MySQL EventListener: Ignore schema creation errors on startup if MySQL is down

docs/src/main/sphinx/admin/event-listeners-mysql.md

@@ -67,4 +67,8 @@ string, user, catalog, and others with information about the query processing.
   - Description
 * - `mysql-event-listener.db.url`
   - JDBC connection URL to the database including credentials
-:::
+* - `mysql-event-listener.terminate-on-initialization-failure`
+  - MySQL event listener initialization can fail if the database is unavailable.
+    This [boolean](prop-type-boolean) switch controls whether to throw an 
+    exception in such cases. Defaults to `true`.
+  :::

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 boolean terminateOnInitializationFailure;
     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.terminateOnInitializationFailure = config.getTerminateOnInitializationFailure();
         this.dao = requireNonNull(dao, "dao is null");
         this.clientTagsJsonCodec = requireNonNull(clientTagsJsonCodec, "clientTagsJsonCodec is null");
         this.sessionPropertiesJsonCodec = requireNonNull(sessionPropertiesJsonCodec, "sessionPropertiesJsonCodec is null");
@@ -77,7 +80,16 @@ public MysqlEventListener(
     @PostConstruct
     public void createTable()
     {
-        dao.createTable();
+        try {
+            dao.createTable();
+        }
+        catch (Exception e) {
+            if (terminateOnInitializationFailure) {
+                throw e;
+            }
+            // 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 +51,17 @@ public boolean isValidUrl()
             throw new RuntimeException(e);
         }
     }
+
+    public boolean getTerminateOnInitializationFailure()
+    {
+        return terminateOnInitializationFailure;
+    }
+
+    @Config("mysql-event-listener.terminate-on-initialization-failure")
+    @ConfigDescription("The MySQL event listener initialization may fail if the database is unavailable. This flag determines whether an exception should be thrown in such cases.")
+    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);
     }