FrankChen021 opened a new pull request, #20717:
URL: https://github.com/apache/druid/pull/20717
### Description
Brokers and Historicals always declare `Trailer: X-Druid-Response-Complete`
and send that trailer after the last chunk of every streamed `/druid/v2` and
`/druid/v2/sql` response.
JDK-8383439 ("Enhance HTTP Client Response Handling", October 2026 CPU)
shipped in JDK 17.0.21, 21.0.13 and 25.0.5. It makes `java.net.http.HttpClient`
require CRLF right after the last chunk (new `ChunkedBodyParser.tryConsumeCRLF`
in `jdk.internal.net.http.ResponseContent`). A trailer section now fails the
response with `java.net.ProtocolException: CR expected`. Older JDKs skipped
those 2 bytes without checking them. So on current JDKs, any `java.net.http`
client that queries a Broker or Historical directly fails at the end of the
response. That includes the Druid JDBC driver (`DruidHttpClientImpl`) and
`ResponseIdentityHeaderTest`, which now fails deterministically on CI since
`setup-java` picked up Zulu 25.0.5. RFC 9112 §7.1 says recipients should accept
trailers, so this looks like a JDK regression. I found no public OpenJDK
report; JDK-8383439 itself is not public.
#### Fix
`QueryResultPusher` now declares and sends trailers only when the request
has `TE: trailers`, which is how RFC 9110 §10.1.4 has a client say it accepts
trailers. Without that header, responses are unchanged apart from the missing
`Trailer` header and trailer section.
No Druid code reads `X-Druid-Response-Complete` or `X-Error-Message`
(`DirectDruidClient` doesn't). The Router drops trailers anyway, because
Jetty's proxy treats `TE` and `Trailer` as hop-by-hop headers. So
Broker→Historical and Router traffic behaves the same as before.
#### Evidence
- **CI on Zulu 25.0.5 fails.** [This
job](https://github.com/apache/druid/actions/runs/40058080998/job/120765742115)
resolved `Zulu 25.0.5+8` (2026-10-24 03:25 UTC). In
`ResponseIdentityHeaderTest`, the three query tests (Broker native, Broker SQL,
Historical native) fail with `java.net.ProtocolException: CR expected`; the
four GET tests pass.
- **CI on Zulu 25.0.4 passes.** [This master
job](https://github.com/apache/druid/actions/runs/40051516682/job/120745017496)
resolved `Zulu 25.0.4+1.1` (01:49 UTC the same day) and
`ResponseIdentityHeaderTest` passed 7/7. Master is green only because nothing
has merged since `setup-java` switched to 25.0.5. It will also start failing on
the 17 and 21 jobs once they resolve 17.0.21 and 21.0.13.
- **Wire format.** A raw-socket capture of a Broker `/druid/v2/sql` response
ends with `0\r\nX-Druid-Response-Complete: true\r\n\r\n`.
- **JDK change.** JDK-8383439 was committed to openjdk `jdk17u`, `jdk21u`
and `jdk25u` on 2026-10-16. The first GA tags that contain it are
`jdk-17.0.21-ga`, `jdk-21.0.13-ga` and `jdk-25.0.5-ga`.
#### Release note
Brokers and Historicals now send the `X-Druid-Response-Complete` and
`X-Error-Message` HTTP trailers only when the request includes the `TE:
trailers` header. Clients that read these trailers must send that header. This
fixes query failures (`java.net.ProtocolException: CR expected`) in
`java.net.http.HttpClient`-based clients, including the Druid JDBC driver, on
JDK 17.0.21, 21.0.13 and 25.0.5.
<hr>
##### Key changed/added classes in this PR
* `QueryResultPusher`
* `QueryResponseTrailerTest` (new embedded test: raw-socket wire check with
and without `TE: trailers`, plus `HttpClient` reads from Broker and Historical)
<hr>
This PR has:
- [x] been self-reviewed.
- [x] added unit tests or modified existing tests to cover new code paths.
- [x] added integration tests.
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