Add discriminant type to allow multiple mempool services (#441)

Overwatch requires all services to have a different service id.
Unfortunately, such service id can't depend on generic parameters,
which means that we can't have two instances of the mempool
service even if they are instantiated with different types.
This commit circuments this limitation by adding another
type parameter.

nodes/nomos-node/src/bridges/mod.rs

@@ -17,6 +17,7 @@ use nomos_http::http::{HttpMethod, HttpRequest, HttpResponse};
 use nomos_mempool::backend::mockpool::MockPool;
 use nomos_mempool::network::adapters::libp2p::Libp2pAdapter;
 use nomos_mempool::network::NetworkAdapter;
+use nomos_mempool::Transaction as TxDiscriminant;
 use nomos_mempool::{MempoolMetrics, MempoolMsg, MempoolService};
 use nomos_network::backends::libp2p::Libp2p;
 use nomos_network::backends::NetworkBackend;
@@ -51,7 +52,7 @@ pub fn mempool_metrics_bridge(
     handle: overwatch_rs::overwatch::handle::OverwatchHandle,
 ) -> HttpBridgeRunner {
     Box::new(Box::pin(async move {
-        get_handler!(handle, MempoolService<Libp2pAdapter<Tx, <Tx as Transaction>::Hash>, MockPool<Tx, <Tx as Transaction>::Hash>>, "metrics" => handle_mempool_metrics_req)
+        get_handler!(handle, MempoolService<Libp2pAdapter<Tx, <Tx as Transaction>::Hash>, MockPool<Tx, <Tx as Transaction>::Hash>, TxDiscriminant>, "metrics" => handle_mempool_metrics_req)
     }))
 }
 
@@ -77,7 +78,7 @@ where
     Box::new(Box::pin(async move {
         let (mempool_channel, mut http_request_channel) =
             build_http_bridge::<
-                MempoolService<A, MockPool<Tx, <Tx as Transaction>::Hash>>,
+                MempoolService<A, MockPool<Tx, <Tx as Transaction>::Hash>, TxDiscriminant>,
                 AxumBackend,
                 _,
             >(handle.clone(), HttpMethod::POST, "addtx")

nodes/nomos-node/src/lib.rs

@@ -20,7 +20,7 @@ use nomos_http::bridge::HttpBridgeService;
 use nomos_http::http::HttpService;
 use nomos_log::Logger;
 use nomos_mempool::network::adapters::libp2p::Libp2pAdapter as MempoolLibp2pAdapter;
-
+use nomos_mempool::Transaction as TxDiscriminant;
 use nomos_mempool::{backend::mockpool::MockPool, MempoolService};
 use nomos_network::backends::libp2p::Libp2p;
 
@@ -56,6 +56,7 @@ type DataAvailability = DataAvailabilityService<
 type Mempool = MempoolService<
     MempoolLibp2pAdapter<Tx, <Tx as Transaction>::Hash>,
     MockPool<Tx, <Tx as Transaction>::Hash>,
+    TxDiscriminant,
 >;
 
 #[derive(Services)]

nomos-services/consensus/src/lib.rs

@@ -42,6 +42,7 @@ use nomos_core::tx::{Transaction, TxSelect};
 use nomos_core::vote::Tally;
 use nomos_mempool::{
     backend::MemPool, network::NetworkAdapter as MempoolAdapter, MempoolMsg, MempoolService,
+    Transaction as TxDiscriminant,
 };
 use nomos_network::NetworkService;
 use overwatch_rs::services::relay::{OutboundRelay, Relay, RelayMessage};
@@ -119,7 +120,7 @@ where
     // underlying networking backend. We need this so we can relay and check the types properly
     // when implementing ServiceCore for CarnotConsensus
     network_relay: Relay<NetworkService<A::Backend>>,
-    mempool_relay: Relay<MempoolService<M, P>>,
+    mempool_relay: Relay<MempoolService<M, P, TxDiscriminant>>,
     _overlay: std::marker::PhantomData<O>,
     // this need to be substituted by some kind DA bo
     _blob_certificate: std::marker::PhantomData<C>,

nomos-services/mempool/src/lib.rs

@@ -2,7 +2,10 @@ pub mod backend;
 pub mod network;
 
 // std
-use std::fmt::{Debug, Error, Formatter};
+use std::{
+    fmt::{Debug, Error, Formatter},
+    marker::PhantomData,
+};
 
 // crates
 use futures::StreamExt;
@@ -19,17 +22,23 @@ use overwatch_rs::services::{
     ServiceCore, ServiceData, ServiceId,
 };
 
-pub struct MempoolService<N, P>
+pub struct MempoolService<N, P, D>
 where
     N: NetworkAdapter<Item = P::Item, Key = P::Key>,
     P: MemPool,
     P::Settings: Clone,
     P::Item: Debug + 'static,
     P::Key: Debug + 'static,
+    D: Discriminant,
 {
     service_state: ServiceStateHandle<Self>,
     network_relay: Relay<NetworkService<N::Backend>>,
     pool: P,
+    // This is an hack because SERVICE_ID has to be univoque and associated const
+    // values can't depend on generic parameters.
+    // Unfortunately, this means that the mempools for certificates and transactions
+    // would have the same SERVICE_ID and break overwatch asumptions.
+    _d: PhantomData<D>,
 }
 
 pub struct MempoolMetrics {
@@ -93,15 +102,31 @@ where
 
 impl<Item: 'static, Key: 'static> RelayMessage for MempoolMsg<Item, Key> {}
 
-impl<N, P> ServiceData for MempoolService<N, P>
+pub struct Transaction;
+pub struct Certificate;
+
+pub trait Discriminant {
+    const ID: &'static str;
+}
+
+impl Discriminant for Transaction {
+    const ID: &'static str = "mempool-txs";
+}
+
+impl Discriminant for Certificate {
+    const ID: &'static str = "mempool-certs";
+}
+
+impl<N, P, D> ServiceData for MempoolService<N, P, D>
 where
     N: NetworkAdapter<Item = P::Item, Key = P::Key>,
     P: MemPool,
     P::Settings: Clone,
     P::Item: Debug + 'static,
     P::Key: Debug + 'static,
+    D: Discriminant,
 {
-    const SERVICE_ID: ServiceId = "Mempool";
+    const SERVICE_ID: ServiceId = D::ID;
     type Settings = Settings<P::Settings, N::Settings>;
     type State = NoState<Self::Settings>;
     type StateOperator = NoOperator<Self::State>;
@@ -109,7 +134,7 @@ where
 }
 
 #[async_trait::async_trait]
-impl<N, P> ServiceCore for MempoolService<N, P>
+impl<N, P, D> ServiceCore for MempoolService<N, P, D>
 where
     P: MemPool + Send + 'static,
     P::Settings: Clone + Send + Sync + 'static,
@@ -117,6 +142,7 @@ where
     P::Item: Clone + Debug + Send + Sync + 'static,
     P::Key: Debug + Send + Sync + 'static,
     N: NetworkAdapter<Item = P::Item, Key = P::Key> + Send + Sync + 'static,
+    D: Discriminant + Send,
 {
     fn init(service_state: ServiceStateHandle<Self>) -> Result<Self, overwatch_rs::DynError> {
         let network_relay = service_state.overwatch_handle.relay();
@@ -125,6 +151,7 @@ where
             service_state,
             network_relay,
             pool: P::new(settings.backend),
+            _d: PhantomData,
         })
     }
 
@@ -133,6 +160,7 @@ where
             mut service_state,
             network_relay,
             mut pool,
+            ..
         } = self;
 
         let network_relay: OutboundRelay<_> = network_relay

nomos-services/mempool/tests/mock.rs

@@ -13,7 +13,7 @@ use overwatch_rs::{overwatch::OverwatchRunner, services::handle::ServiceHandle};
 use nomos_mempool::{
     backend::mockpool::MockPool,
     network::adapters::mock::{MockAdapter, MOCK_TX_CONTENT_TOPIC},
-    MempoolMsg, MempoolService, Settings,
+    MempoolMsg, MempoolService, Settings, Transaction,
 };
 
 #[derive(Services)]
@@ -21,7 +21,7 @@ struct MockPoolNode {
     logging: ServiceHandle<Logger>,
     network: ServiceHandle<NetworkService<Mock>>,
     mockpool: ServiceHandle<
-        MempoolService<MockAdapter, MockPool<MockTransaction<MockMessage>, MockTxId>>,
+        MempoolService<MockAdapter, MockPool<MockTransaction<MockMessage>, MockTxId>, Transaction>,
     >,
 }
 
@@ -73,9 +73,11 @@ fn test_mockmempool() {
     .unwrap();
 
     let network = app.handle().relay::<NetworkService<Mock>>();
-    let mempool = app
-        .handle()
-        .relay::<MempoolService<MockAdapter, MockPool<MockTransaction<MockMessage>, MockTxId>>>();
+    let mempool = app.handle().relay::<MempoolService<
+        MockAdapter,
+        MockPool<MockTransaction<MockMessage>, MockTxId>,
+        Transaction,
+    >>();
 
     app.spawn(async move {
         let network_outbound = network.connect().await.unwrap();