Retry APNs2 frames dropped by a mid-flight connection reset, and add structured push logging

[drn]

Problem

Stacked on #7. Apns2::Delivery has the same latent silent-drop pattern #7 fixed for Apnsp8 — flagged there as a deliberate follow-up rather than folded into that change:

apns2 shares the same latent silent-drop pattern, but its perform has an untested per-notification SSLError rescue that leaves notifications unmarked; applying reconciliation there needs its own analysis + specs. Deliberately scoped out to keep this change regression-safe.

Observed in production: currypizzahouse_ios (a cert-based apns2 app) went completely silent for several hours — no sends, no errors in the logs — then resumed on its own with no restart or config change. Pulling rpush_notifications for that merchant shows the same request pattern succeeding on one attempt and then producing no delivered/failed/retryable outcome at all on another, minutes apart, against the same two device tokens. That's consistent with net-http2 dropping in-flight streams on a connection reset without it ever reaching Apns2::Delivery#perform's rescue blocks.

Root cause

Same as #7: @client.join does not raise on a mid-flight connection reset. net-http2 detects it on its background socket thread and delivers the error to the client's on(:error) callback rather than re-raising into perform; #join then returns normally once the stream set empties. The in-flight notifications never receive their on(:close), so handle_response never runs for them — they're marked neither delivered, failed, nor retryable, and ensure @batch.all_processed completes the batch with them recorded nowhere.

apns2 has a second, distinct version of the same class of bug that apnsp8 doesn't: preparing a request can raise OpenSSL::SSL::SSLError before the notification ever gets a stream. The existing code:

rescue OpenSSL::SSL::SSLError => error
  log_error("Notification #{notification.id} failed with SSL error")
end

logs and moves on to the next notification — the notification is left with no outcome at all, same failure mode as the connection-reset case.

There's also a smaller, permanent-failure variant: handle_response's case has no when nil branch, so a stream that closes with no status code (should one ever surface that way rather than via the dropped-connection path) falls through to else and gets mark_failed'd — permanently — rather than retried.

Fix

Localized to the apns2 transport, reusing the read-only Batch#unresolved helper #7 already added (transport-agnostic, so nothing there needs to change):

• Apns2::Delivery#perform — after #join, reconcile: re-queue any unresolved notification as retryable instead of letting the batch discard it. No-op on the normal path where every stream reported a result.
• #handle_response — an absent status code is now a transport failure → retry, not mark_failed.
• The per-notification SSLError rescue — now retries the notification (via the same connection_lost-style path) instead of logging and dropping it.
• Errno::ECONNRESET was already in the synchronous rescue here (added by BUGS-1850. Retry after Errno::ECONNRESET #2/BUGS-1850) — unchanged.

Also in this PR: structured push logging, for parity with #7

Brings Loggable#log_push_event (added by #7) to this transport: delivered / failed / retrying events on Delivery, device token truncated. The ApnsHttp2 dispatcher's on(:error) callback is updated too — but including the error message, not just its class:

log_push_event(:connection_error, level: :error, error: "#{error.class}: #{error.message}")

This addresses @drn's open review comment on #7 (the apnsp8 dispatcher's equivalent line currently logs only error.class) before the same gap repeats here.

Why this is regression-safe

Same argument as #7: every existing APNs status outcome (200/410/400/429/500/503) is unchanged. Only the "no verdict from APNs" cases move from {silent drop, permanent fail} to {retry} — strictly safer. Batch#unresolved is read-only and shared, unmodified from #7.

Tests

Mirrors #7's apnsp8 coverage for the apns2 transport: the reconciliation sweep on #perform, the no-status #handle_response case, the new SSLError-at-prepare-time path (including that the batch continues to the next notification rather than aborting), and the structured logging format for delivered / failed / retrying, plus the dispatcher's connection_error message.

Could not run the full suite in this environment (native extension build tooling unavailable locally) — syntax-checked all four files (ruby -c) and modeled the specs directly on #7's already-passing apnsp8 equivalents, adjusting only for Apns2::Delivery's 3-arg constructor (no token provider). Relying on CI here.

Base branch

Based on rstojano/apnsp8-retry-dropped-frames (#7) to reuse Batch#unresolved and Loggable#log_push_event without redefining them. Should be re-based onto master once #7 merges — happy to do that flip myself once it lands.

Summary by CodeRabbit

• Bug Fixes

  • Improved APNs delivery reliability by retrying request-preparation, connection, and incomplete-response failures.
  • Prevented individual notification errors from interrupting remaining deliveries.
  • Improved handling of missing-status, retryable, and permanent failure responses.

• Improvements

  • Enhanced delivery and connection error logs with structured details, including retry reasons and error messages.
  • Added structured logging for successful, failed, and retried deliveries.
  • Improved log privacy by shortening device tokens.

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📝 Walkthrough

Walkthrough

APNs2 delivery now retries request-preparation failures, unresolved streams, connection loss, and responses without APNs status. Delivery and dispatcher paths emit structured push events with retry, response, exception, and truncated token data.

Changes

APNs2 delivery reliability

Layer / File(s)	Summary
Transport failure retry flow lib/rpush/daemon/apns2/delivery.rb, spec/unit/daemon/apns2/delivery_spec.rb, spec/functional/apns2_spec.rb	Transport failures, unresolved streams, and missing response statuses now re-queue notifications. Retry timing uses RECONNECT_RETRY_DELAY. Tests cover retryable, permanent, and successful outcomes.
Structured delivery event logging lib/rpush/daemon/apns2/delivery.rb, lib/rpush/daemon/dispatcher/apns_http2.rb, spec/unit/daemon/apns2/delivery_spec.rb, spec/unit/daemon/dispatcher/apns_http2_spec.rb	Delivery and dispatcher errors use structured push events. Logs include retry and response data, exception details, application data, and truncated device tokens. Tests verify event fields and upstream error handling.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Merge Risk: ⚪ Minimal · up to 7a91d

The PR localizes retry and structured logging changes to the APNs2 path, with no actionable merge-blocking risk remaining beyond normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant Delivery
  participant APNs2Client
  participant NotificationBatch
  participant Logger
  Delivery->>APNs2Client: prepare and send notification
  APNs2Client-->>Delivery: response or transport failure
  Delivery->>NotificationBatch: mark notification delivered or retryable
  Delivery->>Logger: emit structured push event
  Delivery->>APNs2Client: retry transport failures after delay

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❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 26.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 15 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: APNs2 retries after connection resets and structured push logging.
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Inline comments:
In `@lib/rpush/daemon/apns2/delivery.rb`:
- Around line 144-146: Update prepare_failed to pass the stable reason
prepare_failed to retry_message_to_log, and provide the exception details
separately through its error field, matching the existing pattern in the APNs
HTTP/2 dispatcher.

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• spec/unit/daemon/dispatcher/apns_http2_spec.rb

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[rstojano]

Fully tested locally, CI to be fixed in another pr. Merging with confidence that no breaking changes were committed.