From 68538e93a26f15bd1795ae89a322672b6a3670a0 Mon Sep 17 00:00:00 2001
From: Denis Arh <denis.arh@kendu.si>
Date: Tue, 9 Apr 2019 08:56:05 +0200
Subject: [PATCH] Make db connect faster (remove initial delay) and more robust

---
 internal/db/connector.go | 74 +++++++++++++++++++++++++++++++++-------
 1 file changed, 61 insertions(+), 13 deletions(-)

diff --git a/internal/db/connector.go b/internal/db/connector.go
index a4b75022e..a7a796104 100644
--- a/internal/db/connector.go
+++ b/internal/db/connector.go
@@ -9,28 +9,72 @@ import (
 	"github.com/titpetric/factory"
 )
 
+const (
+	maxTries = 100
+	delay    = 5 * time.Second
+	timeout  = 1 * time.Minute
+)
+
 func TryToConnect(ctx context.Context, name, dsn, profiler string) (db *factory.DB, err error) {
 	factory.Database.Add(name, dsn)
-	var try = 0
 
-	timeout := time.After(time.Minute)
-	delay := 5 * time.Second
+	var (
+		connErrCh = make(chan error, 1)
+	)
 
-	for {
-		select {
-		case <-ctx.Done():
-			return nil, errors.New("cancelled")
-		case <-timeout:
-			return nil, errors.New("connection timeout")
-		case <-time.After(delay):
+	defer close(connErrCh)
+
+	log.Printf("Connecting to the DB (%q, %q)", name, dsn)
+
+	go func() {
+		var (
+			try = 0
+		)
+
+		for {
 			try++
+
+			if maxTries <= try {
+				err = errors.Errorf("could not connect to %q, in %d tries", name, try)
+				return
+			}
+
 			db, err = factory.Database.Get(name)
 			if err != nil {
-				log.Printf("Failed to connect, try %d, error: %v, retry in %.0fs", try, err, delay.Seconds())
-				continue
+				log.Printf(
+					"could not connect to %q, try %d, error: %v, retry in %.0fs",
+					name,
+					try,
+					err,
+					delay.Seconds(),
+				)
+
+				select {
+				case <-ctx.Done():
+					// Forced break
+					break
+				case <-time.After(delay):
+					// Wait before next try
+					continue
+				}
 			}
+
+			// Connected
+			break
+
 		}
+
+		connErrCh <- err
+	}()
+
+	select {
+	case err = <-connErrCh:
 		break
+	case <-time.After(timeout):
+		// Wait before next try
+		return nil, errors.Errorf("db init for %q timedout", name)
+	case <-ctx.Done():
+		return nil, errors.Errorf("db connection for %q cancelled", name)
 	}
 
 	// @todo: profiling as an external service?
@@ -41,5 +85,9 @@ func TryToConnect(ctx context.Context, name, dsn, profiler string) (db *factory.
 		log.Println("No database query profiler selected")
 	}
 
-	return
+	if err != nil {
+		return nil, err
+	}
+
+	return db, nil
 }