From 47ef1e02b3fd4c6cdb7ca383c1424a0c051f3573 Mon Sep 17 00:00:00 2001
From: Tom Wilkie <tom.wilkie@gmail.com>
Date: Tue, 10 Nov 2015 11:16:06 +0000
Subject: [PATCH] Shortcut app -> UI ws push for certain reports.

---
 app/api_topology.go       |  7 ++++++-
 app/collector.go          | 38 ++++++++++++++++++++++++++++++++++++++
 app/mock_reporter_test.go |  5 +++--
 probe/docker/reporter.go  |  1 +
 report/report.go          |  4 ++++
 5 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/app/api_topology.go b/app/api_topology.go
index 315f7ce8e4..00d86c85ab 100644
--- a/app/api_topology.go
+++ b/app/api_topology.go
@@ -114,7 +114,11 @@ func handleWebsocket(
 	var (
 		previousTopo render.RenderableNodes
 		tick         = time.Tick(loop)
+		wait         = make(chan struct{}, 1)
 	)
+	rep.WaitOn(wait)
+	defer rep.UnWait(wait)
+
 	for {
 		newTopo := renderer.Render(rep.Report()).Prune()
 		diff := render.TopoDiff(previousTopo, newTopo)
@@ -128,9 +132,10 @@ func handleWebsocket(
 		}
 
 		select {
+		case <-wait:
+		case <-tick:
 		case <-quit:
 			return
-		case <-tick:
 		}
 	}
 }
diff --git a/app/collector.go b/app/collector.go
index d97846ab26..394043c523 100644
--- a/app/collector.go
+++ b/app/collector.go
@@ -11,6 +11,8 @@ import (
 // interface for parts of the app, and several experimental components.
 type Reporter interface {
 	Report() report.Report
+	WaitOn(chan struct{})
+	UnWait(chan struct{})
 }
 
 // Adder is something that can accept reports. It's a convenient interface for
@@ -25,12 +27,45 @@ type Collector struct {
 	mtx     sync.Mutex
 	reports []timestampReport
 	window  time.Duration
+	waitableCondition
+}
+
+type waitableCondition struct {
+	sync.Mutex
+	waiters map[chan struct{}]struct{}
+}
+
+func (wc *waitableCondition) WaitOn(waiter chan struct{}) {
+	wc.Lock()
+	wc.waiters[waiter] = struct{}{}
+	wc.Unlock()
+}
+
+func (wc *waitableCondition) UnWait(waiter chan struct{}) {
+	wc.Lock()
+	delete(wc.waiters, waiter)
+	wc.Unlock()
+}
+
+func (wc *waitableCondition) Broadcast() {
+	wc.Lock()
+	for waiter := range wc.waiters {
+		// Non-block write to channel
+		select {
+		case waiter <- struct{}{}:
+		default:
+		}
+	}
+	wc.Unlock()
 }
 
 // NewCollector returns a collector ready for use.
 func NewCollector(window time.Duration) *Collector {
 	return &Collector{
 		window: window,
+		waitableCondition: waitableCondition{
+			waiters: map[chan struct{}]struct{}{},
+		},
 	}
 }
 
@@ -42,6 +77,9 @@ func (c *Collector) Add(rpt report.Report) {
 	defer c.mtx.Unlock()
 	c.reports = append(c.reports, timestampReport{now(), rpt})
 	c.reports = clean(c.reports, c.window)
+	if rpt.Shortcut {
+		c.Broadcast()
+	}
 }
 
 // Report returns a merged report over all added reports. It implements
diff --git a/app/mock_reporter_test.go b/app/mock_reporter_test.go
index 99439e9a0d..9e27941c19 100644
--- a/app/mock_reporter_test.go
+++ b/app/mock_reporter_test.go
@@ -9,5 +9,6 @@ import (
 type StaticReport struct{}
 
 func (s StaticReport) Report() report.Report { return fixture.Report }
-
-func (s StaticReport) Add(report.Report) {}
+func (s StaticReport) Add(report.Report)     {}
+func (s StaticReport) WaitOn(chan struct{})  {}
+func (s StaticReport) UnWait(chan struct{})  {}
diff --git a/probe/docker/reporter.go b/probe/docker/reporter.go
index a2c10c19e6..afd8e565a0 100644
--- a/probe/docker/reporter.go
+++ b/probe/docker/reporter.go
@@ -42,6 +42,7 @@ func (r *Reporter) ContainerUpdated(c Container) {
 
 	// Publish a 'short cut' report container just this container
 	rpt := report.MakeReport()
+	rpt.Shortcut = true
 	rpt.Container.AddNode(report.MakeContainerNodeID(r.hostID, c.ID()), c.GetNode(r.hostID, localAddrs))
 	r.probe.Publish(rpt)
 }
diff --git a/report/report.go b/report/report.go
index aca0ad2fde..88876ea6d8 100644
--- a/report/report.go
+++ b/report/report.go
@@ -63,6 +63,10 @@ type Report struct {
 	// such as in the app, we expect the component to overwrite the window
 	// before serving it to consumers.
 	Window time.Duration
+
+	// Shortcut reports should be propogated to the UI as quickly as possible,
+	// bypassing the usual spy interval, publish interval and app ws interval.
+	Shortcut bool
 }
 
 // MakeReport makes a clean report, ready to Merge() other reports into.