From 184d7c4acb0527bbe91d29f8fde6f6b0e8d22f23 Mon Sep 17 00:00:00 2001
From: sgf <sgf.dma@gmail.com>
Date: Wed, 2 Nov 2022 19:26:39 +0300
Subject: [PATCH] fix(balancer): Update worker index in heap during Swap()
 call.

---
 concurrency-is-not-parallelism/balancer.go          |  6 +++++-
 .../balancer_v2/balancer/balancer.go                | 13 +++++++++----
 .../balancer_v2/balancer/worker/worker.go           |  3 ++-
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/concurrency-is-not-parallelism/balancer.go b/concurrency-is-not-parallelism/balancer.go
index 2b5df4a..6642b18 100644
--- a/concurrency-is-not-parallelism/balancer.go
+++ b/concurrency-is-not-parallelism/balancer.go
@@ -88,7 +88,11 @@ func (w *Worker) work(id string, done chan<- *Done) {
 type Pool []*Worker
 
 func (p Pool) Len() int { return len(p) }
-func (p Pool) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+func (p Pool) Swap(i, j int) {
+    p[i], p[j] = p[j], p[i]
+    p[i].index = i
+    p[j].index = j
+}
 // FIXME: Does it works correctly? Or i need p[i] > p[j] ? The highest-pri
 // worker should be the last.
 func (p Pool) Less(i, j int) bool {
diff --git a/concurrency-is-not-parallelism/balancer_v2/balancer/balancer.go b/concurrency-is-not-parallelism/balancer_v2/balancer/balancer.go
index a09a776..3182b6e 100644
--- a/concurrency-is-not-parallelism/balancer_v2/balancer/balancer.go
+++ b/concurrency-is-not-parallelism/balancer_v2/balancer/balancer.go
@@ -46,7 +46,7 @@ type worker struct {
 }
 
 func (w worker) String() string {
-    return fmt.Sprintf("W %.2d (%v)", w.num, w.pending)
+    return fmt.Sprintf("W %.2d (%v [%v])", w.num, w.pending, w.index)
 }
 
 // Done message is sent by work runner to balancer, when request is completed.
@@ -59,7 +59,11 @@ type Done struct {
 type pool []*worker
 
 func (p pool) Len() int { return len(p) }
-func (p pool) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+func (p pool) Swap(i, j int) {
+    p[i], p[j] = p[j], p[i]
+    p[i].index = i
+    p[j].index = j
+}
 func (p pool) Less(i, j int) bool {
     return p[i].pending < p[j].pending
 }
@@ -119,11 +123,11 @@ out:
 // dispatch sends requests to least loaded worker.
 func (b *Balancer) dispatch(req Requester) {
     w := heap.Pop(&b.pool).(*worker)
-    fmt.Printf("dispatch() '%v': sending to '%v'\n", req, w)
     w.pending++
     heap.Push(&b.pool, w)
+    fmt.Printf("dispatch() '%v': sending to '%v'\n", req, w)
     w.runner.Send(req)
-    fmt.Printf("dispatch() '%v': sent\n", req)
+    fmt.Printf("dispatch() '%v': sent to %v\n", req, w)
 }
 
 // completed re-inserts worker, which finished request, into proper place in the pool.
@@ -133,6 +137,7 @@ func (b *Balancer) completed(done *Done) {
     w.pending--
     heap.Remove(&b.pool, w.index)
     heap.Push(&b.pool, w)
+    fmt.Println("pool", b.pool)
 }
 
 // InitBalancer initializes balancer with provided workers.
diff --git a/concurrency-is-not-parallelism/balancer_v2/balancer/worker/worker.go b/concurrency-is-not-parallelism/balancer_v2/balancer/worker/worker.go
index e79bfbd..5ce0293 100644
--- a/concurrency-is-not-parallelism/balancer_v2/balancer/worker/worker.go
+++ b/concurrency-is-not-parallelism/balancer_v2/balancer/worker/worker.go
@@ -32,8 +32,9 @@ func (w *Runner) Work(id string, done chan<- *balancer.Done) {
         case req := <- w.Requests:
             fmt.Printf("  %v [%v]: start computing '%v'\n", w, id, req)
             req.Send(req.Fn())
-            done <- &balancer.Done{w.id, req}
             fmt.Printf("  %v [%v]: finished '%v'\n", w, id, req)
+            done <- &balancer.Done{w.id, req}
+            fmt.Printf("  %v [%v]: done '%v'\n", w, id, req)
         case <-timeout:
             fmt.Printf("  %v [%v]: i'm still here..\n", w.id, id)
             timeout = time.After(time.Second)
-- 
2.20.1