Mirrors/coredns
1
0
Fork 0
mirror of https://github.com/coredns/coredns.git synced 2025-10-31 02:03:20 -04:00
Code Issues Packages Projects Releases Wiki Activity
Files
9ea8cde36e24cb68d6cb2c5db7b6b08e204db7a8
coredns/middleware/kubernetes/SkyDNS.md

45 lines
3.3 KiB
Markdown
Raw Normal View History

k8s middleware cleanup, testcases, basic SRV (#181) * 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
2016-07-07 01:40:58 -07:00
## DNS Schema
Notes about the SkyDNS record naming scheme. (Copied from SkyDNS project README for reference while
hacking on the k8s middleware.)
### Services
#### A Records
"Normal" (not headless) Services are assigned a DNS A record for a name of the form `my-svc.my-namespace.svc.cluster.local.`
This resolves to the cluster IP of the Service.
"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.`
Unlike normal Services, this resolves to the set of IPs of the pods selected by the Service.
Clients are expected to consume the set or else use standard round-robin selection from the set.
### Pods
#### A Records
When enabled, pods are assigned a DNS A record in the form of `pod-ip-address.my-namespace.pod.cluster.local.`
For example, a pod with ip `1.2.3.4` in the namespace default with a dns name of `cluster.local` would have
an entry: `1-2-3-4.default.pod.cluster.local.`
####A Records and hostname Based on Pod Annotations - A Beta Feature in Kubernetes v1.2
Currently when a pod is created, its hostname is the Pod's `metadata.name` value.
With v1.2, users can specify a Pod annotation, `pod.beta.kubernetes.io/hostname`, to specify what the Pod's hostname should be.
Fix several typos in docs. (#426) Fixes several typos in docs. Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
2016-11-13 23:25:17 -08:00
If the annotation is specified, the annotation value takes precedence over the Pod's name, to be the hostname of the pod.
k8s middleware cleanup, testcases, basic SRV (#181) * 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
2016-07-07 01:40:58 -07:00
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".
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.
If the annotation is specified, the fully qualified Pod hostname will be "<hostname>.<subdomain>.<pod namespace>.svc.<cluster domain>".
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"
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.
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.
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"}}'.
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>
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".
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.
Reference in New Issue Copy Permalink