Reloader

Problem

We would like to watch if some change happens in ConfigMap and/or Secret; then perform a rolling upgrade on relevant DeploymentConfig, Deployment, Daemonset, Statefulset and Rollout

Solution

Reloader can watch changes in ConfigMap and Secret and do rolling upgrades on Pods with their associated DeploymentConfigs, Deployments, Daemonsets Statefulsets and Rollouts.

Enterprise Version

Reloader is available in two different versions:

1. Open Source Version
2. Enterprise Version, which includes:
   • SLA (Service Level Agreement) for support and unique requests
   • Slack support
   • Certified images

Contact [email protected] for info about Reloader Enterprise.

Compatibility

Reloader is compatible with Kubernetes >= 1.19

How to use Reloader

For a Deployment called foo have a ConfigMap called foo-configmap or Secret called foo-secret or both. Then add your annotation (by default reloader.stakater.com/auto) to main metadata of your Deployment

kind: Deployment
metadata:
  annotations:
    reloader.stakater.com/auto: "true"
spec:
  template:
    metadata:

This will discover deploymentconfigs/deployments/daemonsets/statefulset/rollouts automatically where foo-configmap or foo-secret is being used either via environment variable or from volume mount. And it will perform rolling upgrade on related pods when foo-configmap or foo-secretare updated.

You can restrict this discovery to only ConfigMap or Secret objects that are tagged with a special annotation. To take advantage of that, annotate your deploymentconfigs/deployments/daemonsets/statefulset/rollouts like this:

kind: Deployment
metadata:
  annotations:
    reloader.stakater.com/search: "true"
spec:
  template:

and Reloader will trigger the rolling upgrade upon modification of any ConfigMap or Secret annotated like this:

kind: ConfigMap
metadata:
  annotations:
    reloader.stakater.com/match: "true"
data:
  key: value

provided the secret/configmap is being used in an environment variable, or a volume mount.

Please note that reloader.stakater.com/search and reloader.stakater.com/auto do not work together. If you have the reloader.stakater.com/auto: "true" annotation on your deployment, then it will always restart upon a change in configmaps or secrets it uses, regardless of whether they have the reloader.stakater.com/match: "true" annotation or not.

We can also specify a specific configmap or secret which would trigger rolling upgrade only upon change in our specified configmap or secret, this way, it will not trigger rolling upgrade upon changes in all configmaps or secrets used in a deploymentconfig, deployment, daemonset, statefulset or rollout. To do this either set the auto annotation to "false" (reloader.stakater.com/auto: "false") or remove it altogether, and use annotations for Configmap or Secret.

It's also possible to enable auto reloading for all resources, by setting the --auto-reload-all flag. In this case, all resources that do not have the auto annotation set to "false", will be reloaded automatically when their ConfigMaps or Secrets are updated. Notice that setting the auto annotation to an undefined value counts as false as-well.

Configmap

To perform rolling upgrade when change happens only on specific configmaps use below annotation.

For a Deployment called foo have a ConfigMap called foo-configmap. Then add this annotation to main metadata of your Deployment

kind: Deployment
metadata:
  annotations:
    configmap.reloader.stakater.com/reload: "foo-configmap"
spec:
  template:
    metadata:

Use comma separated list to define multiple configmaps.

kind: Deployment
metadata:
  annotations:
    configmap.reloader.stakater.com/reload: "foo-configmap,bar-configmap,baz-configmap"
spec:
  template: 
    metadata:

Secret

To perform rolling upgrade when change happens only on specific secrets use below annotation.

For a Deployment called foo have a Secret called foo-secret. Then add this annotation to main metadata of your Deployment

kind: Deployment
metadata:
  annotations:
    secret.reloader.stakater.com/reload: "foo-secret"
spec:
  template: 
    metadata:

Use comma separated list to define multiple secrets.

kind: Deployment
metadata:
  annotations:
    secret.reloader.stakater.com/reload: "foo-secret,bar-secret,baz-secret"
spec:
  template: 
    metadata:

NOTES

• Reloader also supports sealed-secrets. Here are the steps to use sealed-secrets with Reloader.
• For rollouts Reloader simply triggers a change is up to you how you configure the rollout strategy.
• reloader.stakater.com/auto: "true" will only reload the pod, if the configmap or secret is used (as a volume mount or as an env) in DeploymentConfigs/Deployment/Daemonsets/Statefulsets
• secret.reloader.stakater.com/reload or configmap.reloader.stakater.com/reload annotation will reload the pod upon changes in specified configmap or secret, irrespective of the usage of configmap or secret.
• you may override the auto annotation with the --auto-annotation flag
• you may override the search annotation with the --auto-search-annotation flag and the match annotation with the --search-match-annotation flag
• you may override the configmap annotation with the --configmap-annotation flag
• you may override the secret annotation with the --secret-annotation flag
• you may want to prevent watching certain namespaces with the --namespaces-to-ignore flag
• you may want to watch only a set of namespaces with certain labels by using the --namespace-selector flag
• you may want to watch only a set of secrets/configmaps with certain labels by using the --resource-label-selector flag
• you may want to prevent watching certain resources with the --resources-to-ignore flag
• you can configure logging in JSON format with the --log-format=json option
• you can configure the "reload strategy" with the --reload-strategy=<strategy-name> option (details below)

Reload Strategies

Reloader supports multiple "reload" strategies for performing rolling upgrades to resources. The following list describes them:

• env-vars: When a tracked configMap/secret is updated, this strategy attaches a Reloader specific environment variable to any containers referencing the changed configMap or secret on the owning resource (e.g., Deployment, StatefulSet, etc.). This strategy can be specified with the --reload-strategy=env-vars argument. Note: This is the default reload strategy.
• annotations: When a tracked configMap/secret is updated, this strategy attaches a reloader.stakater.com/last-reloaded-from pod template annotation on the owning resource (e.g., Deployment, StatefulSet, etc.). This strategy is useful when using resource syncing tools like ArgoCD, since it will not cause these tools to detect configuration drift after a resource is reloaded. Note: Since the attached pod template annotation only tracks the last reload source, this strategy will reload any tracked resource should its configMap or secret be deleted and recreated. This strategy can be specified with the --reload-strategy=annotations argument.

Deploying to Kubernetes

You can deploy Reloader by following methods:

Vanilla Manifests

You can apply vanilla manifests by changing RELEASE-NAME placeholder provided in manifest with a proper value and apply it by running the command given below:

kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

By default, Reloader gets deployed in default namespace and watches changes secrets and configmaps in all namespaces.

Reloader can be configured to ignore the resources secrets and configmaps by passing the following arguments (spec.template.spec.containers.args) to its container :

Argument	Description
--resources-to-ignore=configMaps	To ignore configMaps
--resources-to-ignore=secrets	To ignore secrets

Note: At one time only one of these resource can be ignored, trying to do it will cause error in Reloader. Workaround for ignoring both resources is by scaling down the Reloader pods to 0.

Reloader can be configured to only watch secrets/configmaps with one or more labels using the --resource-label-selector parameter. Supported operators are !, in, notin, ==, =, !=, if no operator is found the 'exists' operator is inferred (i.e. key only). Additional examples of these selectors can be found in the Kubernetes Docs.

Note: The old : delimited key value mappings are deprecated and if provided will be translated to key=value. Likewise, if a wildcard value is provided (e.g. key:*) it will be translated to the standalone key which checks for key existence.

These selectors can be combined together, for example with:

--resource-label-selector=reloader=enabled,key-exists,another-label in (value1,value2,value3)

Only configmaps or secrets labeled like the following will be watched:

kind: ConfigMap
apiVersion: v1
metadata:
  ...
  labels:
    reloader: enabled
    key-exists: yes
    another-label: value1

  ...

Reloader can be configured to only watch namespaces labeled with one or more labels using the --namespace-selector parameter. Supported operators are !, in, notin, ==, =, !=, if no operator is found the 'exists' operator is inferred (i.e. key only). Additional examples of these selectors can be found in the Kubernetes Docs.

Note: The old : delimited key value mappings are deprecated and if provided will be translated to key=value. Likewise, if a wildcard value is provided (e.g. key:*) it will be translated to the standalone key which checks for key existence.

These selectors can be combined together, for example with:

--namespace-selector=reloader=enabled,test=true

Only namespaces labeled as below would be watched and eligible for reloads:

kind: Namespace
apiVersion: v1
metadata:
  ...
  labels:
    reloader: enabled
    test: true
  ...

Vanilla Kustomize

You can also apply the vanilla manifests by running the following command

kubectl apply -k https://github.com/stakater/Reloader/deployments/kubernetes

Similarly to vanilla manifests get deployed in default namespace and watches changes secrets and configmaps in all namespaces.

Kustomize

You can write your own kustomization.yaml using ours as a 'base' and write patches to tweak the configuration.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

bases:
  - https://github.com/stakater/Reloader/deployments/kubernetes

namespace: reloader

Helm Charts

Alternatively if you have configured helm on your cluster, you can add Reloader to helm from our public chart repository and deploy it via helm using below-mentioned commands. Follow this guide, in case you have trouble migrating Reloader from Helm2 to Helm3.

helm repo add stakater https://stakater.github.io/stakater-charts

helm repo update

helm install stakater/reloader # For helm3 add --generate-name flag or set the release name

Note: By default Reloader watches in all namespaces. To watch in single namespace, please run following command. It will install Reloader in test namespace which will only watch Deployments, Daemonsets Statefulsets and Rollouts in test namespace.

helm install stakater/reloader --set reloader.watchGlobally=false --namespace test # For helm3 add --generate-name flag or set the release name

Reloader can be configured to ignore the resources secrets and configmaps by using the following parameters of values.yaml file:

Parameter	Description	Type
ignoreSecrets	To ignore secrets. Valid value are either true or false	boolean
ignoreConfigMaps	To ignore configMaps. Valid value are either true or false	boolean

Note: At one time only one of these resource can be ignored, trying to do it will cause error in helm template compilation.

Reloader can be configured to only watch namespaces labeled with one or more labels using the namespaceSelector parameter

Parameter	Description	Type
namespaceSelector	list of comma separated label selectors, if multiple are provided they are combined with the AND operator	string

Reloader can be configured to only watch configmaps/secrets labeled with one or more labels using the resourceLabelSelector parameter

Parameter	Description	Type
resourceLabelSelector	list of comma separated label selectors, if multiple are provided they are combined with the AND operator	string

Note: Both namespaceSelector & resourceLabelSelector can be used together. If they are then both conditions must be met for the configmap or secret to be eligible to trigger reload events. (e.g. If a configMap matches resourceLabelSelector but namespaceSelector does not match the namespace the configmap is in, it will be ignored).

You can also set the log format of Reloader to json by setting logFormat to json in values.yaml and apply the chart.

You can enable to scrape Reloader's Prometheus metrics by setting serviceMonitor.enabled or podMonitor.enabled to true in values.yaml file. Service monitor will be removed in future releases of Reloader in favour of Pod monitor.

Note: Reloading of OpenShift (DeploymentConfig) and/or Argo Rollouts has to be enabled explicitly because it might not be always possible to use it on a cluster with restricted permissions. This can be done by changing the following parameters:

Parameter	Description	Type
isOpenshift	Enable OpenShift DeploymentConfigs. Valid value are either true or false	boolean
isArgoRollouts	Enable Argo Rollouts. Valid value are either true or false	boolean
reloadOnCreate	Enable reload on create events. Valid value are either true or false	boolean
syncAfterRestart	Enable sync after Reloader restarts for Add events, works only when reloadOnCreate is true. Valid value are either true or false	boolean

isOpenShift Recent versions of OpenShift (tested on 4.13.3) require the specified user to be in an uid range which is dynamically assigned by the namespace. The solution is to unset the runAsUser variable via deployment.securityContext.runAsUser=null and let OpenShift assign it at install.

ReloadOnCreate reloadOnCreate controls how Reloader handles secrets being added to the cache for the first time. If reloadOnCreate is set to true:

• Configmaps/secrets being added to the cache will cause Reloader to perform a rolling update of the associated workload.
• When applications are deployed for the first time, Reloader will perform a rolling update of the associated workload.
• If you are running Reloader in HA mode all workloads will have a rolling update performed when a new leader is elected.

If ReloadOnCreate is set to false:

• Updates to configMaps/Secrets that occur while there is no leader will not be picked up by the new leader until a subsequent update of the configmap/secret occurs. In the worst case the window in which there can be no leader is 15s as this is the LeaseDuration.

Help

Documentation

You can find more documentation here

Have a question?

File a GitHub issue.

Talk to us on Slack

Join and talk to us on Slack for discussing Reloader

Contributing

Bug Reports & Feature Requests

Please use the issue tracker to report any bugs or file feature requests.

Developing

1. Deploy Reloader.
2. Run okteto up to activate your development container.
3. make build.
4. ./Reloader

PRs are welcome. In general, we follow the "fork-and-pull" Git workflow.

1. Fork the repo on GitHub
2. Clone the project to your own machine
3. Commit changes to your own branch
4. Push your work back up to your fork
5. Submit a Pull request so that we can review your changes

NOTE: Be sure to merge the latest from "upstream" before making a pull request!

Changelog

View our closed Pull Requests.

License

Apache2 © Stakater

About

Reloader is maintained by Stakater. Like it? Please let us know at [email protected]

See our other projects or contact us in case of professional services and queries on [email protected]

Acknowledgements

• ConfigmapController; We documented here why we re-created Reloader