Monthly Archives: February 2016

Centralized Logging and Monitoring

I have so much chaos in my life, it’s become normal. You become used to it. You have just to relax, calm down, take a deep breath and try to see how you can make things work rather than complain about how they’re wrong.

— Tom Welling

Monitoring many services on a single server poses some difficulties. Monitoring many services on many servers requires a whole new way of thinking and a new set of tools. As you start embracing microservices, containers, and clusters, the number of deployed containers will begin increasing rapidly. The same holds true for servers that form the cluster. We cannot, anymore, log into a node and look at logs. There are too many logs to look at. On top of that, they are distributed among many servers. While yesterday we had two instances of a service deployed on a single server, tomorrow we might have eight instances deployed to six servers. The same holds true for monitoring. Old tools, like Nagios, are not designed to handle constant changes in running servers and services. We already used Consul that provides a different, not to say new, approach to managing near real-time monitoring and reaction when thresholds are reached. However, that is not enough. Real-time information is valuable to detect that something is wrong, but it does not give us information why the failure happened. We can know that a service is not responding, but we cannot know why.
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Blue-Green Deployment

Traditionally, we deploy a new release by replacing the current one. The old release is stopped, and the new one is brought up in its place. The problem with this approach is the downtime occurring from the moment the old release is stopped until the new one is fully operational. No matter how quickly you try to do this process, there will be some downtime. That might be only a millisecond, or it can last for minutes or, in extreme situations, even hours. Having monolithic applications introduces additional problems like, for example, the need to wait a considerable amount of time until the application is initialized. People tried to solve this issue in various ways, and most of them used some variation of the blue-green deployment process. The idea behind it is simple. At any time, one of the releases should be running meaning that, during the deployment process, we must deploy a new release in parallel with the old one. The new and the old releases are called blue and green.
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