Feat(mysql-event-listener): Make startup failure behavior configurable

Add a new configuration key,
`mysql-event-listener.terminate-on-initialization-failure`, to control
how Trino behaves when the MySQL database is unreachable during
startup.

Previously, Trino would fail to start if MySQL was down. With this
option, users can choose whether startup should fail or continue,
improving resilience and flexibility in various deployment scenarios.

Author: danielbelchior

plugin/trino-mysql-event-listener/src/main/java/io/trino/plugin/eventlistener/mysql/MysqlEventListener.java

@@ -50,6 +50,7 @@ public class MysqlEventListener
 
     private static final long MAX_OPERATOR_SUMMARIES_JSON_LENGTH = 16 * 1024 * 1024;
 
+    private final MysqlEventListenerConfig config;
     private final QueryDao dao;
     private final JsonCodec<Set<String>> clientTagsJsonCodec;
     private final JsonCodec<Map<String, String>> sessionPropertiesJsonCodec;
@@ -59,13 +60,15 @@ public class MysqlEventListener
 
     @Inject
     public MysqlEventListener(
+            MysqlEventListenerConfig config,
             QueryDao dao,
             JsonCodec<Set<String>> clientTagsJsonCodec,
             JsonCodec<Map<String, String>> sessionPropertiesJsonCodec,
             JsonCodec<List<QueryInputMetadata>> inputsJsonCodec,
             JsonCodec<QueryOutputMetadata> outputJsonCodec,
             JsonCodec<List<TrinoWarning>> warningsJsonCodec)
     {
+        this.config = requireNonNull(config, "config is null");
         this.dao = requireNonNull(dao, "dao is null");
         this.clientTagsJsonCodec = requireNonNull(clientTagsJsonCodec, "clientTagsJsonCodec is null");
         this.sessionPropertiesJsonCodec = requireNonNull(sessionPropertiesJsonCodec, "sessionPropertiesJsonCodec is null");
@@ -77,7 +80,18 @@ public MysqlEventListener(
     @PostConstruct
     public void createTable()
     {
-        dao.createTable();
+        try {
+            dao.createTable();
+        }
+        catch (Exception e) {
+            if (config.getTerminateOnInitializationFailure()) {
+                throw e;
+            }
+            else {
+                // Log the error but do not terminate, allowing the listener to continue functioning
+                log.warn(e, "Unexpected error while creating MySQL event listener schema at startup. Ignoring error.");
+            }
+        }
     }
 
     @Override

plugin/trino-mysql-event-listener/src/main/java/io/trino/plugin/eventlistener/mysql/MysqlEventListenerConfig.java

@@ -15,6 +15,7 @@
 
 import com.mysql.cj.jdbc.Driver;
 import io.airlift.configuration.Config;
+import io.airlift.configuration.ConfigDescription;
 import io.airlift.configuration.ConfigSecuritySensitive;
 import jakarta.validation.constraints.AssertTrue;
 import jakarta.validation.constraints.NotNull;
@@ -24,6 +25,7 @@
 public class MysqlEventListenerConfig
 {
     private String url;
+    private boolean terminateOnInitializationFailure = true;
 
     @NotNull
     public String getUrl()
@@ -49,4 +51,18 @@ public boolean isValidUrl()
             throw new RuntimeException(e);
         }
     }
+
+    @NotNull
+    public boolean getTerminateOnInitializationFailure()
+    {
+        return terminateOnInitializationFailure;
+    }
+
+    @ConfigDescription("MySQL event listener initialization might fail due to network issues reaching the MySQL server. This flag controls whether to throw an exception in such cases.")
+    @Config("mysql-event-listener.terminate-on-initialization-failure")
+    public MysqlEventListenerConfig setTerminateOnInitializationFailure(boolean terminateOnInitializationFailure)
+    {
+        this.terminateOnInitializationFailure = terminateOnInitializationFailure;
+        return this;
+    }
 }

plugin/trino-mysql-event-listener/src/test/java/io/trino/plugin/eventlistener/mysql/TestMysqlEventListenerConfig.java

@@ -28,17 +28,20 @@ final class TestMysqlEventListenerConfig
     void testDefaults()
     {
         assertRecordedDefaults(recordDefaults(MysqlEventListenerConfig.class)
-                .setUrl(null));
+                .setUrl(null)
+                .setTerminateOnInitializationFailure(true));
     }
 
     @Test
     void testExplicitPropertyMappings()
     {
         Map<String, String> properties = Map.of(
-                "mysql-event-listener.db.url", "jdbc:mysql://example.net:3306");
+                "mysql-event-listener.db.url", "jdbc:mysql://example.net:3306",
+                "mysql-event-listener.terminate-on-initialization-failure", "false");
 
         MysqlEventListenerConfig expected = new MysqlEventListenerConfig()
-                .setUrl("jdbc:mysql://example.net:3306");
+                .setUrl("jdbc:mysql://example.net:3306")
+                .setTerminateOnInitializationFailure(false);
 
         assertFullMapping(properties, expected);
     }