d1bb00bc6a7 // indirect
+	google.golang.org/grpc v1.75.1 // indirect
+	google.golang.org/protobuf v1.36.9 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/lookup => ../../../pkg/lookup