fix(tracing): Add more guards and fallback to control plane tracing config (#14650)

This adds more guards to the control plane tracing values. Additionally, this adds a fallback to re-use the proxy tracing endpoint if control plane tracing is enabled without an endpoint set.

Signed-off-by: Scott Fleener <[email protected]>

Author: sfleen

charts/linkerd-control-plane/values.yaml

@@ -52,7 +52,9 @@ controller:
     # -- Enables trace collection and export in the proxy
     enabled: false
     collector:
-      # -- The collector endpoint to send traces to. Required if tracing is enabled
+      # -- The collector endpoint to send traces to. Required if tracing is
+      # enabled. If this is unset and `proxy.tracing.collector.endpoint` is set,
+      # that endpoint will be re-used here.
       endpoint: ""
 # -- enabling this omits the NET_ADMIN capability in the PSP
 # and the proxy-init container when injecting the proxy;

charts/partials/templates/_trace.tpl

@@ -1,8 +1,11 @@
 {{ define "partials.linkerd.trace" -}}
 {{ if ((.Values.controller.tracing).enabled) -}}
-{{- if empty .Values.controller.tracing.collector.endpoint }}
-{{- fail "controller.tracing.collector.endpoint must be set if control plane tracing is enabled" }}
-{{- end }}
+{{- if (.Values.controller.tracing.collector).endpoint }}
 - -trace-collector={{.Values.controller.tracing.collector.endpoint}}
+{{- else if ((.Values.proxy.tracing).collector).endpoint }}
+- -trace-collector={{.Values.proxy.tracing.collector.endpoint}}
+{{- else }}
+{{- fail "controller.tracing.collector.endpoint or proxy.tracing.collector.endpoint must be set if control plane tracing is enabled" }}
+{{- end }}
 {{ end -}}
 {{- end }}