Add all storages to env command (#1541)

* Add all storages to help command

Signed-off-by: Pavol Loffay <ploffay@redhat.com>

* Fix comment

Signed-off-by: Pavol Loffay <ploffay@redhat.com>

cmd/env/command.go

@@ -42,7 +42,7 @@ their names to upper case and replacing punctuation with underscores. For exampl
 
 The following configuration options are only available via environment variables:`+"\n")
 			fs := new(pflag.FlagSet)
-			fs.String(storage.SpanStorageTypeEnvVar, "cassandra", `The type of backend (cassandra, elasticsearch, kafka, memory) used for trace storage. Multiple backends can be specified (currently only for writing spans) as comma-separated list, e.g. "cassandra,kafka".`)
+			fs.String(storage.SpanStorageTypeEnvVar, "cassandra", fmt.Sprintf("The type of backend %s used for trace storage. Multiple backends can be specified (currently only for writing spans) as comma-separated list, e.g. \"cassandra,kafka\".", storage.AllStorageTypes))
 			fs.String(storage.DependencyStorageTypeEnvVar, "${SPAN_STORAGE}", "The type of backend used for service dependencies storage.")
 			fmt.Fprintln(cmd.OutOrStdout(), strings.Replace(fs.FlagUsagesWrapped(1000), "      --", "      ", -1))
 		},

plugin/storage/factory.go

@@ -50,7 +50,8 @@ const (
 	defaultDownsamplingHashSalt = ""
 )
 
-var allStorageTypes = []string{cassandraStorageType, elasticsearchStorageType, memoryStorageType, kafkaStorageType, badgerStorageType, grpcPluginStorageType}
+// AllStorageTypes defines all available storage backends
+var AllStorageTypes = []string{cassandraStorageType, elasticsearchStorageType, memoryStorageType, kafkaStorageType, badgerStorageType, grpcPluginStorageType}
 
 // Factory implements storage.Factory interface as a meta-factory for storage components.
 type Factory struct {
@@ -95,7 +96,7 @@ func (f *Factory) getFactoryOfType(factoryType string) (storage.Factory, error)
 	case grpcPluginStorageType:
 		return grpc.NewFactory(), nil
 	default:
-		return nil, fmt.Errorf("unknown storage type %s. Valid types are %v", factoryType, allStorageTypes)
+		return nil, fmt.Errorf("unknown storage type %s. Valid types are %v", factoryType, AllStorageTypes)
 	}
 }