[psql] Add migration for Postgresql cluster upgrade from 9.6 to 11

locales/en.json

@@ -429,6 +429,10 @@
     "migration_0015_specific_upgrade": "Starting upgrade of system packages that needs to be upgrade independently...",
     "migration_0015_cleaning_up": "Cleaning up cache and packages not useful anymore...",
     "migration_0015_weak_certs": "The following certificates were found to still use weak signature algorithms and have to be upgraded to be compatible with the next version of nginx: {certs}",
+    "migration_description_0017_postgresql_9p6_to_11": "Migrate databases from PostgreSQL 9.6 to 11",
+    "migration_0017_postgresql_96_not_installed": "PostgreSQL was not installed on your system. Nothing to do.",
+    "migration_0017_postgresql_11_not_installed": "PostgreSQL 9.6 is installed, but not postgresql 11‽ Something weird might have happened on your system :(...",
+    "migration_0017_not_enough_space": "Make sufficient space available in {path} to run the migration.",
     "migrations_already_ran": "Those migrations are already done: {ids}",
     "migrations_cant_reach_migration_file": "Could not access migrations files at the path '%s'",
     "migrations_dependencies_not_satisfied": "Run these migrations: '{dependencies_id}', before migration {id}.",

src/yunohost/data_migrations/0017_postgresql_9p6_to_11.py

@@ -0,0 +1,41 @@
+import subprocess
+
+from moulinette import m18n
+from yunohost.utils.error import YunohostError
+from moulinette.utils.log import getActionLogger
+
+from yunohost.tools import Migration
+from yunohost.utils.filesystem import free_space_in_directory, space_used_by_directory
+
+logger = getActionLogger('yunohost.migration')
+
+
+class MyMigration(Migration):
+
+    "Migrate DBs from Postgresql 9.6 to 11 after migrating to Buster"
+
+    dependencies = ["migrate_to_buster"]
+
+    def run(self):
+
+        if not self.package_is_installed("postgresql-9.6"):
+            logger.warning(m18n.n("migration_0017_postgresql_96_not_installed"))
+            return
+
+        if not self.package_is_installed("postgresql-11"):
+            raise YunohostError("migration_0017_postgresql_11_not_installed")
+
+        if not space_used_by_directory("/var/lib/postgresql/9.6") > free_space_in_directory("/var/lib/postgresql"):
+            raise YunohostError("migration_0017_not_enough_space", path="/var/lib/postgresql/")
+
+        subprocess.check_call("systemctl stop postgresql", shell=True)
+        subprocess.check_call("pg_dropcluster --stop 11 main", shell=True)
+        subprocess.check_call("pg_upgradecluster -m upgrade 9.6 main", shell=True)
+        subprocess.check_call("pg_dropcluster --stop 9.6 main", shell=True)
+        subprocess.check_call("systemctl start postgresql", shell=True)
+
+    def package_is_installed(self, package_name):
+
+        p = subprocess.Popen("dpkg --list | grep '^ii ' | grep -q -w {}".format(package_name), shell=True)
+        p.communicate()
+        return p.returncode == 0