vtctlclient_wrapper.go

/*
Copyright 2017 Google 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 automation

import (
	"bytes"
	"fmt"

	"golang.org/x/net/context"
	"vitess.io/vitess/go/vt/log"
	"vitess.io/vitess/go/vt/logutil"
	"vitess.io/vitess/go/vt/vtctl/vtctlclient"

	logutilpb "vitess.io/vitess/go/vt/proto/logutil"
)

// ExecuteVtctl runs vtctl using vtctlclient. The stream of Event
// messages is concatenated into one output string.
// Additionally, the start and the end of the command will be logged to make
// it easier to debug which command was executed and how long it took.
func ExecuteVtctl(ctx context.Context, server string, args []string) (string, error) {
	var output bytes.Buffer
	loggerToBufferFunc := createLoggerEventToBufferFunction(&output)
	outputLogger := newOutputLogger(loggerToBufferFunc)

	startMsg := fmt.Sprintf("Executing remote vtctl command: %v server: %v", args, server)
	outputLogger.Infof(startMsg)
	log.Info(startMsg)

	err := vtctlclient.RunCommandAndWait(
		ctx, server, args,
		loggerToBufferFunc)

	endMsg := fmt.Sprintf("Executed remote vtctl command: %v server: %v err: %v", args, server, err)
	outputLogger.Infof(endMsg)
	// Log full output to log file (but not to the buffer).
	log.Infof("%v output (starting on next line):\n%v", endMsg, output.String())

	return output.String(), err
}

// createLoggerEventToBufferFunction returns a function to add LoggerEvent
// structs to a given buffer, one line per event.
// The buffer can be used to return a multi-line string with all events.
func createLoggerEventToBufferFunction(output *bytes.Buffer) func(*logutilpb.Event) {
	return func(e *logutilpb.Event) {
		logutil.EventToBuffer(e, output)
		output.WriteRune('\n')
	}
}

// newOutputLogger returns a logger which makes it easy to log to a bytes.Buffer
// output. When calling this function, pass in the result of
// createLoggerEventToBufferFunction().
func newOutputLogger(loggerToBufferFunc func(*logutilpb.Event)) logutil.Logger {
	return logutil.NewCallbackLogger(func(e *logutilpb.Event) {
		loggerToBufferFunc(e)
	})
}