Cerberus

Guardian of Kubernetes and OpenShift Clusters

Cerberus watches the Kubernetes/OpenShift clusters for dead nodes, system component failures/health and exposes a go or no-go signal which can be consumed by other workload generators or applications in the cluster and act accordingly.

Workflow

Install the dependencies

$ pip3 install -r requirements.txt

Usage

Config

Set the supported components to monitor and the tunings like number of iterations to monitor and duration to wait between each check in the config file located at config/config.yaml. A sample config looks like:

cerberus:
    distribution: openshift                              # Distribution can be kubernetes or openshift
    kubeconfig_path: ~/.kube/config                      # Path to kubeconfig
    watch_nodes: True                                    # Set to True for the cerberus to monitor the cluster nodes
    watch_cluster_operators: True                        # Set to True for cerberus to monitor cluster operators. Parameter is optional, will set to True if not specified
    watch_url_routes:                                    # Route url's you want to monitor
        - - https://...
          - Bearer ****                                  #This parameter is optional, specify authorization need for get call to route 
        - - http://...
    watch_namespaces:                                    # List of namespaces to be monitored
        -    openshift-etcd
        -    openshift-apiserver
        -    openshift-kube-apiserver
        -    openshift-monitoring
        -    openshift-kube-controller
        -    openshift-machine-api
        -    openshift-kube-scheduler
        -    openshift-ingress
        -    openshift-sdn
    cerberus_publish_status: True                        # When enabled, cerberus starts a light weight http server and publishes the status
    inspect_components: False                            # Enable it only when OpenShift client is supported to run.
                                                         # When enabled, cerberus collects logs, events and metrics of failed components

    prometheus_url:                                      # The prometheus url/route is automatically obtained in case of OpenShift, please set it when the distribution is Kubernetes.
    prometheus_bearer_token:                             # The bearer token is automatically obtained in case of OpenShift, please set it when the distribution is Kubernetes. This is needed to authenticate with prometheus.
                                                         # This enables Cerberus to query prometheus and alert on observing high Kube API Server latencies.   

    slack_integration: False                             # When enabled, cerberus reports status of failed iterations in the slack channel
                                                         # The following env vars need to be set: SLACK_API_TOKEN ( Bot User OAuth Access Token ) and SLACK_CHANNEL ( channel to send notifications in case of failures )
                                                         # When slack_integration is enabled, a cop can be assigned for each day. The cop of the day is tagged while reporting failures in the slack channel. Values are slack member ID's.
    cop_slack_ID:                                        # (NOTE: Defining the cop id's is optional and when the cop slack id's are not defined, the slack_team_alias tag is used if it is set else no tag is used while reporting failures in the slack channel.)
        Monday:
        Tuesday:
        Wednesday:
        Thursday:
        Friday:
        Saturday:
        Sunday:
    slack_team_alias:                                    # The slack team alias to be tagged while reporting failures in the slack channel when no cop is assigned

tunings:
    iterations: 5                                        # Iterations to loop before stopping the watch, it will be replaced with infinity when the daemon mode is enabled
    sleep_time: 60                                       # Sleep duration between each iteration
    daemon_mode: True                                    # Iterations are set to infinity which means that the cerberus will monitor the resources forever

NOTE: The current implementation can monitor only one cluster from one host. It can be used to monitor multiple clusters provided multiple instances of Cerberus are launched on different hosts.

NOTE: The components especially the namespaces needs to be changed depending on the distribution i.e Kubernetes or OpenShift. The default specified in the config assumes that the distribution is OpenShift. A config file for Kubernetes is located at config/kubernetes_config.yaml

Run

$ python3 start_cerberus.py --config <config_file_location>

Run containerized version

Assuming that the latest docker ( 17.05 or greater with multi-build support ) is intalled on the host, run:

$ docker pull quay.io/openshift-scale/cerberus
$ docker run --name=cerberus --net=host -v <path_to_kubeconfig>:/root/.kube/config -v <path_to_cerberus_config>:/root/cerberus/config/config.yaml -d quay.io/openshift-scale/cerberus:latest
$ docker logs -f cerberus

Similarly, podman can be used to achieve the same:

$ podman pull quay.io/openshift-scale/cerberus
$ podman run --name=cerberus --net=host -v <path_to_kubeconfig>:/root/.kube/config:Z -v <path_to_cerberus_config>:/root/cerberus/config/config.yaml:Z -d quay.io/openshift-scale/cerberus:latest
$ podman logs -f cerberus

The go/no-go signal ( True or False ) gets published at http://<hostname>:8080. Note that the cerberus will only support ipv4 for the time being.

NOTE: The report is generated at /root/cerberus/cerberus.report inside the container, it can mounted to a directory on the host in case we want to capture it.

Report

The report is generated in the run directory and it contains the information about each check/monitored component status per iteration with timestamps. It also displays information about the components in case of failure. For example:

2020-03-26 22:05:06,393 [INFO] Starting ceberus
2020-03-26 22:05:06,401 [INFO] Initializing client to talk to the Kubernetes cluster
2020-03-26 22:05:06,434 [INFO] Fetching cluster info
2020-03-26 22:05:06,739 [INFO] Publishing cerberus status at http://0.0.0.0:8080
2020-03-26 22:05:06,753 [INFO] Starting http server at http://0.0.0.0:8080
2020-03-26 22:05:06,753 [INFO] Daemon mode enabled, cerberus will monitor forever
2020-03-26 22:05:06,753 [INFO] Ignoring the iterations set

2020-03-26 22:05:25,104 [INFO] Iteration 4: Node status: True
2020-03-26 22:05:25,133 [INFO] Iteration 4: Etcd member pods status: True
2020-03-26 22:05:25,161 [INFO] Iteration 4: OpenShift apiserver status: True
2020-03-26 22:05:25,546 [INFO] Iteration 4: Kube ApiServer status: True
2020-03-26 22:05:25,717 [INFO] Iteration 4: Monitoring stack status: True
2020-03-26 22:05:25,720 [INFO] Iteration 4: Kube controller status: True
2020-03-26 22:05:25,746 [INFO] Iteration 4: Machine API components status: True
2020-03-26 22:05:25,945 [INFO] Iteration 4: Kube scheduler status: True
2020-03-26 22:05:25,963 [INFO] Iteration 4: OpenShift ingress status: True
2020-03-26 22:05:26,077 [INFO] Iteration 4: OpenShift SDN status: True
2020-03-26 22:05:26,077 [INFO] HTTP requests served: 0 
2020-03-26 22:05:26,077 [INFO] Sleeping for the specified duration: 5


2020-03-26 22:05:31,134 [INFO] Iteration 5: Node status: True
2020-03-26 22:05:31,162 [INFO] Iteration 5: Etcd member pods status: True
2020-03-26 22:05:31,190 [INFO] Iteration 5: OpenShift apiserver status: True
127.0.0.1 - - [26/Mar/2020 22:05:31] "GET / HTTP/1.1" 200 -
2020-03-26 22:05:31,588 [INFO] Iteration 5: Kube ApiServer status: True
2020-03-26 22:05:31,759 [INFO] Iteration 5: Monitoring stack status: True
2020-03-26 22:05:31,763 [INFO] Iteration 5: Kube controller status: True
2020-03-26 22:05:31,788 [INFO] Iteration 5: Machine API components status: True
2020-03-26 22:05:31,989 [INFO] Iteration 5: Kube scheduler status: True
2020-03-26 22:05:32,007 [INFO] Iteration 5: OpenShift ingress status: True
2020-03-26 22:05:32,118 [INFO] Iteration 5: OpenShift SDN status: False
2020-03-26 22:05:32,118 [INFO] HTTP requests served: 1 
2020-03-26 22:05:32,118 [INFO] Sleeping for the specified duration: 5
+--------------------------------------------------Failed Components--------------------------------------------------+
2020-03-26 22:05:37,123 [INFO] Failed openshfit sdn components: ['sdn-xmqhd']

2020-05-23 23:26:43,041 [INFO] ------------------------- Iteration Stats ---------------------------------------------
2020-05-23 23:26:43,041 [INFO] Time taken to run watch_nodes in iteration 1: 0.0996248722076416 seconds
2020-05-23 23:26:43,041 [INFO] Time taken to run watch_cluster_operators in iteration 1: 0.3672499656677246 seconds
2020-05-23 23:26:43,041 [INFO] Time taken to run watch_namespaces in iteration 1: 1.085144281387329 seconds
2020-05-23 23:26:43,041 [INFO] Time taken to run entire_iteration in iteration 1: 4.107403039932251 seconds
2020-05-23 23:26:43,041 [INFO] ---------------------------------------------------------------------------------------

Slack integration

The user has the option to enable/disable the slack integration ( disabled by default ). To use the slack integration, the user has to first create an app and add a bot to it on slack. SLACK_API_TOKEN and SLACK_CHANNEL environment variables have to be set. SLACK_API_TOKEN refers to Bot User OAuth Access Token and SLACK_CHANNEL refers to the slack channel ID the user wishes to receive the notifications.

Reports when cerberus starts monitoring a cluster in the specified slack channel.
Reports the component failures in the slack channel.
A cop can be assigned for each day of the week. The cop of the day is tagged while reporting failures in the slack channel instead of everyone. (NOTE: Defining the cop id's is optional and when the cop slack id's are not defined, the slack_team_alias tag is used if it is set else no tag is used while reporting failures in the slack channel.)

Go or no-go signal

When the cerberus is configured to run in the daemon mode, it will continuosly monitor the components specified, runs a simple http server at http://0.0.0.0:8080 and publishes the signal i.e True or False depending on the components status. The tools can consume the signal and act accordingly.

Node Problem Detector

node-problem-detector aims to make various node problems visible to the upstream layers in cluster management stack.

Installation

Please follow the instructions in the installation section to setup Node Problem Detector on Kubernetes. The following instructions are setting it up on OpenShift:

Create openshift-node-problem-detector namespace ns.yaml with oc create -f ns.yaml
Add cluster role with oc adm policy add-cluster-role-to-user system:node-problem-detector -z default -n openshift-node-problem-detector
Add security context constraints with oc adm policy add-scc-to-user privileged system:serviceaccount:openshift-node-problem-detector:default
Edit node-problem-detector.yaml to fit your environment.
Edit node-problem-detector-config.yaml to configure node-problem-detector.
Create the ConfigMap with oc create -f node-problem-detector-config.yaml
Create the DaemonSet with oc create -f node-problem-detector.yaml

Once installed you will see node-problem-detector pods in openshift-node-problem-detector namespace. Now enable openshift-node-problem-detector in the config.yaml. Cerberus just monitors KernelDeadlock condition provided by the node problem detector as it is system critical and can hinder node performance.

Alerts

Monitoring metrics and alerting on abnormal behavior is critical as they are the indicators for clusters health. When provided the prometheus url and bearer token in the config, Cerberus looks for KubeAPILatencyHigh alert at the end of each iteration and warns if 99th percentile latency for given requests to the kube-apiserver is above 1 second. It is the official SLI/SLO defined for Kubernetes.

NOTE: The prometheus url and bearer token are automatically picked from the cluster if the distibution is OpenShift since it's the default metrics solution. In case of Kubernetes, they need to be provided in the config if prometheus is deployed.

Use cases

There can be number of use cases, here are some of them:

We run tools to push the limits of Kubernetes/OpenShift to look at the performance and scalability. There are a number of instances where system components or nodes start to degrade, which invalidates the results and the workload generator continues to push the cluster until it is unrecoverable.
When running chaos experiments on a kubernetes/OpenShift cluster, they can potentially break the components unrelated to the targeted components which means that the choas experiment won't be able to find it. The go/no-go signal can be used here to decide whether the cluster recovered from the failure injection as well as to decide whether to continue with the next chaos scenario.

What Kubernetes/OpenShift components can Cerberus monitor?

Following are the components of Kubernetes/OpenShift that Cerberus can monitor today, we will be adding more soon.

Component	Description	Working
Nodes	Watches all the nodes including masters, workers as well as nodes created using custom MachineSets	✔️
Namespaces	Watches all the pods including containers running inside the pods in the namespaces specified in the config	✔️
Cluster Operators	Watches all Cluster Operators	✔️
Master Nodes Schedule	Watches schedule of Master Nodes	✔️
Routes	Watches specified routes	✔️

NOTE: It supports monitoring pods in any namespaces specified in the config, the watch is enabled for system components mentioned in the config by default as they are critical for running the operations on Kubernetes/OpenShift clusters.

Blogs and other useful resources

https://www.openshift.com/blog/openshift-scale-ci-part-4-introduction-to-cerberus-guardian-of-kubernetes/openshift-clouds

worsco / cerberus Goto Github PK

cerberus's Introduction