Populate Connection Context with DataSource

Ensure the datasource is populated in the connection context even when
`getConnection` fails.
For instance, this datasource is used by `HikariJdbcObservationFilter`.
If the datasource is not populated, the filter fails with a NPE.

This commit guarantees that the datasource is populated in the
connection context when `getConnection` fails.

Closes #44

datasource-micrometer/src/main/java/net/ttddyy/observation/tracing/DataSourceObservationListener.java

@@ -246,9 +246,14 @@ private void handleGetConnectionAfter(MethodExecutionContext executionContext) {
 		Connection connection = (Connection) executionContext.getResult();
 		Observation.Scope scopeToUse = executionContext.getCustomValue(Observation.Scope.class.getName(),
 				Observation.Scope.class);
+		ConnectionContext connectionContext = executionContext.getCustomValue(ConnectionContext.class.getName(),
+				ConnectionContext.class);
 
 		if (connection == null) {
-			// Handle closing the observation due to an error from getConnection().
+			// Logic when getConnection failed.
+			// Populate the context with available info. (see gh-44)
+			connectionContext.setDataSource(dataSource);
+			// Handle closing the observation.
 			// For normal case, observation is stopped when connection is closed.
 			// see "handleConnectionClose()".
 			if (scopeToUse != null) {
@@ -273,8 +278,6 @@ private void handleGetConnectionAfter(MethodExecutionContext executionContext) {
 
 			String connectionId = connectionInfo.getConnectionId();
 			this.connectionAttributesManager.put(connectionId, connectionAttributes);
-			ConnectionContext connectionContext = executionContext.getCustomValue(ConnectionContext.class.getName(),
-					ConnectionContext.class);
 			populateFromConnectionAttributes(connectionContext, connectionId);
 
 			// When "getConnection" was successful, a connection is acquired.

datasource-micrometer/src/test/java/net/ttddyy/observation/tracing/DataSourceObservationListenerTests.java

@@ -331,6 +331,13 @@ void connection() throws Exception {
 	@Test
 	void getConnectionFailure() throws Exception {
 		this.registry.observationConfig().observationHandler(new ConnectionTracingObservationHandler(this.tracer));
+		// gh-44: make sure datasource is available in observation filter
+		this.registry.observationConfig().observationFilter((context) -> {
+			DataSource ds = ((DataSourceBaseContext) context).getDataSource();
+			assertThat(ds).as("datasource needs to be available in observation filter").isNotNull();
+			return context;
+		});
+
 		Method getConnection = DataSource.class.getMethod("getConnection");
 		RuntimeException exception = new RuntimeException();