[State Sync] Add storage service API call for fetching the number of …

…accounts at a specific version.

Closes: #9277

state-sync/storage-service/server/src/lib.rs

@@ -8,7 +8,10 @@ use diem_infallible::RwLock;
 use diem_types::{
     account_state_blob::AccountStatesChunkWithProof,
     epoch_change::EpochChangeProof,
-    transaction::default_protocol::{TransactionListWithProof, TransactionOutputListWithProof},
+    transaction::{
+        default_protocol::{TransactionListWithProof, TransactionOutputListWithProof},
+        Version,
+    },
 };
 use serde::{Deserialize, Serialize};
 use std::sync::Arc;
@@ -62,6 +65,9 @@ impl<T: StorageReaderInterface> StorageServiceServer<T> {
             StorageServiceRequest::GetEpochEndingLedgerInfos(request) => {
                 self.get_epoch_ending_ledger_infos(request)
             }
+            StorageServiceRequest::GetNumberOfAccountsAtVersion(version) => {
+                self.get_number_of_accounts_at_version(version)
+            }
             StorageServiceRequest::GetServerProtocolVersion => self.get_server_protocol_version(),
             StorageServiceRequest::GetStorageServerSummary => self.get_storage_server_summary(),
             StorageServiceRequest::GetTransactionOutputsWithProof(request) => {
@@ -112,6 +118,17 @@ impl<T: StorageReaderInterface> StorageServiceServer<T> {
         ))
     }
 
+    fn get_number_of_accounts_at_version(
+        &self,
+        version: Version,
+    ) -> Result<StorageServiceResponse, Error> {
+        let number_of_accounts = self.storage.get_number_of_accounts(version)?;
+
+        Ok(StorageServiceResponse::NumberOfAccountsAtVersion(
+            number_of_accounts,
+        ))
+    }
+
     fn get_server_protocol_version(&self) -> Result<StorageServiceResponse, Error> {
         let server_protocol_version = ServerProtocolVersion {
             protocol_version: STORAGE_SERVER_VERSION,
@@ -205,6 +222,10 @@ pub trait StorageReaderInterface {
         expected_num_transaction_outputs: u64,
     ) -> Result<TransactionOutputListWithProof, Error>;
 
+    /// Returns the number of accounts in the account state tree at the
+    /// specified version.
+    fn get_number_of_accounts(&self, version: u64) -> Result<u64, Error>;
+
     /// Returns a chunk holding a list of account states starting at the
     /// specified account key with *at most* `expected_num_account_states`.
     fn get_account_states_chunk_with_proof(
@@ -312,4 +333,11 @@ impl StorageReaderInterface for StorageReader {
             "Unimplemented! This API call needs to be implemented!".into(),
         ))
     }
+
+    fn get_number_of_accounts(&self, _version: u64) -> Result<u64, Error> {
+        // TODO(joshlind): implement this once DbReaderWriter supports these calls.
+        Err(Error::UnexpectedErrorEncountered(
+            "Unimplemented! This API call needs to be implemented!".into(),
+        ))
+    }
 }

state-sync/storage-service/server/src/tests.rs

@@ -88,6 +88,26 @@ fn test_get_server_protocol_version() {
     );
 }
 
+#[test]
+fn test_get_number_of_accounts_at_version() {
+    // Create a storage service server
+    let storage_server = create_storage_server();
+
+    // Create a request to fetch the number of accounts at the specified version
+    let number_of_accounts_request = StorageServiceRequest::GetNumberOfAccountsAtVersion(10);
+
+    // Process the request
+    let number_of_accounts_response = storage_server
+        .handle_request(number_of_accounts_request)
+        .unwrap();
+
+    // Verify the response is correct (the API call is currently unsupported)
+    assert_matches!(
+        number_of_accounts_response,
+        StorageServiceResponse::StorageServiceError(StorageServiceError::InternalError)
+    );
+}
+
 #[test]
 fn test_get_storage_server_summary() {
     // Create a storage service server

state-sync/storage-service/types/src/lib.rs

@@ -19,8 +19,9 @@ use diem_types::{
 pub enum StorageServiceRequest {
     GetAccountStatesChunkWithProof(AccountStatesChunkWithProofRequest), // Fetches a list of account states with a proof
     GetEpochEndingLedgerInfos(EpochEndingLedgerInfoRequest), // Fetches a list of epoch ending ledger infos
-    GetServerProtocolVersion, // Fetches the protocol version run by the server
-    GetStorageServerSummary,  // Fetches a summary of the storage server state
+    GetNumberOfAccountsAtVersion(Version), // Fetches the number of accounts at the specified version
+    GetServerProtocolVersion,              // Fetches the protocol version run by the server
+    GetStorageServerSummary,               // Fetches a summary of the storage server state
     GetTransactionOutputsWithProof(TransactionOutputsWithProofRequest), // Fetches a list of transaction outputs with a proof
     GetTransactionsWithProof(TransactionsWithProofRequest), // Fetches a list of transactions with a proof
 }
@@ -30,6 +31,7 @@ pub enum StorageServiceRequest {
 pub enum StorageServiceResponse {
     AccountStatesChunkWithProof(AccountStatesChunkWithProof),
     EpochEndingLedgerInfos(EpochChangeProof),
+    NumberOfAccountsAtVersion(u64),
     ServerProtocolVersion(ServerProtocolVersion),
     StorageServiceError(StorageServiceError),
     StorageServerSummary(StorageServerSummary),