Streaming replication and high query cancellation values

I have a couple of questions about how streaming replication works in the presence of a high timeout for query cancellation:

1. Where is the WAL data stored while waiting for the query cancellation, the primary or the secondary? In case of a crash during this interval, could the secondary end up behind the primary due to the WAL data not having been sent over?

2. Can a very high query cancellation value run afoul of wal_keep_segments, or will the primary (assuming it's the one doing the storing) keep that data around until the query completes or is cancelled?

Thanks!
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-- Christophe Pettus
xof(at)thebuild(dot)com