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factory_config.go
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factory_config.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// 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 storage
import (
"fmt"
"io"
"os"
"strings"
)
const (
// SpanStorageTypeEnvVar is the name of the env var that defines the type of backend used for span storage.
SpanStorageTypeEnvVar = "SPAN_STORAGE_TYPE"
// DependencyStorageTypeEnvVar is the name of the env var that defines the type of backend used for dependencies storage.
DependencyStorageTypeEnvVar = "DEPENDENCY_STORAGE_TYPE"
spanStorageFlag = "--span-storage.type"
)
// FactoryConfig tells the Factory which types of backends it needs to create for different storage types.
type FactoryConfig struct {
SpanWriterTypes []string
SpanReaderType string
DependenciesStorageType string
}
// FactoryConfigFromEnvAndCLI reads the desired types of storage backends from SPAN_STORAGE_TYPE and
// DEPENDENCY_STORAGE_TYPE environment variables. Allowed values:
// * `cassandra` - built-in
// * `elasticsearch` - built-in
// * `memory` - built-in
// * `kafka` - built-in
// * `plugin` - loads a dynamic plugin that implements storage.Factory interface (not supported at the moment)
//
// For backwards compatibility it also parses the args looking for deprecated --span-storage.type flag.
// If found, it writes a deprecation warning to the log.
func FactoryConfigFromEnvAndCLI(args []string, log io.Writer) FactoryConfig {
spanStorageType := os.Getenv(SpanStorageTypeEnvVar)
if spanStorageType == "" {
// for backwards compatibility check command line for --span-storage.type flag
spanStorageType = spanStorageTypeFromArgs(args, log)
}
if spanStorageType == "" {
spanStorageType = cassandraStorageType
}
spanWriterTypes := strings.Split(spanStorageType, ",")
if len(spanWriterTypes) > 1 {
fmt.Fprintf(log,
"WARNING: multiple span storage types have been specified. "+
"Only the first type (%s) will be used for reading and archiving.\n\n",
spanWriterTypes[0],
)
}
depStorageType := os.Getenv(DependencyStorageTypeEnvVar)
if depStorageType == "" {
depStorageType = spanWriterTypes[0]
}
// TODO support explicit configuration for readers
return FactoryConfig{
SpanWriterTypes: spanWriterTypes,
SpanReaderType: spanWriterTypes[0],
DependenciesStorageType: depStorageType,
}
}
func spanStorageTypeFromArgs(args []string, log io.Writer) string {
for i, token := range args {
if i == 0 {
continue // skip app name; easier than dealing with +-1 offset
}
if !strings.HasPrefix(token, spanStorageFlag) {
continue
}
fmt.Fprintf(
log,
"WARNING: found deprecated command line option %s, please use environment variable %s instead\n",
token,
SpanStorageTypeEnvVar,
)
if token == spanStorageFlag && i < len(args)-1 {
return args[i+1]
}
if strings.HasPrefix(token, spanStorageFlag+"=") {
return token[(len(spanStorageFlag) + 1):]
}
break
}
return ""
}