lostluck commented on code in PR #34828:
URL: https://github.com/apache/beam/pull/34828#discussion_r2072742789
##########
sdks/go/pkg/beam/runners/prism/internal/stage.go:
##########
@@ -218,58 +223,75 @@ progress:
}
slog.Debug("progress report", "bundle", rb, "index",
index, "prevIndex", previousIndex)
+ var fraction float64
+
// Check if there has been any measurable progress by
the input, or all output pcollections since last report.
slow := previousIndex == index["index"] &&
previousTotalCount == index["totalCount"]
+ checkpointReady := checkpointTickCount >=
checkpointTickCutoff
if slow && unsplit {
- slog.Debug("splitting report", "bundle", rb,
"index", index)
- sr, err := b.Split(ctx, wk, 0.5 /* fraction of
remainder */, nil /* allowed splits */)
- if err != nil {
- slog.Warn("SDK Error from split,
aborting splits", "bundle", rb, "error", err.Error())
- break progress
- }
- if sr.GetChannelSplits() == nil {
- slog.Debug("SDK returned no splits",
"bundle", rb)
- unsplit = false
- continue progress
- }
+ fraction = 0.5
+ } else if checkpointReady && unsplit {
Review Comment:
I guess I'm worried about the situation where we're just oversplitting and
forcing a checkpoint on a perfectly fine running Batch DoFn (processing
efficiently and per element fast).
As it stands, this code looks like it will checkpoint a fast moving bundle
after 1 second. (10 ticks, at 100ms per tick, since a fast moving bundle won't
get a slower progress request rate).
But that's sort of wasteful. A fast moving bundle shouldn't be stopped. We
might just want to only do this if the bundle is moving fast, but the input
index isn't moving? Perhaps this is a reason why Dataflow has explicit Batch
and Streaming modes of execution.
One almost wants to do it based on the number or amount of output data
instead, in order to allow the watermark to progress.... But that would be much
harder, and is overthinking it for now.
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