dnsimple / erldns / 31485274997

88%

Build Type

push

github

Committed by web-flow

Commit Message

Reach the custom decoders without raising through dns_json (#364)

`dns_json` reports a type name it does not know by raising out of
`binary_to_dns_type/1`, and `json_record_to_erlang/1` catches that to
fall through to the configured custom decoders. So every ALIAS, URL and
POOL record was decoded by way of a failed name lookup, a
`string:to_integer/1` walk of a non-numeric binary as unicode graphemes,
an exception, a stacktrace capture, and a discarded debug log -- before
the decoder that actually handles it ever ran. Exceptions as control
flow, once per record, on the path a whole zone goes through.

The type name is now checked first: one recognised by `dns_names` or
spelled as a bare number is decoded as before, anything else is handed
to the custom decoders directly. The raise stays where it belongs, for
records that are genuinely malformed.

Measured over a synthetic 50k-record zone, decoding the whole zone:

    custom types    before      after
    0%              19.1 ms     17.9 ms
    50%            964.7 ms     12.4 ms
    95%          1,848.5 ms      7.5 ms

The cost was linear per custom record, so it scaled with how much of a
zone was custom rather than with anything about the zone's size.

Separately, `apply_context_options/1` read `application:get_env(erldns,
zones)` once for every record in a zone to fetch a value that cannot
change mid-decode. It is read once per zone now and threaded down like
the decoders already were.

Coverage Stats

20 of 21 new or added lines in 1 file covered. (95.24%)

3 existing lines in 2 files now uncovered.

1745 of 1988 relevant lines covered (87.78%)

5055.04 hits per line