I’m working on a Spring application that connects to an external Oracle database. The external connection can be intermittent, and when it’s down, I need to store the data locally. Here’s my approach:
When an insert operation (remoteDatabase.Save(newObject)) fails due to a connection issue, I catch the exception.
In the catched block, I save the object to a local SQLite database (localDatabase.Save(newObject)).
Is this a reasonable approach? Are there any best practices or alternative solutions for handling intermittent external database connections in Spring applications?
Details:
Spring framework version: [Specify your Spring version]
External database: Oracle
Local database: SQLite
Connection testing: Separate thread checks if the external connection is up
Exception handling: Catch exceptions during remoteDatabase.Save(newObject) and fallback to localDatabase.Save(newObject)
Any insights or suggestions would be greatly appreciated!
I have tried to grep the exception from the remote database by doing the Global Exception Handling but with no luck...
The exception I was trying do handle or trigger by was:
> 2024-06-21 14:28:15.278 --- thread_id="1" thread_name="main"
> thread_priority="5" --- [DEBUG] Spring test ApplicationContext cache
> statistics: [DefaultContextCache@171b82ea size = 1, maxSize = 32,
> parentContextCount = 0, hitCount = 6, missCount = 1, failureCount = 0]
> 2024-06-21 14:28:15.280 --- thread_id="1" thread_name="main"
> thread_priority="5" --- [DEBUG] Creating new transaction with name
> [org.springframework.data.jpa.repository.support.SimpleJpaRepository.count]:
> PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly 2024-06-21
> 14:28:15.280 --- thread_id="1" thread_name="main" thread_priority="5"
> --- [DEBUG] Opened new EntityManager [SessionImpl(1913887027<open>)] for JPA transaction 2024-06-21 14:28:15.280 --- thread_id="1"
> thread_name="main" thread_priority="5" --- [DEBUG] Creating new JDBC
> DriverManager Connection to [jdbc:oracle:thin:@localhost:1522:FREE]
> 2024-06-21 14:28:15.284 --- thread_id="1" thread_name="main"
> thread_priority="5" --- [DEBUG] Unable to acquire JDBC Connection
> [n/a] java.sql.SQLRecoverableException: IO Error: The Network Adapter
> could not establish the connection at
> oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:907)
> ~[ojdbc10-19.22.0.0.jar:19.22.0.0.0] at
> oracle.jdbc.driver.PhysicalConnection.connect(PhysicalConnection.java:820)
> ~[ojdbc10-19.22.0.0.jar:19.22.0.0.0] at
> oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:80)
> ~[ojdbc10-19.22.0.0.jar:19.22.0.0.0] at
> oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:820)
> ~[ojdbc10-19.22.0.0.jar:19.22.0.0.0] at
> oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:624)
> ~[ojdbc10-19.22.0.0.jar:19.22.0.0.0] at
> java.sql/java.sql.DriverManager.getConnection(DriverManager.java:683)
> ~[java.sql:?] at
> java.sql/java.sql.DriverManager.getConnection(DriverManager.java:191)
> ~[java.sql:?] <log cuntinues but have been cut down from here....>
Your approach to handling intermittent connections with an external Oracle database by falling back to a local SQLite database in a Spring application is a reasonable one. Here are some best practices and suggestions to ensure the robustness and efficiency of your solution:
Ensure that your operations are properly wrapped in transactions to maintain data consistency. Spring provides excellent support for transaction management which you can leverage.
@Transactional
public void saveData(MyObject newObject) {
try {
remoteDatabase.save(newObject);
} catch (Exception e) {
// Log the exception
logger.error("Failed to save to remote database, saving locally.", e);
localDatabase.save(newObject);
}
}
Catch specific exceptions related to database connectivity issues. This prevents catching unexpected exceptions and potentially masking other issues.
try {
remoteDatabase.save(newObject);
} catch (SQLRecoverableException e) {
// Specific handling for connectivity issues
logger.error("Connectivity issue detected, saving locally.", e);
localDatabase.save(newObject);
} catch (SQLException e) {
// Handling other SQL exceptions
logger.error("SQL error occurred, saving locally.", e);
localDatabase.save(newObject);
} catch (Exception e) {
// Catch-all for other exceptions
logger.error("Unexpected error, saving locally.", e);
localDatabase.save(newObject);
}
Consider implementing a retry mechanism for operations that fail due to connectivity issues. You can also use a message queue to asynchronously process save operations, ensuring that your application remains responsive.
import org.springframework.retry.annotation.Backoff;
import org.springframework.retry.annotation.Retryable;
@Service
public class DataService {
@Retryable(
value = { SQLRecoverableException.class },
maxAttempts = 3,
backoff = @Backoff(delay = 5000)
)
public void saveData(MyObject newObject) throws SQLRecoverableException {
remoteDatabase.save(newObject);
}
public void saveDataWithFallback(MyObject newObject) {
try {
saveData(newObject);
} catch (SQLRecoverableException e) {
logger.error("Failed after retries, saving locally.", e);
localDatabase.save(newObject);
}
}
}
Implement a message queue (e.g., RabbitMQ, Kafka) to handle failed save operations asynchronously. This allows the main application to continue functioning without blocking on database operations.
public void saveData(MyObject newObject) {
try {
remoteDatabase.save(newObject);
} catch (SQLRecoverableException e) {
// Send the object to a message queue for later processing
messageQueue.send(newObject);
}
}
Implement a scheduled task that periodically attempts to re-process the locally saved data when the connection is restored.
@Scheduled(fixedDelay = 60000) // 1 minute
public void retryFailedSaves() {
List<MyObject> failedSaves = localDatabase.getAll();
for (MyObject obj : failedSaves) {
try {
remoteDatabase.save(obj);
localDatabase.delete(obj); // Remove from local DB after successful save
} catch (SQLRecoverableException e) {
logger.error("Retry failed, will try again later.", e);
}
}
}
Implement monitoring and alerting to notify you when the external database connection is down or when local saves are happening too frequently.
Your current approach is sound, but can be enhanced by:
These enhancements will make your application more resilient to intermittent external database connections.