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SyncSet

Overview

SyncSet and SelectorSyncSet objects facilitate resource management (create, update, delete, patch) in hive-managed clusters.

To use SyncSet objects to manage resources, you must create them in the same namespace as the ClusterDeployment resource that they manage. If you want to manage resources in clusters that match a specific label use SelectorSyncSet instead. These objects apply changes to clusters in any namespace that match the clusterDeploymentSelector that you set.

With both SyncSets and SelectorSyncSets, the individual resources and patches are reapplied when 2 hours have passed since their last reconciliation (by default) or if their contents are updated in the SyncSet or SelectorSyncSets.

The default syncSetReapplyInterval can be overridden by specifying a string duration within the hiveconfig such as syncSetReapplyInterval: "1h" for a one hour reapply interval.

SyncSet Object Definition

SyncSets may contain a list of resource object definitions to create and a list of patches to be applied to existing objects.

---
apiVersion: hive.openshift.io/v1
kind: SyncSet
metadata:
  name: mygroup
spec:
  clusterDeploymentRefs:
  - name: ClusterName

  resourceApplyMode: Upsert

  resources:
  - apiVersion: user.openshift.io/v1
    kind: Group
    metadata:
      name: mygroup
    users:
    - myuser

  patches:
  - kind: ConfigMap
    apiVersion: v1
    name: foo
    namespace: default
    patch: |-
      { "data": { "foo": "new-bar" } }
    patchType: merge
    
  secretMappings:
  - sourceRef:
      name: ad-bind-password
      namespace: default
    targetRef:
      name: ad-bind-password
      namespace: openshift-config
Field Usage
clusterDeploymentRefs List of ClusterDeployment names in the current namespace which the SyncSet will apply to.
resourceApplyMode Defaults to "Upsert", which indicates that objects will be created and updated to match the SyncSet. Existing SyncSet resources that are not listed in the SyncSet are not deleted. Specify "Sync" to allow deleting existing objects that were previously in the resources list. This includes deleting all resources when the entire SyncSet is deleted.
resources A list of resource object definitions. Resources will be created in the referenced clusters.
patches A list of patches to apply to existing resources in the referenced clusters. You can include any valid cluster object type in the list. By default, the patch applyMode value is "AlwaysApply", which applies the patch every 2 hours.
secretMappings A list of secret mappings. The secrets will be copied from the existing sources to the target resources in the referenced clusters

Example of SyncSet use

In this example you can change the replicaset of a deployment running on top of a Hive managed OpenShift cluster.

  • Get the required information of the deployment
$ oc get deployment <deployment name> -o yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    app: sise
  name: sise-deploy
  namespace: default
spec:
  replicas: 2
  xxxxxxx
  • Create the SyncSet object in the cluster deployment namespace in Hive managed cluster as mentioned below.
oc create -f <syncset_file.yaml> -n <namespace>

SyncSet File:

apiVersion: hive.openshift.io/v1
kind: SyncSet
metadata:
  name: sise-deploy-syncset
spec:
  clusterDeploymentRefs:
  - name: <cluster name>

  patches:
  - kind: Deployment
    apiVersion: extensions/v1beta1
    name: sise-deploy
    namespace: default
    patch: |-
      { "spec": { "replicas": 3 } }
    patchType: strategic
  • To see the syncset status, run as below.
oc get clustersync <clusterdeployment name> -o yaml

SelectorSyncSet Object Definition

SelectorSyncSet functions identically to SyncSet but is applied to clusters matching clusterDeploymentSelector in any namespace.

---
apiVersion: hive.openshift.io/v1
kind: SelectorSyncSet
metadata:
  name: mygroup
spec:
  resources:
  - apiVersion: user.openshift.io/v1
    kind: Group
    metadata:
      name: mygroup
    users:
    - abutcher
  clusterDeploymentSelector:
    matchLabels:
      cluster-group: abutcher
Field Usage
clusterDeploymentSelector A key/value label pair which selects matching ClusterDeployments in any namespace.

Diagnosing SyncSet Failures

To find the status of the syncset, check the cluster deployment's ClusterSync object in the cluster deployment namespace. Every cluster deployment has an associated ClusterSync object that records status within ClusterSync.Status.SyncSets.

oc get clustersync -n <namespace>

To see details, run as below.

oc get clustersync <clusterdeployment name> -o yaml

All (Selector)SyncSets for a given ClusterDeployment are handled by a single replica of the hive-clustersync StatefulSet. The replica pods are named hive-clustersync-N where N is an integer such that 0 <= N < #replicas. ClusterSync.Status.ControlledByReplica indicates which replica is responsible for (the CD associated with) the ClusterSync. Use this to determine which replica's pod logs to examine when debugging syncset operations. For example:

$ REPLICA=`oc get clustersync -n <namespace> <clusterdeployment name> -o json | jq -r .status.controlledByReplica`
$ oc logs -n hive hive-clustersync-$REPLICA | grep <clusterdeployment name>

Note: This value is only set/updated when the cluster is installed, reachable, and not deleted.

Note: This value indicates the replica that most recently handled the ClusterSync. If the hive-clustersync statefulset is scaled up or down, the controlling replica can change, potentially causing logs to be spread across multiple pods.

Changing ResourceApplyMode

Changing the resourceApplyMode from "Sync" to "Upsert" will remove SyncSet resources tracked for deletion within the corresponding ClusterSync object. It is possible that the ClusterSync controller could process a resource removal and a resourceApplyMode change simultaneously and when this occurs resources no longer tracked in the SyncSet will be orphaned rather than deleted.

Likewise, changing the resourceApplyMode from "Upsert" to "Sync" will add SyncSet resources to resources tracked for deletion within the corresponding ClusterSync object. When the ClusterSync controller processes a resource removal and a resourceApplyMode change simultaneously, resources removed will be orphaned rather than deleted.