[mirror] Don't fail when running experiments are missing mirror status

The `mirrorNet` function checks the status of other running experiments
to look for conflicts in the network being used for the mirror GRE
tunnels. Not every experiment will be using the mirror app, so don't
fail if the app status is missing.

Author: activeshadow

src/go/cmd/phenix-app-mirror/main.go

@@ -199,17 +199,10 @@ func preStart(exp *types.Experiment) error {
 
 	cluster := cluster(exp)
 
-	for _, host := range app.Hosts() {
-		cfg, ok := status.Mirrors[host.Hostname()]
-		if !ok {
-			continue
-		}
-
-		name := cfg.MirrorName
-
+	for _, cfg := range status.Mirrors {
 		// Ignoring errors here since in most cases all the mirrors would have
 		// already been removed when the previous experiment was stopped.
-		deleteMirror(name, amd.MirrorBridge, cluster)
+		deleteMirror(cfg.MirrorName, cfg.MirrorBridge, cluster)
 	}
 
 	// Ignoring errors here since in most cases all the taps would have already
@@ -252,7 +245,7 @@ func postStart(exp *types.Experiment) (ferr error) {
 
 		// clean up any mirrors already created for this mirror
 		for _, mirror := range status.Mirrors {
-			deleteMirror(mirror.MirrorName, amd.MirrorBridge, cluster)
+			deleteMirror(mirror.MirrorName, mirror.MirrorBridge, cluster)
 		}
 	}()
 
@@ -331,7 +324,7 @@ func postStart(exp *types.Experiment) (ferr error) {
 		// name).
 		name := util.RandomString(15)
 
-		cfg := MirrorConfig{MirrorName: name, IP: ip.String()}
+		cfg := MirrorConfig{MirrorName: name, MirrorBridge: amd.MirrorBridge, IP: ip.String()}
 
 		status.Mirrors[host.Hostname()] = cfg
 
@@ -440,17 +433,9 @@ func cleanup(exp *types.Experiment) error {
 		return fmt.Errorf("decoding app status: %w", err)
 	}
 
-	for _, host := range app.Hosts() {
-		cfg, ok := status.Mirrors[host.Hostname()]
-		if !ok {
-			log.Error("missing mirror config for %s in experiment status", host.Hostname())
-			continue
-		}
-
-		name := cfg.MirrorName
-
-		if err := deleteMirror(name, amd.MirrorBridge, cluster); err != nil {
-			log.Error("removing mirror %s from cluster: %v", name, err)
+	for _, cfg := range status.Mirrors {
+		if err := deleteMirror(cfg.MirrorName, cfg.MirrorBridge, cluster); err != nil {
+			log.Error("removing mirror %s from cluster: %v", cfg.MirrorName, err)
 		}
 	}
 
@@ -528,19 +513,22 @@ func mirrorNet(md *MirrorAppMetadataV1) (netaddr.IPPrefix, error) {
 
 	running, err := types.RunningExperiments()
 	if err != nil {
-		return netaddr.IPPrefix{}, fmt.Errorf("getting running experiments: %w", err)
+		// Log the error, but don't escalate it. Instead, just assume there's no
+		// other experiments running and let things (potentially) fail
+		// spectacularly.
+		log.Error("getting running experiments: %v", err)
+		return subnet, nil
 	}
 
 	var used []netaddr.IPPrefix
 
 	for _, exp := range running {
 		var status MirrorAppStatus
 
-		if err := exp.Status.ParseAppStatus("mirror", &status); err != nil {
-			return netaddr.IPPrefix{}, fmt.Errorf("parsing mirror app status for experiment %s: %w", exp.Metadata.Name, err)
+		// Not every experiment uses the mirror app, so don't worry about errors.
+		if err := exp.Status.ParseAppStatus("mirror", &status); err == nil {
+			used = append(used, netaddr.MustParseIPPrefix(status.Subnet))
 		}
-
-		used = append(used, netaddr.MustParseIPPrefix(status.Subnet))
 	}
 
 	subnet, err = putil.UnusedSubnet(subnet, used)

src/go/cmd/phenix-app-mirror/types.go

@@ -76,6 +76,7 @@ type MirrorAppStatus struct {
 }
 
 type MirrorConfig struct {
-	MirrorName string `structs:"mirrorName" mapstructure:"mirrorName"`
-	IP         string `structs:"ip" mapstructure:"ip"`
+	MirrorName   string `structs:"mirrorName" mapstructure:"mirrorName"`
+	MirrorBridge string `structs:"mirrorBridge" mapstructure:"mirrorBridge"`
+	IP           string `structs:"ip" mapstructure:"ip"`
 }