| // 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) |
| } |
| } |