Add notifications_schema table & verify on daemon startup

cmd/icinga-notifications/main.go

@@ -45,6 +45,10 @@ func main() {
 		logger.Fatalf("Cannot connect to the database: %+v", err)
 	}
 
+	if err := internal.CheckSchema(ctx, db); err != nil {
+		logger.Fatalf("%+v", err)
+	}
+
 	channel.UpsertPlugins(ctx, conf.ChannelsDir, logs.GetChildLogger("channel"), db)
 
 	runtimeConfig := config.NewRuntimeConfig(logs, db)

internal/schema.go

@@ -0,0 +1,72 @@
+package internal
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/icinga/icinga-go-library/backoff"
+	"github.com/icinga/icinga-go-library/database"
+	"github.com/icinga/icinga-go-library/retry"
+)
+
+const (
+	// Both MySQL and PostgreSQL schema versions are currently the same, but they can
+	// evolve independently in the future, so can't be merged into a single constant.
+	expectedMysqlSchemaVersion    = "v1.0"
+	expectedPostgresSchemaVersion = "v1.0"
+)
+
+// CheckSchema verifies that the database schema version matches the expected version for the database driver.
+func CheckSchema(ctx context.Context, db *database.DB) error {
+	var expectedSchemaVersion string
+	switch db.DriverName() {
+	case database.MySQL:
+		expectedSchemaVersion = expectedMysqlSchemaVersion
+	case database.PostgreSQL:
+		expectedSchemaVersion = expectedPostgresSchemaVersion
+	default:
+		return fmt.Errorf("unsupported database driver %q", db.DriverName())
+	}
+
+	if hasSchemaTable, err := db.HasTable(ctx, "notifications_schema"); err != nil {
+		return fmt.Errorf("cannot verify existence of database schema table: %w", err)
+	} else if !hasSchemaTable {
+		return errors.New(
+			"notifications_schema table does not exist, please make sure you have applied all" +
+				" database migrations after upgrading Icinga Notifications",
+		)
+	}
+
+	var dbResult []string
+	err := retry.WithBackoff(
+		ctx,
+		func(ctx context.Context) error {
+			qs := `SELECT version FROM notifications_schema ORDER BY timestamp DESC LIMIT 1`
+			if err := db.SelectContext(ctx, &dbResult, qs); err != nil {
+				return database.CantPerformQuery(err, qs)
+			}
+			return nil
+		},
+		retry.Retryable,
+		backoff.DefaultBackoff,
+		db.GetDefaultRetrySettings(),
+	)
+	if err != nil {
+		return err
+	}
+
+	if len(dbResult) == 0 {
+		return errors.New("no database schema version found")
+	}
+
+	if actualSchemaVersion := dbResult[0]; actualSchemaVersion != expectedSchemaVersion {
+		return fmt.Errorf(
+			"unexpected database schema version: %s (expected %s), please make sure you have applied all"+
+				" database migrations after upgrading Icinga Notifications",
+			actualSchemaVersion, expectedSchemaVersion,
+		)
+	}
+
+	return nil
+}

schema/mysql/schema.sql

@@ -1,3 +1,30 @@
+DROP PROCEDURE IF EXISTS assert_correct_schema_version;
+DELIMITER //
+-- This procedure can be used in upgrade scripts to assert that the schema version in the database matches the
+-- expected version before applying the upgrade. This is important to prevent users from accidentally skipping
+-- intermediate upgrade scripts, which could lead to an inconsistent database state. For instance, since every
+-- upgrade script knows its predecessor's version, we can just do "CALL assert_correct_schema_version('v1.0')"
+-- at the beginning of the 1.x upgrade scripts to ensure that the 1.0 script has been applied before.
+CREATE PROCEDURE assert_correct_schema_version(expected_version text)
+    READS SQL DATA
+    COMMENT 'Asserts that the schema version in the database matches the expected version and raises an error if not.'
+BEGIN
+    DECLARE actual_version text;
+    DECLARE error_message text;
+    SELECT version INTO actual_version FROM notifications_schema ORDER BY timestamp DESC LIMIT 1;
+    IF actual_version IS NULL THEN
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Schema version not found in notifications_schema table.';
+    ELSEIF actual_version != expected_version THEN
+        -- MySQL/MariaDB doesn't seem to allow to directly use CONCAT in the SIGNAL statement[^1],
+        -- so we need to set it to a variable first.
+        -- [^1]: https://bugs.mysql.com/bug.php?id=114001
+        SET error_message = CONCAT('Schema version mismatch: expected ', expected_version, ', got ', actual_version, '. Please apply all previous upgrade scripts in order before applying this one.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = error_message;
+    END IF;
+END;
+//
+DELIMITER ;
+
 CREATE TABLE available_channel_type (
     type varchar(255) NOT NULL,
     name text NOT NULL,
@@ -453,3 +480,14 @@ CREATE TABLE browser_session (
 
 CREATE INDEX idx_browser_session_authenticated_at ON browser_session (authenticated_at DESC);
 CREATE INDEX idx_browser_session_username_agent ON browser_session (username, user_agent(512));
+
+CREATE TABLE notifications_schema (
+    id int NOT NULL AUTO_INCREMENT,
+    version varchar(64) NOT NULL,
+    timestamp bigint NOT NULL,
+
+    CONSTRAINT pk_notifications_schema PRIMARY KEY (id),
+    CONSTRAINT uk_notifications_schema_version UNIQUE (version)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
+
+INSERT INTO notifications_schema(version, timestamp) VALUES('v1.0', UNIX_TIMESTAMP() * 1000);

schema/mysql/upgrades/1.0.sql

@@ -0,0 +1,34 @@
+DROP PROCEDURE IF EXISTS assert_correct_schema_version;
+DELIMITER //
+-- This procedure can be used in upgrade scripts to assert that the schema version in the database matches the
+-- expected version before applying the upgrade. This is important to prevent users from accidentally skipping
+-- intermediate upgrade scripts, which could lead to an inconsistent database state. For instance, since every
+-- upgrade script knows its predecessor's version, we can just do "CALL assert_correct_schema_version('v1.0')"
+-- at the beginning of the 1.x upgrade scripts to ensure that the 1.0 script has been applied before.
+CREATE PROCEDURE assert_correct_schema_version(expected_version text)
+    READS SQL DATA
+    COMMENT 'Asserts that the schema version in the database matches the expected version and raises an error if not.'
+BEGIN
+    DECLARE actual_version text;
+    DECLARE error_message text;
+    SELECT version INTO actual_version FROM notifications_schema ORDER BY timestamp DESC LIMIT 1;
+    IF actual_version IS NULL THEN
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Schema version not found in notifications_schema table.';
+    ELSEIF actual_version != expected_version THEN
+        SET error_message = CONCAT('Schema version mismatch: expected ', expected_version, ', got ', actual_version, '. Please apply all previous upgrade scripts in order before applying this one.');
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = error_message;
+    END IF;
+END;
+//
+DELIMITER ;
+
+CREATE TABLE notifications_schema (
+    id int NOT NULL AUTO_INCREMENT,
+    version varchar(64) NOT NULL,
+    timestamp bigint NOT NULL,
+
+    CONSTRAINT pk_notifications_schema PRIMARY KEY (id),
+    CONSTRAINT uk_notifications_schema_version UNIQUE (version)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
+
+INSERT INTO notifications_schema(version, timestamp) VALUES('v1.0', UNIX_TIMESTAMP() * 1000);

schema/pgsql/schema.sql

@@ -30,6 +30,26 @@ CREATE OR REPLACE FUNCTION anynonarrayliketext(anynonarray, text)
     $$;
 CREATE OPERATOR ~~ (LEFTARG=anynonarray, RIGHTARG=text, PROCEDURE=anynonarrayliketext);
 
+-- This procedure can be used in upgrade scripts to assert that the schema version in the database matches the
+-- expected version before applying the upgrade. This is important to prevent users from accidentally skipping
+-- intermediate upgrade scripts, which could lead to an inconsistent database state. For instance, since every
+-- upgrade script knows its predecessor's version, we can just do "CALL assert_correct_schema_version('v1.0')"
+-- at the beginning of the 1.x upgrade scripts to ensure that the 1.0 script has been applied before.
+CREATE OR REPLACE PROCEDURE assert_correct_schema_version(expected_version text)
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    actual_version text := (SELECT version FROM notifications_schema ORDER BY timestamp DESC LIMIT 1);
+BEGIN
+    IF actual_version IS NULL THEN
+        RAISE 'Schema version not found in notifications_schema table.';
+    ELSIF actual_version != expected_version THEN
+        RAISE 'Schema version mismatch: expected %, got %. Please apply all previous upgrade scripts in order before applying this one.', expected_version, actual_version;
+    END IF;
+END;
+$$;
+COMMENT ON PROCEDURE assert_correct_schema_version IS 'Asserts that the schema version in the database matches the expected version and raises an error if not.';
+
 CREATE TABLE available_channel_type (
     type varchar(255) NOT NULL,
     name text NOT NULL,
@@ -499,3 +519,14 @@ CREATE TABLE browser_session (
 
 CREATE INDEX idx_browser_session_authenticated_at ON browser_session (authenticated_at DESC);
 CREATE INDEX idx_browser_session_username_agent ON browser_session (username, user_agent);
+
+CREATE TABLE notifications_schema (
+    id serial,
+    version varchar(64) NOT NULL,
+    timestamp bigint NOT NULL,
+
+    CONSTRAINT pk_notifications_schema PRIMARY KEY (id),
+    CONSTRAINT uk_notifications_schema_version UNIQUE (version)
+);
+
+INSERT INTO notifications_schema(version, timestamp) VALUES('v1.0', EXTRACT(EPOCH from NOW()) * 1000);

schema/pgsql/upgrades/1.0.sql

@@ -0,0 +1,30 @@
+-- This procedure can be used in upgrade scripts to assert that the schema version in the database matches the
+-- expected version before applying the upgrade. This is important to prevent users from accidentally skipping
+-- intermediate upgrade scripts, which could lead to an inconsistent database state. For instance, since every
+-- upgrade script knows its predecessor's version, we can just do "CALL assert_correct_schema_version('v1.0')"
+-- at the beginning of the 1.x upgrade scripts to ensure that the 1.0 script has been applied before.
+CREATE OR REPLACE PROCEDURE assert_correct_schema_version(expected_version text)
+    LANGUAGE plpgsql
+AS $$
+DECLARE
+    actual_version text := (SELECT version FROM notifications_schema ORDER BY timestamp DESC LIMIT 1);
+BEGIN
+    IF actual_version IS NULL THEN
+        RAISE 'Schema version not found in notifications_schema table.';
+    ELSIF actual_version != expected_version THEN
+        RAISE 'Schema version mismatch: expected %, got %. Please apply all previous upgrade scripts in order before applying this one.', expected_version, actual_version;
+    END IF;
+END;
+$$;
+COMMENT ON PROCEDURE assert_correct_schema_version IS 'Asserts that the schema version in the database matches the expected version and raises an error if not.';
+
+CREATE TABLE notifications_schema (
+  id serial,
+  version varchar(64) NOT NULL,
+  timestamp bigint NOT NULL,
+
+  CONSTRAINT pk_notifications_schema PRIMARY KEY (id),
+  CONSTRAINT uk_notifications_schema_version UNIQUE (version)
+);
+
+INSERT INTO notifications_schema(version, timestamp) VALUES('v1.0', EXTRACT(EPOCH from NOW()) * 1000);