DDP over bad connectivity in emerging markets?

camacazze · March 9, 2018, 10:38am

I have heard that DDP on Meteor is very bad if GPRS/3G/HSPA/4G connectivity is bad.

It just doesn’t work. Is this true? Bcoz this is very common in emerging markets, in interiors.

Is this a serious problem? I have been told that the reactivity doesn’t work under these circumstances. It fails.

Does anyone have info about this?? Is a nice mobile connectivity prerequisite for DDP etc. to work??

My question is in the context of Meteor on Web & also talking to a Native Android app. I am building a platform for politicians in India to communicate with their supporters/volunteers. Working with bad network is a given with Indian interiors. Mainly with regard to data connectivity. LinkedIn recently came up with their Lite version of Android app, which even works with 2G.

Is Meteor/DDP/AndroidDDP graceful with this or does it just snap??

Thanks.

robfallows · March 9, 2018, 10:55am

I think this issue is not DDP, but websockets.

This may help your understanding:

github.com

meteor/meteor/blob/4d32c1ca3daa6c5c4bc4ad2a8535f8f8387e82f9/packages/ddp/README.md#supported-transports

# ddp
[Source code of released version](https://github.com/meteor/meteor/tree/master/packages/ddp) | [Source code of development version](https://github.com/meteor/meteor/tree/devel/packages/ddp)
***

DDP (Distributed Data Protocol) is the stateful websocket protocol
that Meteor uses to communicate between the client and the server. For
more information about DDP, see the [DDP project
page](https://www.meteor.com/ddp) or the [DDP
specification](https://github.com/meteor/meteor/blob/devel/packages/ddp/DDP.md).

This package is used by nearly every Meteor application and provides a
full implementation of DDP in JavaScript. API documentation is on the
[main Meteor documentation page](https://docs.meteor.com/), under
"Publish and subscribe", "Methods", and "Server connections". Note in
particular that clients can use
[`DDP.connect`](https://docs.meteor.com/api/connections.html#DDP-connect) to open a DDP
connection to any DDP service on the Internet.

### Supported platforms

This file has been truncated. show original

You can completely disable websockets with the DISABLE_WEBSOCKETS environment variable.

github.com

meteor/meteor/blob/5e32a127631f7a6d21e90ffaeec979e92e0c6aac/packages/ddp-server/stream_server.js#L61-L71


// If you know your server environment (eg, proxies) will prevent websockets
// from ever working, set $DISABLE_WEBSOCKETS and SockJS clients (ie,
// browsers) will not waste time attempting to use them.
// (Your server will still have a /websocket endpoint.)
if (process.env.DISABLE_WEBSOCKETS) {
  serverOptions.websocket = false;
} else {
  serverOptions.faye_server_options = {
    extensions: websocketExtensions()
  };
}

camacazze · March 10, 2018, 12:46pm

What is the current status of Websockets’ performance when connectivity is bad?

How bad is it? And will disabling them altogether, mean that reactivity will cease? What is the benefit of disabling Websockets, apart from what is mentioned in the code (proxies)?

My situation entails too many Android native Apps, connecting to the Server on Android DDP, along with a few Web based clients.

I have read the links you have posted. Many, many thanks for that.

How much does Re-connection feature of DDP help? Doesn’t it make the problem go away?

Do you have any thoughts? @copleykj @serkandurusoy @storyteller Sir!

serkandurusoy · March 10, 2018, 1:54pm

Websockets basically enables you to create “connected clients” and DDP is esentially a client/server data synchronization built on top of that.

Now if you have “connection” problems, the idea of “connected clients” automatically becomes something to reconsider because you’ll have to figure out how to best handle the “disconnected” state. Luckily you can use the offline-related packages you can find on atmosphere to make your user experience as seamless as possible.

It is really not that hard and with some extra work, you can manage it quite nicely to achieve good UX. After all, meteor gives you the “connected” part out of box, which in my opinion, is usually the hard part to get right.

Also, you might want to give appsync a chance because that’s something purpose built around offline-first paradigms, but its developer experience might be lesser for you because it is still a beta product with tooling not being very well evolved.

coagmano · March 11, 2018, 8:46am

From the DDP Readme that @robfallows linked:

It also supports a second transport, EJSON over HTTP long polling. It will automatically fall back to this transport if websockets are not available. This is not as efficient as websockets, but it works in older browsers. It uses the sockjs library for long polling.

This means that the behaviour of your app doesn’t change, as the websocket is emulated over HTTP long polling.

The delay for reactive data to make it’s way across the connection will be a bit longer. You’ll need to test how serious the penalty is, and if it gives you a benefit in poor-connection areas