Add DatabaseStartupValidator to wait for db to be available on boot

This is to make the app resilient in the case where the app boots before the database is available.

ui/resources/application.properties

@@ -3,6 +3,7 @@ logging.level.org.apache.tika.parser=error
 logging.level.org.apache.fontbox=error
 logging.level.org.apache.pdfbox=error
 logging.level.org.vibur=warn
+logging.level.org.springframework.jdbc.support.DatabaseStartupValidator=debug
 
 # Management actuators
 management.endpoints.web.exposure.include=loggers

ui/src/bamboo/config/DatabaseStartupConfig.java

@@ -0,0 +1,29 @@
+package bamboo.config;
+
+import org.springframework.boot.autoconfigure.orm.jpa.EntityManagerFactoryDependsOnPostProcessor;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.jdbc.support.DatabaseStartupValidator;
+
+import javax.sql.DataSource;
+import java.util.concurrent.TimeUnit;
+
+@Configuration
+public class DatabaseStartupConfig {
+    @Bean
+    public DatabaseStartupValidator databaseStartupValidator(DataSource dataSource) {
+        var validator = new DatabaseStartupValidator();
+        validator.setDataSource(dataSource);
+        validator.setTimeout((int) TimeUnit.DAYS.toSeconds(7));
+        return validator;
+    }
+
+    /**
+     * This makes EntityManagerFactory depend on DatabaseStartupValidator to block startup
+     * until the database is ready.
+     */
+    @Bean
+    public static EntityManagerFactoryDependsOnPostProcessor databaseStartupDependency() {
+        return new EntityManagerFactoryDependsOnPostProcessor("databaseStartupValidator");
+    }
+}