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* Removing unnecessary gitignore pattern
* Updating Makefile to run unittests for subpackages
* Adding Corefile validation to ignore overlapping zones
* Fixing SRV query handling
* Updating README.md now that SRV works
* Fixing debug message, adding code comment
* Clarifying implementation of zone normalization
* "Overlapping zones" is ill-defined. Reimplemented zone overlap/subzone
checking to contain these functions in k8s middleware and provide
better code comments explaining the normalization.
* Separate build verbosity from test verbosity
* Cleaning up comments to match repo code style
* Merging warning messages into single message
* Moving function docs to before function declaration
* Adding test cases for k8sclient connector
* Tests cover connector create and setting base url
* Fixed bugs in connector create and setting base url functions
* Updaing README to group and order development work
* Priority focused on achieving functional parity with SkyDNS.
* Adding work items to README and cleaning up formatting
* More README format cleaning
* List formating
* Refactoring k8s API call to allow dependency injection
* Add test cases for data parsing from k8s into dataobject structures
* URL is dependency-injected to allow replacement with a mock http
server during test execution
* Adding more data validation for JSON parsing tests
* Adding test case for GetResourceList()
* Adding notes about SkyDNS embedded IP and port record names
* Marked test case implemented.
* Fixing formatting for example command.
* Fixing formatting
* Adding notes about Docker image building.
* Adding SkyDNS work item
* Updating TODO list
* Adding name template to Corefile to specify how k8s record names are assembled
* Adding template support for multi-segment zones
* Updating example CoreFile for k8s with template comment
* Misc whitespace cleanup
* Adding SkyDNS naming notes
* Adding namespace filtering to CoreFile config
* Updating example k8sCoreFile to specify namespaces
* Removing unused codepath
* Adding check for valid namespace
* More README TODO restructuring to focus effort
* Adding template validation while parsing CoreFile
* Record name template is considered invalid if it contains a symbol of the form ${bar} where the symbol
"${bar}" is not an accepted template symbol.
* Refactoring generation of answer records
* Parse typeName out of query string
* Refactor answer record creation as operation over list of ServiceItems
* Moving k8s API caching into SkyDNS equivalency segment
* Adding function to assemble record names from template
* Warning: This commit may be broken. Syncing to get laptop code over to dev machine.
* More todo notes
* Adding comment describing sample test data.
* Update k8sCorefile
* Adding comment
* Adding filtering support for kubernetes "type"
* Required refactoring to support reuse of the StringInSlice function.
* Cleaning up formatting
* Adding note about SkyDNS supporting word "any".
* baseUrl -> baseURL
* Also removed debug statement from core/setup/kubernetes.go
* Fixing test breaking from Url -> URL naming changes
* Changing record name template language ${...} -> {...}
* Fix formatting with go fmt
* Updating all k8sclient data getters to return error value
* Adding error message to k8sclient data accessors
* Cleaning up setup for kubernetes
* Removed verbose nils in initial k8s middleware instance
* Set reasonable defaults if CoreFile has no parameters in the
kubernetes block. (k8s endpoint, and name template)
* Formatting cleanup -- go fmt
45 lines
3.3 KiB
Markdown
45 lines
3.3 KiB
Markdown
## DNS Schema
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Notes about the SkyDNS record naming scheme. (Copied from SkyDNS project README for reference while
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hacking on the k8s middleware.)
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### Services
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#### A Records
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"Normal" (not headless) Services are assigned a DNS A record for a name of the form `my-svc.my-namespace.svc.cluster.local.`
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This resolves to the cluster IP of the Service.
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"Headless" (without a cluster IP) Services are also assigned a DNS A record for a name of the form `my-svc.my-namespace.svc.cluster.local.`
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Unlike normal Services, this resolves to the set of IPs of the pods selected by the Service.
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Clients are expected to consume the set or else use standard round-robin selection from the set.
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### Pods
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#### A Records
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When enabled, pods are assigned a DNS A record in the form of `pod-ip-address.my-namespace.pod.cluster.local.`
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For example, a pod with ip `1.2.3.4` in the namespace default with a dns name of `cluster.local` would have
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an entry: `1-2-3-4.default.pod.cluster.local.`
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####A Records and hostname Based on Pod Annotations - A Beta Feature in Kubernetes v1.2
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Currently when a pod is created, its hostname is the Pod's `metadata.name` value.
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With v1.2, users can specify a Pod annotation, `pod.beta.kubernetes.io/hostname`, to specify what the Pod's hostname should be.
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If the annotation is specified, the annotation value takes precendence over the Pod's name, to be the hostname of the pod.
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For example, given a Pod with annotation `pod.beta.kubernetes.io/hostname: my-pod-name`, the Pod will have its hostname set to "my-pod-name".
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v1.2 introduces a beta feature where the user can specify a Pod annotation, `pod.beta.kubernetes.io/subdomain`, to specify what the Pod's subdomain should be.
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If the annotation is specified, the fully qualified Pod hostname will be "<hostname>.<subdomain>.<pod namespace>.svc.<cluster domain>".
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For example, given a Pod with the hostname annotation set to "foo", and the subdomain annotation set to "bar", in namespace "my-namespace", the pod will set its own FQDN as "foo.bar.my-namespace.svc.cluster.local"
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If there exists a headless service in the same namespace as the pod and with the same name as the subdomain, the cluster's KubeDNS Server will also return an A record for the Pod's fully qualified hostname.
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Given a Pod with the hostname annotation set to "foo" and the subdomain annotation set to "bar", and a headless Service named "bar" in the same namespace, the pod will see it's own FQDN as "foo.bar.my-namespace.svc.cluster.local". DNS will serve an A record at that name, pointing to the Pod's IP.
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With v1.2, the Endpoints object also has a new annotation `endpoints.beta.kubernetes.io/hostnames-map`. Its value is the json representation of map[string(IP)][endpoints.HostRecord], for example: '{"10.245.1.6":{HostName: "my-webserver"}}'.
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If the Endpoints are for a headless service, then A records will be created with the format <hostname>.<service name>.<pod namespace>.svc.<cluster domain>
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For the example json, if endpoints are for a headless service named "bar", and one of the endpoints has IP "10.245.1.6", then a A record will be created with the name "my-webserver.bar.my-namespace.svc.cluster.local" and the A record lookup would return "10.245.1.6".
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This endpoints annotation generally does not need to be specified by end-users, but can used by the internal service controller to deliver the aforementioned feature.
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