Initial commit: Open sourcing all of the Maple Open Technologies code.

cloud/maplefile-backend/pkg/distributedmutex/distributelocker.go

@@ -0,0 +1,220 @@
+// File Path: monorepo/cloud/maplefile-backend/pkg/distributedmutex/distributedmutex.go
+package distributedmutex
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/bsm/redislock"
+	"github.com/redis/go-redis/v9"
+	"go.uber.org/zap"
+)
+
+// Adapter provides interface for abstracting distributedmutex generation.
+type Adapter interface {
+	// Blocking acquire - waits until lock is obtained or timeout
+	Acquire(ctx context.Context, key string)
+	Acquiref(ctx context.Context, format string, a ...any)
+	Release(ctx context.Context, key string)
+	Releasef(ctx context.Context, format string, a ...any)
+
+	// Non-blocking operations for leader election
+	// TryAcquire attempts to acquire a lock without blocking
+	// Returns true if lock was acquired, false if already held by someone else
+	TryAcquire(ctx context.Context, key string, ttl time.Duration) (bool, error)
+
+	// Extend renews the TTL of an existing lock
+	// Returns error if the lock is not owned by this instance
+	Extend(ctx context.Context, key string, ttl time.Duration) error
+
+	// IsOwner checks if this instance owns the given lock
+	IsOwner(ctx context.Context, key string) (bool, error)
+}
+
+type distributedLockerAdapter struct {
+	Logger        *zap.Logger
+	Redis         redis.UniversalClient
+	Locker        *redislock.Client
+	LockInstances map[string]*redislock.Lock
+	Mutex         *sync.Mutex // Add a mutex for synchronization with goroutines
+}
+
+// NewAdapter constructor that returns the default DistributedLocker generator.
+func NewAdapter(loggerp *zap.Logger, redisClient redis.UniversalClient) Adapter {
+	loggerp = loggerp.Named("DistributedMutex")
+	loggerp.Debug("distributed mutex starting and connecting...")
+
+	// Create a new lock client.
+	locker := redislock.New(redisClient)
+
+	loggerp.Debug("distributed mutex initialized")
+
+	return distributedLockerAdapter{
+		Logger:        loggerp,
+		Redis:         redisClient,
+		Locker:        locker,
+		LockInstances: make(map[string]*redislock.Lock, 0),
+		Mutex:         &sync.Mutex{}, // Initialize the mutex
+	}
+}
+
+// Acquire function blocks the current thread if the lock key is currently locked.
+func (a distributedLockerAdapter) Acquire(ctx context.Context, k string) {
+	startDT := time.Now()
+	a.Logger.Debug(fmt.Sprintf("locking for key: %v", k))
+
+	// Retry every 250ms, for up-to 20x
+	backoff := redislock.LimitRetry(redislock.LinearBackoff(250*time.Millisecond), 20)
+
+	// Obtain lock with retry
+	lock, err := a.Locker.Obtain(ctx, k, time.Minute, &redislock.Options{
+		RetryStrategy: backoff,
+	})
+	if err == redislock.ErrNotObtained {
+		nowDT := time.Now()
+		diff := nowDT.Sub(startDT)
+		a.Logger.Error("could not obtain lock",
+			zap.String("key", k),
+			zap.Time("start_dt", startDT),
+			zap.Time("now_dt", nowDT),
+			zap.Any("duration_in_minutes", diff.Minutes()))
+		return
+	} else if err != nil {
+		a.Logger.Error("failed obtaining lock",
+			zap.String("key", k),
+			zap.Any("error", err),
+		)
+		return
+	}
+
+	// DEVELOPERS NOTE:
+	// The `map` datastructure in Golang is not concurrently safe, therefore we
+	// need to use mutex to coordinate access of our `LockInstances` map
+	// resource between all the goroutines.
+	a.Mutex.Lock()
+	defer a.Mutex.Unlock()
+
+	if a.LockInstances != nil { // Defensive code.
+		a.LockInstances[k] = lock
+	}
+}
+
+// Acquiref function blocks the current thread if the lock key is currently locked.
+func (u distributedLockerAdapter) Acquiref(ctx context.Context, format string, a ...any) {
+	k := fmt.Sprintf(format, a...)
+	u.Acquire(ctx, k)
+	return
+}
+
+// Release function blocks the current thread if the lock key is currently locked.
+func (a distributedLockerAdapter) Release(ctx context.Context, k string) {
+	a.Logger.Debug(fmt.Sprintf("unlocking for key: %v", k))
+
+	lockInstance, ok := a.LockInstances[k]
+	if ok {
+		defer lockInstance.Release(ctx)
+	} else {
+		a.Logger.Error("could not obtain to unlock", zap.String("key", k))
+	}
+	return
+}
+
+// Releasef
+func (u distributedLockerAdapter) Releasef(ctx context.Context, format string, a ...any) {
+	k := fmt.Sprintf(format, a...) //TODO: https://github.com/bsm/redislock/blob/main/README.md
+	u.Release(ctx, k)
+	return
+}
+
+// TryAcquire attempts to acquire a lock without blocking.
+// Returns true if lock was acquired, false if already held by someone else.
+func (a distributedLockerAdapter) TryAcquire(ctx context.Context, k string, ttl time.Duration) (bool, error) {
+	a.Logger.Debug(fmt.Sprintf("trying to acquire lock for key: %v with ttl: %v", k, ttl))
+
+	// Try to obtain lock without retries (non-blocking)
+	lock, err := a.Locker.Obtain(ctx, k, ttl, &redislock.Options{
+		RetryStrategy: redislock.NoRetry(),
+	})
+
+	if err == redislock.ErrNotObtained {
+		// Lock is held by someone else
+		a.Logger.Debug("lock not obtained, already held by another instance",
+			zap.String("key", k))
+		return false, nil
+	}
+
+	if err != nil {
+		// Actual error occurred
+		a.Logger.Error("failed trying to obtain lock",
+			zap.String("key", k),
+			zap.Error(err))
+		return false, err
+	}
+
+	// Successfully acquired lock
+	a.Mutex.Lock()
+	defer a.Mutex.Unlock()
+
+	if a.LockInstances != nil {
+		a.LockInstances[k] = lock
+	}
+
+	a.Logger.Debug("successfully acquired lock",
+		zap.String("key", k),
+		zap.Duration("ttl", ttl))
+
+	return true, nil
+}
+
+// Extend renews the TTL of an existing lock.
+// Returns error if the lock is not owned by this instance.
+func (a distributedLockerAdapter) Extend(ctx context.Context, k string, ttl time.Duration) error {
+	a.Logger.Debug(fmt.Sprintf("extending lock for key: %v with ttl: %v", k, ttl))
+
+	a.Mutex.Lock()
+	lockInstance, ok := a.LockInstances[k]
+	a.Mutex.Unlock()
+
+	if !ok {
+		err := fmt.Errorf("lock not found in instances map")
+		a.Logger.Error("cannot extend lock, not owned by this instance",
+			zap.String("key", k),
+			zap.Error(err))
+		return err
+	}
+
+	// Extend the lock TTL
+	err := lockInstance.Refresh(ctx, ttl, nil)
+	if err != nil {
+		a.Logger.Error("failed to extend lock",
+			zap.String("key", k),
+			zap.Error(err))
+		return err
+	}
+
+	a.Logger.Debug("successfully extended lock",
+		zap.String("key", k),
+		zap.Duration("ttl", ttl))
+
+	return nil
+}
+
+// IsOwner checks if this instance owns the given lock.
+func (a distributedLockerAdapter) IsOwner(ctx context.Context, k string) (bool, error) {
+	a.Mutex.Lock()
+	lockInstance, ok := a.LockInstances[k]
+	a.Mutex.Unlock()
+
+	if !ok {
+		// Not in our instances map
+		return false, nil
+	}
+
+	// Get the lock metadata to check if we still own it
+	metadata := lockInstance.Metadata()
+
+	// If metadata is empty, we don't own it
+	return metadata != "", nil
+}