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leon-thomm / Ryven

Flow-based visual scripting for Python
https://ryven.org
MIT License
3.76k stars 439 forks source link

Async Nodes, block the Node computation without freezing the UI thread #149

Closed ArEnSc closed 1 year ago

ArEnSc commented 1 year ago

@leon-thomm Hey quick question is there a way to wait the thread that operates the node execution then have it wake up when an async task is done? I have async nodes and the only way I can sorta fix this is if I add a delay node in between thanks!

leon-thomm commented 1 year ago

The whole application is single threaded. Such functionality must be implemented on node level, you just have to write it yourself. I think nothing stops your nodes from exploiting concurrency, even starting threads and processes and have the node update itself on completion or messages - it rather comes down to the use case and what design is intuitive.

leon-thomm commented 1 year ago

I experimented with multi-threading in Ryven itself a while ago, especially for separating execution of the GUI thread and the flow execution, but I decided it's generally not worth the struggle. It is either extremely unsafe or requires a lot of abstraction, which comes at a cost in Python.

ArEnSc commented 1 year ago

@leon-thomm so that threading bridge code is pretty much dead code? I was trying to figure out where it was being triggered, Also could you let me know where the entry point of an exec execution would happen? When you say it's single threaded you mean the UI thread is blocked when there is a long computation ?

leon-thomm commented 1 year ago

so that threading bridge code is pretty much dead code?

not dead code but not implementing threading right now

I was trying to figure out where it was being triggered

In a few places, it's a ryvencore-qt thing - primarily in FlowCommands.py (see FlowUndoCommand).

Also could you let me know where the entry point of an exec execution would happen?

That's happening in ryvencore. The current version of Ryven runs on ryvencore v0.3. An update doesn't happen without a reason, either direct interaction from the user (using the node), or something else that the user or node developer set up. In early versions, update messages were always passed from node output to node input directly (quite literally, the node output object calling the connection object, which then calls the node input object, which then triggers its node's update method). This was gradually replaced by a central FlowExecutor class, see here and here. This was standardized in the WIP ryvencore v0.4 which will power the next Ryven release, so everything will go through the FlowExecutor.

When you say it's single threaded you mean the UI thread is blocked when there is a long computation ?

yes, i.e. threading and concurrency should be built into the nodes themselves if it is needed.

ArEnSc commented 1 year ago

@leon-thomm thank you for your answers! it means a lot I have gotten this to work for something I am working on just trying to figure out more of the details