Delve into advanced Kubernetes features like monitoring, alerting, logging, and auto-scaling. Gain insights into creating resilient, self-adaptive clusters and applications with minimal manual intervention.

The world of DevOps has exploded with the help of technologies like Kubernetes and Docker.  
In this course, you will learn about more advanced Kubernetes features such as monitoring, alerting, logging, and scaling - crucial concepts for any DevOps professional. You will learn how to monitor clusters, how to send alerts when potential issues arise, and how to query the whole system’s metrics and logs. 
By the end of this course, you will have the required knowledge to make your clusters and applications truly dynamic and resilient, so that they require minimal manual involvement and are self-adaptive.

Advanced Kubernetes Techniques: Monitoring, Logging, Auto-Scaling

# GKE's Fluentd DaemonSet

If you're using the GKE cluster, logging is already set up, even though you might not know about it. By default, every GKE cluster comes with a **Fluentd DaemonSet** that is configured to forward logs to **GCP StackDriver**. It is running in the `kube-system` Namespace.

Let's describe **GKE's Fluentd DaemonSet** and see whether there is any useful information we might find.

```shell
kubectl -n kube-system \
  describe ds -l k8s-app=fluentd-gcp
```

The **output**, limited to the relevant parts, is as follows.

```
...
Pod Template:
  Labels:     k8s-app=fluentd-gcp
              kubernetes.io/cluster-service=true
              version=v3.1.0
...
  Containers:
   fluentd-gcp:
    Image: gcr.io/stackdriver-agents/stackdriver-logging-agent:0.3-1.5.34-1-k8s-1
    ...
```

We can see that, among others, the DaemonSet's Pod Template has the label `k8s-app=fluentd-gcp`. We'll need it soon. Also, we can see that one of the containers is based on the `stackdriver-logging-agent` image. Just as **Papertrail** extended **Fluentd**, Google did the same.

# Output the logs of Fluentd containers

Now that we know that Stackdriver-specific **Fluentd** is running in our cluster as a *DaemonSet*, the logical conclusion would be that there is already a UI we can use to explore the logs. UI is indeed available but, before we see it in action, we'll output the logs of the **Fluentd** containers and verify that everything is working as expected.

```shell
kubectl -n kube-system \
  logs -l k8s-app=fluentd-gcp \
  -c fluentd-gcp
```

Unless you already enabled *Stackdriver Logging API*, the output should contain at least one message similar to the one that follows.

```
...
18-12-12 21:36:41 +0000 [warn]: Dropping 1 log message(s) error="7:Stackdriver Logging API has not been used in project 152824630010 before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/logging.googleapis.com/overview?project=152824630010 then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry." error_code="7"
```


Fortunately, the warning already tells us not only what the issue is, but also what to do. Open the link from the log entry in your favorite browser, and click the *ENABLE* button.

## Wait until the action propagates

Now that we enabled *Stackdriver Logging API*, **Fluentd** will be able to ship log entries there. All we have to do is wait for a minute or two until the action propagates.

Let's see the Stackdriver UI.

```shell
open "https://console.cloud.google.com/logs/viewer"
```

Please type *random-logger* in the *Filter by label or text search* field and select *GKE Container* from the drop-down list. The **output** should display all the logs that contain *random-logger* text.


This lesson focuses on combining GCP StackDriver with a GKE cluster.

Before Getting Started

Autoscaling Deployments and StatefulSets

Auto-Scaling Nodes Of A Kubernetes Cluster

Collecting and Querying Metrics and Sending Alerts

Debugging Issues Discovered Through Metrics and Alerts

Extending HorizontalPodAutoscaler With Custom Metrics

Visualizing Metrics And Alerts

Collecting And Querying Logs

Conclusion

Combine GCP StackDriver with a GKE Cluster

GKE’s Fluentd DaemonSet #