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Description

In ingress server mode, the apisix-standalone backend built a new reqwest::Client for every server on every sync and dropped it when the sync finished. No TCP or TLS connection was ever reused across syncs, unlike apisix and api7ee, which already share a pooled client keyed by TLS material.

apisix-standalone now accepts the same shared client. BackendOptions gets a shared_client field, init_backend passes it through, and Backend::new wraps it per server with HttpClient::with_shared_client. Per-server tokens and the request timeout are applied per request, so sharing one client across servers is safe. The one-shot CLI still passes None and builds its own clients as before. adc-backend-core re-exports reqwest::Client so the standalone crate needs no new dependency.

The new test apisix_standalone_backends_reuse_one_connection_across_builds builds the backend three times against a plain TCP stub that counts accepted connections and asserts exactly one. With sharing disabled it fails with 3 connections.

Not changed here: there is still no global connection cap and no explicit idle limits on the pooled clients.

Fixes # (issue)

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible

No user-facing documentation covers the client pool, so only the code comment on init_backend was updated. The e2e suites that need a real gateway were not run locally.

Summary by CodeRabbit

• New Features
  • Standalone API gateways can now reuse a shared HTTP client across servers when one is configured, helping avoid repeated connection setup.
  • Configurations without a shared client continue using separately configured clients. The shared-client option is now available consistently across supported backend configurations. This change affects connection handling without changing the way existing configurations that omit the option operate. Users can continue to choose the existing per-server behavior or configure a shared client for their standalone gateway.

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Walkthrough

The APISIX standalone backend now accepts an optional shared HTTP client. The CLI passes the client to the backend, and a test checks connection reuse across three pings.

Changes: Shared HTTP client reuse

Layer / File(s)	Summary
Configure and verify shared client reuse rust/crates/adc-backend-core/src/lib.rs, rust/crates/adc-backend-apisix-standalone/src/backend.rs, rust/crates/adc-cli/src/pipeline.rs, rust/crates/adc-backend-apisix-standalone/tests/common/mod.rs, rust/crates/adc-cli/src/server/backend.rs	adc-backend-core re-exports reqwest::Client. APISIX standalone backend options accept an optional shared client, and the CLI passes it through. When supplied, the backend uses a clone with each server’s URL, token, and timeout. A test checks that three pings accept one TCP connection.

Priority: Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant CLI
  participant Backend
  participant HttpClient
  participant HTTPStub as HTTP stub
  CLI->>Backend: Pass options with shared_client
  Backend->>HttpClient: Clone client with server URL, token, and timeout
  HttpClient->>HTTPStub: Send three ping requests over one TCP connection
  HTTPStub-->>HttpClient: Return HTTP 200 responses

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Suggested labels: test/build

Merge Risk: Low · up to 85bb1

The new connection-reuse test may fail intermittently. The change remains mergeable with that test reliability issue understood or fixed.

Pre-merge checks: 6

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
E2e Test Quality Review		The PR adds a focused end-to-end test. It builds the real apisix-standalone backend three times, calls ping, reaches a real TCP HTTP stub, and asserts that one TCP connection is accepted. The test…
Security Check		No security issue was introduced in the reviewed diff. (1) No new logging, serialization, or response path exposes tokens, headers, or TLS keys; HttpClient::with_shared_client marks X-API-KEY sens…
Title check		The title names the change: the apisix-standalone backend now reuses connections across syncs in server mode. The PR objectives say the change passes a shared pooled HTTP client through BackendOptions…

Full details: E2e Test Quality Review

Explanation

The PR adds a focused end-to-end test. It builds the real apisix-standalone backend three times, calls ping, reaches a real TCP HTTP stub, and asserts that one TCP connection is accepted. The test uses clear naming, a direct assertion, and no execution-order dependency. The stub is justified because connection acceptance must be measured. The implementation passes the shared client through build_backend and init_backend, while the None path remains available for one-shot use. No blocking test-quality, scope, error-handling, or concurrency defect is introduced by the changed code.

Full details: Security Check

Explanation

No security issue was introduced in the reviewed diff. (1) No new logging, serialization, or response path exposes tokens, headers, or TLS keys; HttpClient::with_shared_client marks X-API-KEY sensitive, and existing header formatting redacts credential headers. (2) No database persistence changed. (3) No mutating endpoint or permission logic changed. (4) No resource lookup or ownership logic changed. (5) TLS material remains keyed in the shared-client pool by verification mode, CA, client certificate, and client key; the shared client does not change TLS flags. (6) The shared reqwest::Client has no shared auth headers; each HttpClient attaches its server-specific token to each request. (7) No secret-reference resolution path changed. The new client re-export and test do not create a security finding.

Full details: Title check

Explanation

The title names the change: the apisix-standalone backend now reuses connections across syncs in server mode. The PR objectives say the change passes a shared pooled HTTP client through BackendOptions and init_backend, wraps it per server, and stops each sync from building a new reqwest::Client. The title covers the main fix and the affected area. It does not name the mechanism (the shared client), but it is specific and accurate. The title follows the conventional commit form with a scope.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

Prompt to fix review comments

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Inline comments:
Review comments at @rust/crates/adc-cli/src/server/backend.rs:
- Around line 165-169: Update the stream.read loop to accumulate input until a
complete HTTP request is available, then send exactly one response for that
request rather than responding to each nonempty read. Preserve the existing
write-failure exit behavior.

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Commits

Reviewing files that changed from the base of the PR and between ddf966f and 85bb187.

Files selected for processing: 5

• rust/crates/adc-backend-apisix-standalone/src/backend.rs
• rust/crates/adc-backend-apisix-standalone/tests/common/mod.rs
• rust/crates/adc-backend-core/src/lib.rs
• rust/crates/adc-cli/src/pipeline.rs
• rust/crates/adc-cli/src/server/backend.rs

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