/
file_writer.go
73 lines (64 loc) · 2.08 KB
/
file_writer.go
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// Copyright 2019 Preferred Networks, 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 metrics
import (
"os"
"strings"
)
// FileWriter is a Writer that writes metrics to a file.
type FileWriter struct {
file *os.File
formatter Formatter
}
// NewFileWriter creates a new FileWriter with an output device or file at the given path, and the formatter that
// formats metrics to a string
// If /dev/stdout or stdout is given, the standard out is set.
// If /dev/stderr or stderr is given, the standard error is set.
// Otherwise, the file of a given path is set and it will be truncated if it exists.
// Returns error if failed to create a file.
func NewFileWriter(dest string, formatter Formatter) (*FileWriter, error) {
var file *os.File
if dest == "/dev/stdout" || strings.ToLower(dest) == "stdout" {
file = os.Stdout
} else if dest == "/dev/stderr" || strings.ToLower(dest) == "stderr" {
file = os.Stderr
} else {
f, err := os.Create(dest)
if err != nil {
return nil, err
}
file = f
}
return &FileWriter{
file: file,
formatter: formatter,
}, nil
}
// FileName returns the name of file underlying this FileWriter.
func (w *FileWriter) FileName() string { return w.file.Name() }
// Write implements Writer interface.
// Returns error if failed to format with the underlying formatter.
func (w *FileWriter) Write(metrics *Metrics) error {
str, err := w.formatter.Format(metrics)
if err != nil {
return err
}
_, err = w.file.WriteString(str)
if err != nil {
return err
}
_, err = w.file.Write([]byte{'\n'})
return err
}
var _ = Writer(&FileWriter{})