locking

I am new to Python and I am trying to save the results of five different processes to one excel file (each process write to a different sheet). I have read different posts here, but still can't get it done as I'm very confused about pool.map, queues, and locks, and I'm not sure what is required here to fulfill this task. This is my code so far: list_of_days = ["2017.03.20", "2017.03.21", "2017.03.22", "2017.03.23", "2017.03.24"] results = pd.DataFrame() if __name__ == '__main__': global list_of_days writer = pd.ExcelWriter('myfile.xlsx', engine='xlsxwriter') nr_of_cores = multiprocessing.cpu

Assume we have a method like this public static void method(string param) { ** critical section ** // There are a lot of methods calls // switch cases // if conditions // read and write in dictionary // new class initiations ** critical section ** } how we can make it thread safe while thousand of concurrent calls happen? Could delegates help? I read here that Modifying event is not thread-safe, but invoking a Delegate is thread-safe. Since a Delegate is immutable type so it is thread safe. Does that mean that delegates make my code thread safe? Here is a couple of concepts: in the above

Let’s say I have a table called Withdrawals (id, amount, user_id, status). Whenever I a withdrawal is initiated this is the flow: Verify if user has sufficient balance (which is calculated as sum of amount received - sum of withdrawals amount) Insert row with amount, user_id and status=‘pending’ Call 3rd party software through gRPC to initiate a withdrawal (actually send money), wait for a response Update row with status = ‘completed’ as soon we a positive response or delete the entry if the withdrawal failed. However, I have a concurrency problem in this flow. Let’s say the user makes 2 full

The ReadUncommitted IsolationLevel in SSIS is a bug acknowledged by Microsoft for the following but 'Wont fix' as described below. http://connect.microsoft.com/SQLServer/feedback/details/498891/ssis-setting-isolationlevel-to-readuncommitted-still-uses-read-committed#details What would be the workaround(s) for the same? yes, but you have to inform the sql command on your source instead of selecting a table and set the isolation level before the execution: SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED select * from test_isolation and the package should have the serializable isolation level

I am trying to implement a queue in C that causes a process to non-busy wait until there is an element in the queue to consume. I have tried two different things to try to achieve this. The first problem I have is if the enqueue/dequeue operations have if conditionals to check the bounds( if (q->count == QUEUESIZE) ), the call to sem_wait will return immediately because no other process has obtained a lock. If I change the conditional to while (q->count == QUEUESIZE), I believe the consumer process will 'busy wait' until the semaphore is posted by the producer process, which is not my goal of

I'm developing a php / mysql application that handles multiple simultaneous users. I'm thinking of the best approach to take when it comes to locking / warning against records that are currently being viewed / edited. The scenario to avoid is two users viewing the record, one making a change, then the other doing likewise - with the potential that one change might overwrite the previous. In the latest versions of WordPress they use some method to detect this, but it does not seem wholly reliable - often returning false positives, at least in my experience. I assume some form of ajax must be in