feat(sources): add gRPC max connection age

[fpytloun]

Summary

Adds optional gRPC server keepalive configuration for source-side gRPC servers:

• keepalive.max_connection_age_secs
• keepalive.max_connection_age_grace_secs

The settings are wired into the Vector source and OpenTelemetry gRPC source, sharing the same gRPC server helper. Defaults preserve current behavior.

Closes #19457.

Design note

Tonic 0.11 does not expose native server max_connection_age / grace APIs. I tested a tonic 0.14 upgrade path, but it cascaded into broader hyper, generated-code, and Vector sink transport compatibility work. To keep this PR focused and reviewable, this implementation enforces the source-side gRPC connection lifetime at the accepted IO layer without changing sink behavior or upgrading tonic.

A future tonic upgrade can replace this with native server-side max-age support once the wider tonic/hyper migration is handled separately.

Tests

• make generate-component-docs
• cargo fmt --all -- --check
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_keepalive
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_grpc_keepalive
• cargo test --no-default-features --features sources-vector --lib sources::vector::test::max_connection_age_closes_idle_connection
• cargo test --no-default-features --features sources-vector,sinks-vector --lib sources::vector::tests::receive
• cargo clippy --no-default-features --features sources-vector,sources-opentelemetry --lib -- -D warnings -A clippy::manual_option_zip
• Docker Compose E2E using a docker-buildx-built PR image with sources-vector,sinks-vector,sources-demo_logs,sinks-console: Vector source configured with keepalive.max_connection_age_secs = 3 received 76 forwarded events over 16 seconds with no client/server errors, confirming delivery continues past repeated server-side connection expiry.

The Clippy allow is for an existing Rust 1.96 lint in unrelated config loading code.

Follow-up validation

After review feedback, the connection-age fallback was tightened so the local lifetime wrapper only closes an expired connection once that connection is idle. The active-request tracking is per accepted connection and is held until the response body is dropped, avoiding a global drain across unrelated connections and avoiding mid-response socket closure.

Additional local validation after the follow-up change:

• cargo fmt --all -- --check
• cargo test --no-default-features --features sources-vector --lib sources::util::grpc::tests::max_connection_age_service_tracks
• cargo test --no-default-features --features sources-vector --lib sources::vector::test::max_connection_age_closes_idle_connection
• cargo test --no-default-features --features sources-vector,sinks-vector --lib sources::vector::tests::receive
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_keepalive
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_grpc_keepalive
• cargo clippy --no-default-features --features sources-vector,sources-opentelemetry --lib -- -D warnings -A clippy::manual_option_zip
• Docker Compose E2E using a docker-buildx-built PR image with max_connection_age_secs = 3 and max_connection_age_grace_secs = 1:
  • server received 86 forwarded events over 18s
  • reconnects were directly visible in debug logs after idle expiry
  • no Vector ERROR/panic lines were observed

[chatgpt-codex-connector]

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Reviewed commit: e9ac53ed0a

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[fpytloun]

Updated the PR after review feedback.

Changes pushed in 04865ba3c9:

• tightened the connection-age fallback so expired connections are closed only once the accepted connection is idle
• made active request tracking per accepted connection instead of global
• held the active guard through response body lifetime
• added regression coverage for response-body lifetime and per-connection isolation
• fixed the PR title to Conventional Commit format

Validation rerun locally: fmt, targeted config/vector tests, targeted clippy, and Docker Compose E2E. The E2E now directly shows reconnects in debug logs after idle expiry while forwarded events continue and no Vector ERROR/panic lines appear.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 04865ba3c9

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[fpytloun]

Follow-up update for the remaining review thread:

• stopped accepting further socket reads after max_connection_age + grace elapses, so new HTTP/2 streams cannot keep an aged connection alive indefinitely
• still allow writes/flushes while existing response bodies are active, so in-flight responses can drain before the connection fully closes
• kept active request tracking per accepted connection
• added regression coverage for:
  • read expiry before write expiry
  • response-body lifetime tracking
  • per-connection active counters
  • vector-source reconnect using observed accepted-connection count growth after deadline

Validation rerun on 9297bd86e8:

• cargo fmt --all -- --check
• cargo test --no-default-features --features sources-vector --lib sources::util::grpc::tests::max_connection_age
• cargo test --no-default-features --features sources-vector --lib sources::vector::test::max_connection_age_closes_idle_connection
• cargo test --no-default-features --features sources-vector,sinks-vector --lib sources::vector::tests::receive
• cargo test --no-default-features --features sources-vector,sinks-vector --lib sources::vector::tests::max_connection_age_allows_client_reconnect
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_keepalive
• cargo test --no-default-features --features sources-vector,sources-opentelemetry --lib config_grpc_keepalive
• cargo clippy --no-default-features --features sources-vector,sources-opentelemetry --lib -- -D warnings -A clippy::manual_option_zip
• Docker Compose E2E from the PR image: server received 86 forwarded events, client showed 3 client connection bound logs, server showed 4 DEBUG broken-pipe close logs, and there were no Vector ERROR/panic lines.

A delegated code review pass was also clean after the final reconnect coverage was added.