Append, rather than set, '/pods' to the path in discovery.kubelet (#6013

)

* Append, rather than set, '/pods' to the path in discovery.kubelet

---------

Signed-off-by: Pete Wall <[email protected]>
Co-authored-by: Paulin Todev <[email protected]>

CHANGELOG.md

@@ -101,6 +101,8 @@ v0.39.0-rc.0 (2024-01-05)
 - `discovery.lightsail` now supports additional parameters for configuring HTTP client settings. (@ptodev)
 - Add `sample_age_limit` to remote_write config to drop samples older than a specified duration. (@marctc)
 
+- Handle paths in the Kubelet URL for `discovery.kubelet`. (@petewall)
+
 ### Bugfixes
 
 - Update `pyroscope.ebpf` to fix a logical bug causing to profile to many kthreads instead of regular processes https://github.com/grafana/pyroscope/pull/2778 (@korniltsev)

component/discovery/kubelet/kubelet.go

@@ -129,11 +129,10 @@ func NewKubeletDiscovery(args Arguments) (*Discovery, error) {
 		Transport: transport,
 		Timeout:   30 * time.Second,
 	}
-	// ensure the path is the kubelet pods endpoint
-	args.URL.Path = "/pods"
+	// Append the path to the kubelet pods endpoint
 	return &Discovery{
 		client:           client,
-		url:              args.URL.String(),
+		url:              args.URL.String() + "/pods",
 		targetNamespaces: args.Namespaces,
 	}, nil
 }

component/discovery/kubelet/kubelet_test.go

@@ -1,12 +1,14 @@
 package kubelet
 
 import (
+	"net/url"
 	"testing"
 
 	"github.com/prometheus/prometheus/discovery/targetgroup"
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
+	"github.com/grafana/agent/component/common/config"
 	"github.com/grafana/river"
 	"github.com/stretchr/testify/require"
 )
@@ -105,3 +107,20 @@ func TestDiscoveryPodWithoutPod(t *testing.T) {
 	require.NoError(t, err)
 	require.Len(t, kubeletDiscovery.discoveredPodSources, 2)
 }
+
+func TestWithDefaultKubeletHost(t *testing.T) {
+	kubeletDiscovery, err := NewKubeletDiscovery(DefaultConfig)
+	require.NoError(t, err)
+	require.Equal(t, "https://localhost:10250/pods", kubeletDiscovery.url)
+}
+
+func TestWithCustomPath(t *testing.T) {
+	kubeletProxyUrl, _ := url.Parse("https://kubernetes.default.svc.cluster.local:443/api/v1/nodes/cluster-node-1/proxy")
+	kubeletDiscovery, err := NewKubeletDiscovery(Arguments{
+		URL: config.URL{
+			URL: kubeletProxyUrl,
+		},
+	})
+	require.NoError(t, err)
+	require.Equal(t, "https://kubernetes.default.svc.cluster.local:443/api/v1/nodes/cluster-node-1/proxy/pods", kubeletDiscovery.url)
+}

docs/sources/flow/reference/components/discovery.kubelet.md

@@ -35,7 +35,7 @@ The following arguments are supported:
 
 Name | Type | Description | Default | Required
 ---- | ---- | ----------- | ------- | --------
-`url` | `string` | URL of the Kubelet server. | | no
+`url` | `string` | URL of the Kubelet server. | "https://localhost:10250" | no
 `bearer_token` | `secret` | Bearer token to authenticate with. | | no
 `bearer_token_file` | `string` | File containing a bearer token to authenticate with. | | no
 `refresh_interval` | `duration` | How often the Kubelet should be polled for scrape targets | `5s` | no
@@ -49,6 +49,10 @@ One of the following authentication methods must be provided if kubelet authenti
 The `namespaces` list limits the namespaces to discover resources in. If
 omitted, all namespaces are searched.
 
+`discovery.kubelet` appends a `/pods` path to `url` to request the available pods.
+You can have additional paths in the `url`.
+For example, if `url` is `https://kubernetes.default.svc.cluster.local:443/api/v1/nodes/cluster-node-1/proxy`, then `discovery.kubelet` sends a request on `https://kubernetes.default.svc.cluster.local:443/api/v1/nodes/cluster-node-1/proxy/pods`
+
 ## Blocks
 
 The following blocks are supported inside the definition of