[pkg/ottl] Add client metadata access to OTTL contexts

.chloggen/33288-metadata.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: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Added metadata access path to all OTTL contexts for accessing client request metadata
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33288]
+
+# (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: []

connector/countconnector/go.mod

@@ -58,6 +58,7 @@ require (
 	github.com/twmb/murmur3 v1.1.8 // indirect
 	github.com/ua-parser/uap-go v0.0.0-20240611065828-3a4781585db6 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/client v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/consumer/xconsumer v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/featuregate v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/internal/fanoutconsumer v0.132.1-0.20250814180350-eb9588bb3b55 // indirect

connector/signaltometricsconnector/go.mod

@@ -62,6 +62,7 @@ require (
 	github.com/twmb/murmur3 v1.1.8 // indirect
 	github.com/ua-parser/uap-go v0.0.0-20240611065828-3a4781585db6 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/client v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/consumer/xconsumer v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/featuregate v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/internal/fanoutconsumer v0.132.1-0.20250814180350-eb9588bb3b55 // indirect

connector/sumconnector/go.mod

@@ -57,6 +57,7 @@ require (
 	github.com/twmb/murmur3 v1.1.8 // indirect
 	github.com/ua-parser/uap-go v0.0.0-20240611065828-3a4781585db6 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/client v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/consumer/xconsumer v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/featuregate v1.38.1-0.20250814180350-eb9588bb3b55 // indirect

internal/filter/go.mod

@@ -51,6 +51,7 @@ require (
 	github.com/twmb/murmur3 v1.1.8 // indirect
 	github.com/ua-parser/uap-go v0.0.0-20240611065828-3a4781585db6 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/client v1.38.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/collector/pdata/pprofile v0.132.1-0.20250814180350-eb9588bb3b55 // indirect
 	go.opentelemetry.io/contrib/bridges/otelzap v0.12.0 // indirect

pkg/ottl/README.md

@@ -54,6 +54,8 @@ To see a list of available Paths for each Open Telemetry Signal, checkout the li
 | `Log`                   | [Log](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/pkg/ottl/contexts/ottllog/README.md)                     |
 | `Profile`               | [Profile](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/pkg/ottl/contexts/ottlprofile/README.md)             |
 
+**Note:** All OTTL contexts support accessing client metadata from the incoming request context using the `metadata` path. This allows you to access HTTP headers, gRPC metadata, and other client-provided information. See the individual context documentation for details.
+
 OTTL does not support cross-signal interactions at this time. That means you cannot write a statement like
 
 ```

pkg/ottl/contexts/internal/ctxcommon/parser.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxcache"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxcontext"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxerror"
 )
 
@@ -60,6 +61,10 @@ func PathExpressionParser[K any](
 			}
 		}
 
+		if path.Name() == ctxcontext.Name {
+			return ctxcontext.PathExpressionParser[K]()(path)
+		}
+
 		// Allow cache access only on this context
 		if path.Name() == ctxcache.Name {
 			if pathContext == contextName {

pkg/ottl/contexts/internal/ctxcontext/README.md

@@ -0,0 +1,21 @@
+# Context Context (OTTL)
+
+The Context Context exposes request-related data from the Go `context.Context` passed through the Collector, such as client information and incoming gRPC metadata. Use these paths via the top-level `context` segment, optionally followed by sub-segments.
+
+## Paths
+
+The following paths are supported.
+
+| path                               | field accessed                                                                                             | type              |
+|------------------------------------|------------------------------------------------------------------------------------------------------------|-------------------|
+| context.client.addr                | the remote address string from the client info                                                             | string            |
+| context.client.metadata            | client metadata attached to the request via `go.opentelemetry.io/collector/client`                         | client.Metadata   |
+| context.client.metadata[""]        | the first value for a specific metadata key. Returns nil if key missing or has 0 or more than 1 values     | string or nil     |
+| context.client.auth.attributes     | map of all auth attributes extracted from `client.Info.Auth` with values stringified (JSON for non-string) | map[string]string |
+| context.client.auth.attributes[""] | specific auth attribute value as a string (JSON for non-string values). Missing keys return empty string   | string            |
+| context.grpc.metadata              | incoming gRPC metadata from the context (if present)                                                       | metadata.MD       |
+| context.grpc.metadata[""]          | values slice for a specific incoming gRPC metadata key. Returns nil if not present                         | []string or nil   |
+
+All setters for these paths return an error; the context is read-only within OTTL expressions.
+
+