[#14312] Add more developer friendly schema validation error

build.gradle

@@ -27,14 +27,14 @@ buildscript {
             exclude group: "org.gradle"
         }
         classpath "org.liquibase:liquibase-gradle-plugin:3.1.0"
-        classpath "org.liquibase:liquibase-core:4.27.0"
+        classpath "org.liquibase:liquibase-core:5.0.3"
     }
 }
 
 configurations {
     staticAnalysis
 
-    liquibaseRuntime.extendsFrom testImplementation
+    liquibaseRuntime.extendsFrom implementation
 }
 
 
@@ -61,6 +61,7 @@ dependencies {
     implementation("com.mailjet:mailjet-client:5.2.5")
     implementation("com.sendgrid:sendgrid-java:4.10.3")
     implementation(platform("org.eclipse.jetty:jetty-bom:11.0.20"))
+    implementation("org.liquibase:liquibase-core:5.0.3")
     implementation("org.eclipse.jetty:jetty-slf4j-impl")
     implementation("org.eclipse.jetty:jetty-server")
     implementation("org.eclipse.jetty:jetty-webapp")
@@ -81,7 +82,6 @@ dependencies {
     testImplementation("com.deque.html.axe-core:selenium:4.11.2")
     testImplementation(testng)
     testImplementation("org.testcontainers:testcontainers-postgresql:2.0.5")
-    testImplementation("org.liquibase:liquibase-core:4.27.0")
     testImplementation("org.mockito:mockito-core:5.21.0")
     // For supporting authorization code flow locally
     testImplementation("com.google.oauth-client:google-oauth-client-jetty:1.39.0")

src/main/java/teammates/common/exception/PendingDatabaseMigrationsException.java

@@ -0,0 +1,19 @@
+package teammates.common.exception;
+
+/**
+ * Exception thrown when there are unapplied database migrations.
+ */
+public class PendingDatabaseMigrationsException extends Exception {
+
+    private final String migrationStatus;
+
+    public PendingDatabaseMigrationsException(String message, String migrationStatus) {
+        super(message);
+        this.migrationStatus = migrationStatus;
+    }
+
+    public String getMigrationStatus() {
+        return migrationStatus;
+    }
+
+}

src/main/java/teammates/liquibase/LiquibaseStatusChecker.java

@@ -0,0 +1,94 @@
+package teammates.liquibase;
+
+import java.util.List;
+import java.util.Optional;
+
+import teammates.common.exception.PendingDatabaseMigrationsException;
+import teammates.common.util.Config;
+
+import liquibase.Contexts;
+import liquibase.LabelExpression;
+import liquibase.Liquibase;
+import liquibase.changelog.ChangeSet;
+import liquibase.database.Database;
+import liquibase.database.DatabaseFactory;
+import liquibase.exception.DatabaseException;
+import liquibase.exception.LiquibaseException;
+import liquibase.resource.ClassLoaderResourceAccessor;
+import liquibase.resource.ResourceAccessor;
+
+/**
+ * Checks whether the liquibase status is successful.
+ */
+public final class LiquibaseStatusChecker {
+
+    private static final String CHANGELOG_FILE = "db/changelog/db.changelog-root.xml";
+    private static final String GRADLE_CHANGELOG_FILE_PREFIX = "src/main/resources/";
+
+    private LiquibaseStatusChecker() {
+        // utility class
+    }
+
+    /**
+     * Asserts that liquibase reports successful status.
+     */
+    public static void assertSuccessStatus() throws LiquibaseException, PendingDatabaseMigrationsException {
+        assertDatabaseUpToDate();
+    }
+
+    /**
+     * Fails fast when Liquibase reports unapplied changesets.
+     */
+    private static void assertDatabaseUpToDate() throws LiquibaseException, PendingDatabaseMigrationsException {
+        Optional<String> pendingMigrationStatus = getPendingMigrationStatus();
+        if (pendingMigrationStatus.isEmpty()) {
+            return;
+        }
+
+        throw new PendingDatabaseMigrationsException(
+                "Database schema is out of date. Apply pending Liquibase migrations before starting the server.",
+                pendingMigrationStatus.get());
+    }
+
+    private static Optional<String> getPendingMigrationStatus() throws LiquibaseException {
+        List<ChangeSet> unrunChangeSets = listUnrunChangeSets();
+        return unrunChangeSets.isEmpty()
+                ? Optional.empty()
+                : Optional.of(formatPendingMigrationStatus(unrunChangeSets));
+    }
+
+    private static List<ChangeSet> listUnrunChangeSets() throws LiquibaseException {
+        try (ResourceAccessor resourceAccessor = new ClassLoaderResourceAccessor();
+                Liquibase liquibase = createLiquibase(resourceAccessor)) {
+            normalizeChangeSetFilePaths(liquibase);
+            return liquibase.listUnrunChangeSets(new Contexts(), new LabelExpression());
+        } catch (Exception e) {
+            throw new LiquibaseException("Failed to check Liquibase status", e);
+        }
+    }
+
+    /**
+     * Normalizes file paths to match the paths used in the Gradle build,
+     * so that the unrun changesets can be correctly identified.
+     */
+    private static void normalizeChangeSetFilePaths(Liquibase liquibase) throws LiquibaseException {
+        for (ChangeSet changeSet : liquibase.getDatabaseChangeLog().getChangeSets()) {
+            changeSet.setFilePath(GRADLE_CHANGELOG_FILE_PREFIX + changeSet.getFilePath());
+        }
+    }
+
+    private static Liquibase createLiquibase(ResourceAccessor resourceAccessor) throws DatabaseException {
+        Database database = DatabaseFactory.getInstance().openDatabase(
+                Config.getDbConnectionUrl(),
+                Config.POSTGRES_USERNAME,
+                Config.POSTGRES_PASSWORD,
+                null,
+                resourceAccessor);
+        return new Liquibase(CHANGELOG_FILE, resourceAccessor, database);
+    }
+
+    private static String formatPendingMigrationStatus(List<ChangeSet> unrunChangeSets) {
+        return unrunChangeSets.size() + " pending Liquibase changeset(s).";
+    }
+
+}

src/main/java/teammates/main/Application.java

@@ -10,6 +10,8 @@
 
 import teammates.common.util.Config;
 import teammates.common.util.Logger;
+import teammates.liquibase.LiquibaseStatusChecker;
+import teammates.main.util.DevServerStartupErrorHandler;
 import teammates.ui.servlets.DevServerLoginServlet;
 
 /**
@@ -75,12 +77,37 @@ public void lifeCycleStopped(LifeCycle event) {
         server.setHandler(webapp);
         server.setStopAtShutdown(true);
         server.addEventListener(customLifeCycleListener);
+        webapp.setThrowUnavailableOnStartupException(true);
 
-        server.start();
+        // Fail fast checks.
+        try {
+            LiquibaseStatusChecker.assertSuccessStatus();
+        } catch (Exception e) {
+            throw transformStartupException(e);
+        }
+
+        try {
+            server.start();
+        } catch (Exception e) {
+            stopServer(server);
+            throw transformStartupException(e);
+        }
 
         // By using the server.join() the server thread will join with the current thread.
         // See https://docs.oracle.com/javase/8/docs/api/java/lang/Thread.html#join-- for more details.
         server.join();
     }
 
+    private static void stopServer(Server server) {
+        try {
+            server.stop();
+        } catch (Exception e) {
+            log.severe("Failed to stop server after web application startup failure.", e);
+        }
+    }
+
+    private static Exception transformStartupException(Exception e) {
+        return Config.IS_DEV_SERVER ? DevServerStartupErrorHandler.transform(e) : e;
+    }
+
 }

src/main/java/teammates/main/exception/DevServerStartupException.java

@@ -0,0 +1,13 @@
+package teammates.main.exception;
+
+/**
+ * Exception thrown when an error occurs during dev server startup.
+ */
+public class DevServerStartupException extends RuntimeException {
+
+    public DevServerStartupException(String message) {
+        // Null cause to avoid printing the stack trace twice.
+        super(message, null, true, false);
+    }
+
+}

src/main/java/teammates/main/exception/package-info.java

@@ -0,0 +1,5 @@
+
+/**
+ * Contains exception classes for the main package.
+ */
+package teammates.main.exception;

src/main/java/teammates/main/util/DevServerStartupErrorHandler.java

@@ -0,0 +1,63 @@
+package teammates.main.util;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Function;
+
+import teammates.common.exception.PendingDatabaseMigrationsException;
+import teammates.main.exception.DevServerStartupException;
+
+/**
+ * Handles startup errors with dev-server-friendly messages where possible.
+ */
+public final class DevServerStartupErrorHandler {
+
+    private static final String SCHEMA_OUT_OF_DATE_MESSAGE = String.join(System.lineSeparator(),
+            "",
+            "============================================================",
+            "Database schema is not up to date:",
+            "%s",
+            "",
+            "Your local database schema is out of date.",
+            "Run: ./gradlew liquibaseUpdate",
+            "Then restart the local server.",
+            "",
+            "For more details, see docs/how-to/schema-migration.md",
+            "============================================================",
+            "");
+
+    /**
+     * A list of builders that can recognize startup errors and provide a dev-server-friendly message.
+     */
+    private static final List<Function<Throwable, Optional<String>>> ERROR_MESSAGE_BUILDERS = List.of(
+            DevServerStartupErrorHandler::buildPendingDatabaseMigrationsMessage);
+
+    private DevServerStartupErrorHandler() {
+        // Utility class
+    }
+
+    /**
+     * Transforms a recognized startup error into a dev-server-friendly exception.
+     * Returns the original exception when no builder recognizes it.
+     */
+    public static Exception transform(Exception e) {
+        return ERROR_MESSAGE_BUILDERS.stream()
+                .map(builder -> builder.apply(e))
+                .flatMap(optional -> optional.stream())
+                .findFirst()
+                .<Exception>map(message -> new DevServerStartupException(message))
+                .orElse(e);
+    }
+
+    /**
+     * Builds a dev-server-friendly message for a pending database migrations error.
+     */
+    private static Optional<String> buildPendingDatabaseMigrationsMessage(Throwable error) {
+        if (!(error instanceof PendingDatabaseMigrationsException)) {
+            return Optional.empty();
+        }
+        PendingDatabaseMigrationsException pendingMigrationsFailure = (PendingDatabaseMigrationsException) error;
+        return Optional.of(String.format(SCHEMA_OUT_OF_DATE_MESSAGE, pendingMigrationsFailure.getMigrationStatus()));
+    }
+
+}

src/main/java/teammates/main/util/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Contains utility classes for the main package.
+ */
+package teammates.main.util;