[Core Improvement] Reign in the amount of content sent to the frontend client when things are updated.

[JackUrb]

Noted in #393, a lot of data gets sent to the client as an environment grows. As seen in #386, this is not a sustainable practice. Moving forward we'll need to be able to send update packets from the server rather than the entire contents of an environment's json every time a window in that json gets updated. The client should only request the complete contents when the environment changes or if an inconsistency is detected (can be done using a hash of the stored data).

[xssChauhan]

@JackUrb I would like to help with this

[JackUrb]

Hi @xssChauhan - this is a fairly involved change that I've already started work for, but one segment I haven't touched is the last part (the hashing step). This involves sending a request from the web client to a new endpoint with an env id and window id and receiving in return a hash/checksum of the layout and data of that window. You can then also implement the same hash/checksum function on the web side. Does this seem like something you'd want to work on?

[xssChauhan]

@JackUrb This is certainly interesting. Would be glad to work on it. Where do i begin?

[JackUrb]

Alright so you'll start in the server file by introducing a new endpoint. This should be something like the exists handler: https://github.com/facebookresearch/visdom/blob/ec91e738e100a9cbf946c332c7783ffd12c644b5/py/visdom/server.py#L155
It will take a window and eid in the same way:
https://github.com/facebookresearch/visdom/blob/ec91e738e100a9cbf946c332c7783ffd12c644b5/py/visdom/server.py#L506
Then it should perform a hash operation on the json stored in handler.state[eid]['jsons']. Preferably this will be an MD5 of the json string. It should then return that hash by using handler.write().

[xssChauhan]

@JackUrb Understood. Is there a branch for this already? Or do i make one from master only?

[JackUrb]

You can start a new branch for this - it's somewhat independent of the rest of the work

[xssChauhan]

Cool. Getting started now. Thank you for the starting pointers.

[xssChauhan]

@JackUrb Here's my implementation for the hash handler. Will you please take a look at it and tell me your review?

[JackUrb]

@xssChauhan - feel free to open it as a pull request and I can better comment there!

[xssChauhan]

@JackUrb Shall i also add a function to get the hash of window in visdom/init.py?

This function would be similar to visdom.Visdom.win_exists

[JackUrb]

We actually need the function in both __init__.py and main.js as well. Also you'll need to get the window rather than the whole json for an environment in your current implementation

[JackUrb]

The one in init should call the server endpoint, the one in main should perform its own hash