mempool: add nop mempool (backport cometbft#1643) (cometbft#1681)

* mempool: add `nop` mempool (cometbft#1643)

* add `nop` mempool

See
[ADR-111](cometbft#1585)

* implement NopMempool and NopMempoolReactor

modify node.go logic

I had to add NopMempoolReactor to pass it to RPC in order not to change
it.

* check config instead of asserting for nil

* start writing docs

* add changelog

* move changelog

* expand docs

* remove unused func arguments

* add simple test

* make linter happy again

* doc fixes

Co-authored-by: Sergio Mena <sergio@informal.systems>

* rename mempoolReactor to waitSyncP2PReactor

* improve changelog message

* allow empty string for backwards compatibility

cometbft#1643 (comment)

* make ErrNotAllowed private

* mention `create_empty_blocks` in toml

https://github.com/cometbft/cometbft/pull/1643/files#r1400434715

* return nil instead of closed channel

https://github.com/cometbft/cometbft/pull/1643/files#r1400252575

The reader will block forever, which is exactly what we need.

* grammar fixes

Co-authored-by: lasaro <lasaro@informal.systems>

* update changelog entry

* adapt ADR to implementation

* remove old ToC entry

---------

Co-authored-by: Andy Nogueira <me@andynogueira.dev>
Co-authored-by: Sergio Mena <sergio@informal.systems>
Co-authored-by: lasaro <lasaro@informal.systems>
(cherry picked from commit bc83503)

# Conflicts:
#	config/config.go
#	config/toml.go
#	docs/architecture/README.md
#	docs/architecture/adr-111-nop-mempool.md
#	docs/core/configuration.md
#	node/node.go
#	node/setup.go

* fix merge conflicts

* add a missing ToC line

---------

Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>

.changelog/unreleased/features/1643-nop-mempool.md

@@ -0,0 +1,17 @@
+- `[mempool]` Add `nop` mempool ([\#1643](https://github.com/cometbft/cometbft/pull/1643))
+
+  If you want to use it, change mempool's `type` to `nop`:
+
+  ```toml
+  [mempool]
+
+  # The type of mempool for this node to use.
+  #
+  # Possible types:
+  # - "flood" : concurrent linked list mempool with flooding gossip protocol
+  # (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.
+  type = "nop"
+  ```

config/config.go

@@ -28,6 +28,9 @@ const (
 	// Default is v0.
 	MempoolV0 = "v0"
 	MempoolV1 = "v1"
+
+	MempoolTypeFlood = "flood"
+	MempoolTypeNop   = "nop"
 )
 
 // NOTE: Most of the structs & relevant comments + the
@@ -151,6 +154,9 @@ func (cfg *Config) ValidateBasic() error {
 	if err := cfg.Instrumentation.ValidateBasic(); err != nil {
 		return fmt.Errorf("error in [instrumentation] section: %w", err)
 	}
+	if !cfg.Consensus.CreateEmptyBlocks && cfg.Mempool.Type == MempoolTypeNop {
+		return fmt.Errorf("`nop` mempool does not support create_empty_blocks = false")
+	}
 	return nil
 }
 
@@ -721,6 +727,17 @@ type MempoolConfig struct {
 	//  1) "v0" - (default) FIFO mempool.
 	//  2) "v1" - prioritized mempool (deprecated; will be removed in the next release).
 	Version string `mapstructure:"version"`
+
+	// The type of mempool for this node to use.
+	//
+	//  Possible types:
+	//  - "flood" : concurrent linked list mempool with flooding gossip protocol
+	//  (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.
+	Type string `mapstructure:"type"`
+
 	// RootDir is the root directory for all data. This should be configured via
 	// the $CMTHOME env variable or --home cmd flag rather than overriding this
 	// struct field.
@@ -802,6 +819,7 @@ type MempoolConfig struct {
 // DefaultMempoolConfig returns a default configuration for the CometBFT mempool
 func DefaultMempoolConfig() *MempoolConfig {
 	return &MempoolConfig{
+		Type:      MempoolTypeFlood,
 		Version:   MempoolV0,
 		Recheck:   true,
 		Broadcast: true,
@@ -839,6 +857,12 @@ func (cfg *MempoolConfig) WalEnabled() bool {
 // ValidateBasic performs basic validation (checking param bounds, etc.) and
 // returns an error if any check fails.
 func (cfg *MempoolConfig) ValidateBasic() error {
+	switch cfg.Type {
+	case MempoolTypeFlood, MempoolTypeNop:
+	case "": // allow empty string to be backwards compatible
+	default:
+		return fmt.Errorf("unknown mempool type: %q", cfg.Type)
+	}
 	if cfg.Size < 0 {
 		return errors.New("size can't be negative")
 	}

config/config_test.go

@@ -37,6 +37,11 @@ func TestConfigValidateBasic(t *testing.T) {
 	// tamper with timeout_propose
 	cfg.Consensus.TimeoutPropose = -10 * time.Second
 	assert.Error(t, cfg.ValidateBasic())
+	cfg.Consensus.TimeoutPropose = 3 * time.Second
+
+	cfg.Consensus.CreateEmptyBlocks = false
+	cfg.Mempool.Type = MempoolTypeNop
+	assert.Error(t, cfg.ValidateBasic())
 }
 
 func TestTLSConfiguration(t *testing.T) {
@@ -121,6 +126,9 @@ func TestMempoolConfigValidateBasic(t *testing.T) {
 		assert.Error(t, cfg.ValidateBasic())
 		reflect.ValueOf(cfg).Elem().FieldByName(fieldName).SetInt(0)
 	}
+
+	reflect.ValueOf(cfg).Elem().FieldByName("Type").SetString("invalid")
+	assert.Error(t, cfg.ValidateBasic())
 }
 
 func TestStateSyncConfigValidateBasic(t *testing.T) {

config/toml.go

@@ -345,6 +345,16 @@ dial_timeout = "{{ .P2P.DialTimeout }}"
 #   2) "v1" - prioritized mempool (deprecated; will be removed in the next release).
 version = "{{ .Mempool.Version }}"
 
+# The type of mempool for this node to use.
+#
+#  Possible types:
+#  - "flood" : concurrent linked list mempool with flooding gossip protocol
+#  (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.
+type = "flood"
+
 recheck = {{ .Mempool.Recheck }}
 broadcast = {{ .Mempool.Broadcast }}
 wal_dir = "{{ js .Mempool.WalPath }}"

docs/architecture/README.md

@@ -84,6 +84,7 @@ therefore they have links to it and refer to CometBFT as "Tendermint" or "Tender
 - [ADR-075: RPC Event Subscription Interface](./adr-075-rpc-subscription.md)
 - [ADR-079: Ed25519 Verification](./adr-079-ed25519-verification.md)
 - [ADR-081: Protocol Buffers Management](./adr-081-protobuf-mgmt.md)
+- [ADR-111: `nop` Mempool](./adr-111-nop-mempool.md)
 
 ### Deprecated