Merge pull request #6626 from corda/bugfix/ENT-5654-run-migration-scripts-completes-with-unexpected-error

ENT-5654: Fixed migration error message, improved success message

node-api/src/main/kotlin/net/corda/nodeapi/internal/persistence/SchemaMigration.kt

@@ -92,6 +92,25 @@ open class SchemaMigration(
         }
     }
 
+    /**
+     * Returns the count of pending database migration changes
+     * @param schemas The set of MappedSchemas to check
+     * @param forceThrowOnMissingMigration throws an exception if a mapped schema is missing the migration resource. Can be set to false
+     *                                      when allowing hibernate to create missing schemas in dev or tests.
+     */
+    fun getPendingChangesCount(schemas: Set<MappedSchema>, forceThrowOnMissingMigration: Boolean) : Int {
+        val resourcesAndSourceInfo = prepareResources(schemas, forceThrowOnMissingMigration)
+
+        // current version of Liquibase appears to be non-threadsafe
+        // this is apparent when multiple in-process nodes are all running migrations simultaneously
+        mutex.withLock {
+            dataSource.connection.use { connection ->
+                val (_, changeToRunCount, _) = prepareRunner(connection, resourcesAndSourceInfo)
+                return changeToRunCount;
+            }
+        }
+    }
+
     /**
      * Synchronises the changelog table with the schema descriptions passed in without applying any of the changes to the database.
      * This can be used when migrating a CorDapp that had its schema generated by hibernate to liquibase schema migration, or when