[processor/schematransformerprocessor] Initial PR (open-telemetry#8371)

**Description:**
As part of the [accepted specification](https://github.com/open-telemetry/opentelemetry-specification/blob/e16e1a781bdf62a8fcfa1a12963844749de23e7a/specification/schemas/overview.md#collector-assisted-schema-transformation), there needs to be a processor within the collector that is able to allow for transformations of semantic convention versions . This is my initial draft, I wrote this before https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/8344/files shared their solution to it.

**Link to tracking Issue:**
open-telemetry#8495
Original raised in the collector but should be shifted to the contrib a I can tell.

**Testing:**
It currently does nothing and there is the initial testing set up within the components.

**Documentation:** 
Added a minimal README, will expand upon it once more work has been added to the collector.

.github/CODEOWNERS

@@ -100,6 +100,7 @@ processor/resourcedetectionprocessor/                @open-telemetry/collector-c
 processor/resourceprocessor                          @open-telemetry/collector-contrib-approvers @dmitryax
 processor/resourcedetectionprocessor/internal/azure  @open-telemetry/collector-contrib-approvers @mx-psi
 processor/routingprocessor/                          @open-telemetry/collector-contrib-approvers @jpkrohling
+processor/schemaprocessor/                           @open-telemetry/collector-contrib-approvers @MovieStoreGuy
 processor/spanmetricsprocessor/                      @open-telemetry/collector-contrib-approvers @albertteoh
 processor/spanprocessor/                             @open-telemetry/collector-contrib-approvers @boostchicken @pmm-sumo
 processor/tailsamplingprocessor/                     @open-telemetry/collector-contrib-approvers @jpkrohling

CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### 🚀 New components 🚀
 
+- `schemaprocessor`: Starting the initial work to allow from translating from semantic convention to another (#8371)
+
 ### 💡 Enhancements 💡
 
 - `k8sclusterreceiver`: Validate that k8s API supports a resource before setting up a watcher for it (#9523)

cmd/configschema/go.mod

@@ -692,6 +692,8 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/reso
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/routingprocessor => ../../processor/routingprocessor/
 
+replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor => ../../processor/schemaprocessor
+
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/spanmetricsprocessor => ../../processor/spanmetricsprocessor/
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/spanprocessor => ../../processor/spanprocessor/

go.mod

@@ -704,6 +704,8 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/tail
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor => ./processor/transformprocessor
 
+replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor => ./processor/schemaprocessor
+
 replace github.com/open-telemetry/opentelemetry-collector-contrib/receiver/activedirectorydsreceiver => ./receiver/activedirectorydsreceiver
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/receiver/awscontainerinsightreceiver => ./receiver/awscontainerinsightreceiver

processor/schemaprocessor/Makefile

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

processor/schemaprocessor/README.md

@@ -0,0 +1,54 @@
+# Schema Transformer Processor
+
+🚧 _Currently under development, subject to change_ 🚧
+
+Supported Pipelines: traces, metrics, logs
+
+The _Schema Processor_ is used to convert existing telemetry data or signals to a version of the semantic convention defined as part of the configuration.
+The processor works by using a set of target schema URLs that are used to match incoming signals.
+On a match, the processor will fetch the schema translation file (if not cached) set by the incoming signal and apply the transformations
+required to export as the target semantic convention version.
+
+Furthermore, it is also possible for organisations and vendors to publish their own semantic conventions and be used by this processor, 
+be sure to follow [schema overview](https://opentelemetry.io/docs/reference/specification/schemas/overview/) for all the details.
+
+## Caching Schema Translation Files
+
+In order to improve efficiency of the processor, the `prefetch` option allows the processor to start downloading and preparing
+the translations needed for signals that match the schema URL.
+
+## Schema Formats
+
+A schema URl is made up in two parts, _Schema Family_ and _Schema Version_, the schema URL is broken down like so:
+
+```text
+|                       Schema URL                           |
+| https://example.com/telemetry/schemas/ |  |      1.0.1     |
+|             Schema Family              |  | Schema Version |
+```
+
+The final path in the schema URL _MUST_ be the schema version and the preceding portion of the URL is the _Schema Family_.
+To read about schema formats, please read more [here](https://opentelemetry.io/docs/reference/specification/schemas/overview/#schema-url)
+
+## Targets Schemas
+
+Targets define a set of schema URLs with a schema identifier that will be used to translate any schema URL that matches the target URL to that version.
+In the event that the processor matches a signal to a target, the processor will translate the signal from the published one to the defined identifier;
+for example using the configuration below, a signal published with the `https://opentelemetry.io/schemas/1.8.0` schema will be translated 
+by the collector to the `https//opentelemetry.io/schemas/1.6.1` schema.
+Within the schema targets, no duplicate schema families are allowed and will report an error if detected.
+
+
+# Example
+
+```yaml
+processors:
+  schema:
+    prefetch:
+    - https://opentelemetry.io/schemas/1.9.0
+    targets:
+    - https://opentelemetry.io/schemas/1.6.1
+    - http://example.com/telemetry/schemas/1.0.1
+```
+
+For more complete examples, please refer to [config.yml](./testdata/config.yml).

processor/schemaprocessor/config.go

@@ -0,0 +1,74 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schemaprocessor // import "github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor"
+
+import (
+	"errors"
+	"fmt"
+
+	"go.opentelemetry.io/collector/config"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor/internal/schema"
+)
+
+var (
+	errRequiresTargets  = errors.New("requires schema targets")
+	errDuplicateTargets = errors.New("duplicate targets detected")
+)
+
+// Config defines the user provided values for the Schema Processor
+type Config struct {
+	config.ProcessorSettings `mapstructure:",squash"`
+
+	// PreCache is a list of schema URLs that are downloaded
+	// and cached at the start of the collector runtime
+	// in order to avoid fetching data that later on could
+	// block processing of signals. (Optional field)
+	Prefetch []string `mapstructure:"prefetch"`
+
+	// Targets define what schema families should be
+	// translated to, allowing older and newer formats
+	// to conform to the target schema identifier.
+	Targets []string `mapstructure:"targets"`
+}
+
+func (c *Config) Validate() error {
+	for _, schemaURL := range c.Prefetch {
+		_, _, err := schema.GetFamilyAndIdentifier(schemaURL)
+		if err != nil {
+			return err
+		}
+	}
+	// Not strictly needed since it would just pass on
+	// any data that doesn't match targets, however defining
+	// this processor with no targets is wasteful.
+	if len(c.Targets) == 0 {
+		return fmt.Errorf("no schema targets defined: %w", errRequiresTargets)
+	}
+
+	families := make(map[string]struct{})
+	for _, target := range c.Targets {
+		family, _, err := schema.GetFamilyAndIdentifier(target)
+		if err != nil {
+			return err
+		}
+		if _, exist := families[family]; exist {
+			return errDuplicateTargets
+		}
+		families[family] = struct{}{}
+	}
+
+	return nil
+}

processor/schemaprocessor/config_test.go

@@ -0,0 +1,98 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schemaprocessor
+
+import (
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/config"
+	"go.opentelemetry.io/collector/service/servicetest"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor/internal/schema"
+)
+
+func TestLoadConfig(t *testing.T) {
+	t.Parallel()
+
+	factories, err := componenttest.NopFactories()
+	require.NoError(t, err, "Must not error on creating Nop factories")
+
+	factory := NewFactory()
+	factories.Processors[typeStr] = factory
+
+	cfg, err := servicetest.LoadConfigAndValidate(path.Join("testdata", "config.yml"), factories)
+	require.NoError(t, err, "Must not error when loading configuration")
+
+	pcfg := cfg.Processors[config.NewComponentIDWithName(typeStr, "with-all-options")]
+	assert.Equal(t, pcfg, &Config{
+		ProcessorSettings: config.NewProcessorSettings(config.NewComponentIDWithName(typeStr, "with-all-options")),
+		Prefetch: []string{
+			"https://opentelemetry.io/schemas/1.9.0",
+		},
+		Targets: []string{
+			"https://opentelemetry.io/schemas/1.4.2",
+			"https://example.com/otel/schemas/1.2.0",
+		},
+	})
+}
+
+func TestConfigurationValidation(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		scenario    string
+		target      []string
+		expectError error
+	}{
+		{scenario: "No targets", target: nil, expectError: errRequiresTargets},
+		{
+			scenario:    "One target of incomplete schema family",
+			target:      []string{"opentelemetry.io/schemas/1.0.0"},
+			expectError: schema.ErrInvalidFamily,
+		},
+		{
+			scenario:    "One target of incomplete schema identifier",
+			target:      []string{"https://opentelemetry.io/schemas/1"},
+			expectError: schema.ErrInvalidIdentifier,
+		},
+		{
+			scenario: "Valid target(s)",
+			target: []string{
+				"https://opentelemetry.io/schemas/1.9.0",
+			},
+			expectError: nil,
+		},
+		{
+			scenario: "Duplicate targets",
+			target: []string{
+				"https://opentelemetry.io/schemas/1.9.0",
+				"https://opentelemetry.io/schemas/1.0.0",
+			},
+			expectError: errDuplicateTargets,
+		},
+	}
+
+	for _, tc := range tests {
+		cfg := &Config{
+			Targets: tc.target,
+		}
+
+		assert.ErrorIs(t, cfg.Validate(), tc.expectError, tc.scenario)
+	}
+}

processor/schemaprocessor/factory.go

@@ -0,0 +1,107 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schemaprocessor // import "github.com/open-telemetry/opentelemetry-collector-contrib/processor/schemaprocessor"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config"
+	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/processor/processorhelper"
+)
+
+const typeStr = "schema"
+
+var processorCapabilities = consumer.Capabilities{MutatesData: true}
+
+// factory will store any of the precompiled schemas in future
+type factory struct{}
+
+// newDefaultConfiguration returns the configuration for schema transformer processor
+// with the default values being used throughout it
+func newDefaultConfiguration() config.Processor {
+	return &Config{
+		ProcessorSettings: config.NewProcessorSettings(config.NewComponentID(typeStr)),
+	}
+}
+
+func NewFactory() component.ProcessorFactory {
+	f := &factory{}
+	return component.NewProcessorFactory(
+		typeStr,
+		newDefaultConfiguration,
+		component.WithLogsProcessor(f.createLogsProcessor),
+		component.WithMetricsProcessor(f.createMetricsProcessor),
+		component.WithTracesProcessor(f.createTracesProcessor),
+	)
+}
+
+func (f factory) createLogsProcessor(
+	ctx context.Context,
+	set component.ProcessorCreateSettings,
+	cfg config.Processor,
+	next consumer.Logs,
+) (component.LogsProcessor, error) {
+	transformer, err := newTransformer(ctx, cfg, set)
+	if err != nil {
+		return nil, err
+	}
+	return processorhelper.NewLogsProcessor(
+		cfg,
+		next,
+		transformer.processLogs,
+		processorhelper.WithCapabilities(processorCapabilities),
+		processorhelper.WithStart(transformer.start),
+	)
+}
+
+func (f factory) createMetricsProcessor(
+	ctx context.Context,
+	set component.ProcessorCreateSettings,
+	cfg config.Processor,
+	next consumer.Metrics,
+) (component.MetricsProcessor, error) {
+	transformer, err := newTransformer(ctx, cfg, set)
+	if err != nil {
+		return nil, err
+	}
+	return processorhelper.NewMetricsProcessor(
+		cfg,
+		next,
+		transformer.processMetrics,
+		processorhelper.WithCapabilities(processorCapabilities),
+		processorhelper.WithStart(transformer.start),
+	)
+}
+
+func (f factory) createTracesProcessor(
+	ctx context.Context,
+	set component.ProcessorCreateSettings,
+	cfg config.Processor,
+	next consumer.Traces,
+) (component.TracesProcessor, error) {
+	transformer, err := newTransformer(ctx, cfg, set)
+	if err != nil {
+		return nil, err
+	}
+	return processorhelper.NewTracesProcessor(
+		cfg,
+		next,
+		transformer.processTraces,
+		processorhelper.WithCapabilities(processorCapabilities),
+		processorhelper.WithStart(transformer.start),
+	)
+}

processor/schemaprocessor/factory_test.go

@@ -0,0 +1,15 @@
+// Copyright  The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schemaprocessor_test