Add a simple mempool module prototype

The prototype expects that new transactions will be delivered to
it by means of NewRequests events and stores them in an in-memory
map. It uses hashes for transaction and batch IDs.
To support crash-recovery, persistent storage should be added for
the transactions.

pkg/mempool/simplemempool/internal/common/common.go

@@ -0,0 +1,24 @@
+package common
+
+import (
+	"github.com/filecoin-project/mir/pkg/pb/requestpb"
+	t "github.com/filecoin-project/mir/pkg/types"
+)
+
+// ModuleConfig sets the module ids. All replicas are expected to use identical module configurations.
+type ModuleConfig struct {
+	Self   t.ModuleID // id of this module
+	Hasher t.ModuleID
+	Crypto t.ModuleID
+}
+
+// ModuleParams sets the values for the parameters of an instance of the protocol.
+// All replicas are expected to use identical module parameters.
+type ModuleParams struct {
+	MaxTransactionsInBatch int
+}
+
+// State represents the common state accessible to all parts of the module implementation.
+type State struct {
+	TxByID map[t.TxID]*requestpb.Request
+}

pkg/mempool/simplemempool/internal/parts/computeids/computeids.go

@@ -0,0 +1,66 @@
+package computeids
+
+import (
+	"github.com/filecoin-project/mir/pkg/dsl"
+	mpdsl "github.com/filecoin-project/mir/pkg/mempool/dsl"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/common"
+	mppb "github.com/filecoin-project/mir/pkg/pb/mempoolpb"
+	"github.com/filecoin-project/mir/pkg/pb/requestpb"
+	"github.com/filecoin-project/mir/pkg/serializing"
+	t "github.com/filecoin-project/mir/pkg/types"
+)
+
+//
+func IncludeComputationOfTransactionAndBatchIDs(
+	m dsl.Module,
+	mc *common.ModuleConfig,
+	params *common.ModuleParams,
+	commonState *common.State,
+) {
+	mpdsl.UponRequestTransactionIDs(m, func(txs []*requestpb.Request, origin *mppb.RequestTransactionIDsOrigin) error {
+		txMsgs := make([][][]byte, len(txs))
+		for i, tx := range txs {
+			txMsgs[i] = serializing.RequestForHash(tx)
+		}
+
+		dsl.HashRequest(m, mc.Hasher, txMsgs, &computeHashForTransactionIDsContext{origin})
+		return nil
+	})
+
+	dsl.UponHashResult(m, func(hashes [][]byte, context *computeHashForTransactionIDsContext) error {
+		txIDs := make([]t.TxID, len(hashes))
+		for i, hash := range hashes {
+			txIDs[i] = t.TxID(hash)
+		}
+
+		mpdsl.TransactionIDsResponse(m, t.ModuleID(context.origin.Module), txIDs, context.origin)
+		return nil
+	})
+
+	mpdsl.UponRequestBatchID(m, func(txIDs []t.TxID, origin *mppb.RequestBatchIDOrigin) error {
+		data := make([][]byte, len(txIDs))
+		for i, txID := range txIDs {
+			data[i] = txID.Bytes()
+		}
+
+		dsl.HashOneMessage(m, mc.Hasher, data, &computeHashForBatchIDContext{origin})
+		return nil
+	})
+
+	dsl.UponOneHashResult(m, func(hash []byte, context *computeHashForBatchIDContext) error {
+		mpdsl.BatchIDResponse(m, t.ModuleID(context.origin.Module), t.BatchID(hash), context.origin)
+		return nil
+	})
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Context data structures                                                                                            //
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+type computeHashForTransactionIDsContext struct {
+	origin *mppb.RequestTransactionIDsOrigin
+}
+
+type computeHashForBatchIDContext struct {
+	origin *mppb.RequestBatchIDOrigin
+}

pkg/mempool/simplemempool/internal/parts/formbatches/formbatches.go

@@ -0,0 +1,77 @@
+package formbatches
+
+import (
+	"github.com/filecoin-project/mir/pkg/dsl"
+	mpdsl "github.com/filecoin-project/mir/pkg/mempool/dsl"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/common"
+	mppb "github.com/filecoin-project/mir/pkg/pb/mempoolpb"
+	"github.com/filecoin-project/mir/pkg/pb/requestpb"
+	t "github.com/filecoin-project/mir/pkg/types"
+)
+
+type State struct {
+	*common.State
+	NewTxIDs []t.TxID
+}
+
+// IncludeBatchCreation registers event handlers for processing new transactions and forming batches.
+func IncludeBatchCreation(
+	m dsl.Module,
+	mc *common.ModuleConfig,
+	params *common.ModuleParams,
+	commonState *common.State,
+) {
+	state := &State{
+		State:    commonState,
+		NewTxIDs: nil,
+	}
+
+	dsl.UponNewRequests(m, func(txs []*requestpb.Request) error {
+		mpdsl.RequestTransactionIDs(m, mc.Self, txs, &requestTxIDsContext{txs})
+		return nil
+	})
+
+	mpdsl.UponTransactionIDsResponse(m, func(txIDs []t.TxID, context *requestTxIDsContext) error {
+		for i := range txIDs {
+			state.TxByID[txIDs[i]] = context.txs[i]
+		}
+		state.NewTxIDs = append(state.NewTxIDs, txIDs...)
+		return nil
+	})
+
+	mpdsl.UponRequestBatch(m, func(origin *mppb.RequestBatchOrigin) error {
+		var txIDs []t.TxID
+		var txs []*requestpb.Request
+		batchSize := 0
+
+		var i int
+		var txID t.TxID
+
+		for i, txID = range state.NewTxIDs {
+			tx := state.TxByID[txID]
+
+			// TODO: add other limitations (if any) here.
+			if i == params.MaxTransactionsInBatch {
+				break
+			}
+
+			txIDs = append(txIDs, txID)
+			txs = append(txs, tx)
+			batchSize += len(tx.Data)
+		}
+
+		state.NewTxIDs = state.NewTxIDs[i:]
+
+		// Note that a batch may be empty.
+		mpdsl.NewBatch(m, t.ModuleID(origin.Module), txIDs, txs, origin)
+		return nil
+	})
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Context data structures                                                                                            //
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+type requestTxIDsContext struct {
+	txs []*requestpb.Request
+}

pkg/mempool/simplemempool/internal/parts/lookuptxs/lockuptxs.go

@@ -0,0 +1,30 @@
+package lookuptxs
+
+import (
+	"github.com/filecoin-project/mir/pkg/dsl"
+	mpdsl "github.com/filecoin-project/mir/pkg/mempool/dsl"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/common"
+	mppb "github.com/filecoin-project/mir/pkg/pb/mempoolpb"
+	"github.com/filecoin-project/mir/pkg/pb/requestpb"
+	t "github.com/filecoin-project/mir/pkg/types"
+)
+
+// IncludeTransactionLookupByID registers event handlers for transaction looking up transactions in the mempool by
+// their IDs.
+func IncludeTransactionLookupByID(
+	m dsl.Module,
+	mc *common.ModuleConfig,
+	params *common.ModuleParams,
+	commonState *common.State,
+) {
+	mpdsl.UponRequestTransactions(m, func(txIDs []t.TxID, origin *mppb.RequestTransactionsOrigin) error {
+		present := make([]bool, len(txIDs))
+		txs := make([]*requestpb.Request, len(txIDs))
+		for i, txID := range txIDs {
+			txs[i], present[i] = commonState.TxByID[txID]
+		}
+
+		mpdsl.TransactionsResponse(m, t.ModuleID(origin.Module), present, txs, origin)
+		return nil
+	})
+}

pkg/mempool/simplemempool/simplemempool.go

@@ -0,0 +1,49 @@
+package simplemempool
+
+import (
+	"github.com/filecoin-project/mir/pkg/dsl"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/common"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/parts/computeids"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/parts/formbatches"
+	"github.com/filecoin-project/mir/pkg/mempool/simplemempool/internal/parts/lookuptxs"
+	"github.com/filecoin-project/mir/pkg/modules"
+	"github.com/filecoin-project/mir/pkg/pb/requestpb"
+	t "github.com/filecoin-project/mir/pkg/types"
+)
+
+// ModuleConfig sets the module ids. All replicas are expected to use identical module configurations.
+type ModuleConfig = common.ModuleConfig
+
+// ModuleParams sets the values for the parameters of an instance of the protocol.
+// All replicas are expected to use identical module parameters.
+type ModuleParams = common.ModuleParams
+
+// DefaultModuleConfig returns a valid module config with default names for all modules.
+func DefaultModuleConfig() *ModuleConfig {
+	return &ModuleConfig{
+		Self:   "availability",
+		Hasher: "hasher",
+		Crypto: "crypto",
+	}
+}
+
+// NewModule creates a new instance of a simple mempool module implementation. It passively waits for
+// eventpb.NewRequests events and stores them in a local map.
+//
+// On a batch request, this implementation creates a batch that consists of as many requests received since the
+// previous batch request as possible with respect to params.MaxTransactionsInBatch.
+//
+// This implementation uses the hash function provided by the mc.Hasher module to compute transaction IDs and batch IDs.
+func NewModule(mc *ModuleConfig, params *ModuleParams) modules.Module {
+	m := dsl.NewModule(mc.Self)
+
+	commonState := &common.State{
+		TxByID: make(map[t.TxID]*requestpb.Request),
+	}
+
+	computeids.IncludeComputationOfTransactionAndBatchIDs(m, mc, params, commonState)
+	formbatches.IncludeBatchCreation(m, mc, params, commonState)
+	lookuptxs.IncludeTransactionLookupByID(m, mc, params, commonState)
+
+	return m
+}