objectiser/scribble-operator

Scribble Operator for Kubernetes

Table of Contents

• Scribble Operator for Kubernetes
  • Installing the operator
    • Kubernetes
    • OpenShift
  • Creating a new Scribble instance
  • Accessing the UI
    • Kubernetes
    • OpenShift
  • Auto injection of Scribble Agent sidecars
  • Agent as DaemonSet
  • Secrets support
  • Define sampling strategies
  • Schema migration
    • Cassandra
  • Removing an instance
  • Uninstalling the operator

Important

The Scribble Operator version is related to the version of the Scribble components (Query, Collector, Agent) up to the minor portion. The patch version portion does not follow the ones from the Scribble components. For instance, the Operator version 1.8.1 uses the Scribble Docker images tagged with version 1.8 by default.

Installing the operator

Kubernetes

Note	Make sure your kubectl command is properly configured to talk to a valid Kubernetes cluster. If you don’t have one yet, check minikube out.

To install the operator, run:

kubectl create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/crds/io_v1alpha1_jaeger_crd.yaml
kubectl create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/service_account.yaml
kubectl create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role.yaml
kubectl create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role_binding.yaml
kubectl create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/operator.yaml

At this point, there should be a scribble-operator deployment available:

$ kubectl get deployment scribble-operator
NAME              DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
scribble-operator   1         1         1            1           48s

The operator is now ready to create Scribble instances!

OpenShift

The instructions from the previous section also work on OpenShift given that the operator-openshift.yaml is used instead of operator.yaml. Make sure to install the RBAC rules, the CRD and the operator as a privileged user, such as system:admin.

oc login -u system:admin

oc create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/crds/io_v1alpha1_jaeger_crd.yaml
oc create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/service_account.yaml
oc create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role.yaml
oc create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role_binding.yaml
oc create -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/operator-openshift.yaml

Once the operator is installed, grant the role scribble-operator to users who should be able to install individual Scribble instances. The following example creates a role binding allowing the user developer to create Scribble instances:

oc create \
  rolebinding developer-scribble-operator \
  --role=scribble-operator \
  --user=developer

After the role is granted, switch back to a non-privileged user.

Creating a new Scribble instance

Example custom resources, for different configurations of Scribble, can be found here.

The simplest possible way to install is by creating a YAML file like the following:

simplest.yaml

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: simplest

The YAML file can then be used with kubectl:

kubectl apply -f simplest.yaml

In a few seconds, a new in-memory all-in-one instance of Scribble will be available, suitable for quick demos and development purposes. To check the instances that were created, list the jaeger objects:

$ kubectl get jaeger
NAME        CREATED AT
simplest    28s

To get the pod name, query for the pods belonging to the simplest Scribble instance:

$ kubectl get pods -l jaeger=simplest
NAME                        READY     STATUS    RESTARTS   AGE
simplest-6499bb6cdd-kqx75   1/1       Running   0          2m

Similarly, the logs can be queried either from the pod directly using the pod name obtained from the previous example, or from all pods belonging to our instance:

$ kubectl logs -l jaeger=simplest
...
{"level":"info","ts":1535385688.0951214,"caller":"healthcheck/handler.go:133","msg":"Health Check state change","status":"ready"}

For reference, here’s how a more complex all-in-one instance can be created:

all-in-one.yaml

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: my-jaeger
spec:
  strategy: allInOne # (1)
  allInOne:
    image: objectiser/all-in-one:1.8 # (2)
    options: # (3)
      log-level: debug # (4)
  storage:
    type: memory # (5)
    options: # (6)
      memory: # (7)
        max-traces: 100000
  ingress:
    enabled: false # (8)
  agent:
    strategy: DaemonSet # (9)
  annotations:
    scheduler.alpha.kubernetes.io/critical-pod: "" # (10)

1. The default strategy is allInOne. The only other possible value is production.

2. The image to use, in a regular Docker syntax

3. The (non-storage related) options to be passed verbatim to the underlying binary. Refer to the Scribble documentation and/or to the --help option from the related binary for all the available options.

4. The option is a simple key: value map. In this case, we want the option --log-level=debug to be passed to the binary.

5. The storage type to be used. By default it will be memory, but can be any other supported storage type (e.g. elasticsearch, cassandra, kafka, etc).

6. All storage related options should be placed here, rather than under the 'allInOne' or other component options.

7. Some options are namespaced and we can alternatively break them into nested objects. We could have specified memory.max-traces: 100000.

8. By default, an ingress object is created for the query service. It can be disabled by setting its enabled option to false. If deploying on OpenShift, this will be represented by a Route object.

9. By default, the operator assumes that agents are deployed as sidecars within the target pods. Specifying the strategy as "DaemonSet" changes that and makes the operator deploy the agent as DaemonSet. Note that your tracer client will probably have to override the "JAEGER_AGENT_HOST" env var to use the node’s IP.

10. Define annotations to be applied to all deployments (not services). These can be overridden by annotations defined on the individual components.

Accessing the UI

Kubernetes

The operator creates a Kubernetes ingress route, which is the Kubernetes' standard for exposing a service to the outside world, but it comes with no Ingress providers by default. Check the documentation on what’s the most appropriate way to achieve that for your platform, but the following commands should provide a good start on minikube:

minikube addons enable ingress

Once that is done, the UI can be found by querying the Ingress object:

$ kubectl get ingress
NAME             HOSTS     ADDRESS          PORTS     AGE
simplest-query   *         192.168.122.34   80        3m

Important

an Ingress object is not created when the operator is started with the --platform=openshift flag, such as when using the resource operator-openshift.yaml.

In this example, the Scribble UI is available at http://192.168.122.34

OpenShift

When using the operator-openshift.yaml resource, the Operator will automatically create a Route object for the query services. Check the hostname/port with the following command:

oc get routes

Note	make sure to use https with the hostname/port you get from the command above, otherwise you’ll see a message like: "Application is not available".

By default, the Scribble UI is protected with OpenShift’s OAuth service and any valid user is able to login. For development purposes, the user/password combination developer/developer can be used. To disable this feature and leave the Scribble UI unsecured, set the Ingress property security to none:

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: disable-oauth-proxy
spec:
  ingress:
    security: none

Auto injection of Scribble Agent sidecars

The operator can also inject Scribble Agent sidecars in Deployment workloads, provided that the deployment has the annotation inject-jaeger-agent with a suitable value. The values can be either "true" (as string), or the Scribble instance name, as returned by kubectl get jaegers. When "true" is used, there should be exactly one Scribble instance for the same namespace as the deployment, otherwise, the operator can’t figure out automatically which Scribble instance to use.

The following snippet shows a simple application that will get a sidecar injected, with the Scribble Agent pointing to the single Scribble instance available in the same namespace:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    inject-jaeger-agent: "true" # (1)
spec:
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: acme/myapp:myversion

1. Either "true" (as string) or the Scribble instance name

Agent as DaemonSet

By default, the Operator expects the agents to be deployed as sidecars to the target applications. This is convenient for several purposes, like in a multi-tenant scenario or to have better load balancing, but there are scenarios where it’s desirable to install the agent as a DaemonSet. In that case, specify the Agent’s strategy to DaemonSet, as follows:

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: my-jaeger
spec:
  agent:
    strategy: DaemonSet

Important

if you attempt to install two Scribble instances on the same cluster with DaemonSet as the strategy, only one will end up deploying a DaemonSet, as the agent is required to bind to well-known ports on the node. Because of that, the second daemon set will fail to bind to those ports.

Your tracer client will then most likely need to be told where the agent is located. This is usually done by setting the env var JAEGER_AGENT_HOST and should be set to the value of the Kubernetes node’s IP, like:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: acme/myapp:myversion
        env:
        - name: JAEGER_AGENT_HOST
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP

Secrets support

The Operator supports passing secrets to the Collector, Query and All-In-One deployments. This can be used for example, to pass credentials (username/password) to access the underlying storage backend (for ex: Elasticsearch). The secrets are available as environment variables in the (Collector/Query/All-In-One) nodes.

    storage:
      type: elasticsearch
      options:
        es:
          server-urls: http://elasticsearch:9200
      secretName: jaeger-secrets

The secret itself would be managed outside of the scribble-operator CR.

Define sampling strategies

The operator can be used to define sampling strategies that will be supplied to tracers that have been configured to use a remote sampler:

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: with-sampling
spec:
  strategy: allInOne
  sampling:
    options:
      default_strategy:
        type: probabilistic
        param: 50

This example defines a default sampling strategy that is probabilistic, with a 50% chance of the trace instances being sampled.

Refer to the Scribble documentation on Collector Sampling Configuration to see how service and endpoint sampling can be configured. The JSON representation described in that documentation can be used in the operator by converting to YAML.

Schema migration

Cassandra

When the storage type is set to Cassandra, the operator will automatically create a batch job that creates the required schema for Scribble to run. This batch job will block the Scribble installation, so that it starts only after the schema is successfuly created. The creation of this batch job can be disabled by setting the enabled property to false:

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: cassandra-without-create-schema
spec:
  strategy: allInOne
  storage:
    type: cassandra
    cassandraCreateSchema:
      enabled: false # (1)

1. Defaults to true

Further aspects of the batch job can be configured as well. An example with all the possible options is shown below:

apiVersion: io.objectiser/v1alpha1
kind: Scribble
metadata:
  name: cassandra-with-create-schema
spec:
  strategy: allInOne # (1)
  storage:
    type: cassandra
    options: # (2)
      cassandra:
        servers: cassandra
        keyspace: jaeger_v1_datacenter3
    cassandraCreateSchema: # (3)
      datacenter: "datacenter3"
      mode: "test"

1. The same works for production

2. These options are for the regular Scribble components, like collector and query

3. The options for the create-schema job

Note

the default create-schema job uses MODE=prod, which implies a replication factor of 2, using NetworkTopologyStrategy as the class, effectively meaning that at least 3 nodes are required in the Cassandra cluster. If a SimpleStrategy is desired, set the mode to test, which then sets the replication factor of 1. Refer to the create-schema script for more details.

Removing an instance

To remove an instance, just use the delete command with the file used for the instance creation:

kubectl delete -f simplest.yaml

Alternatively, you can remove a Scribble instance by running:

kubectl delete jaeger simplest

Note	deleting the instance will not remove the data from a permanent storage used with this instance. Data from in-memory instances, however, will be lost.

Uninstalling the operator

Similar to the installation, just run:

kubectl delete -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/operator.yaml
kubectl delete -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role_binding.yaml
kubectl delete -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/role.yaml
kubectl delete -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/service_account.yaml
kubectl delete -f https://raw.githubusercontent.com/objectiser/scribble-operator/master/deploy/crds/io_v1alpha1_jaeger_crd.yaml