history.Sync: Don't operate on closed channel

[yhabteab]

Before

diff --git a/pkg/icingadb/history/sync.go b/pkg/icingadb/history/sync.go
index 4be0e71..fb31d31 100644
--- a/pkg/icingadb/history/sync.go
+++ b/pkg/icingadb/history/sync.go
@@ -140,7 +140,9 @@ func (s Sync) deleteFromRedis(ctx context.Context, key string, input <-chan redi
                }
        }).Stop()
 
-       bulks := com.Bulk(ctx, input, s.redis.Options.HScanCount, com.NeverSplit[redis.XMessage])
+       justKidding := make(chan redis.XMessage)
+       close(justKidding)
+       bulks := com.Bulk(ctx, justKidding, s.redis.Options.HScanCount, com.NeverSplit[redis.XMessage])
        stream := "icinga:history:stream:" + key
        for {
                select {

↓

2024-03-28T15:00:22.430+0100    FATAL   main    ERR wrong number of arguments for 'xdel' command
can't perform "[xdel icinga:history:stream:flapping]"
github.com/icinga/icingadb/pkg/icingaredis.WrapCmdErr
        /Users/yhabteab/Workspace/go/icingadb/pkg/icingaredis/utils.go:121
github.com/icinga/icingadb/pkg/icingadb/history.Sync.deleteFromRedis
        /Users/yhabteab/Workspace/go/icingadb/pkg/icingadb/history/sync.go:157
github.com/icinga/icingadb/pkg/icingadb/history.Sync.Sync.func3
        /Users/yhabteab/Workspace/go/icingadb/pkg/icingadb/history/sync.go:96
golang.org/x/sync/errgroup.(*Group).Go.func1
        /Users/yhabteab/go/pkg/mod/golang.org/x/sync@v0.6.0/errgroup/errgroup.go:78
runtime.goexit
        /opt/homebrew/Cellar/go/1.22.1/libexec/src/runtime/asm_arm64.s:1222
exit status 1

After

No crash

fixes #713

[julianbrost]

Have you checked that closing the channel is the only situation how len(bulk) == 0 could happen, i.e. that there a no nil or zero-length slices actually sent to the channel?

[yhabteab]

i.e. that there a no nil or zero-length slices actually sent to the channel?

This is never going to happen!

icingadb/pkg/com/bulker.go

Lines 114 to 117 in 51e5434

	if len(buf) > 0 {
	b.ch <- buf
	buf = make([]T, 0, count)
	}

icingadb/pkg/com/bulker.go

Lines 130 to 132 in 51e5434

	if len(buf) > 0 {
	b.ch <- buf
	}

[yhabteab]

In case redis.Options.HScanCount is set to <= 1:

icingadb/pkg/com/bulker.go

Lines 165 to 171 in 51e5434

	case item, ok := <-ch:
	if !ok {
	return
	}
	select {
	case out <- []T{item}: