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Add history size and continue-as-new suggestion #178

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May 21, 2022
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Add history size and continue-as-new suggestion #178

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Add history size and continue-as-new suggestion
dnr Apr 29, 2022
a6f251e
Merge branch 'master' into wfsize
dnr May 21, 2022
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reword comments
dnr May 21, 2022
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7 changes: 7 additions & 0 deletions temporal/api/history/v1/message.proto
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Expand Up @@ -171,6 +171,13 @@ message WorkflowTaskStartedEventAttributes {
string identity = 2;
// TODO: ? Appears unused?
string request_id = 3;
// True if this workflow should continue-as-new soon because its history size (in
// either event count or bytes) is getting large.
bool suggest_continue_as_new = 4;
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@cretz cretz May 6, 2022 •
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I am not convinced this is valuable. Before merging this, can we discuss what the actual values to drive this might be in the server? Like 80% of max events or count? 50%? 20% (as suggested in description w/ 10k)? That's a large swing.

Also Max has suggested atomic snapshotting at some point which would obviate the need for this. Are we sure we want it as an event field? Can the SDK derive it or is its dependence on a server config the reason we need it here?

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We had a quick meeting and came to a rough consensus:

  • yes, the server should send a boolean suggestion (in addition to total size in bytes and count)
  • the suggestion should be based on values from dynamic config so that an operator can tune it
  • the sdk should expose all three values so users can either write while !shouldContinueAsNew { ... }, or else use the raw values to make decisions

For defaults, I'll throw out suggestions of 2000 events or 2MB size, but we can discuss this on the implementation PR. Of course, workflows with large payloads will want to use the raw values.

Atomic snapshotting sounds great but I think that's a ways off and this is a quick win. The downsides of the SDK deriving it are that it wouldn't be tunable by an operator in one place, and we'd have to use markers to preserve determinism. This is essentially a fixed marker implemented by the server, if I understand it.

If no other objections, I'll merge this soon.

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👍 I was hoping we could know the defaults here just in case there isn't a reasonable default. I doubt I personally will ever use this in workflows vs just doing my own checks, but maybe others will.

No objections from me.

// Total history size in bytes, which the workflow might use to decide when to
// continue-as-new regardless of the suggestion. Note that history event count is
// just the event id of this event, so we don't include it explicitly here.
int64 history_size_bytes = 5;
}

message WorkflowTaskCompletedEventAttributes {
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