mirror of https://github.com/hashicorp/consul
Documentation for catalog sync w/ K8S (#4710)
* website: docs for catalog sync * website: document consul-k8s * website: document helm options * Add new helm fields * website: fix the description of the sync page * website: address feedback * website: clarify coredns requirement * website: clarify that the server cluster can run anywhere (NOTE: This was squashed to make cherry-picking to stable-website easier)pull/4723/head
Mitchell Hashimoto
GitHub
commit
f680026a7d
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@ -85,6 +85,13 @@ and consider if they're appropriate for your deployment.
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in production.** Otherwise, other changes to the chart may inadvertently
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upgrade your Consul version.
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- <a name="v-global-imagek8s" href="#v-global-imagek8s">`imageK8S`</a> (`string: "hashicorp/consul-k8s:latest"`) -
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The name of the Docker image (including any tag) for the
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[consul-k8s](https://github.com/hashicorp/consul-k8s) binary. This is
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used by components such as catalog sync. **This should be pinned to a specific
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version when running in production.** Otherwise, other changes to the chart may
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inadvertently upgrade the version.
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- <a name="v-global-datacenter" href="#v-global-datacenter">`datacenter`</a> (`string: "dc1"`) -
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The name of the datacenter that the agent cluster should register as.
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This must not be changed once the cluster is bootstrapped and running,
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@ -237,6 +244,32 @@ and consider if they're appropriate for your deployment.
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then be used to [configure kube-dns](/docs/platform/k8s/dns.html). The Helm
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chart _does not_ automatically configure kube-dns.
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* <a name="v-synccatalog" href="#v-synccatalog">`syncCatalog`</a> - Values that
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configure running the [service sync](/docs/platform/k8s/service-sync.html)
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process.
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- <a name="v-synccatalog-enabled" href="#v-synccatalog-enabled">`enabled`</a> (`boolean: false`) -
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If true, the chart will install all the resources necessary for the
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catalog sync process to run.
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- <a name="v-synccatalog-image" href="#v-synccatalog-image">`image`</a> (`string: global.imageK8S`) -
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The name of the Docker image (including any tag) for
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[consul-k8s](/docs/platform/k8s/index.html#quot-consul-k8s-quot-project)
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to run the sync program.
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- <a name="v-synccatalog-k8sprefix" href="#v-synccatalog-k8sprefix">`k8sPrefix`</a> (`string: ""`) -
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A prefix to prepend to all services registered in Kubernetes from Consul.
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This defaults to `""` where no prefix is prepended; Consul services are
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synced with the same name to Kubernetes.
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- <a name="v-synccatalog-toconsul" href="#v-synccatalog-toconsul">`toConsul`</a> (`boolean: true`) -
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If true, will sync Kubernetes services to Consul. This can be disabled to
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have a one-way sync.
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- <a name="v-synccatalog-tok8s" href="#v-synccatalog-tok8s">`toK8S`</a> (`boolean: true`) -
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If true, will sync Consul services to Kubernetes. This can be disabled to
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have a one-way sync.
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* <a name="v-ui" href="#v-ui">`ui`</a> - Values that configure the Consul UI.
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- <a name="v-ui-enabled" href="#v-ui-enabled">`enabled`</a> (`boolean: global.enabled`) -
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@ -42,3 +42,18 @@ vice versa) over a fully encrypted connection.
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**And more!** Consul can run directly on Kubernetes, so in addition to the
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native integrations provided by Consul itself, any other tool built for
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Kubernetes can choose to leverage Consul.
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## "consul-k8s" Project
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The dedicated [consul-k8s project](https://github.com/hashicorp/consul-k8s)
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contains the integration functionality between Consul and Kubernetes.
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You generally will not need to invoke this project directly since the
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[Helm chart](/docs/platform/k8s/helm.html) automates the installation and
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configuration of the project when necessary.
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We may integrate this functionality directly into Consul in the future,
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but the separate project allows us to iterate and version the Kubernetes
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functionality separately. Additionally, a lot of the functionality works
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across multiple Consul versions, so you're able to update and resolve any
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Kubernetes integration issues without also upgrading Consul itself which
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can be more difficult.
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@ -0,0 +1,284 @@
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---
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layout: "docs"
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page_title: "Service Sync - Kubernetes"
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sidebar_current: "docs-platform-k8s-service-sync"
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description: |-
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The services in Kubernetes and Consul can be automatically synced so that Kubernetes services are available to Consul agents and services in Consul can be available as first-class Kubernetes services.
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---
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# Syncing Kubernetes and Consul Services
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The services in Kubernetes and Consul can be automatically synced so that Kubernetes
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services are available to Consul agents and services in Consul can be available
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as first-class Kubernetes services. This functionality is provided by the
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[consul-k8s project](https://github.com/hashicorp/consul-k8s) and can be
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automatically installed and configured using the
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[Consul Helm chart](/docs/platform/k8s/helm.html).
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**Why sync Kubernetes services to Consul?** Kubernetes services synced to the
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Consul catalog enable Kubernetes services to be accessed by any node that
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is part of the Consul cluster, including other distinct Kubernetes clusters.
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For non-Kubernetes nodes, they can access services using the standard
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[Consul DNS](/docs/agent/dns.html) or HTTP API.
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**Why sync Consul services to Kubernetes?** Syncing Consul services to
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Kubernetes services enables non-Kubernetes services (such as external to
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the cluster) to be accessed in a native Kubernetes way: using kube-dns,
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environment variables, etc. This makes it very easy to automate external
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service discovery, including hosted services like databases.
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## Installation and Configuration
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The service sync is done using an external long-running process in the
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[consul-k8s project](https://github.com/hashicorp/consul-k8s). This process
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can run either in or out of a Kubernetes cluster. However, running this within
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the Kubernetes cluster is generally easier since it is automated using the
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[Helm chart](/docs/platform/k8s/helm.html).
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The Consul server cluster can run either in or out of a Kubernetes cluster.
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The Consul server cluster does not need to be running on the same machine
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or same platform as the sync process. The sync process needs to be configured
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with the address to the Consul cluster as well as any additional access
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information such as ACL tokens.
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To install the sync, enable the catalog sync feature using
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[Helm values](/docs/platform/k8s/helm.html#configuration-values-) and
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upgrade the installation using `helm upgrade` for existing installs or
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`helm install` for a fresh install.
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```yaml
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syncCatalog:
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enabled: true
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```
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This will enable services to sync _in both directions_. You can also choose
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to only sync Kubernetes services to Consul or vice versa by disabling a direction.
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See the [Helm configuration](/docs/platform/k8s/helm.html#configuration-values-)
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for more information.
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-> **Before installing,** please read the introduction paragraphs for the
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reference documentation below for both
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[Kubernetes to Consul](/docs/platform/k8s/service-sync.html#kubernetes-to-consul) and
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[Consul to Kubernetes](/docs/platform/k8s/service-sync.html#consul-to-kubernetes)
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sync to understand how the syncing works.
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### Authentication
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The sync process must authenticate to both Kubernetes and Consul to read
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and write services.
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For Consul, the process accepts both the standard CLI flag `-token` and
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the environment variable `CONSUL_HTTP_TOKEN`. This should be set to an
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Consul [ACL token](/docs/guides/acl.html) if ACLs are enabled. This
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can also be configured using the Helm chart to read from a Kubernetes
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secret.
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For Kubernetes, a valid kubeconfig file must be provided with cluster
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and auth information. The sync process will look into the default locations
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for both in-cluster and out-of-cluster authentication. If `kubectl` works,
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then the sync program should work.
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## Kubernetes to Consul
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This sync registers Kubernetes services to the Consul catalog automatically.
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This enables discovery and connection to Kubernetes services using native
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Consul service discovery such as DNS or HTTP. This is particularly useful for
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non-Kubernetes nodes. This also causes all discoverable services to be part of
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a central service catalog in Consul for further syncing into alternate
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Kubernetes clusters or other platforms.
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### Kubernetes Service Types
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Not all Kubernetes services are externally accessible. The sync program by
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default will only sync services of the following types or configurations.
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If a service type is not listed below, then the sync program will ignore that
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service type.
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#### NodePort
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[NodePort services](https://kubernetes.io/docs/concepts/services-networking/service/#nodeport)
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register a static port that every node in the K8S cluster listens on.
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For NodePort services, a Consul service instance will be created for each
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node that has the representative pod running. While Kubernetes configures
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a static port on all nodes in the cluster, this limits the number of service
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instances to be equal to the nodes running the target pods.
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The service instances will be registered to the Kubernetes node name
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that each instance lives on. This is guaranteed unique by Kubernetes. An
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existing node entry will be used if it is already part of the Consul
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cluster (for example if you're running a client agent on all Kubernetes
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nodes). This allows the normal agent health checks for that node to continue
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working.
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#### LoadBalancer
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For LoadBalancer services, a single service instance will be registered with
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the external IP of the created load balancer. Because this is already a load
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balancer, only one service instance will be registered with Consul rather
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than registering each individual pod endpoint.
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#### External IPs
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Any service type may specify an
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"[external IP](https://kubernetes.io/docs/concepts/services-networking/service/#external-ips)"
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configuration. The external IP must be configured by some other system, but
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any service discovery will resolve to this set of IP addresses rather than a
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virtual IP.
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If an external IP list is present, a service instance in Consul will be created
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for each external IP. It is assumed that if an external IP is present that it
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is routable and configured by some other system.
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### Sync Enable/Disable
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By default, all valid services (as explained above) are synced. This default
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can be changed as configuration to the sync process. Syncing can also be
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explicitly enabled or disabled using an annotation:
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```yaml
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kind: Service
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apiVersion: v1
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metadata:
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name: my-service
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annotations:
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"consul.hashicorp.com/service-sync": false
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```
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### Service Name
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When a Kubernetes service is synced to Consul, the name of the service in Consul
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by default will be the value of the "name" metadata on that Kubernetes service.
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This makes it so that service sync works with zero configuration changes.
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This can be overridden using an annotation to specify the Consul service name:
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```yaml
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kind: Service
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apiVersion: v1
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metadata:
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name: my-service
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annotations:
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"consul.hashicorp.com/service-name": my-consul-service
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```
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**If a conflicting service name exists in Consul,** the sync program will
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register additional instances to that same service. Therefore, services inside
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and outside of Kubernetes should have different names unless you want either
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side to potentially connect. This default behavior also enables gracefully
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transitioning a service from outside of K8S to inside, and vice versa.
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### Service Ports
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When syncing the Kubernetes service to Consul, the Consul service port will be
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the first defined port in the service. Additionally, all ports will be
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registered in the service instance metadata with the key "port-X" where X is
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the name of the port and the value is the externally accessible port.
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||||
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||||
The default service port can be overridden using an annotation:
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```yaml
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kind: Service
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apiVersion: v1
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metadata:
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name: my-service
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annotations:
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"consul.hashicorp.com/service-port": "http"
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```
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The annotation value may a name of a port (recommended) or an exact port value.
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### Service Tags
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A service registered in Consul from Kubernetes will always have the tag "k8s" added
|
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to it. Additional tags can be specified with a comma-separated annotation value
|
||||
as shown below. This will also automatically include the "k8s" tag which can't
|
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be disabled. The values should be specified comma-separated without any
|
||||
additional whitespace.
|
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|
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```yaml
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kind: Service
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apiVersion: v1
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||||
metadata:
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name: my-service
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annotations:
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"consul.hashicorp.com/service-tags": "primary,foo"
|
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```
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### Service Meta
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||||
|
||||
A service registered in Consul from Kubernetes will set the `external-source` key to
|
||||
"kubernetes". This can be used by API consumers, the UI, CLI, etc. to filter
|
||||
service instances that are set in k8s. The Consul UI (in Consul 1.2.3 and later)
|
||||
will read this value to show a Kubernetes icon next to all externally
|
||||
registered services from Kubernetes.
|
||||
|
||||
Additional metadata can be specified using annotations. The "KEY" below can be
|
||||
set to any key. This allows setting multiple meta values:
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||||
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```yaml
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||||
kind: Service
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apiVersion: v1
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||||
metadata:
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name: my-service
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||||
annotations:
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||||
"consul.hashicorp.com/service-meta-KEY": "value"
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||||
```
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## Consul to Kubernetes
|
||||
|
||||
This syncs Consul services into first-class Kubernetes services.
|
||||
Each Consul service is synced to an
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||||
[ExternalName](https://kubernetes.io/docs/concepts/services-networking/service/#externalname)
|
||||
service in Kubernetes. The external name is configured to be the Consul
|
||||
DNS entry.
|
||||
|
||||
This enables external services to be discovered using native Kubernetes
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||||
tooling. This can be used to ease software migration into or out of Kubernetes,
|
||||
across platforms, to and from hosted services, and more.
|
||||
|
||||
-> **Requires Consul DNS via CoreDNS in Kubernetes:** This feature requires that
|
||||
[Consul DNS](/docs/platform/k8s/dns.html) is configured within Kubernetes.
|
||||
Additionally, **[CoreDNS](https://kubernetes.io/docs/tasks/administer-cluster/dns-custom-nameservers/#config-coredns)
|
||||
is required (instead of kube-dns)** to resolve an
|
||||
issue with resolving `externalName` services pointing to custom domains.
|
||||
In the future we hope to remove this requirement by syncing the instance
|
||||
addresses directly into service endpoints.
|
||||
|
||||
### Sync Enable/Disable
|
||||
|
||||
All Consul services visible to the sync process based on its given ACL token
|
||||
will be synced to Kubernetes.
|
||||
|
||||
There is no way to change this behavior per service. For the opposite sync
|
||||
direction (Kubernetes to Consul), you can use Kubernetes annotations to disable
|
||||
a sync per service. This is not currently possible for Consul to Kubernetes
|
||||
sync and the ACL token must be used to limit what services are synced.
|
||||
|
||||
In the future, we hope to support per-service configuration.
|
||||
|
||||
### Service Name
|
||||
|
||||
When a Consul service is synced to Kubernetes, the name of the Kubernetes
|
||||
service will exactly match the name of the Consul service.
|
||||
|
||||
To change this default exact match behavior, it is possible to specify a
|
||||
prefix to be added to service names within Kubernetes by using the
|
||||
`-k8s-service-prefix` flag. This can also be specified in the Helm
|
||||
configuration.
|
||||
|
||||
**If a conflicting service is found,** the service will not be synced. This
|
||||
does not match the Kubernetes to Consul behavior, but given the current
|
||||
implementation we must do this because Kubernetes can't mix both CNAME and
|
||||
Endpoint-based services.
|
||||
|
||||
### Kubernetes Service Labels and Annotations
|
||||
|
||||
Any Consul services synced to Kubernetes will be labeled and annotated.
|
||||
An annotation `consul.hashicorp.com/synced` will be set to "true" to note
|
||||
that this is a synced service from Consul.
|
||||
|
||||
Additionally, a label `consul=true` will be specified so that label selectors
|
||||
can be used with `kubectl` and other tooling to easily filter all Consul-synced
|
||||
services.
|
||||
|
||||
|
|
@ -311,6 +311,9 @@
|
|||
<li<%= sidebar_current("docs-platform-k8s-dns") %>>
|
||||
<a href="/docs/platform/k8s/dns.html">Consul DNS</a>
|
||||
</li>
|
||||
<li<%= sidebar_current("docs-platform-k8s-service-sync") %>>
|
||||
<a href="/docs/platform/k8s/service-sync.html">Service Sync</a>
|
||||
</li>
|
||||
</ul>
|
||||
</li>
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue