DO NOT MERGE: Kill scheduler on overlay v2

[graydon]

This removes the Action Scheduler / Action Queues from core on the overlay-v2-shared branch. The hypothesis here is that it's no longer needed with the overlay process doing all the networking.

[Copilot]

Pull request overview

This PR removes the in-process Action Scheduler/Action Queues and routes main-thread “actions” through the VirtualClock’s ASIO io_context, consistent with the overlay-v2-shared hypothesis that networking work is handled elsewhere.

Changes:

• Removed util::Scheduler implementation and its unit tests.
• Simplified VirtualClock action posting to enqueue std::function<void()> and forward them to ASIO, removing scheduler-driven fairness/load-shedding.
• Updated Application / ApplicationImpl / AppConnector main-thread posting APIs to drop Scheduler::ActionType.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/util/Timer.h	Removes scheduler ownership/typing from VirtualClock and updates related comments/APIs.
src/util/Timer.cpp	Removes scheduler integration from crank() and posts pending actions directly to ASIO.
src/util/test/SchedulerTests.cpp	Deletes scheduler unit tests.
src/util/Scheduler.h	Deletes scheduler interface.
src/util/Scheduler.cpp	Deletes scheduler implementation.
src/process/ProcessManagerImpl.h	Adds missing <map> include for std::map member usage.
src/main/ApplicationImpl.h	Updates postOnMainThread signature to remove action type.
src/main/ApplicationImpl.cpp	Routes main-thread posts through new VirtualClock::postAction(std::function<void()>&&) API.
src/main/Application.h	Updates Application::postOnMainThread signature to remove action type.
src/main/AppConnector.h	Updates connector postOnMainThread signature to remove action type.
src/main/AppConnector.cpp	Updates connector call-through to match new Application API.

Comments suppressed due to low confidence (1)

src/util/Timer.cpp:416

• This loop holds mPendingActionQueueMutex while calling asio::post repeatedly. That can unnecessarily block background threads calling postAction(), and it makes the critical section include allocations and executor bookkeeping. Consider swapping the queue into a local variable under the lock, then posting without holding the mutex.

    // Transfer any pending actions to ASIO, counting them as "progress" also.
    {
        LOCK_GUARD(mPendingActionQueueMutex, guard);
        while (!mPendingActionQueue.empty())
        {
            asio::post(mIOContext, std::move(mPendingActionQueue.front()));
            mPendingActionQueue.pop();
            progressCount++;
        }
    }

[chatgpt-codex-connector]

💡 Codex Review

stellar-core/src/herder/PendingEnvelopes.cpp

Lines 603 to 604 in 383f329

	auto& vec = mPendingQSetFetches[h];
	vec.push_back(envelope);

Request missing quorum sets instead of only tracking them

When an SCP envelope references a quorum set that is not already cached, this only appends the envelope to mPendingQSetFetches; unlike the txset path below, no IPC request is sent and the Rust overlay has no qset fetch path. On a fresh node or after a validator changes quorum sets, those envelopes stay in FETCHING indefinitely, so SCP cannot process messages from that validator.

---

stellar-core/overlay/src/main.rs

Line 729 in 383f329

self.overlay_handle.submit_tx(tx, 0, 0);

Relay peer transactions beyond the first hop

When a transaction is learned from a peer, the handler only inserts it into the local Rust mempool. Since only local Core submissions call broadcast_tx, any topology that is not fully connected will stop transaction propagation at the origin's direct peers, leaving validators further away unable to nominate the transaction.

---

stellar-core/overlay/src/xdr.rs

Line 93 in 383f329

return Err(XdrError::UnsupportedFeeBump);

Preserve fee-bump transactions in the Rust overlay

For every TransactionEnvelope::TxFeeBump, parsing returns UnsupportedFeeBump; the submit and receive paths then drop the transaction after C++ has already reported PENDING to the caller. Fee-bump transactions are valid Stellar transactions, so this makes them impossible to propagate or include through the new overlay.

---

stellar-core/src/herder/HerderImpl.cpp

Lines 656 to 658 in 383f329

	mApp.getOverlayManager().broadcastTransaction(env, tx->getFullFee(),
	tx->getNumOperations());
	return TxSubmitStatus::TX_STATUS_PENDING;

Keep standalone submissions in a local path

In RUN_STANDALONE mode RustOverlayManager::start() skips starting the IPC connection, but recvTransaction still sends the transaction to the overlay and immediately returns PENDING. In standalone/manual-close workflows this send is a no-op and triggerNextLedger reads an empty overlay mempool, so submitted transactions disappear instead of being included.

---

stellar-core/src/overlay/RustOverlayManager.cpp

Line 60 in 383f329

return mApp.getHerder().getSCPStateForPeer(ledgerSeq);

Post SCP state collection to the main thread

This callback is invoked by OverlayIPC::readerLoop, so it traverses Herder/SCP state from the IPC reader thread while the main thread may be mutating the same state. The neighboring receive callbacks post back to the main thread; peer GET_SCP_STATE requests should do the same or otherwise synchronize access to avoid races and corrupted SCP snapshots.

---

stellar-core/src/herder/HerderImpl.cpp

Lines 1616 to 1618 in 383f329

	std::tie(proposedSet, applicableProposedSet) =
	makeTxSetFromTransactions(txPhases, mApp, lowerBoundCloseTimeOffset,
	upperBoundCloseTimeOffset, invalidTxPhases);

Evict invalid mempool entries after txset building

makeTxSetFromTransactions reports invalid entries through invalidTxPhases, but the new overlay path never sends those hashes back to Rust for removal. High-fee invalid or stale transactions can therefore be returned at the top of every nomination request until age eviction, crowding out valid lower-fee transactions because only a bounded number of candidates is requested each round.

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 1d11f6b304

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[chatgpt-codex-connector]

Throttle unresolved peer retries outside the 1s loop

When a configured DNS peer has never resolved or connected, it is absent from peer_hostnames, so every reconnect tick treats it as unknown_addrs and launches another DNS-resolution task, even though spawn_peer_retry_task is already doing exponential backoff for the same unresolved hosts. With this interval at 1s, a slow or missing Kubernetes DNS record will be retried every second (and can overlap for multiple peers), bypassing the intended backoff and potentially issuing duplicate raw dials when it finally resolves; track in-flight/unresolved hosts or leave them solely to the retry task.

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[chatgpt-codex-connector]

Remove deleted scheduler files from the VS project

When building through Builds/VisualStudio/stellar-core.vcxproj, the project still references ..\..\src\util\Scheduler.cpp, ..\..\src\util\test\SchedulerTests.cpp, and ..\..\src\util\Scheduler.h; after this deletion those files no longer exist, so the Visual Studio build will fail even though the source files were removed. Please delete the stale project/filter entries along with the scheduler sources.

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