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Eliminate test flakes in recently-added heap tests #65

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merged 2 commits into from
Apr 19, 2024
Merged

Eliminate test flakes in recently-added heap tests #65

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12ae6b1
perhaps the sift up/down is not entirely deterministic?
jhump Apr 19, 2024
fd992d0
make linter happy
jhump Apr 19, 2024
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35 changes: 22 additions & 13 deletions picker/leastloaded_heap_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
package picker

import (
"sort"
"testing"

"github.com/bufbuild/httplb/conn"
Expand Down Expand Up @@ -42,22 +43,18 @@ func TestLeastLoadedConnHeap(t *testing.T) {
}
verifyHeap(t, heap, counts)

// Note: order may not be intuitive, due to how
// nodes in the heap are sifted up and down as an item
// is popped, but it is deterministic.

// No repeats since they all have weight zero.
verifyPicks(t, heap, counts, "abdecf")
verifyPicks(t, heap, counts, "abcdef")
// Now they all have weight one, so they all repeat. But
// we don't see any item a third time until we've seen
// all of 'em 2x.
verifyPicks(t, heap, counts, "fdabce")
verifyPicks(t, heap, counts, "abcdef")

verifyReleases(t, heap, counts, "aabb")

// Now a and b have a load of zero, but the others have load 2.
// So we'll pick them next.
verifyPicks(t, heap, counts, "abba")
verifyPicks(t, heap, counts, "aabb")

snapshot := snapshotHeap(heap)
// Update state with new connections. We should forget
Expand All @@ -84,10 +81,10 @@ func TestLeastLoadedConnHeap(t *testing.T) {
verifyHeap(t, heap, counts)

// g and h have less load, so we favor them.
verifyPicks(t, heap, counts, "hggh")
verifyPicks(t, heap, counts, "gghh")
// Now everything has load == 2. So next four picks sees
// each of the four items.
verifyPicks(t, heap, counts, "hefg")
verifyPicks(t, heap, counts, "efgh")

// No-op update
heap.update(conns.FromSlice([]conn.Conn{
Expand Down Expand Up @@ -168,13 +165,25 @@ func TestLeastLoadedConnHeap(t *testing.T) {

func verifyPicks(t *testing.T, heap *leastLoadedConnHeap, counts map[string]uint64, ids string) {
t.Helper()
for _, ch := range ids {
id := string(ch)
expected := make([]string, len(ids))
actuals := make([]string, len(ids))
for i, ch := range ids {
expectedID := string(ch)
item := heap.acquire(0)
require.Equal(t, id, connID(item.conn))
counts[id]++
actualID := connID(item.conn)
expected[i] = expectedID
actuals[i] = actualID
counts[actualID]++
verifyHeap(t, heap, counts)
}
// Order can be non-intuitive, due to internal state of the heap, how
// it models a binary tree inside the slice, and the details of sifting
// things up and down the tree when state changes. So we just sort the
// expected and actuals: the identities of which connections were
// picked is more important than the order of picking.
sort.Strings(expected)
sort.Strings(actuals)
require.Equal(t, expected, actuals)
}

func verifyReleases(t *testing.T, heap *leastLoadedConnHeap, counts map[string]uint64, ids string) {
Expand Down
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