add pubsub exporter config for ordering

Some readme fixes

exporter/googlecloudpubsubexporter/README.md

@@ -19,7 +19,7 @@ This exporter sends OTLP messages to a Google Cloud [Pubsub](https://cloud.googl
 The following configuration options are supported:
 
 * `project` (Optional): The Google Cloud Project of the topics.
-* `topic` (Required): The topic name to receive OTLP data over. The topic name should be a fully qualified resource
+* `topic` (Required): The topic name to send OTLP data over. The topic name should be a fully qualified resource
   name (eg: `projects/otel-project/topics/otlp`).
 * `compression` (Optional): Set the payload compression, only `gzip` is supported. Default is no compression.
 * `watermark` Behaviour of how the `ce-time` attribute is set (see watermark section for more info)
@@ -31,17 +31,25 @@ The following configuration options are supported:
   or switching between [global and regional service endpoints](https://cloud.google.com/pubsub/docs/reference/service_apis_overview#service_endpoints).
 * `insecure` (Optional): allows performing “insecure” SSL connections and transfers, useful when connecting to a local
   emulator instance. Only has effect if Endpoint is not ""
+* `ordering`: Configures the [PubSub ordering](https://cloud.google.com/pubsub/docs/ordering) feature, see 
+  [ordering](#ordering) section for more info.
+  * `enabled` (default = `false`): Enables the ordering. Default is disabled.
+  * `from_resource_attribute` (no default): resource attribute that will be used as the ordering key. Required when
+    `ordering.enabled` is `true`. If the resource attribute is missing or has an empty value, the messages will not be
+    ordered for this resource.
+  * `remove_resource_attribute` (default = `false`): if the ordering key resource attribute specified 
+    `from_resource_attribute` should be removed from the resource attributes.
 
 ```yaml
 exporters:
   googlecloudpubsub:
     project: my-project
-    topic: otlp-traces
+    topic: projects/my-project/topics/otlp-traces
 ```
 
 ## Pubsub topic
 
-The Google Cloud [Pubsub](https://cloud.google.com/pubsub) export doesn't automatic create topics, it expects the topic
+The Google Cloud [Pubsub](https://cloud.google.com/pubsub) exporter doesn't automatically create topics, it expects the topic
 to be created upfront. Security wise it's best to give the collector its own service account and give the
 topic `Pub/Sub Publisher` permission.
 
@@ -74,11 +82,11 @@ up to 20% of the cost. This can be done by setting the `compression` to `gzip`.
 exporters:
   googlecloudpubsub:
     project: my-project
-    topic: otlp-traces
+    topic: projects/my-project/topics/otlp-traces
     compression: gzip
 ```
 
-The exporter with add the `content-encoding` attribute to the message. The receiver will look at this attribute
+The exporter will add the `content-encoding` attribute to the message. The receiver will look at this attribute
 to detect the compression that is used on the payload.
 
 Only `gzip` is supported.
@@ -100,7 +108,7 @@ timestamp , if you want to behaviour to have effect as the default is `0s`.
 exporters:
   googlecloudpubsub:
     project: my-project
-    topic: otlp-traces
+    topic: projects/my-project/topics/otlp-traces
     watermark: 
       behavior: earliest
       allow_drift: 1h
@@ -119,3 +127,35 @@ scenario is `behavior: earliest` with a reasonable `allow_drift` of `1h`.
 
 Allowed behavior values are `current` or `earliest`. For `allow_drift` the default is `0s`, so make sure to set the 
 value.
+
+## Ordering
+
+When ordering is enabled (`ordering.enabled`), you are required to specify a resource attribute key that will be used as
+the ordering key (`ordering.from_resource_attribute`). If this resource attribute is only meant to be used as an
+ordering key, you may want to choose to get this resource attribute key (`ordering.from_resource_attribute`) removed
+before publishing to PubSub by enabling the `ordering.remove_resource_attribute` configuration.
+
+```yaml
+exporters:
+  googlecloudpubsub:
+    project: my-project
+    topic: projects/my-project/topics/otlp-traces
+    ordering:
+      enabled: true
+      from_resource_attribute: some.resource.attribute.key
+      remove_resource_attribute: true
+```
+
+### Notes
+
+While the PubSub topic doesn't require any configuration for ordering, you will need to enable ordering on your 
+subscription(s) if you need it. Enabling ordering on a subscription is only possible at creation.
+For composite ordering keys you'd need to compose the resource attribute value before exporting e.g., by using a
+[transform processor](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/transformprocessor)
+.
+
+Empty values in the ordering key are accepted but won't be ordered, see [PubSub ordering documentation](https://cloud.google.com/pubsub/docs/ordering)
+for more details.
+
+PubSub requires one publish request per ordering key value, so this exporter groups the signals per ordering key before 
+publishing.

exporter/googlecloudpubsubexporter/config.go

@@ -10,6 +10,7 @@ import (
 
 	"go.opentelemetry.io/collector/config/configretry"
 	"go.opentelemetry.io/collector/exporter/exporterhelper"
+	"go.uber.org/multierr"
 )
 
 var topicMatcher = regexp.MustCompile(`^projects/[a-z][a-z0-9\-]*/topics/`)
@@ -34,6 +35,8 @@ type Config struct {
 	Compression string `mapstructure:"compression"`
 	// Watermark defines the watermark (the ce-time attribute on the message) behavior
 	Watermark WatermarkConfig `mapstructure:"watermark"`
+	// Ordering configures the ordering keys
+	Ordering OrderingConfig `mapstructure:"ordering"`
 }
 
 // WatermarkConfig customizes the behavior of the watermark
@@ -46,15 +49,27 @@ type WatermarkConfig struct {
 	AllowedDrift time.Duration `mapstructure:"allowed_drift"`
 }
 
+// OrderingConfig customizes the behavior of the ordering
+type OrderingConfig struct {
+	// Enabled indicates if ordering is enabled
+	Enabled bool `mapstructure:"enabled"`
+	// FromResourceAttribute is a resource attribute that will be used as the ordering key.
+	FromResourceAttribute string `mapstructure:"from_resource_attribute"`
+	// RemoveResourceAttribute indicates if the ordering key should be removed from the resource attributes.
+	RemoveResourceAttribute bool `mapstructure:"remove_resource_attribute"`
+}
+
 func (config *Config) Validate() error {
+	var errors error
 	if !topicMatcher.MatchString(config.Topic) {
-		return fmt.Errorf("topic '%s' is not a valid format, use 'projects/<project_id>/topics/<name>'", config.Topic)
+		errors = multierr.Append(errors, fmt.Errorf("topic '%s' is not a valid format, use 'projects/<project_id>/topics/<name>'", config.Topic))
 	}
-	_, err := config.parseCompression()
-	if err != nil {
-		return err
+	if _, err := config.parseCompression(); err != nil {
+		errors = multierr.Append(errors, err)
 	}
-	return config.Watermark.validate()
+	errors = multierr.Append(errors, config.Watermark.validate())
+	errors = multierr.Append(errors, config.Ordering.validate())
+	return errors
 }
 
 func (config *WatermarkConfig) validate() error {
@@ -65,6 +80,13 @@ func (config *WatermarkConfig) validate() error {
 	return err
 }
 
+func (cfg *OrderingConfig) validate() error {
+	if cfg.Enabled && cfg.FromResourceAttribute == "" {
+		return fmt.Errorf("'from_resource_attribute' is required if ordering is enabled")
+	}
+	return nil
+}
+
 func (config *Config) parseCompression() (compression, error) {
 	switch config.Compression {
 	case "gzip":

exporter/googlecloudpubsubexporter/config_test.go

@@ -34,18 +34,21 @@ func TestLoadConfig(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, sub.Unmarshal(cfg))
 
-	customConfig := factory.CreateDefaultConfig().(*Config)
+	expectedConfig := factory.CreateDefaultConfig().(*Config)
 
-	customConfig.ProjectID = "my-project"
-	customConfig.UserAgent = "opentelemetry-collector-contrib {{version}}"
-	customConfig.TimeoutSettings = exporterhelper.TimeoutConfig{
+	expectedConfig.ProjectID = "my-project"
+	expectedConfig.UserAgent = "opentelemetry-collector-contrib {{version}}"
+	expectedConfig.TimeoutSettings = exporterhelper.TimeoutConfig{
 		Timeout: 20 * time.Second,
 	}
-	customConfig.Topic = "projects/my-project/topics/otlp-topic"
-	customConfig.Compression = "gzip"
-	customConfig.Watermark.Behavior = "earliest"
-	customConfig.Watermark.AllowedDrift = time.Hour
-	assert.Equal(t, cfg, customConfig)
+	expectedConfig.Topic = "projects/my-project/topics/otlp-topic"
+	expectedConfig.Compression = "gzip"
+	expectedConfig.Watermark.Behavior = "earliest"
+	expectedConfig.Watermark.AllowedDrift = time.Hour
+	expectedConfig.Ordering.Enabled = true
+	expectedConfig.Ordering.FromResourceAttribute = "ordering_key"
+	expectedConfig.Ordering.RemoveResourceAttribute = true
+	assert.Equal(t, expectedConfig, cfg)
 }
 
 func TestTopicConfigValidation(t *testing.T) {
@@ -100,3 +103,14 @@ func TestWatermarkDefaultMaxDriftValidation(t *testing.T) {
 	assert.NoError(t, c.Validate())
 	assert.Equal(t, time.Duration(9223372036854775807), c.Watermark.AllowedDrift)
 }
+
+func TestOrderConfigValidation(t *testing.T) {
+	factory := NewFactory()
+	c := factory.CreateDefaultConfig().(*Config)
+	c.Topic = "projects/project/topics/my-topic"
+	assert.NoError(t, c.Validate())
+	c.Ordering.Enabled = true
+	assert.Error(t, c.Validate())
+	c.Ordering.FromResourceAttribute = "key"
+	assert.NoError(t, c.Validate())
+}

exporter/googlecloudpubsubexporter/factory.go

@@ -81,6 +81,11 @@ func createDefaultConfig() component.Config {
 			Behavior:     "current",
 			AllowedDrift: 0,
 		},
+		Ordering: OrderingConfig{
+			Enabled:                 false,
+			FromResourceAttribute:   "",
+			RemoveResourceAttribute: false,
+		},
 	}
 }
 

exporter/googlecloudpubsubexporter/testdata/config.yaml

@@ -8,3 +8,7 @@ googlecloudpubsub/customname:
   watermark:
     behavior: earliest
     allowed_drift: 1h
+  ordering:
+    enabled: true
+    from_resource_attribute: ordering_key
+    remove_resource_attribute: true