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Migrate thread safety to RCLConsensus (RIPD-1389):
Moves thread safety from generic Consensus to RCLConsensus and switch generic Consensus to adaptor design.
This commit is contained in:
Brad Chase
@@ -480,69 +480,87 @@ struct Ledger
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//... implementation specific
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};
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```
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[heading Generic Consensus Interface]
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Following the
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[@https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern CRTP]
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idiom, generic =Consensus= relies on a deriving class implementing a set of
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helpers and callbacks that encapsulate implementation specific details of the
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algorithm. Below are excerpts of the generic consensus implementation and of
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helper types that will interact with the concrete implementing class.
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[heading PeerProposal] The =PeerProposal= type represents the signed position taken
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by a peer during consensus. The only type requirement is owning an instance of a
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generic =ConsensusProposal=.
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```
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// Represents our proposed position or a peer's proposed position
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// and is provided with the generic code
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template <class NodeID_t, class LedgerID_t, class Position_t> class ConsensusProposal;
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struct PeerPosition
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{
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ConsensusProposal<
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NodeID_t,
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typename Ledger::ID,
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typename TxSet::ID> const &
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proposal() const;
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// ... implementation specific
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};
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```
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[heading Generic Consensus Interface]
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The generic =Consensus= relies on =Adaptor= template class to implement a set
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of helper functions that plug the consensus algorithm into a specific application.
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The =Adaptor= class also defines the types above needed by the algorithm. Below
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are excerpts of the generic consensus implementation and of helper types that will
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interact with the concrete implementing class.
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```
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// Represents a transction under dispute this round
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template <class Tx_t, class NodeID_t> class DisputedTx;
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template <class Derived, class Traits> class Consensus
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// Represents how the node participates in Consensus this round
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enum class ConsensusMode { proposing, observing, wrongLedger, switchedLedger};
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// Measure duration of phases of consensus
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class ConsensusTimer
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{
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protected:
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enum class Mode { proposing, observing, wrongLedger, switchedLedger};
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// Measure duration of phases of consensus
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class Stopwatch
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{
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public:
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std::chrono::milliseconds read() const;
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// details omitted ...
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};
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// Initial ledger close times, not rounded by closeTimeResolution
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// Used to gauge degree of synchronization between a node and its peers
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struct CloseTimes
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{
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std::map<NetClock::time_point, int> peers;
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NetClock::time_point self;
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};
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// Encapsulates the result of consensus.
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struct Result
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{
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//! The set of transactions consensus agrees go in the ledger
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TxSet_t set;
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//! Our proposed position on transactions/close time
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Proposal_t position;
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//! Transactions which are under dispute with our peers
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using Dispute_t = DisputedTx<Tx_t, NodeID_t>;
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hash_map<typename Tx_t::ID, Dispute_t> disputes;
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// Set of TxSet ids we have already compared/created disputes
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hash_set<typename TxSet_t::ID> compares;
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// Measures the duration of the establish phase for this consensus round
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Stopwatch roundTime;
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// Indicates state in which consensus ended. Once in the accept phase
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// will be either Yes or MovedOn
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ConsensusState state = ConsensusState::No;
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};
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public:
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std::chrono::milliseconds read() const;
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// details omitted ...
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};
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// Initial ledger close times, not rounded by closeTimeResolution
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// Used to gauge degree of synchronization between a node and its peers
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struct ConsensusCloseTimes
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{
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std::map<NetClock::time_point, int> peers;
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NetClock::time_point self;
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};
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// Encapsulates the result of consensus.
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template <class Adaptor>
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struct ConsensusResult
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{
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//! The set of transactions consensus agrees go in the ledger
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Adaptor::TxSet_t set;
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//! Our proposed position on transactions/close time
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ConsensusProposal<...> position;
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//! Transactions which are under dispute with our peers
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hash_map<Adaptor::Tx_t::ID, DisputedTx<...>> disputes;
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// Set of TxSet ids we have already compared/created disputes
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hash_set<typename Adaptor::TxSet_t::ID> compares;
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// Measures the duration of the establish phase for this consensus round
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ConsensusTimer roundTime;
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// Indicates state in which consensus ended. Once in the accept phase
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// will be either Yes or MovedOn
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ConsensusState state = ConsensusState::No;
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};
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template <class Adaptor>
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class Consensus
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{
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public:
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Consensus(clock_type, Adaptor &, beast::journal);
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// Kick-off the next round of consensus.
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void startRound(
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NetClock::time_point const& now,
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@@ -568,26 +586,20 @@ public:
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The stub below shows the set of callback/helper functions required in the implementing class.
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```
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struct Traits
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struct Adaptor
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{
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using Ledger_t = Ledger;
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using TxSet_t = TxSet;
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using NodeID_t = ...; // Integer-like std::uint32_t to uniquely identify a node
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using Ledger_t = Ledger;
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using TxSet_t = TxSet;
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using PeerProposal_t = PeerProposal;
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using NodeID_t = ...; // Integer-like std::uint32_t to uniquely identify a node
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};
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class ConsensusImp : public Consensus<ConsensusImp, Traits>
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{
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// Attempt to acquire a specific ledger from the network.
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boost::optional<Ledger> acquireLedger(Ledger::ID const & ledgerID);
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// Acquire the transaction set associated with a proposed position.
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boost::optional<TxSet> acquireTxSet(TxSet::ID const & setID);
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// Get peers' proposed positions. Returns an iterable
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// with value_type convertable to ConsensusPosition<...>
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auto const & proposals(Ledger::ID const & ledgerID);
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// Whether any transactions are in the open ledger
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bool hasOpenTransactions() const;
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@@ -602,24 +614,27 @@ class ConsensusImp : public Consensus<ConsensusImp, Traits>
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// application thinks consensus should use as the prior ledger.
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Ledger::ID getPrevLedger(Ledger::ID const & prevLedgerID,
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Ledger const & prevLedger,
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Mode mode);
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ConsensusMode mode);
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// Called when consensus operating mode changes
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void onModeChange(ConsensuMode before, ConsensusMode after);
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// Called when ledger closes. Implementation should generate an initial Result
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// with position based on the current open ledger's transactions.
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Result onClose(Ledger const &, Ledger const & prev, Mode mode);
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ConsensusResult onClose(Ledger const &, Ledger const & prev, ConsensusMode mode);
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// Called when ledger is accepted by consensus
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void onAccept(Result const & result,
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void onAccept(ConsensusResult const & result,
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RCLCxLedger const & prevLedger,
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NetClock::duration closeResolution,
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CloseTimes const & rawCloseTimes,
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Mode const & mode);
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ConsensusCloseTimes const & rawCloseTimes,
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ConsensusMode const & mode);
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// Propose the position to peers.
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void propose(ConsensusProposal<...> const & pos);
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// Relay a received peer proposal on to other peer's.
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void relay(ConsensusProposal<...> const & pos);
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void relay(PeerPosition_t const & pos);
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// Relay a disputed transaction to peers
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void relay(TxSet::Tx const & tx);
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@@ -111,6 +111,7 @@ INPUT = \
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../src/test/jtx/WSClient.h \
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../src/ripple/consensus/Consensus.h \
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../src/ripple/consensus/ConsensusProposal.h \
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../src/ripple/consensus/ConsensusTypes.h \
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../src/ripple/consensus/DisputedTx.h \
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../src/ripple/consensus/LedgerTiming.h \
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../src/ripple/consensus/Validations.h \
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