Rework the way database is open/re-open in aptly

Allow database to be initialized without opening, unify all the
open paths to retry on failure.

In API router make sure open requests are matched with acks in explicit
way.

This also enables re-open attempts in all the aptly commands, so it
should make running aptly CLI much easier now hopefully.

Fix up system tests for oldoldstable ;)

api/api.go

@@ -23,11 +23,18 @@ func apiVersion(c *gin.Context) {
 	c.JSON(200, gin.H{"Version": aptly.Version})
 }
 
+type dbRequestKind int
+
 const (
-	acquiredb = iota
+	acquiredb dbRequestKind = iota
 	releasedb
 )
 
+type dbRequest struct {
+	kind dbRequestKind
+	err  chan<- error
+}
+
 // Flushes all collections which cache in-memory objects
 func flushColections() {
 	// lock everything to eliminate in-progress calls
@@ -52,50 +59,48 @@ func flushColections() {
 }
 
 // Periodically flushes CollectionFactory to free up memory used by
-// collections, flushing caches. If the two channels are provided,
-// they are used to acquire and release the database.
+// collections, flushing caches.
 //
 // Should be run in goroutine!
-func cacheFlusher(requests chan int, acks chan error) {
+func cacheFlusher() {
 	ticker := time.Tick(15 * time.Minute)
 
 	for {
 		<-ticker
 
-		// if aptly API runs in -no-lock mode,
-		// caches are flushed when DB is closed anyway, no need
-		// to flush them here
-		if requests == nil {
-			flushColections()
-		}
+		flushColections()
 	}
 }
 
-// Acquire database lock and release it when not needed anymore. Two
-// channels must be provided. The first one is to receive requests to
-// acquire/release the database and the second one is to send acks.
+// Acquire database lock and release it when not needed anymore.
 //
 // Should be run in a goroutine!
-func acquireDatabase(requests chan int, acks chan error) {
+func acquireDatabase(requests <-chan dbRequest) {
 	clients := 0
-	for {
-		request := <-requests
-		switch request {
+	for request := range requests {
+		var err error
+
+		switch request.kind {
 		case acquiredb:
 			if clients == 0 {
-				acks <- context.ReOpenDatabase()
-			} else {
-				acks <- nil
+				err = context.ReOpenDatabase()
+			}
+
+			request.err <- err
+
+			if err == nil {
+				clients++
 			}
-			clients++
 		case releasedb:
 			clients--
 			if clients == 0 {
 				flushColections()
-				acks <- context.CloseDatabase()
+				err = context.CloseDatabase()
 			} else {
-				acks <- nil
+				err = nil
 			}
+
+			request.err <- err
 		}
 	}
 }

api/router.go

@@ -20,35 +20,35 @@ func Router(c *ctx.AptlyContext) http.Handler {
 		// We use a goroutine to count the number of
 		// concurrent requests. When no more requests are
 		// running, we close the database to free the lock.
-		requests := make(chan int)
-		acks := make(chan error)
+		requests := make(chan dbRequest)
 
-		go acquireDatabase(requests, acks)
-		go cacheFlusher(requests, acks)
+		go acquireDatabase(requests)
 
 		router.Use(func(c *gin.Context) {
 			var err error
 
-			requests <- acquiredb
+			errCh := make(chan error)
+			requests <- dbRequest{acquiredb, errCh}
+
+			err = <-errCh
+			if err != nil {
+				c.Fail(500, err)
+				return
+			}
 
 			defer func() {
-				requests <- releasedb
-				err = <-acks
+				requests <- dbRequest{releasedb, errCh}
+				err = <-errCh
 				if err != nil {
 					c.Fail(500, err)
 				}
 			}()
 
-			err = <-acks
-			if err != nil {
-				c.Fail(500, err)
-				return
-			}
 			c.Next()
 		})
 
 	} else {
-		go cacheFlusher(nil, nil)
+		go cacheFlusher()
 	}
 
 	root := router.Group("/api")