chore: remove non-CAT mempool implementations (#2803)

Part 1 of celestiaorg/celestia-app#6573
Closes #1382
Closes #2802


## Summary

- Remove v0 (flood/CListMempool) and v1 (priority) mempool
implementations, which have been dead code since celestia-app v6
forcibly overrides any non-CAT mempool configuration
- The CAT mempool is now the only supported mempool type (besides nop),
reducing user confusion where operators may configure "flood" or
"priority" thinking their setting is honored
- Migrate all tests (consensus, node, fuzz, e2e) from CListMempool to
cat.TxPool


## Test plan

- [x] `make build` passes
- [x] `go test ./mempool/...` passes
- [x] `go test ./config/...` passes
- [x] `go test ./consensus/...` passes
- [x] `go test ./node/...` passes
- [x] `go vet ./test/fuzz/...` passes
- [x] `make lint` passes with 0 issues

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: rootulp

.changelog/unreleased/breaking-changes/6573-remove-non-cat-mempools.md

@@ -0,0 +1 @@
+Remove non-CAT mempool implementations (v0/flood and v1/priority). The CAT mempool is now the only supported mempool type (besides nop).

config/config.go

@@ -40,13 +40,8 @@ const (
 	DefaultNodeKeyName  = "node_key.json"
 	DefaultAddrBookName = "addrbook.json"
 
-	MempoolTypeFlood          = "flood"
-	MempoolTypeNop            = "nop"
-	MempoolTypePriority       = "priority"
-	MempoolTypeCAT            = "cat"
-	LegacyMempoolTypeFlood    = "v0"
-	LegacyMempoolTypePriority = "v1"
-	LegacyMempoolTypeCAT      = "v2"
+	MempoolTypeNop = "nop"
+	MempoolTypeCAT = "cat"
 )
 
 // NOTE: Most of the structs & relevant comments + the
@@ -763,18 +758,12 @@ func DefaultFuzzConnConfig() *FuzzConnConfig {
 //-----------------------------------------------------------------------------
 // MempoolConfig
 
-// MempoolConfig defines the configuration options for the CometBFT mempool
-//
-// Note: Until v0.37 there was a `Version` field to select which implementation
-// of the mempool to use. Two versions used to exist: the current, default
-// implementation (previously called v0), and a prioritized mempool (v1), which
-// was removed (see https://github.com/cometbft/cometbft/issues/260).
+// MempoolConfig defines the configuration options for the CometBFT mempool.
 type MempoolConfig struct {
 	// The type of mempool for this node to use.
 	//
 	//  Possible types:
-	//  - "flood" : concurrent linked list mempool with flooding gossip protocol
-	//  (default)
+	//  - "cat"   : content addressable mempool (default)
 	//  - "nop"   : nop-mempool (short for no operation; the ABCI app is
 	//  responsible for storing, disseminating and proposing txs).
 	//  "create_empty_blocks=false" is not supported.
@@ -914,8 +903,7 @@ func (cfg *MempoolConfig) WalEnabled() bool {
 // returns an error if any check fails.
 func (cfg *MempoolConfig) ValidateBasic() error {
 	switch cfg.Type {
-	case MempoolTypeFlood, MempoolTypeNop, MempoolTypePriority, LegacyMempoolTypePriority, LegacyMempoolTypeFlood, MempoolTypeCAT, LegacyMempoolTypeCAT:
-	case "": // allow empty string to be backwards compatible
+	case MempoolTypeCAT, MempoolTypeNop:
 	default:
 		return fmt.Errorf("unknown mempool type: %q", cfg.Type)
 	}

config/toml_test.go

@@ -96,7 +96,7 @@ func TestMempoolTypeNotInTemplate(t *testing.T) {
 
 	// The mempool type field should not appear in the generated config.
 	// Use a specific pattern to avoid matching unrelated fields like trace_type.
-	for _, mempoolType := range []string{"cat", "flood", "nop", "priority"} {
+	for _, mempoolType := range []string{"cat", "nop"} {
 		pattern := fmt.Sprintf("type = \"%s\"", mempoolType)
 		assert.NotContains(t, configContent, pattern,
 			"Config should not contain mempool type field")

consensus/byzantine_test.go

@@ -22,7 +22,7 @@ import (
 	"github.com/cometbft/cometbft/libs/log"
 	"github.com/cometbft/cometbft/libs/service"
 	cmtsync "github.com/cometbft/cometbft/libs/sync"
-	mempl "github.com/cometbft/cometbft/mempool"
+	"github.com/cometbft/cometbft/mempool/cat"
 	"github.com/cometbft/cometbft/proxy"
 
 	"github.com/cometbft/cometbft/p2p"
@@ -96,11 +96,14 @@ func TestByzantinePrevoteEquivocation(t *testing.T) {
 		proxyAppConnMem := proxy.NewAppConnMempool(abcicli.NewLocalClient(mtx, app), proxy.NopMetrics())
 
 		// Make Mempool
-		mempool := mempl.NewCListMempool(config.Mempool,
+		mempool := cat.NewTxPool(
+			log.TestingLogger(),
+			config.Mempool,
 			proxyAppConnMem,
 			state.LastBlockHeight,
-			mempl.WithPreCheck(sm.TxPreCheck(state)),
-			mempl.WithPostCheck(sm.TxPostCheck(state)))
+			cat.WithPreCheck(sm.TxPreCheck(state)),
+			cat.WithPostCheck(sm.TxPostCheck(state)),
+		)
 
 		if thisConfig.Consensus.WaitForTxs() {
 			mempool.EnableTxsAvailable()

consensus/common_test.go

@@ -32,6 +32,7 @@ import (
 	cmtpubsub "github.com/cometbft/cometbft/libs/pubsub"
 	cmtsync "github.com/cometbft/cometbft/libs/sync"
 	mempl "github.com/cometbft/cometbft/mempool"
+	"github.com/cometbft/cometbft/mempool/cat"
 	"github.com/cometbft/cometbft/p2p"
 	"github.com/cometbft/cometbft/privval"
 	cmtstate "github.com/cometbft/cometbft/proto/tendermint/state"
@@ -424,12 +425,15 @@ func newStateWithConfigAndBlockStore(
 	memplMetrics := mempl.NopMetrics()
 
 	// Make Mempool
-	mempool := mempl.NewCListMempool(config.Mempool,
+	mempool := cat.NewTxPool(
+		log.TestingLogger(),
+		config.Mempool,
 		proxyAppConnMem,
 		state.LastBlockHeight,
-		mempl.WithMetrics(memplMetrics),
-		mempl.WithPreCheck(sm.TxPreCheck(state)),
-		mempl.WithPostCheck(sm.TxPostCheck(state)))
+		cat.WithMetrics(memplMetrics),
+		cat.WithPreCheck(sm.TxPreCheck(state)),
+		cat.WithPostCheck(sm.TxPostCheck(state)),
+	)
 
 	if thisConfig.Consensus.WaitForTxs() {
 		mempool.EnableTxsAvailable()

consensus/reactor_test.go

@@ -31,6 +31,7 @@ import (
 	cmtrand "github.com/cometbft/cometbft/libs/rand"
 	cmtsync "github.com/cometbft/cometbft/libs/sync"
 	mempl "github.com/cometbft/cometbft/mempool"
+	"github.com/cometbft/cometbft/mempool/cat"
 	"github.com/cometbft/cometbft/p2p"
 	p2pmock "github.com/cometbft/cometbft/p2p/mock"
 	cmtcons "github.com/cometbft/cometbft/proto/tendermint/consensus"
@@ -165,12 +166,15 @@ func TestReactorWithEvidence(t *testing.T) {
 		proxyAppConnMem := proxy.NewAppConnMempool(abcicli.NewLocalClient(mtx, app), proxy.NopMetrics())
 
 		// Make Mempool
-		mempool := mempl.NewCListMempool(config.Mempool,
+		mempool := cat.NewTxPool(
+			log.TestingLogger(),
+			config.Mempool,
 			proxyAppConnMem,
 			state.LastBlockHeight,
-			mempl.WithMetrics(memplMetrics),
-			mempl.WithPreCheck(sm.TxPreCheck(state)),
-			mempl.WithPostCheck(sm.TxPostCheck(state)))
+			cat.WithMetrics(memplMetrics),
+			cat.WithPreCheck(sm.TxPreCheck(state)),
+			cat.WithPostCheck(sm.TxPostCheck(state)),
+		)
 
 		if thisConfig.Consensus.WaitForTxs() {
 			mempool.EnableTxsAvailable()

mempool/bench_test.go

@@ -2,91 +2,13 @@ package mempool
 
 import (
 	"crypto/rand"
-	"crypto/sha256"
 	"testing"
 
-	"fmt"
-
 	"github.com/stretchr/testify/require"
 
-	"github.com/cometbft/cometbft/abci/example/kvstore"
-	abci "github.com/cometbft/cometbft/abci/types"
-	"github.com/cometbft/cometbft/proxy"
 	"github.com/cometbft/cometbft/types"
 )
 
-func TestCacheAfterUpdate(t *testing.T) {
-	app := kvstore.NewInMemoryApplication()
-	cc := proxy.NewLocalClientCreator(app)
-	mp, cleanup := newMempoolWithApp(cc)
-	defer cleanup()
-
-	// reAddIndices & txsInCache can have elements > numTxsToCreate
-	// also assumes max index is 255 for convenience
-	// txs in cache also checks order of elements
-	tests := []struct {
-		numTxsToCreate int
-		updateIndices  []int
-		reAddIndices   []int
-		txsInCache     []int
-	}{
-		{1, []int{}, []int{1}, []int{1, 0}},    // adding new txs works
-		{2, []int{1}, []int{}, []int{1, 0}},    // update doesn't remove tx from cache
-		{2, []int{2}, []int{}, []int{2, 1, 0}}, // update adds new tx to cache
-		{2, []int{1}, []int{1}, []int{1, 0}},   // re-adding after update doesn't make dupe
-	}
-	for tcIndex, tc := range tests {
-		for i := 0; i < tc.numTxsToCreate; i++ {
-			tx := kvstore.NewTx(fmt.Sprintf("%d", i), "value")
-			err := mp.CheckTx(tx, func(resp *abci.ResponseCheckTx) {
-				require.False(t, resp.IsErr())
-			}, TxInfo{})
-			require.NoError(t, err)
-		}
-
-		updateTxs := []*types.CachedTx{}
-		for _, v := range tc.updateIndices {
-			tx := kvstore.NewTx(fmt.Sprintf("%d", v), "value")
-			updateTxs = append(updateTxs, types.Tx(tx).ToCachedTx())
-		}
-		err := mp.Update(int64(tcIndex), updateTxs, abciResponses(len(updateTxs), abci.CodeTypeOK), nil, nil)
-		require.NoError(t, err)
-
-		for _, v := range tc.reAddIndices {
-			tx := kvstore.NewTx(fmt.Sprintf("%d", v), "value")
-			_ = mp.CheckTx(tx, func(resp *abci.ResponseCheckTx) {
-				require.False(t, resp.IsErr())
-			}, TxInfo{})
-		}
-
-		cache := mp.cache.(*LRUTxCache)
-		node := cache.GetList().Front()
-		counter := 0
-		for node != nil {
-			require.NotEqual(t, len(tc.txsInCache), counter,
-				"cache larger than expected on testcase %d", tcIndex)
-
-			nodeVal := node.Value.(types.TxKey)
-			expTx := kvstore.NewTx(fmt.Sprintf("%d", tc.txsInCache[len(tc.txsInCache)-counter-1]), "value")
-			expectedBz := sha256.Sum256(expTx)
-			// Reference for reading the errors:
-			// >>> sha256('\x00').hexdigest()
-			// '6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d'
-			// >>> sha256('\x01').hexdigest()
-			// '4bf5122f344554c53bde2ebb8cd2b7e3d1600ad631c385a5d7cce23c7785459a'
-			// >>> sha256('\x02').hexdigest()
-			// 'dbc1b4c900ffe48d575b5da5c638040125f65db0fe3e24494b76ea986457d986'
-
-			require.EqualValues(t, expectedBz, nodeVal, "Equality failed on index %d, tc %d", counter, tcIndex)
-			counter++
-			node = node.Next()
-		}
-		require.Equal(t, len(tc.txsInCache), counter,
-			"cache smaller than expected on testcase %d", tcIndex)
-		mp.Flush()
-	}
-}
-
 func TestCacheRemove(t *testing.T) {
 	cache := NewLRUTxCache(100)
 	numTxs := 10