From cc5662f1e83bfc4b3119e87210024eb92d543c9b Mon Sep 17 00:00:00 2001
From: Fabian Reinartz <fab.reinartz@gmail.com>
Date: Tue, 6 Oct 2015 21:07:16 +0200
Subject: [PATCH] Integrate alert provider with notify persistence

---
 provider/mem.go |  3 ++-
 provider/sql.go | 52 ++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/provider/mem.go b/provider/mem.go
index e90f30c2..dd0dfd34 100644
--- a/provider/mem.go
+++ b/provider/mem.go
@@ -42,13 +42,14 @@ func NewMemData() *MemData {
 type memAlertIterator struct {
 	ch   <-chan *types.Alert
 	done chan struct{}
+	err  error
 }
 
 func (ai memAlertIterator) Next() <-chan *types.Alert {
 	return ai.ch
 }
 
-func (ai memAlertIterator) Err() error { return nil }
+func (ai memAlertIterator) Err() error { return ai.err }
 func (ai memAlertIterator) Close()     { close(ai.done) }
 
 // MemAlerts implements an Alerts provider based on in-memory data.
diff --git a/provider/sql.go b/provider/sql.go
index f820527c..9535ef25 100644
--- a/provider/sql.go
+++ b/provider/sql.go
@@ -176,9 +176,6 @@ func (a *SQLAlerts) Subscribe() AlertIterator {
 		done = make(chan struct{})
 	)
 	alerts, err := a.getPending()
-	if err != nil {
-		panic(err)
-	}
 
 	i := a.next
 	a.next++
@@ -207,17 +204,45 @@ func (a *SQLAlerts) Subscribe() AlertIterator {
 	return memAlertIterator{
 		ch:   ch,
 		done: done,
+		err:  err,
 	}
 }
 
 func (a *SQLAlerts) GetPending() AlertIterator {
-	return nil
+	var (
+		ch   = make(chan *types.Alert, 200)
+		done = make(chan struct{})
+	)
+
+	alerts, err := a.getPending()
+
+	go func() {
+		defer close(ch)
+
+		for _, a := range alerts {
+			select {
+			case ch <- a:
+			case <-done:
+				return
+			}
+		}
+	}()
+
+	return memAlertIterator{
+		ch:   ch,
+		done: done,
+		err:  err,
+	}
 }
 
 func (a *SQLAlerts) getPending() ([]*types.Alert, error) {
 	rows, err := a.db.Query(`
-		SELECT labels, annotations, starts_at, ends_at, updated_at, timeout
-		FROM alerts
+		SELECT a.labels, a.annotations, a.starts_at, a.ends_at, a.updated_at, a.timeout
+		FROM 
+			alerts AS a LEFT OUTER JOIN notify_info AS n
+			ON a.fingerprint == n.fingerprint
+		WHERE
+			NOT (n.delivered AND n.resolved)
 	`)
 	if err != nil {
 		return nil, err
@@ -267,6 +292,13 @@ func (a *SQLAlerts) Put(alerts ...*types.Alert) error {
 		return err
 	}
 
+	// The insert invariant requires that there are no two alerts with the same
+	// fingerprint that have overlapping activity range ([StartsAt:EndsAt]).
+	// Such alerts are merged into a single one with the union of both intervals
+	// as its new activity interval.
+	// The exact merge procedure is defined on the Alert structure. Here, we just
+	// care about finding intersecting alerts for each new inserts, deleting them
+	// if existant, and insert the new alert we retrieved by merging.
 	overlap, err := tx.Prepare(`
 		SELECT id(), annotations, starts_at, ends_at, updated_at, timeout FROM alerts
 		WHERE fingerprint = $1 AND $2 =< ends_at OR $3 >= starts_at
@@ -299,7 +331,7 @@ func (a *SQLAlerts) Put(alerts ...*types.Alert) error {
 	for _, alert := range alerts {
 		fp := alert.Fingerprint()
 
-		// Retrieve all overlapping alerts and delete them.
+		// Retrieve all intersecting alerts and delete them.
 		olaps, err := overlap.Query(fp, alert.StartsAt, alert.EndsAt)
 		if err != nil {
 			tx.Rollback()
@@ -377,6 +409,12 @@ func (a *SQLAlerts) Put(alerts ...*types.Alert) error {
 			tx.Rollback()
 			return err
 		}
+
+		a.mtx.RLock()
+		for _, ch := range a.listeners {
+			ch <- alert
+		}
+		a.mtx.RUnlock()
 	}
 
 	tx.Commit()