问题描述:

I am building an API that will take a long time to return data, up to 60 seconds while a conversion takes place. While running, I would like to keep the users informed of any errors and notify them which process in the conversion stage we are at.

This is pretty easy on the client since I can simply send a WebSocket event, but for a public API, that's not very practical.

I know I can request a notification URL and send updates to the given URL, but it seems cumbersome and potentially resource heavy. Is there another more efficient means to send progress notifications?

Ideally, the user consuming the api would be able to setup.

.on("error", function(err) {

//handle error

});

or something to that effect.

网友答案:

You're not really clear on who the consumers of your API are, what kinds of clients they're using, or what the workflow will look like. So there's a lot of different answers depending on what you're looking for and what resources you have available.

A non-exhaustive list:

REST endpoint polling

Understood that you aren't a fan, but this remains one of the best ways to do it for a wide range of clients, is one of only two (that I know of) ways to do it for purely browser-based clients. Performance wise, it's not awful if you setup your caching strategy appropriately and set throttle limits on your clients (which you should be doing anyway). I disagree that it's a PITA for clients to use consume, but that's opinion and you obviously feel differently. A way to mitigate that PITA is to offer an SDK that handles that mechanism for consumers.

Web Sockets

I get that you might be dealing with clients who aren't starting off in the web, but if a client can make a RESTful request, you could set the server to do the web socket upgrade if the client advertises interest in establishing same. I'm not a fan of this option as it feels more complex to me (more moving parts), but it's an option if you like web sockets and all/most of your clients will be web socket capable. Or you could just have the REST response be the URL to the web socket you're opening for that client.

Web Hooks

If your clients are likely to be other machines (esp. servers), then a web hook is a very good approach, especially if the event you want to raise can happen more than once and at unpredictable intervals. In this scheme, the client makes a REST request to you, part of the data they send you includes a URL that you will POST data to (in a format you specify in your API) when the event occurs. Obviously, they either have to leave that URL open to your POST or else you can agree upon some kind of credentialing that your server will respect.

TCP Socket

Similar to the Web Socket option, in that you'd probably have a REST request hit your endpoint, and then respond with the socket connection information/URI to a custom TCP socket. This is a bit nonstandard, but can be very useful and efficient in the right use cases. I haven't used it in a while so they may have changed it, but this is how Heroku's API used to handle streaming logs.

Pub/Sub or Message Queue or similar

Redis can do this, as can many others. In this scenario you're making a more generic solution where there might be more than one event channel clients can subscribe to, and so on. I dislike exposing Redis directly for security reasons, which means you'll still need to figure out how to handle the comms between Redis and the client (see above), but using it under the hood will at least buy you some of the conceptual logic of handling publishers and subscribers and so on; useful if you have more than one event as I said. This is a more heavyweight solution than the above, though, and will increase your sysadmin overhead by some amount (depending on your high availability needs, etc)

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