Fix pipeline setup under serverless (#36973)

* fix pipeline setup under serverless

* add docs, fix errors

* fix fix linter

filebeat/fileset/pipelines.go

@@ -37,6 +37,7 @@ type PipelineLoader interface {
 	LoadJSON(path string, json map[string]interface{}) ([]byte, error)
 	Request(method, path string, pipeline string, params map[string]string, body interface{}) (int, []byte, error)
 	GetVersion() version.V
+	IsServerless() bool
 }
 
 // MultiplePipelineUnsupportedError is an error returned when a fileset uses multiple pipelines but is
@@ -65,16 +66,17 @@ func (reg *ModuleRegistry) LoadPipelines(esClient PipelineLoader, overwrite bool
 			// check that all the required Ingest Node plugins are available
 			requiredProcessors := fileset.GetRequiredProcessors()
 			reg.log.Debugf("Required processors: %s", requiredProcessors)
-			if len(requiredProcessors) > 0 {
+			// APIs do not exist on serverless
+			if len(requiredProcessors) > 0 && !esClient.IsServerless() {
 				err := checkAvailableProcessors(esClient, requiredProcessors)
 				if err != nil {
-					return fmt.Errorf("error loading pipeline for fileset %s/%s: %v", module.config.Module, fileset.name, err)
+					return fmt.Errorf("error loading pipeline for fileset %s/%s: %w", module.config.Module, fileset.name, err)
 				}
 			}
 
 			pipelines, err := fileset.GetPipelines(esClient.GetVersion())
 			if err != nil {
-				return fmt.Errorf("error getting pipeline for fileset %s/%s: %v", module.config.Module, fileset.name, err)
+				return fmt.Errorf("error getting pipeline for fileset %s/%s: %w", module.config.Module, fileset.name, err)
 			}
 
 			// Filesets with multiple pipelines can only be supported by Elasticsearch >= 6.5.0
@@ -88,7 +90,7 @@ func (reg *ModuleRegistry) LoadPipelines(esClient PipelineLoader, overwrite bool
 			for _, pipeline := range pipelines {
 				err = LoadPipeline(esClient, pipeline.id, pipeline.contents, overwrite, reg.log.With("pipeline", pipeline.id))
 				if err != nil {
-					err = fmt.Errorf("error loading pipeline for fileset %s/%s: %v", module.config.Module, fileset.name, err)
+					err = fmt.Errorf("error loading pipeline for fileset %s/%s: %w", module.config.Module, fileset.name, err)
 					break
 				}
 				pipelineIDsLoaded = append(pipelineIDsLoaded, pipeline.id)
@@ -169,7 +171,7 @@ func interpretError(initialErr error, body []byte) error {
 				"This is the response I got from Elasticsearch: %s", body)
 		}
 
-		return fmt.Errorf("couldn't load pipeline: %v. Additionally, error decoding response body: %s",
+		return fmt.Errorf("couldn't load pipeline: %w. Additionally, error decoding response body: %s",
 			initialErr, body)
 	}
 
@@ -194,5 +196,5 @@ func interpretError(initialErr error, body []byte) error {
 			"This is the response I got from Elasticsearch: %s", body)
 	}
 
-	return fmt.Errorf("couldn't load pipeline: %v. Response body: %s", initialErr, body)
+	return fmt.Errorf("couldn't load pipeline: %w. Response body: %s", initialErr, body)
 }