feat(charts): make honorTimestamps configurable for PodMonitors (#15080)

**Why is this PR necessary?**
In clusters with frequent pod restarts, Prometheus may drop scrapes
due to duplicate timestamps reported by the exporter. Allowing
honorTimestamps to be disabled lets Prometheus use scrape time
instead, preventing those drops.

**What does it do?**
Adds an optional honorTimestamps field to the controller, proxy and
serviceMirror PodMonitors in the linkerd-control-plane chart. The
field is rendered only when set, preserving backward compatibility.

**References:**
N/A

**Notes:**
N/A

Signed-off-by: bezarsnba <bezarsnba@gmail.com>

Author: bezarsnba

charts/linkerd-control-plane/templates/podmonitor.yaml

@@ -22,6 +22,9 @@ spec:
   podMetricsEndpoints:
     - interval: {{ $podMonitor.scrapeInterval }}
       scrapeTimeout: {{ $podMonitor.scrapeTimeout }}
+      {{- if not (kindIs "invalid" $podMonitor.controller.honorTimestamps) }}
+      honorTimestamps: {{ $podMonitor.controller.honorTimestamps }}
+      {{- end }}
       relabelings:
         - sourceLabels:
             - __meta_kubernetes_pod_container_port_name
@@ -60,6 +63,9 @@ spec:
   podMetricsEndpoints:
     - interval: {{ $podMonitor.scrapeInterval }}
       scrapeTimeout: {{ $podMonitor.scrapeTimeout }}
+      {{- if not (kindIs "invalid" $podMonitor.serviceMirror.honorTimestamps) }}
+      honorTimestamps: {{ $podMonitor.serviceMirror.honorTimestamps }}
+      {{- end }}
       relabelings:
         - sourceLabels:
             - __meta_kubernetes_pod_label_linkerd_io_control_plane_component
@@ -99,6 +105,9 @@ spec:
   podMetricsEndpoints:
     - interval: {{ $podMonitor.scrapeInterval }}
       scrapeTimeout: {{ $podMonitor.scrapeTimeout }}
+      {{- if not (kindIs "invalid" $podMonitor.proxy.honorTimestamps) }}
+      honorTimestamps: {{ $podMonitor.proxy.honorTimestamps }}
+      {{- end }}
       relabelings:
         - sourceLabels:
             - __meta_kubernetes_pod_container_name

charts/linkerd-control-plane/values.yaml

@@ -722,12 +722,22 @@ podMonitor:
       matchNames:
         - {{ .Release.Namespace }}
         - linkerd-viz
+    # -- Sets honorTimestamps for the control-plane PodMonitor endpoint. When set to false
+    # Prometheus uses scrape time instead of exporter-provided timestamps.
+    honorTimestamps: false
   serviceMirror:
     # -- Enables the creation of PodMonitor for the Service Mirror component
     enabled: true
+    # -- Sets honorTimestamps for the Service Mirror PodMonitor endpoint. When set to false,
+    # Prometheus uses scrape time instead of exporter-provided timestamps.
+    honorTimestamps: false
   proxy:
     # -- Enables the creation of PodMonitor for the data-plane
     enabled: true
+    # -- Sets honorTimestamps for the proxy PodMonitor endpoint. When set to false,
+    # Prometheus uses scrape time instead of exporter-provided timestamps,
+    # preventing duplicate timestamp drops in clusters with frequent pod restarts.
+    honorTimestamps: false
 
 
 # Egress related configuration