Reintroduce progressive HTTP read timeout support

[zchuango]

What problem does this PR solve?

Issue Number: Related to #3133, follow-up pr #3409 and #3453

Problem Summary:

Progressive HTTP response reads currently have no independent idle timeout after ReadProgressiveAttachmentBy() is called. A reader may therefore wait indefinitely when the peer stops sending body data while keeping the connection open.

PR #3409 introduced progressive-read timeout support, but post-merge CI exposed a lifecycle and synchronization problem around the timer callback and reader completion path. In particular, the timer callback could race with reader completion/error delivery, which made HttpTest.progressive_read_timeout_preserves_reader_error unstable and could replace the reader's original error with the timeout status.

This PR restores the feature with explicit synchronization and independent timer-state ownership.

What is changed and the side effects?

Changed:

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[zchuango]

@wwbmmm @chenBright Please carefully review this feature. We have conducted multiple rounds of tests both online and offline, and no abnormal issues have been found. For details, see the following test screenshots and evidence.

Additional validation evidence for commit fc865456fcc21f2e8325e3e9b0c27f7d6fce7b21.

Local stress testing

• ASan: 200/200 rounds passed.
• 6 focused progressive-read timeout tests per round.
• 1,200 total test invocations.
• 0 failures.
• 0 sanitizer errors.
• Bazel 8.3.1: 20/20 runs passed.
• 120 total focused test invocations.

The attached archive contains:

• sanitized ASan log;
• sanitized Bazel log;
• ASan reproduction script;
• Bazel reproduction script;
• SHA256 checksums for every included file.

Archive:

progressive-read-timeout-test-evidence-fc865456.zip

Archive SHA256:

3641592B51D1BCE19F5BA1796FB2F91C27E5980D94CC9E040847D16AF2CFBAA4

GitHub Actions reruns

Five of six complete Linux workflow attempts passed.

Attempt #5 failed only in the existing
clang-unittest-bazel-with-babylon-and-new-pb job, in
RdmaTest.v3_server_rejects_oversized_pb_size.

The other 10 Linux jobs in that attempt passed. This PR does not modify RDMA
code or that test. The subsequent complete attempt #6 passed all 11 Linux jobs,
including the previously failing job.

• Attempt #5
• Attempt #6 — all jobs passed

Validation Screenshots

ASan stress test: 200/200 rounds passed

Bazel 8.3.1 stress test: 20/20 runs passed

GitHub Actions attempt #6: all Linux jobs passed

[Copilot]

Pull request overview

Reintroduces progressive HTTP/1.x response read idle-timeout support for Controller::ReadProgressiveAttachmentBy() by wiring the response socket identity through the HTTP protocol path and adding a synchronized watchdog timer that can fail the underlying socket when the progressive body stream becomes idle.

Changes:

• Add a new client-side Controller API (set_progressive_read_timeout_ms) and internal timeout reader wrapper that monitors idle gaps between progressive body parts and fails the socket on timeout.
• Propagate the underlying HTTP socket id into the controller/RPA path so the watchdog can address and fail the correct connection.
• Add unit tests and update the HTTP C++ examples to demonstrate/validate progressive read timeout behavior (including unsupported HTTP/2 behavior).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/brpc_http_rpc_protocol_unittest.cpp	Adds progressive-read timeout focused tests and test helpers for controlled streaming/reading behavior.
src/brpc/policy/http_rpc_protocol.h	Extends HttpContext to retain the socket id used for progressive reads.
src/brpc/policy/http_rpc_protocol.cpp	Sets the HttpContext socket id during parsing and forwards it into the controller’s progressive attachment setup.
src/brpc/errno.proto	Adds EPROGREADTIMEOUT errno for progressive read idle timeout.
src/brpc/details/controller_private_accessor.h	Adds an accessor overload to store the progressive-read socket id alongside _rpa.
src/brpc/controller.h	Exposes set_progressive_read_timeout_ms() API and stores timeout/socket-id fields in Controller.
src/brpc/controller.cpp	Implements timeout watchdog state/task + wrapper reader, errno registration, and hooks timeout handling into ReadProgressiveAttachmentBy().
example/http_c++/http_server.cpp	Adds a flag path to simulate a stall mid-progressive response for timeout demonstration.
example/http_c++/http_client.cpp	Adds optional progressive read mode and timeout flag, then reads response progressively with a reader callback.

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[zchuango]

@wwbmmm @chenBright The Copilot review comments have been addressed and all CI checks have passed on the latest commit 5d03b498492c8b0d066ad2432a5a3d0636f555bb.

Could you please take another look when convenient?