[receiver/influxdbreceiver] Add the /ping endpoint for enhanced compa…

…tibility (#29662)

**Description:** This PR supplements the receiver `influxdbreceiver`
with an implementation of the `/ping`
[endpoint](https://docs.influxdata.com/influxdb/v2/api/#operation/GetPing).
Various third-party applications use this to check the availability of
the receiver before sending metrics, e.g. checkmk.

**Link to tracking Issue:** #29594

**Testing:** Basic tests and end to end testing with the third party
application
[checkmk](https://docs.checkmk.com/latest/en/metrics_exporter.html).

**Documentation:** No additional documentation has been added.
- The user does not interact directly with this endpoint.
- There are no configuration options.

.chloggen/influxdbreceiver-add_ping_endpoint.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# 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: receiver/influxdbreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Endpoint `/ping` added to enhance compatibility with third party products"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [29594]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

receiver/influxdbreceiver/receiver.go

@@ -73,6 +73,7 @@ func (r *metricsReceiver) Start(_ context.Context, host component.Host) error {
 	router := http.NewServeMux()
 	router.HandleFunc("/write", r.handleWrite)        // InfluxDB 1.x
 	router.HandleFunc("/api/v2/write", r.handleWrite) // InfluxDB 2.x
+	router.HandleFunc("/ping", r.handlePing)
 
 	r.wg.Add(1)
 	r.server, err = r.httpServerSettings.ToServer(host, r.settings, router)
@@ -201,3 +202,7 @@ func (r *metricsReceiver) handleWrite(w http.ResponseWriter, req *http.Request)
 
 	w.WriteHeader(http.StatusNoContent)
 }
+
+func (r *metricsReceiver) handlePing(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusNoContent)
+}