B4J Question Critical sections / semaphores

[wl]

Hi,

I understand that server class instances run in their own threads and that a callsubdelayed to a code module will cause the method to be called to be run on the main thread.

However, I want to have as much logic as possible in the Server class (and not in the code module), but for some parts of code - thus inside the server class - (reading an updating a global Map for example) I want it to run inside a critical section/semaphore and avoid multiple server class instances (on different threads) at the same time.

How would I do this: a simple mechanism to avoid a block of code in different server class instances (and thus threads) to run a the same time. I can invent all kinds of suboptimal solutions where a part runs on the main thread and then calls a method back on the Server class instance/thread again, but this is all so cumbersome ...

Eg:

Start Critical section
if not (GlobalMap.ContainsKey(someKey)) then
GlobalMap.Put(someKey, someValue) 'I do not want separate threads adding the same key (which would fail)
end if
End CriticalSection

Thanks

 

[Erel]

reading an updating a global Map for example

You can use a concurrent map and update it from different threads at the same time.

jBuilderUtils includes a read-write lock that can be used as a regular lock as well: https://www.b4x.com/android/forum/threads/b4x-cloudkvs-synchronized-key-value-store.63536/#content
https://www.b4x.com/android/forum/threads/lock-writelock-writerelease.63612/#content