error-reporting-with-kubernetes-events

README

error-reporting-with-kubernetes-events

This repo serves as a demonstration of how Box utilizes Kubernetes CustomResourceDefinitions, to communicate amongst containerized services and Kubernetes Events to report errors from one containerized service to another.

At Box, we have several services running on our clusters that make up the control plane, performing necessary processing and operational tasks on behalf of the various application services running on the cluster. Application level services (being separate from the control plane), can trigger additional processing in the control plane. CustomResourceDefinitions are used for triggering the processing and passing parameters to the computation. A control plane service does some checking of the passed parameters. If there is any unexpected values in the parameters, Kubernetes Events are used to relay the error information back to the application container.

Prerequisites

Even though the code should work in later versions, this example is tested with Kubernetes 1.7.5. More specifically:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.5", GitCommit:"17d7182a7ccbb167074be7a87f0a68bd00d58d97", GitTreeState:"clean", BuildDate:"2017-08-31T19:32:12Z", GoVersion:"go1.9", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.5", GitCommit:"17d7182a7ccbb167074be7a87f0a68bd00d58d97", GitTreeState:"clean", BuildDate:"2017-10-04T09:07:46Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

NOTE: Because of the lack of availability of CustomResourceDefinitions, this example will not work with Kubernetes versions earlier than 1.7.

Using minikube you can start a Kubernetes server at v1.7.5.

minikube start --kubernetes-version v1.7.5

brew can be used to install an old kubectl at v1.7.5.

You should use the Docker daemon in the minikube vm. Follow the instructions here

The code in this example has been tested using these versions of Docker:

$ docker version
Client:
 Version:      17.11.0-ce
 API version:  1.23
 Go version:   go1.9.2
 Git commit:   1caf76c
 Built:        unknown-buildtime
 OS/Arch:      darwin/amd64

Server:
 Version:      17.06.0-ce
 API version:  1.30 (minimum version 1.12)
 Go version:   go1.8.3
 Git commit:   02c1d87
 Built:        Fri Jun 23 21:51:55 2017
 OS/Arch:      linux/amd64
 Experimental: false

NOTE: For older versions of Docker, we have seen problems with the COPY command in Dockerfiles while copying a large number of files.

Build

Build the Docker containers

From project root execute:

docker build  -f cmd/controlplane/Dockerfile \
   -t boxinc/error-reporting-with-kubernetes-events:controlplane  .

Run

Start the control plane app and define the CustomResourceDefinition

From repo root:

kubectl  apply  -f cmd/controlplane/config.yml

Expected output:

customresourcedefinition "pkis.box.com" configured
namespace "controlplane" configured
deployment "controlplane" configured

Start the applications that trigger processing in the control plane app

From repo root:

kubectl apply  -f cmd/app1/config.yml
kubectl apply  -f cmd/app2/config.yml

Expected output:

namespace "app1" configured
pki "app1-pki" configured
deployment "app1" configured

namespace "app2" configured
pki "app2-pki" configured
deployment "app2" created

Expected Behavior

All pods except the pod for app1 should transition to Running state eventually.

$ kubectl get pods --all-namespaces
NAMESPACE      NAME                            READY     STATUS              RESTARTS   AGE
app1           app1-647877271-lrpbd            0/1       ContainerCreating   0          1d
app2           app2-3513338968-9hf6l           1/1       Running             1          1d
controlplane   controlplane-1148696967-13dgv   1/1       Running             0          1d
....

There is an error in app1's config.yml to demonstrate the error handling using Kubernetes Events

The events history in kubectl describe output provides diagnostic information to the application owner so that she can fix the error easily.

kubectl describe pod app1-647877271-lrpbd --namespace app1

Events:
  FirstSeen   LastSeen   Count   From         SubObjectPath   Type      Reason         Message
  ---------   --------   -----   ----         -------------   --------   ------         -------
  ....
  1d      1m      24   controlplane            Warning      pki ServiceName error   ServiceName: appp1 in pki: app1-pki is not found in allowedNames: [app1 app2]
  ....

The shown error line is generated by the controlplane app and placed at the event stream of the problematic pod. More details about generating this error event can be found at the controlplane application's implementation.

The application programmer can easily rootcause that the serviceName field in config.yml has a typo.

spec:
  # This service name has a typo
  serviceName: appp1

Support

Need to contact us directly? Email oss@box.com and be sure to include the name of this project in the subject.

Copyright and License

Copyright 2017 Box, Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.