server/config: don't render ReadinessIndicatorFile to multus CNI config

For whatever reason calling os.Stat() on the readiness indicator file
from CmdAdd()/CmdDel() when multus is running in server mode and is
containerized often returns "file not found", which triggers the
polling behavior of GetReadinessIndicatorFile(). This greatly delays
CNI operations that should be pretty quick. Even if an exponential
backoff is used, os.Stat() can still return "file not found"
multiple times, even though the file clearly exists.

But it turns out we don't need to check the readiness file in server
mode when running with MultusConfigFile == "auto". In this mode the
server starts the ConfigManager which (a) waits until the file exists
and (b) fsnotify watches the readiness and (c) exits the daemon
immediately if the file is deleted or moved.

This means we can assume that while the daemon is running and the
server is handling CNI requests that the readiness file exists;
otherwise the daemon would have exited. Thus CmdAdd/CmdDel don't
need to run a lot of possibly failing os.Stat() calls in the CNI
hot paths.

Signed-off-by: Dan Williams <[email protected]>

pkg/server/config/generator.go

@@ -128,6 +128,9 @@ func (mc *MultusConf) Generate() (string, error) {
 	mc.MultusAutoconfigDir = ""
 	mc.MultusMasterCni = ""
 	mc.ForceCNIVersion = false
+	// Readiness indicator file existence is already handled by the
+	// ConfigManager via an fsnotify watch, so CmdAdd/CmdDel don't need to.
+	mc.ReadinessIndicatorFile = ""
 
 	data, err := json.Marshal(mc)
 	return string(data), err