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Serverless development is a hot topic lately. Development & operations of a web service can be greatly simplified by writing your application logic as short-lived functions, and relying on outside organizations for the development of all the other components in your stack (e.g. databases, gateways, container engines, etc). The term “serverless” is a bit funny because of course there are still servers in your stack, and they may even be your own servers, but the main idea is you no longer have to worry about your own long-running application code.
This all sounds great, but an issue arises: in this serverless world, how do you support long-lived connections (e.g. HTTP streaming/WebSocket connections) for realtime data push, without long-running application code? By delegating connection management to another component, of course! In this article we’ll talk about how to build a simple chat service with Pushpin, using Microcule for running the backend worker function.
One of the most useful features of Pushpin is the ability to combine a request for historical data with a request to listen for updates. For example, an HTTP streaming request can respond immediately with some initial data before converting into a pubsub subscription. As of version 1.12.0, this ability is made even more powerful:
- Stream hold responses (
Grip-Hold: stream) from the origin server can now have a response body of unlimited size. This works by streaming the body from the origin server to the client before processing the GRIP instruction headers. Note that this only works for
responseholds, the response body is still limited to 100,000 bytes.
- Responses from the origin server may contain a
nextlink using the
Grip-Linkheader, to tell Pushpin to make a request to a specified URL after the current request to the origin finishes, and to leave the request with the client open while doing this. The response body of any such subsequent request is appended to the ongoing response to the client. This enables the server to reply with a large response to the client by serving a bunch of smaller chunks to Pushpin, and it also allows the server to defer the preparation of GRIP hold instructions until a later request in the session.
- Stream hold responses (
Are you all about realtime apps? Well, now you can be famous and win $500 to teach the Internet. Fanout is excited to team up with the hack.guides() 2016 Tutorial Contest. Any realtime app submitted to the contest that uses Pushpin or Fanout Cloud will qualify for a chance to win a $500 prize.
See the contest here: http://tutorials.pluralsight.com/contest
The blog content is all the same, and Livefyre commenting is still here as well as RSS/Atom feeds and the SubToMe buttons. The reason for the migration (and thus the differences) are mostly internal:
Monday evening we had a particularly nasty outage: JWT authentication was broken, preventing anyone from using our HTTP API to publish data. The reason we didn’t catch this early on is because our manual test scripts turned out to be broken (reporting auth success when auth had failed.. yeesh!), and there was no authentication coverage in our external monitoring to fall back on.
In a perfect world, our external monitoring would test authentication. I’m happy to report that we are now doing this with Runscope! Getting this to work right was a little tricky since we use JWT, but it was made possible thanks to Runscope’s scripting feature.
Pushpin is the open source reverse proxy for the realtime web. One of the benefits of Pushpin functioning as a proxy is that it can be combined with an API management system, such as Mashape’s Kong. Kong is the open source management layer for APIs. To use Kong with Pushpin, simply chain the two together on the same network path.
Why would you want to use an API management system with Pushpin? Realtime web services have many of the same concerns as request/response web services, and it can be helpful to centrally manage those aspects.
RethinkDB is a modern NoSQL database that makes it easy to build realtime web services. One of its standout features is called Changefeeds. Applications can query tables for ongoing changes, and RethinkDB will push any changes to applications as they happen. The Changefeeds feature is interesting for many reasons:
- You don’t need a separate message queue to wake up workers that operate on new data.
- Database writes made from anywhere will propagate out as changes. Use the RethinkDB dashboard to muck with data? Run a migration script? Listeners will hear about it.
- Filtering/squashing of change events within RethinkDB. In many cases it may be easier to filter events using ReQL than using a message queue and filtering workers.
This makes RethinkDB a compelling part of a realtime web service stack. In this article, we’ll describe how to use RethinkDB to implement a leaderboard API with realtime updates. Emphasis on API. Unlike other leaderboard examples you may have seen elsewhere, the focus here will be to create a clean API definition and use RethinkDB as part of the implementation. If you’re not sure what it means for an API to have realtime capabilities, check out this guide.
We’ll use the following components to build the leaderboard API:
- Database: RethinkDB, hosted on a Rackspace server.
- Web service: Django, hosted by Heroku.
- Realtime push to clients: Pushpin, hosted by Fanout Cloud.
Since the server app targets Heroku, we’ll be using environment variables for configuration and foreman for local testing.
Read on to see how it’s done. You can also look at the source.
New to the subject of realtime APIs? This article is the place to start! We’ll discuss the most common design approaches and their pros/cons, as well as link to the documentation of 16 public realtime APIs that you can use for inspiration.
One of the most interesting features of the Pushpin proxy is its ability to gateway between WebSocket clients and plain HTTP backend servers. In this article, we’ll demonstrate how to build a WebSocket service using Express as the HTTP backend behind Pushpin.