blob: f44eb3333acac07beee4722131871f6a0ab724ae [file] [log] [blame]
// Copyright 2017 The LUCI Authors.
//
// 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 lib
import (
"context"
"os"
"github.com/danjacques/gofslock/fslock"
"github.com/maruel/subcommands"
"go.chromium.org/luci/common/logging"
)
// RunExclusive runs the command with the specified context and environment while
// holding an exclusive mmutex lock.
func RunExclusive(ctx context.Context, env subcommands.Env, command func(context.Context) error) error {
lockFilePath, drainFilePath, err := computeMutexPaths(env)
if err != nil {
return err
}
logging.Infof(ctx, "[mmutex][exclusive] LockFilePath: %s, DrainFilePath: %s.", lockFilePath, drainFilePath)
if len(lockFilePath) == 0 {
return command(ctx)
}
file, err := os.OpenFile(drainFilePath, os.O_RDONLY|os.O_CREATE, 0666)
if err != nil {
return err
}
if err = file.Close(); err != nil {
return err
}
// Remove the drain file in case the lock can never be acquired.
defer RemoveDrainFile(ctx, drainFilePath)
blocker := createLockBlocker(ctx)
return fslock.WithBlocking(lockFilePath, blocker, func() error {
// Remove the drain file immediately after acquiring the lock in order
// to decrease the likelihood that a crash occurs, leaving the drain
// file sitting around indefinitely.
if err := os.Remove(drainFilePath); err != nil {
logging.Errorf(ctx, "[mmutex][exclusive] Failed to remove drain file after acquiring the lock: %s", drainFilePath)
return err
}
logging.Infof(ctx, "[mmutex][exclusive] Lock acquired and drain file removed.")
return command(ctx)
})
}
func RemoveDrainFile(ctx context.Context, drainFilePath string) {
if err := os.Remove(drainFilePath); err != nil && !os.IsNotExist(err) {
logging.Errorf(ctx, "[mmutex][exclusive] Failed to remove drain file: %s", err)
}
}