From 91efd86f2e4762bf26b97bf7f803df591e7a6ac7 Mon Sep 17 00:00:00 2001
From: Tom Wilkie <tom@weave.works>
Date: Tue, 8 Sep 2015 18:16:03 +0000
Subject: [PATCH] Only fetch weave status report once per tick.

---
 probe/main.go           |  9 +++++++--
 probe/overlay/weave.go  | 39 ++++++++++++++++++---------------------
 probe/process/walker.go |  2 +-
 probe/tag_report.go     |  6 ++++++
 4 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/probe/main.go b/probe/main.go
index e256905936..c4016bbcf2 100644
--- a/probe/main.go
+++ b/probe/main.go
@@ -114,6 +114,7 @@ func main() {
 	var (
 		endpointReporter = endpoint.NewReporter(hostID, hostName, *spyProcs, *useConntrack)
 		processCache     = process.NewCachingWalker(process.NewWalker(*procRoot))
+		tickers          = []Ticker{processCache}
 		reporters        = []Reporter{
 			endpointReporter,
 			host.NewReporter(hostID, hostName, localNets),
@@ -143,6 +144,7 @@ func main() {
 		if err != nil {
 			log.Fatalf("failed to start Weave tagger: %v", err)
 		}
+		tickers = append(tickers, weave)
 		taggers = append(taggers, weave)
 		reporters = append(reporters, weave)
 	}
@@ -188,8 +190,11 @@ func main() {
 
 			case <-spyTick:
 				start := time.Now()
-				if err := processCache.Update(); err != nil {
-					log.Printf("error reading processes: %v", err)
+
+				for _, ticker := range tickers {
+					if err := ticker.Tick(); err != nil {
+						log.Printf("error doing ticker: %v", err)
+					}
 				}
 
 				r = r.Merge(doReport(reporters))
diff --git a/probe/overlay/weave.go b/probe/overlay/weave.go
index b9699cdd33..ea605bf25d 100644
--- a/probe/overlay/weave.go
+++ b/probe/overlay/weave.go
@@ -43,6 +43,7 @@ var ipMatch = regexp.MustCompile(`([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3
 type Weave struct {
 	url    string
 	hostID string
+	status weaveStatus
 }
 
 type weaveStatus struct {
@@ -75,24 +76,30 @@ func NewWeave(hostID, weaveRouterAddress string) (*Weave, error) {
 	}, nil
 }
 
-func (w Weave) update() (weaveStatus, error) {
+// Tick implements Ticker
+func (w *Weave) Tick() error {
 	var result weaveStatus
 	req, err := http.NewRequest("GET", w.url, nil)
 	if err != nil {
-		return result, err
+		return err
 	}
 	req.Header.Add("Accept", "application/json")
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		return result, err
+		return err
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
-		return result, fmt.Errorf("Weave Tagger: got %d", resp.StatusCode)
+		return fmt.Errorf("Weave Tagger: got %d", resp.StatusCode)
+	}
+
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return err
 	}
 
-	return result, json.NewDecoder(resp.Body).Decode(&result)
+	w.status = result
+	return nil
 }
 
 type psEntry struct {
@@ -101,7 +108,7 @@ type psEntry struct {
 	ips               []string
 }
 
-func (w Weave) ps() ([]psEntry, error) {
+func (w *Weave) ps() ([]psEntry, error) {
 	var result []psEntry
 	cmd := exec.Command("weave", "--local", "ps")
 	out, err := cmd.StdoutPipe()
@@ -132,7 +139,7 @@ func (w Weave) ps() ([]psEntry, error) {
 	return result, scanner.Err()
 }
 
-func (w Weave) tagContainer(r report.Report, containerIDPrefix, macAddress string, ips []string) {
+func (w *Weave) tagContainer(r report.Report, containerIDPrefix, macAddress string, ips []string) {
 	for nodeid, nmd := range r.Container.Nodes {
 		idPrefix := nmd.Metadata[docker.ContainerID][:12]
 		if idPrefix != containerIDPrefix {
@@ -149,13 +156,8 @@ func (w Weave) tagContainer(r report.Report, containerIDPrefix, macAddress strin
 }
 
 // Tag implements Tagger.
-func (w Weave) Tag(r report.Report) (report.Report, error) {
-	status, err := w.update()
-	if err != nil {
-		return r, nil
-	}
-
-	for _, entry := range status.DNS.Entries {
+func (w *Weave) Tag(r report.Report) (report.Report, error) {
+	for _, entry := range w.status.DNS.Entries {
 		if entry.Tombstone > 0 {
 			continue
 		}
@@ -181,14 +183,9 @@ func (w Weave) Tag(r report.Report) (report.Report, error) {
 }
 
 // Report implements Reporter.
-func (w Weave) Report() (report.Report, error) {
+func (w *Weave) Report() (report.Report, error) {
 	r := report.MakeReport()
-	status, err := w.update()
-	if err != nil {
-		return r, err
-	}
-
-	for _, peer := range status.Router.Peers {
+	for _, peer := range w.status.Router.Peers {
 		r.Overlay.Nodes[report.MakeOverlayNodeID(peer.Name)] = report.MakeNodeWith(map[string]string{
 			WeavePeerName:     peer.Name,
 			WeavePeerNickName: peer.NickName,
diff --git a/probe/process/walker.go b/probe/process/walker.go
index 4a88c45cd9..1f89a610b5 100644
--- a/probe/process/walker.go
+++ b/probe/process/walker.go
@@ -40,7 +40,7 @@ func (c *CachingWalker) Walk(f func(Process)) error {
 }
 
 // Update updates cached copy of process list
-func (c *CachingWalker) Update() error {
+func (c *CachingWalker) Tick() error {
 	newCache := []Process{}
 	err := c.source.Walk(func(p Process) {
 		newCache = append(newCache, p)
diff --git a/probe/tag_report.go b/probe/tag_report.go
index 15024d77ae..b220e65800 100644
--- a/probe/tag_report.go
+++ b/probe/tag_report.go
@@ -16,6 +16,12 @@ type Reporter interface {
 	Report() (report.Report, error)
 }
 
+// Ticker 'ticks' every spyDuration - useful for updating
+// cached state shared between Taggers and Reporters
+type Ticker interface {
+	Tick() error
+}
+
 // Apply tags the report with all the taggers.
 func Apply(r report.Report, taggers []Tagger) report.Report {
 	var err error