feat: run HTTP server standalone without Kubernetes

Extract /healthz, /conditions and /debug/pprof into a new httpexporter
package so those endpoints are available when --enable-k8s-exporter=false.
Previously the HTTP server was started only inside the k8s exporter, making
it unavailable in non-Kubernetes environments. The new httpexporter tracks
conditions in-memory via ExportProblems and starts on --port regardless of
whether the Kubernetes API server is reachable.

Signed-off-by: Tobias Giese <tgiese@nvidia.com>

Author: tobiasgiese

README.md

@@ -75,6 +75,7 @@ certain backends. Some of them can be disabled at compile-time using a build tag
 |----------|:-----------|:--------------------|
 | Kubernetes exporter | Kubernetes exporter reports node problems to Kubernetes API server: temporary problems get reported as Events, and permanent problems get reported as Node Conditions. |
 | Prometheus exporter | Prometheus exporter reports node problems and metrics locally as Prometheus metrics |
+| HTTP exporter | HTTP exporter serves the local `/healthz`, `/conditions` and `/debug/pprof` endpoints. It keeps node conditions in memory and does not require a Kubernetes API server, so it also works when `--enable-k8s-exporter` is `false`. |
 | [Stackdriver exporter](https://github.com/kubernetes/node-problem-detector/blob/master/config/exporter/stackdriver-exporter.json) | Stackdriver exporter reports node problems and metrics to Stackdriver Monitoring API. | disable_stackdriver_exporter
 
 # Usage
@@ -122,8 +123,14 @@ For example, to run without auth, use the following config:
    http://APISERVER_IP:APISERVER_PORT?inClusterConfig=false
    ```
    Refer to [heapster docs](https://github.com/kubernetes/heapster/blob/master/docs/source-configuration.md#kubernetes) for a complete list of available options.
-* `--address`: The address to bind the node problem detector server.
-* `--port`: The port to bind the node problem detector server. Use 0 to disable.
+
+#### For HTTP exporter
+
+The HTTP exporter serves `/healthz`, `/conditions` and `/debug/pprof`. It does not talk to the
+Kubernetes API server, so these endpoints are available even when `--enable-k8s-exporter` is `false`.
+
+* `--address`: The address to bind the node problem detector server, default to `127.0.0.1`.
+* `--port`: The port to bind the node problem detector server, default to 20256. Use 0 to disable.
 
 #### For Prometheus exporter
 

cmd/nodeproblemdetector/node_problem_detector.go

@@ -25,6 +25,7 @@ import (
 	_ "k8s.io/node-problem-detector/cmd/nodeproblemdetector/problemdaemonplugins"
 	"k8s.io/node-problem-detector/cmd/options"
 	"k8s.io/node-problem-detector/pkg/exporters"
+	"k8s.io/node-problem-detector/pkg/exporters/httpexporter"
 	"k8s.io/node-problem-detector/pkg/exporters/k8sexporter"
 	"k8s.io/node-problem-detector/pkg/exporters/prometheusexporter"
 	"k8s.io/node-problem-detector/pkg/problemdaemon"
@@ -51,6 +52,10 @@ func npdMain(ctx context.Context, npdo *options.NodeProblemDetectorOptions) erro
 
 	// Initialize exporters.
 	defaultExporters := []types.Exporter{}
+	if he := httpexporter.NewExporterOrDie(npdo); he != nil {
+		defaultExporters = append(defaultExporters, he)
+		klog.Info("HTTP exporter started.")
+	}
 	if ke := k8sexporter.NewExporterOrDie(ctx, npdo); ke != nil {
 		defaultExporters = append(defaultExporters, ke)
 		klog.Info("K8s exporter started.")

pkg/exporters/httpexporter/http_exporter.go

@@ -0,0 +1,104 @@
+/*
+Copyright 2026 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package httpexporter
+
+import (
+	"net"
+	"net/http"
+	"net/http/pprof"
+	"strconv"
+	"sync"
+
+	"k8s.io/klog/v2"
+
+	"k8s.io/node-problem-detector/cmd/options"
+	"k8s.io/node-problem-detector/pkg/types"
+	"k8s.io/node-problem-detector/pkg/util"
+)
+
+type httpExporter struct {
+	mu         sync.RWMutex
+	conditions map[string]types.Condition
+}
+
+// NewExporterOrDie creates the standalone HTTP exporter and starts the server.
+// Returns nil if --port is 0 (disabled). Panics on bind errors.
+func NewExporterOrDie(npdo *options.NodeProblemDetectorOptions) types.Exporter {
+	if npdo.ServerPort <= 0 {
+		return nil
+	}
+
+	he := &httpExporter{
+		conditions: make(map[string]types.Condition),
+	}
+
+	addr := net.JoinHostPort(npdo.ServerAddress, strconv.Itoa(npdo.ServerPort))
+	mux := he.buildMux()
+	go func() {
+		if err := http.ListenAndServe(addr, mux); err != nil {
+			klog.Fatalf("Failed to start HTTP server: %v", err)
+		}
+	}()
+
+	klog.Infof("HTTP exporter started on %s", addr)
+	return he
+}
+
+func (he *httpExporter) buildMux() *http.ServeMux {
+	mux := http.NewServeMux()
+
+	// Add healthz http request handler. Always return ok now, add more health check
+	// logic in the future.
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		if _, err := w.Write([]byte("ok")); err != nil {
+			klog.Errorf("Failed to write response: %v", err)
+		}
+	})
+
+	// Add the handler to serve condition http request.
+	mux.HandleFunc("/conditions", func(w http.ResponseWriter, r *http.Request) {
+		util.ReturnHTTPJson(w, he.getConditions())
+	})
+
+	// register pprof
+	mux.HandleFunc("/debug/pprof/", pprof.Index)
+	mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+	mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+	mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+	mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+
+	return mux
+}
+
+func (he *httpExporter) ExportProblems(status *types.Status) {
+	he.mu.Lock()
+	defer he.mu.Unlock()
+	for _, cdt := range status.Conditions {
+		he.conditions[cdt.Type] = cdt
+	}
+}
+
+func (he *httpExporter) getConditions() []types.Condition {
+	he.mu.RLock()
+	defer he.mu.RUnlock()
+	conditions := make([]types.Condition, 0, len(he.conditions))
+	for _, c := range he.conditions {
+		conditions = append(conditions, c)
+	}
+	return conditions
+}