Scaling Your Node.js Apps by Fernando Doglio

Author:Fernando Doglio
Language: eng
Format: epub
ISBN: 9781484239919
Publisher: Apress

In this scenario, all services depend on Redis, but Redis is not set up to be able to handle any type of problems; in fact, there is only one instance of Redis running. If it fails, your entire system will be rendered useless. The fix for this one is easy enough; just change the way you have your Redis running. You’d probably set it up as a cluster, or with Sentinel,13 so your master nodes will have a slave assigned just in case.

Getting rid of single points of failure can be as easy as setting up a cluster or as hard as adding redundancy to your entire platform. It mostly depends on how far you can take the process until it no longer provides enough bang for your buck.

Let me give you another example, going back to Figure 4-3. After you set up your minimum Redis cluster (which by definition will already contain three master nodes and three slave nodes) you realize that all nodes could fail, because they’re servers you actually have inside your own datacenter. So you decide to move to the cloud and deploy your own Redis cluster in AWS. You then realize that all those servers could still be unreachable if there is a region-level outage, so you again redeploy on a multi-region setup. Great, but what if Amazon goes out of business (unlikely, I know, but bear with me for a second)? You now redeploy your multi-zone Redis cluster in Azure as well, and you have both multi-zone load balancers and extra logic in your code to determine when to pick each one.

You’re now paying a whole lot more money for a level of stability that you might never need.

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