[exporter/loadbalancingexporter] support k8s service resolver (#22776)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Add k8s service resolver for exporter/loadbalancingexporter

The exporter/loadbalancingexporter component currently supports both
static and dns resolvers, and does not currently support the ability to
load balance pods when the collector application is running in a
kubernetes environment. (Backends address discovery is achieved by
monitoring kubernetes endpoints resources). This pr provides that
capability.


**Link to tracking Issue:** <Issue number if applicable>
suitable for scenarios where services are located in a k8s cluster
#18412

**Testing:** <Describe what testing was performed and which tests were
added.>

**Documentation:** <Describe the documentation added.>

Signed-off-by: Yuan Fang <[email protected]>

.chloggen/add-k8s-resolver-to-loadbalancing-exporter.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: loadbalancingexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Added kubernetes service resolver to loadbalancingexporter.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [22776]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

cmd/configschema/go.mod

@@ -680,6 +680,7 @@ require (
 	k8s.io/kube-openapi v0.0.0-20230501164219-8b0f38b5fd1f // indirect
 	k8s.io/kubelet v0.27.3 // indirect
 	k8s.io/utils v0.0.0-20230308161112-d77c459e9343 // indirect
+	sigs.k8s.io/controller-runtime v0.15.0 // indirect
 	sigs.k8s.io/json v0.0.0-20221116044647-bc3834ca7abd // indirect
 	sigs.k8s.io/structured-merge-diff/v4 v4.2.3 // indirect
 	sigs.k8s.io/yaml v1.3.0 // indirect

cmd/otelcontribcol/go.mod

@@ -689,6 +689,7 @@ require (
 	k8s.io/kube-openapi v0.0.0-20230501164219-8b0f38b5fd1f // indirect
 	k8s.io/kubelet v0.27.3 // indirect
 	k8s.io/utils v0.0.0-20230308161112-d77c459e9343 // indirect
+	sigs.k8s.io/controller-runtime v0.15.0 // indirect
 	sigs.k8s.io/json v0.0.0-20221116044647-bc3834ca7abd // indirect
 	sigs.k8s.io/structured-merge-diff/v4 v4.2.3 // indirect
 	sigs.k8s.io/yaml v1.3.0 // indirect

exporter/loadbalancingexporter/README.md

@@ -39,13 +39,16 @@ This also supports service name based exporting for traces. If you have two or m
 Refer to [config.yaml](./testdata/config.yaml) for detailed examples on using the processor.
 
 * The `otlp` property configures the template used for building the OTLP exporter. Refer to the OTLP Exporter documentation for information on which options are available. Note that the `endpoint` property should not be set and will be overridden by this exporter with the backend endpoint.
-* The `resolver` accepts either a `static` node, or a `dns`. If both are specified, `dns` takes precedence.
+* The `resolver` accepts a `static` node, a `dns` or a `k8s` service. If all three are specified, `k8s` takes precedence.
 * The `hostname` property inside a `dns` node specifies the hostname to query in order to obtain the list of IP addresses.
 * The `dns` node also accepts the following optional properties:
   * `hostname` DNS hostname to resolve.
   * `port` port to be used for exporting the traces to the IP addresses resolved from `hostname`. If `port` is not specified, the default port 4317 is used.
   * `interval` resolver interval in go-Duration format, e.g. `5s`, `1d`, `30m`. If not specified, `5s` will be used.
   * `timeout` resolver timeout in go-Duration format, e.g. `5s`, `1d`, `30m`. If not specified, `1s` will be used.
+* The `k8s` node accepts the following optional properties:
+  * `service` Kubernetes service to resolve, e.g. `lb-svc.lb-ns`. If no namespace is specified, an attempt will be made to infer the namespace for this collector, and if this fails it will fall back to the `default` namespace.
+  * `ports` port to be used for exporting the traces to the addresses resolved from `service`. If `ports` is not specified, the default port 4317 is used. When multiple ports are specified, two backends are added to the load balancer as if they were at different pods.
 * The `routing_key` property is used to route spans to exporters based on different parameters. This functionality is currently enabled only for `trace` pipeline types. It supports one of the following values:
     * `service`: exports spans based on their service name. This is useful when using processors like the span metrics, so all spans for each service are sent to consistent collector instances for metric collection. Otherwise, metrics for the same services are sent to different collectors, making aggregations inaccurate. 
     * `traceID` (default): exports spans based on their `traceID`.
@@ -94,6 +97,49 @@ service:
         - loadbalancing
 ```
 
+Kubernetes resolver example
+```yaml
+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: localhost:4317
+
+processors:
+
+exporters:
+  logging:
+  loadbalancing:
+    routing_key: "service"
+    protocol:
+      otlp:
+        # all options from the OTLP exporter are supported
+        # except the endpoint
+        timeout: 1s
+    resolver:
+      # use k8s service resolver, if collector runs in kubernetes environment
+      k8s:
+        service: lb-svc.kube-public
+        ports:
+          - 15317
+          - 16317
+
+service:
+  pipelines:
+    traces:
+      receivers:
+        - otlp
+      processors: []
+      exporters:
+        - loadbalancing
+    logs:
+      receivers:
+        - otlp
+      processors: []
+      exporters:
+        - loadbalancing
+```
+
 For testing purposes, the following configuration can be used, where both the load balancer and all backends are running locally:
 ```yaml
 receivers:

exporter/loadbalancingexporter/config.go

@@ -32,6 +32,7 @@ type Protocol struct {
 type ResolverSettings struct {
 	Static *StaticResolver `mapstructure:"static"`
 	DNS    *DNSResolver    `mapstructure:"dns"`
+	K8sSvc *K8sSvcResolver `mapstructure:"k8s"`
 }
 
 // StaticResolver defines the configuration for the resolver providing a fixed list of backends
@@ -46,3 +47,9 @@ type DNSResolver struct {
 	Interval time.Duration `mapstructure:"interval"`
 	Timeout  time.Duration `mapstructure:"timeout"`
 }
+
+// K8sSvcResolver defines the configuration for the DNS resolver
+type K8sSvcResolver struct {
+	Service string  `mapstructure:"service"`
+	Ports   []int32 `mapstructure:"ports"`
+}