Use a single, shared executor for running transactions

PiperOrigin-RevId: 312338832

Author: wilhuff

firestore/src/ios/firestore_ios.cc

@@ -53,7 +53,9 @@ FirestoreInternal::FirestoreInternal(App* app)
 FirestoreInternal::FirestoreInternal(
  App* app, std::unique_ptr<CredentialsProvider> credentials)
  : app_(NOT_NULL(app)),
- firestore_core_(CreateFirestore(app, std::move(credentials))) {
+ firestore_core_(CreateFirestore(app, std::move(credentials))),
+ transaction_executor_(absl::ShareUniquePtr(Executor::CreateConcurrent(
+ "com.google.firebase.firestore.transaction", /*threads=*/5))) {
  ApplyDefaultSettings();
 }
 
@@ -130,8 +132,7 @@ Future<void> FirestoreInternal::RunTransaction(TransactionFunction* update) {
 
 Future<void> FirestoreInternal::RunTransaction(
  std::function<Error(Transaction&, std::string&)> update) {
- auto executor = absl::ShareUniquePtr(Executor::CreateConcurrent(
- "com.google.firebase.firestore.transaction", /*threads=*/5));
+ auto executor = transaction_executor_;
  auto promise =
  promise_factory_.CreatePromise<void>(AsyncApi::kRunTransaction);
 

firestore/src/ios/firestore_ios.h

@@ -27,6 +27,10 @@ class Transaction;
 class TransactionFunction;
 class WriteBatch;
 
+namespace util {
+class Executor;
+}
+
 class FirestoreInternal {
  public:
  // Note: call `set_firestore_public` immediately after construction.
@@ -145,6 +149,8 @@ class FirestoreInternal {
  // TODO(b/136119216): revamp this mechanism on both iOS and Android.
  std::mutex listeners_mutex_;
  std::unordered_set<ListenerRegistrationInternal*> listeners_;
+
+ std::shared_ptr<util::Executor> transaction_executor_;
 };
 
 } // namespace firestore