Queue: Make WorkerPools and Queues flushable (#10001)

* Make WorkerPools and Queues flushable

Adds Flush methods to Queues and the WorkerPool
Further abstracts the WorkerPool
Adds a final step to Flush the queues in the defer from PrintCurrentTest
Fixes an issue with Settings inheritance in queues

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Change to for loop

* Add IsEmpty and begin just making the queues composed WorkerPools

* subsume workerpool into the queues and create a flushable interface

* Add manager command

* Move flushall to queue.Manager and add to testlogger

* As per @guillep2k

* as per @guillep2k

* Just make queues all implement flushable and clean up the wrapped queue flushes

* cope with no timeout

Co-authored-by: Lauris BH <lauris@nix.lv>

routers/private/manager.go

@@ -0,0 +1,41 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package private
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/private"
+	"code.gitea.io/gitea/modules/queue"
+
+	"gitea.com/macaron/macaron"
+)
+
+// FlushQueues flushes all the Queues
+func FlushQueues(ctx *macaron.Context, opts private.FlushOptions) {
+	if opts.NonBlocking {
+		// Save the hammer ctx here - as a new one is created each time you call this.
+		baseCtx := graceful.GetManager().HammerContext()
+		go func() {
+			err := queue.GetManager().FlushAll(baseCtx, opts.Timeout)
+			if err != nil {
+				log.Error("Flushing request timed-out with error: %v", err)
+			}
+		}()
+		ctx.JSON(http.StatusAccepted, map[string]interface{}{
+			"err": "Flushing",
+		})
+		return
+	}
+	err := queue.GetManager().FlushAll(ctx.Req.Request.Context(), opts.Timeout)
+	if err != nil {
+		ctx.JSON(http.StatusRequestTimeout, map[string]interface{}{
+			"err": err,
+		})
+	}
+	ctx.PlainText(http.StatusOK, []byte("success"))
+}