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k8s middleware cleanup, testcases, basic SRV (#181)

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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
This commit is contained in:
Michael Richmond
2016-07-07 01:40:58 -07:00
committed by Miek Gieben
parent 558c34a23e
commit 289f53d386
19 changed files with 1610 additions and 304 deletions
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125
middleware/kubernetes/README.md
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@@ -14,7 +14,7 @@ are constructed as "myservice.mynamespace.coredns.local" where:
kubernetes [zones...]
~~~
* `zones` zones kubernetes should be authorative for.
* `zones` zones kubernetes should be authorative for. Overlapping zones are ignored.
~~~
@@ -88,7 +88,7 @@ The kubernetes control client can be downloaded from the generic URL:
`http://storage.googleapis.com/kubernetes-release/release/${K8S_VERSION}/bin/${GOOS}/${GOARCH}/${K8S_BINARY}`
For example, the kubectl client for Linux can be downloaded using the command:
`curl -sSL "http://storage.googleapis.com/kubernetes-release/release/v1.2.4/bin/linux/amd64/kubectl"
`curl -sSL "http://storage.googleapis.com/kubernetes-release/release/v1.2.4/bin/linux/amd64/kubectl"`
The following `setup_kubectl.sh` script can be stored in the same directory as
kubectl to setup
@@ -248,37 +248,100 @@ return the IP addresses for all services with "nginx" in the service name.
TBD:
* How does this relate the the k8s load-balancer configuration?
* Do wildcards search across namespaces?
* Initial implementation assumes that a namespace maps to the first DNS label below the zone managed by the kubernetes middleware. This assumption may need to be revised.
* Initial implementation assumes that a namespace maps to the first DNS label
below the zone managed by the kubernetes middleware. This assumption may
need to be revised.
## TODO
* Implement namespace filtering to different zones.
* Implement IP selection and ordering (internal/external).
* Implement SRV-record queries using naive lookup.
* Flatten service and namespace names to valid DNS characters. (service names
and namespace names in k8s may use uppercase and non-DNS characters. Implement
flattening to lower case and mapping of non-DNS characters to DNS characters
in a standard way.)
* Do we need to generate synthetic zone records for namespaces?
* Implement wildcard-based lookup.
* Improve lookup to reduce size of query result obtained from k8s API.
(namespace-based?, other ideas?)
* How to support label specification in Corefile to allow use of labels to
indicate zone? (Is this even useful?) For example, the following configuration
exposes all services labeled for the "staging" environment and tenant "customerB"
in the zone "customerB.stage.local":
* SkyDNS compatibility/equivalency:
* Kubernetes packaging and execution
* Automate packaging to allow executing in Kubernetes. That is, add Docker
container build as target in Makefile. Also include anything else needed
to simplify launch as the k8s DNS service.
Note: Dockerfile already exists in coredns repo to build the docker image.
This work item should identify how to pass configuration and run as a SkyDNS
replacement.
* Identify any kubernetes changes necessary to use coredns as k8s DNS server. That is,
how do we consume the "--cluster-dns=" and "--cluster-domain=" arguments.
* Work out how to pass CoreDNS configuration via kubectl command line and yaml
service definition file.
* Ensure that resolver in each kubernetes container is configured to use
coredns instance.
* Update kubernetes middleware documentation to describe running CoreDNS as a
SkyDNS replacement. (Include descriptions of different ways to pass CoreFile
to coredns command.)
* Expose load-balancer IP addresses.
* Calculate SRV priority based on number of instances running.
(See SkyDNS README.md)
* Functional work
* Implement wildcard-based lookup. Minimally support `*`, consider `?` as well.
* Note from Miek on PR 181: "SkyDNS also supports the word `any`.
* Implement SkyDNS-style synthetic zones such as "svc" to group k8s objects. (This
should be optional behavior.) Also look at "pod" synthetic zones.
* Implement test cases for SkyDNS equivalent functionality.
* SkyDNS functionality, as listed in SkyDNS README: https://github.com/kubernetes/kubernetes/blob/release-1.2/cluster/addons/dns/README.md
* A records in form of `pod-ip-address.my-namespace.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`.
* SRV records in form of
`_my-port-name._my-port-protocol.my-namespace.svc.cluster.local`
CNAME records for both regular services and headless services.
See SkyDNS README.
* A Records and hostname Based on Pod Annotations (k8s beta 1.2 feature).
See SkyDNS README.
* Note: the embedded IP and embedded port record names are weird. I
would need to know the IP/port in order to create the query to lookup
the name. Presumably these are intended for wildcard queries.
* Performance
* Improve lookup to reduce size of query result obtained from k8s API.
(namespace-based?, other ideas?)
* Caching of k8s API dataset.
* DNS response caching is good, but we should also cache at the http query
level as well. (Take a look at https://github.com/patrickmn/go-cache as
a potential expiring cache implementation for the http API queries.)
* Push notifications from k8s for data changes rather than pull via API?
* Additional features:
* Implement namespace filtering to different zones. That is, zone "a.b"
publishes services from namespace "foo", and zone "x.y" publishes services
from namespaces "bar" and "baz". (Basic version implemented -- need test cases.)
* Reverse IN-ADDR entries for services. (Is there any value in supporting
reverse lookup records?
* How to support label specification in Corefile to allow use of labels to
indicate zone? (Is this even useful?) For example, the following
configuration exposes all services labeled for the "staging" environment
and tenant "customerB" in the zone "customerB.stage.local":
~~~
kubernetes customerB.stage.local {
# Use url for k8s API endpoint
endpoint http://localhost:8080
label "environment" : "staging", "tenant" : "customerB"
}
~~~
* Test with CoreDNS caching. CoreDNS caching for DNS response is working using
the `cache` directive. Tested working using 20s cache timeout and A-record queries.
* DNS response caching is good, but we should also cache at the http query
level as well. (Take a look at https://github.com/patrickmn/go-cache as
a potential expiring cache implementation for the http API queries.)
kubernetes customerB.stage.local {
# Use url for k8s API endpoint
endpoint http://localhost:8080
label "environment" : "staging", "tenant" : "customerB"
}
Note: label specification/selection is a killer feature for segmenting
test vs staging vs prod environments.
* Implement IP selection and ordering (internal/external). Related to
wildcards and SkyDNS use of CNAMES.
* Flatten service and namespace names to valid DNS characters. (service names
and namespace names in k8s may use uppercase and non-DNS characters. Implement
flattening to lower case and mapping of non-DNS characters to DNS characters
in a standard way.)
* Expose arbitrary kubernetes repository data as TXT records?
* Support custom user-provided templates for k8s names. A string provided
in the middleware configuration like `{service}.{namespace}.{type}` defines
the template of how to construct record names for the zone. This example
would produce `myservice.mynamespace.svc.cluster.local`. (Basic template
implemented. Need to slice zone out of current template implementation.)
* DNS Correctness
* Do we need to generate synthetic zone records for namespaces?
* Do we need to generate synthetic zone records for the skydns synthetic zones?
* Test cases
* ~~Implement test cases for http data parsing using dependency injection
for http get operations.~~
* Test with CoreDNS caching. CoreDNS caching for DNS response is working
using the `cache` directive. Tested working using 20s cache timeout
and A-record queries. Automate testing with cache in place.
* Automate CoreDNS performance tests. Initially for zone files, and for
pre-loaded k8s API cache.
* Automate integration testing with kubernetes.