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

middleware/kubernetes/util/util.go

@@ -0,0 +1,12 @@
+// Package kubernetes/util provides helper functions for the kubernetes middleware
+package util
+
+// StringInSlice check whether string a is a member of slice.
+func StringInSlice(a string, slice []string) bool {
+	for _, b := range slice {
+		if b == a {
+			return true
+		}
+	}
+	return false
+}

middleware/kubernetes/util/util_test.go

@@ -0,0 +1,33 @@
+package util
+
+import (
+	"testing"
+)
+
+type InSliceData struct {
+	Slice   []string
+	String  string
+	InSlice bool
+}
+
+// Test data for TestStringInSlice cases.
+var testdataInSlice = []struct {
+	Slice          []string
+	String         string
+	ExpectedResult bool
+}{
+	{[]string{"a", "b", "c"}, "a", true},
+	{[]string{"a", "b", "c"}, "d", false},
+	{[]string{"a", "b", "c"}, "", false},
+	{[]string{}, "a", false},
+	{[]string{}, "", false},
+}
+
+func TestStringInSlice(t *testing.T) {
+	for _, example := range testdataInSlice {
+		actualResult := StringInSlice(example.String, example.Slice)
+		if actualResult != example.ExpectedResult {
+			t.Errorf("Expected stringInSlice result '%v' for example string='%v', slice='%v'. Instead got result '%v'.", example.ExpectedResult, example.String, example.Slice, actualResult)
+		}
+	}
+}