Omnipotent Service Level Indicators

Feb 11, 2019

Your SLOs (Service Level Objectives) are what keep making your company money, and what keep you honest as a deployer of your application. At it’s core, an SLO is simply an objective of a specific attribute of your service such as availability, throughput, response time, etc.

Without ensuring that the SLOs you are creating are met as time progresses, you’ll run into angry customers, tarnishing the relationship that you had with them up to that point. At the same time, you will facilitate underconfident employees who will feel that the loss of your customer due to an error in service was either their personal fault, or that your mistakes as their leader are now compromising their job security by creating potential revenue uncertainty for the company. The solution to ensuring that your SLOs are met is simply an investment of time in optimizing your SLIs (Service Level Indicators).

Within the deployment of, we use creative SLIs to give us reliable metrics throughout our deployment environments. We capture ALL of the telemetry between our microservices and scrape the metrics with Prometheus so that we can graph the data using Grafana, and perform other queries on the data when required. Grafana is awesome because it allows us to create multiple dashboards for simultaneous viewing which Prometheus does not support out of the box.

Beyond Grafana, we run AlertManager with custom rules for alerting us when our SLOs are not being met. Our SLO for uptime is a 4 nine SLO (99.99% uptime,) and use AlertManager to tell us when our past 10 minute SLO has not been met. We run a Prometheus query for each environment to check whether !(200 <= response status codes < 404) start to occur for more than 0.01% of responses, and other queries regarding communication between services. But how are we able to collect so much telemetry in the first place?

Enter Istio! This Service Mesh for Kubernetes allows us to:

  • Secure communication between pods using mTLS (beneficial for cross-cloud deployments)
  • Automatically collect Telemetry between pods,
  • Give every pod an L7 reverse proxy SideCar container (Envoy Proxy,) which reads from the Istio Global Virtual Service rules and Routing rules to give us the ability to:
    • Route a dynamically specified amount of trafic to our staging environment,
    • Route arbitrary device types to an environment of our choice as recorded by the L7 reverse proxy.

Since these specifications are all specified in deployment yaml files, it becomes easy to listen to a webhook sent by AlertManager regarding a 500 (or other status code) response coming from your Canary Environment and then automatically apply a

sed 's/weight: 10/weight: 0/' routing-canary.yaml && kubectl apply -f routing-canary.

change, making your SLIs literally a self-healing omnipotent force in your DevOps arsenal!!!!! >:D

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