go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/mmutex/lib/shared.go (about)

     1  // Copyright 2017 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package lib
    16  
    17  import (
    18  	"context"
    19  
    20  	"github.com/danjacques/gofslock/fslock"
    21  	"github.com/maruel/subcommands"
    22  	"go.chromium.org/luci/common/logging"
    23  )
    24  
    25  // RunShared runs the command with the specified context and environment while
    26  // holding a shared mmutex lock.
    27  func RunShared(ctx context.Context, env subcommands.Env, command func(context.Context) error) error {
    28  	lockFilePath, drainFilePath, err := computeMutexPaths(env)
    29  	if err != nil {
    30  		return err
    31  	}
    32  
    33  	logging.Infof(ctx, "[mmutex][shared] LockFilePath: %s, DrainFilePath: %s.", lockFilePath, drainFilePath)
    34  	if len(lockFilePath) == 0 {
    35  		return command(ctx)
    36  	}
    37  
    38  	blocker := createLockBlocker(ctx)
    39  
    40  	// Use the same retry mechanism for checking if the drain file still exists
    41  	// as we use to request the file lock.
    42  	if err = blockWhileFileExists(drainFilePath, blocker); err != nil {
    43  		return err
    44  	}
    45  
    46  	return fslock.WithSharedBlocking(lockFilePath, blocker, func() error {
    47  		logging.Infof(ctx, "[mmutex][shared] Lock acquired.")
    48  		return command(ctx)
    49  	})
    50  }