Re: [quicwg/base-drafts] Clarify QPACK eviction races (#1237)

[Mike Bishop <[e-mail]>]

MikeBishop commented on this pull request.



> +any eviction-prone entries, which are dynamic table entries that might be
+evicted soon.  Rather than reference an eviction-prone entry, the encoder SHOULD
+emit an Indexed-Duplicate representation (see {{indexed-duplicate}}), and
+reference the duplicate instead.
+
+To identify eviction-prone entries, the encoder can maintain a draining index,
+which is the smallest absolute index in the dynamic table that it will emit a
+reference for.  As new entries are inserted, the encoder increments the
+draining index such that the amount of free and draining space in the dyanmic
+table is larger than its target threshold.
+
+~~~~~~~~~~  drawing
+   +----------------+-----------------------+------------+
+   | Eviction-prone |     Referenceable     | Free Space |
+   |    Entries     |        Entries        |            |
+   +----------------+-----------------------+------------+

I'm with @afrind.  The pathological case I think you're describing is an encoder that won't / isn't permitted to block deciding that it should duplicate an old entry, but still can't use either one.  If it doesn't duplicate it more than once, that should be okay.

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