CouchbaseClient.ExecuteGetOrCreateWithLock.cs

public static IGetOperationResult<T> ExecuteGetOrCreateWithLock<T>(this ICouchbaseClient client,
    string key, Func<T> defaultNewValue, TimeSpan keyExpiration, TimeSpan lockExpiration)
{
    var initialGetResult = client.ExecuteGetWithLock<T>(key, lockExpiration);

    if (initialGetResult.StatusCode == (int) StatusCodeEnums.NotFound ||
        (initialGetResult.InnerResult != null &&
            initialGetResult.InnerResult.StatusCode == (int) StatusCodeEnums.NotFound))
    {
        // Key not found. We'll have to create it with the default value and make sure we get the lock.
        // There may be other threads racing at this moment, we have to make sure we create the record
        // and acquire lock over this newly created key. AFAIK CB API does not allow this to happen
        // atomically, so we have to perform two operations, each with its own race conditions.
        var storeResult = client.ExecuteStore(StoreMode.Add, key, defaultNewValue(), keyExpiration);
        if (!storeResult.Success)
        {
            // "Add" operation failed; either it was a generic error, or a racing thread beat us to it.
            return new GetOperationResult<T>
            {
                Cas = storeResult.Cas,
                Exception = storeResult.Exception,
                InnerResult = storeResult,
                Message = storeResult.Message,
                StatusCode = storeResult.StatusCode,
                Success = false,
                Value = default (T)
            };
        }
        // Finally try to get the created record with a lock. There may be yet another thread racing between
        // adding a record and acquiring a lock.
        return client.ExecuteGetWithLock<T>(key, lockExpiration);
    }
    // If the key was found or there was any other kind of error except missing key, just return the original result.
    return initialGetResult;
}