feat: improve grpc get_balance response (#6755)

Description
---
- Improved the wallet grpc method `get_balance` response by implementing
an event-driven balance cache update. All events that could change the
balance are monitored and consecutive calls to the wallet backend are
only made when the balance changed.
- Cleaned up unused events (events that were monitored somewhere but
never set) in `pub enum TransactionEvent`.
- Added a missing shutdown signal to grpc method `async fn
stream_transaction_events` in the wallet grpc server.

Closes #6754

Motivation and Context
---
When calling the wallet grpc method `get_balance` repeatedly and quickly
in succession on wallets with many outputs, resources are wasted in the
wallet when nothing changes, and the client experiences unnecessary long
response times.

How Has This Been Tested?
---
System-level testing on a large wallet with an external grpc client. See
logs with response times below.

```
[wallet::ui::grpc::get_balance_debounced] TRACE start_event_monitor
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 172.28ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 29.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 36.00µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 26.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 145.39ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 22.00µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 33.70µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 25.40µs
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'true'
[wallet::ui::grpc::get_balance_debounced] TRACE set_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 156.75ms
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 35.70µs
[wallet::ui::grpc::get_balance_debounced] TRACE is_refresh_needed 'false'
[wallet::ui::grpc] TRACE 'get_balance' completed in 23.40µs
```

What process can a PR reviewer use to test or verify this change?
---
System-level testing with an external grpc client.

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Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

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applications/minotari_app_grpc/proto/wallet.proto

@@ -47,7 +47,7 @@ service Wallet {
   rpc GetTransactionInfo (GetTransactionInfoRequest) returns (GetTransactionInfoResponse);
   // Returns all transactions' details
   rpc GetCompletedTransactions (GetCompletedTransactionsRequest) returns (stream GetCompletedTransactionsResponse);
-  // Returns the balance
+  // Returns the balance, but uses a debouncer in the background to prevent spamming the wallet
   rpc GetBalance (GetBalanceRequest) returns (GetBalanceResponse);
   // Returns unspent amounts
   rpc GetUnspentAmounts (Empty) returns (GetUnspentAmountsResponse);

applications/minotari_console_wallet/src/grpc/get_balance_debounced.rs

@@ -0,0 +1,200 @@
+//  Copyright 2021. The Tari Project
+//
+//  Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
+//  following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
+//  disclaimer.
+//
+//  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
+//  following disclaimer in the documentation and/or other materials provided with the distribution.
+//
+//  3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
+//  products derived from this software without specific prior written permission.
+//
+//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+//  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+//  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+//  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+//  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+//  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use std::sync::Arc;
+
+use log::{info, trace, warn};
+use minotari_app_grpc::tari_rpc::GetBalanceResponse;
+use minotari_wallet::{
+    connectivity_service::{WalletConnectivityHandle, WalletConnectivityInterface},
+    output_manager_service::{
+        handle::{OutputManagerEvent, OutputManagerHandle},
+        service::Balance,
+    },
+    transaction_service::handle::{TransactionEvent, TransactionServiceHandle},
+};
+use tari_shutdown::ShutdownSignal;
+use tokio::sync::Mutex;
+use tonic::Status;
+
+const LOG_TARGET: &str = "wallet::ui::grpc::get_balance_debounced";
+
+/// This struct is used to get the balance of the wallet, implementing a debouncer. When the `get_balance` method is
+/// called the first time, the balance will be fetched from the backend after starting a task to monitor wallet events
+/// that could change the balance. When these wallet events are received, a flag will be set to indicate that the
+/// balance needs to be updated. When ever a client requests the balance, it will be fetched from the backend if the
+/// flag is set and clear the flag, otherwise the cached balance will be returned.
+#[derive(Clone)]
+pub struct GetBalanceDebounced {
+    balance: Arc<Mutex<Balance>>,
+    refresh_needed: Arc<Mutex<bool>>,
+    output_manager_service: OutputManagerHandle,
+    transaction_service: TransactionServiceHandle,
+    wallet_connectivity: WalletConnectivityHandle,
+    shutdown_signal: ShutdownSignal,
+    event_monitor_started: Arc<Mutex<bool>>,
+}
+
+impl GetBalanceDebounced {
+    /// Create a new GetBalanceDebounced instance.
+    pub fn new(
+        output_manager_service: OutputManagerHandle,
+        transaction_service: TransactionServiceHandle,
+        wallet_connectivity: WalletConnectivityHandle,
+        shutdown_signal: ShutdownSignal,
+    ) -> Self {
+        Self {
+            balance: Arc::new(Mutex::new(Balance {
+                available_balance: 0.into(),
+                pending_incoming_balance: 0.into(),
+                pending_outgoing_balance: 0.into(),
+                time_locked_balance: None,
+            })),
+            refresh_needed: Arc::new(Mutex::new(true)),
+            output_manager_service,
+            transaction_service,
+            wallet_connectivity,
+            shutdown_signal,
+            event_monitor_started: Arc::new(Mutex::new(false)),
+        }
+    }
+
+    async fn start_event_monitor(&mut self) {
+        trace!(target: LOG_TARGET, "start_event_monitor");
+        let self_clone = self.clone();
+        tokio::spawn(async move {
+            self_clone.monitor_events().await;
+        });
+        let mut lock = self.event_monitor_started.lock().await;
+        *lock = true;
+    }
+
+    async fn is_event_monitor_started(&self) -> bool {
+        *self.event_monitor_started.lock().await
+    }
+
+    /// Get the balance of the wallet. This function will return the cached balance of the wallet if it is current, or
+    /// fetch the balance from the output manager service if new wallet events were received that could change the
+    /// balance.
+    pub async fn get_balance(&mut self) -> Result<GetBalanceResponse, Status> {
+        if !self.is_event_monitor_started().await {
+            self.start_event_monitor().await;
+        }
+        let balance = if self.is_refresh_needed().await {
+            let mut output_manager_service = self.output_manager_service.clone();
+            let balance = match output_manager_service.get_balance().await {
+                Ok(b) => b,
+                Err(e) => return Err(Status::not_found(format!("GetBalance error! {}", e))),
+            };
+            self.update_balance(balance.clone()).await;
+            self.set_refresh_needed(false).await;
+            balance
+        } else {
+            (*self.balance.lock().await).clone()
+        };
+        Ok(GetBalanceResponse {
+            available_balance: balance.available_balance.into(),
+            pending_incoming_balance: balance.pending_incoming_balance.into(),
+            pending_outgoing_balance: balance.pending_outgoing_balance.into(),
+            timelocked_balance: balance.time_locked_balance.unwrap_or_default().into(),
+        })
+    }
+
+    async fn update_balance(&mut self, balance: Balance) {
+        let mut lock = self.balance.lock().await;
+        *lock = balance;
+    }
+
+    async fn is_refresh_needed(&self) -> bool {
+        let refresh_needed = *self.refresh_needed.lock().await;
+        trace!(target: LOG_TARGET, "is_refresh_needed '{}'", refresh_needed);
+        refresh_needed
+    }
+
+    async fn set_refresh_needed(&self, refresh_needed: bool) {
+        let mut lock = self.refresh_needed.lock().await;
+        if *lock != refresh_needed {
+            trace!(target: LOG_TARGET, "set_refresh_needed '{}'", refresh_needed);
+            *lock = refresh_needed;
+        }
+    }
+
+    async fn monitor_events(&self) {
+        let mut shutdown_signal = self.shutdown_signal.clone();
+        let mut transaction_service_events = self.transaction_service.get_event_stream();
+        let mut base_node_changed = self.wallet_connectivity.clone().get_current_base_node_watcher();
+        let mut output_manager_service_events = self.output_manager_service.get_event_stream();
+
+        loop {
+            tokio::select! {
+                result = transaction_service_events.recv() => {
+                    match result {
+                        Ok(msg) => {
+                            match (*msg).clone() {
+                                TransactionEvent::ReceivedTransaction(..) |
+                                TransactionEvent::ReceivedTransactionReply(..) |
+                                TransactionEvent::ReceivedFinalizedTransaction(_) |
+                                TransactionEvent::TransactionSendResult(..) |
+                                TransactionEvent::TransactionCompletedImmediately(..) |
+                                TransactionEvent::TransactionCancelled(..) |
+                                TransactionEvent::TransactionBroadcast(..) |
+                                TransactionEvent::DetectedTransactionUnconfirmed { .. } |
+                                TransactionEvent::DetectedTransactionConfirmed { .. } |
+                                TransactionEvent::TransactionMinedUnconfirmed { .. } |
+                                TransactionEvent::TransactionMined { .. } |
+                                TransactionEvent::TransactionValidationStateChanged(..) => {
+                                    self.set_refresh_needed(true).await;
+                                },
+                                _ => (),
+                            }
+                        },
+                        Err(e) => {
+                            warn!(target: LOG_TARGET, "transaction_service_events '{}'", e);
+                        },
+                    }
+                },
+                _ = base_node_changed.changed() => {
+                    self.set_refresh_needed(true).await;
+                },
+                result = output_manager_service_events.recv() => {
+                    match result {
+                        Ok(msg) => {
+                            if let OutputManagerEvent::TxoValidationSuccess(_) = &*msg {
+                                self.set_refresh_needed(true).await;
+                            }
+                        },
+                        Err(e) => {
+                            warn!(target: LOG_TARGET, "output_manager_service_events '{}'", e);
+                        },
+                    }
+                },
+                _ = shutdown_signal.wait() => {
+                    info!(
+                        target: LOG_TARGET,
+                        "get_balance_debounced event monitor shutting down because the shutdown signal was received"
+                    );
+                    break;
+                }
+            }
+        }
+    }
+}

applications/minotari_console_wallet/src/grpc/mod.rs

@@ -1,6 +1,7 @@
 // Copyright 2022 The Tari Project
 // SPDX-License-Identifier: BSD-3-Clause
 
+mod get_balance_debounced;
 mod wallet_grpc_server;
 
 use minotari_app_grpc::tari_rpc::TransactionEvent;