[pkg/ottl] add MarshalLogObject to ottlmetric context (#38293)

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #38103

---------

Signed-off-by: odubajDT <[email protected]>
Co-authored-by: Edmo Vamerlatti Costa <[email protected]>
Co-authored-by: Tyler Helmuth <[email protected]>
Co-authored-by: Evan Bradley <[email protected]>

Author: 4 people

.chloggen/ottl-marshall-logobject.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: bug_fix
+
+# 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: "Change the `ottlmetric` context to properly display the `TransformContext` value in debug logs"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [38103]
+
+# (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: []

pkg/ottl/contexts/ottlmetric/metrics.go

@@ -4,11 +4,13 @@
 package ottlmetric // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/ottlmetric"
 
 import (
+	"errors"
 	"fmt"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
+	"go.uber.org/zap/zapcore"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxcache"
@@ -17,6 +19,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxmetric"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxresource"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/ctxscope"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/contexts/internal/logging"
 )
 
 // Experimental: *NOTE* this constant is subject to change or removal in the future.
@@ -38,6 +41,15 @@ type TransformContext struct {
 	resourceMetrics      pmetric.ResourceMetrics
 }
 
+func (tCtx TransformContext) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
+	err := encoder.AddObject("resource", logging.Resource(tCtx.resource))
+	err = errors.Join(err, encoder.AddObject("scope", logging.InstrumentationScope(tCtx.instrumentationScope)))
+	err = errors.Join(err, encoder.AddObject("metric", logging.Metric(tCtx.metric)))
+	err = errors.Join(err, encoder.AddObject("cache", logging.Map(tCtx.cache)))
+
+	return err
+}
+
 type TransformContextOption func(*TransformContext)
 
 func NewTransformContext(metric pmetric.Metric, metrics pmetric.MetricSlice, instrumentationScope pcommon.InstrumentationScope, resource pcommon.Resource, scopeMetrics pmetric.ScopeMetrics, resourceMetrics pmetric.ResourceMetrics, options ...TransformContextOption) TransformContext {