update AccountService with getForUpdateById and save

src/main/kotlin/ltd/lulz/repository/AccountRepository.kt

@@ -2,8 +2,14 @@ package ltd.lulz.repository
 
 import java.util.UUID
 import ltd.lulz.model.AccountEntity
+import org.springframework.data.r2dbc.repository.Query
 import org.springframework.data.repository.reactive.ReactiveCrudRepository
 import org.springframework.stereotype.Repository
+import reactor.core.publisher.Mono
 
 @Repository
-interface AccountRepository : ReactiveCrudRepository<AccountEntity, UUID>
+interface AccountRepository : ReactiveCrudRepository<AccountEntity, UUID> {
+
+    @Query("SELECT * FROM accounts WHERE id = :id FOR UPDATE NOWAIT")
+    fun findByIdForUpdate(id: UUID): Mono<AccountEntity>
+}

src/main/kotlin/ltd/lulz/service/AccountService.kt

@@ -5,6 +5,7 @@ import java.util.UUID
 import ltd.lulz.model.AccountEntity
 import ltd.lulz.repository.AccountRepository
 import org.springframework.stereotype.Service
+import org.springframework.transaction.annotation.Transactional
 import reactor.core.publisher.Mono
 
 private val log = KotlinLogging.logger {}
@@ -20,4 +21,12 @@ class AccountService(
 
     fun getById(id: UUID): Mono<AccountEntity> = accountRepository.findById(id)
         .doOnNext { log.debug { "found account by id: ${it.id}" } }
+
+    @Transactional
+    fun getForUpdateById(id: UUID): Mono<AccountEntity> = accountRepository.findByIdForUpdate(id)
+        .doOnNext { log.trace { "account with id: ${it.id} locked for update" } }
+
+    @Transactional
+    fun save(entity: AccountEntity): Mono<AccountEntity> = accountRepository.save(entity)
+        .doOnNext { log.trace { "account with id: ${it.id} saved" } }
 }