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rpc: handle shutdown during long poll and wait methods

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The waitTipChanged() now returns nullopt if the node is shutting down.

Previously it would return the last known tip during shutdown, but
this creates an ambiguous circumstance in the scenario where the
node is started and quickly shutdown, before notifications().TipBlock()
is set.

The getblocktemplate, waitfornewblock and waitforblockheight RPC
are updated to handle this. Existing behavior is preserved.

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>
This commit is contained in:
Sjors Provoost
2025-02-19 10:28:43 +01:00
parent a3bf43343f
commit 64a2795fd4
4 changed files with 63 additions and 28 deletions
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28
src/node/interfaces.cpp
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@@ -1070,22 +1070,34 @@ public:
return BlockRef{tip->GetBlockHash(), tip->nHeight};
}
BlockRef waitTipChanged(uint256 current_tip, MillisecondsDouble timeout) override
std::optional<BlockRef> waitTipChanged(uint256 current_tip, MillisecondsDouble timeout) override
{
Assume(timeout >= 0ms); // No internal callers should use a negative timeout
if (timeout < 0ms) timeout = 0ms;
if (timeout > std::chrono::years{100}) timeout = std::chrono::years{100}; // Upper bound to avoid UB in std::chrono
auto deadline{std::chrono::steady_clock::now() + timeout};
{
WAIT_LOCK(notifications().m_tip_block_mutex, lock);
notifications().m_tip_block_cv.wait_for(lock, timeout, [&]() EXCLUSIVE_LOCKS_REQUIRED(notifications().m_tip_block_mutex) {
// We need to wait for m_tip_block to be set AND for the value
// to differ from the current_tip value.
return (notifications().TipBlock() && notifications().TipBlock() != current_tip) || chainman().m_interrupt;
// For callers convenience, wait longer than the provided timeout
// during startup for the tip to be non-null. That way this function
// always returns valid tip information when possible and only
// returns null when shutting down, not when timing out.
notifications().m_tip_block_cv.wait(lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(notifications().m_tip_block_mutex) {
return notifications().TipBlock() || chainman().m_interrupt;
});
if (chainman().m_interrupt) return {};
// At this point TipBlock is set, so continue to wait until it is
// different then `current_tip` provided by caller.
notifications().m_tip_block_cv.wait_until(lock, deadline, [&]() EXCLUSIVE_LOCKS_REQUIRED(notifications().m_tip_block_mutex) {
return Assume(notifications().TipBlock()) != current_tip || chainman().m_interrupt;
});
}
// Must release m_tip_block_mutex before locking cs_main, to avoid deadlocks.
LOCK(::cs_main);
return BlockRef{chainman().ActiveChain().Tip()->GetBlockHash(), chainman().ActiveChain().Tip()->nHeight};
if (chainman().m_interrupt) return {};
// Must release m_tip_block_mutex before getTip() locks cs_main, to
// avoid deadlocks.
return getTip();
}
std::unique_ptr<BlockTemplate> createNewBlock(const BlockCreateOptions& options) override