Add support for reading passwords from files

Allow providing passwords via `_FILE` environment variables for Etcd and PostgreSQL users (standby, admin, superuser). If the primary password environment variable is not set, the configuration script will read the password from the filesystem path specified in the corresponding `_FILE` variable.

This change also adds support for the `ETCD_USER` environment variable.

Author: SavedByGrace251

ENVIRONMENT.rst

@@ -9,6 +9,10 @@ Environment Configuration Settings
 - **ETCD_CACERT**: Etcd CA certificate. If present it will enable validation.
 - **ETCD_CERT**: Etcd client certificate.
 - **ETCD_KEY**: Etcd client certificate key. Can be empty if the key is part of certificate.
+- **ETCD_USER**: Etcd client username.
+- **ETCD_PASSWORD**: Etcd client password. Takes precedence over ``ETCD_PASSWORD_FILE`` when both are set.
+- **ETCD_PASSWORD_FILE**: Etcd client password file. The file content is used as Patroni etcd password when
+  ``ETCD_PASSWORD`` is not set.
 - **PGHOME**: filesystem path where to put PostgreSQL home directory (/home/postgres by default)
 - **APIPORT**: TCP port to Patroni API connections (8008 by default)
 - **BACKUP_SCHEDULE**: cron schedule for doing backups via WAL-G ('00 01 * * *' by default)
@@ -19,14 +23,20 @@ Environment Configuration Settings
 - **PGDATA**: location of PostgreSQL data directory, by default PGROOT/pgdata.
 - **PGUSER_STANDBY**: username for the replication user, 'standby' by default.
 - **PGPASSWORD_STANDBY**: a password for the replication user, 'standby' by default.
+- **PGPASSWORD_STANDBY_FILE**: password file for ``PGPASSWORD_STANDBY``. Used when
+  ``PGPASSWORD_STANDBY`` is not set.
 - **STANDBY_HOST**: hostname or IP address of the primary to stream from.
 - **STANDBY_PORT**: TCP port on which the primary is listening for connections. Patroni will use "5432" if not set.
 - **STANDBY_PRIMARY_SLOT_NAME**: replication slot to use on the primary.
 - **PGUSER_ADMIN**: username for the default admin user, 'admin' by default.
 - **PGPASSWORD_ADMIN**: a password for the default admin user, 'cola' by default.
+- **PGPASSWORD_ADMIN_FILE**: password file for ``PGPASSWORD_ADMIN``. Used when
+  ``PGPASSWORD_ADMIN`` is not set.
 - **USE_ADMIN**: whether to use the admin user or not.
 - **PGUSER_SUPERUSER**: username for the superuser, 'postgres' by default.
 - **PGPASSWORD_SUPERUSER**: a password for the superuser, 'zalando' by default
+- **PGPASSWORD_SUPERUSER_FILE**: password file for ``PGPASSWORD_SUPERUSER``. Used when
+  ``PGPASSWORD_SUPERUSER`` is not set.
 - **ALLOW_NOSSL**: set to allow clients to connect without SSL enabled.
 - **PGPORT**: port PostgreSQL listens to for client connections, 5432 by default
 - **PGVERSION**: Specifies the version of postgreSQL to reference in the bin_dir variable (/usr/lib/postgresql/PGVERSION/bin) if postgresql.bin_dir wasn't set in SPILO_CONFIGURATION

postgres-appliance/scripts/configure_spilo.py

@@ -529,6 +529,23 @@ def has_dual_stack():
     return info[0][4][0]
 
 
+def set_password_from_file(placeholders, password_keys):
+    for password_key in password_keys:
+        if placeholders.get(password_key):
+            continue
+
+        password_file_key = password_key + '_FILE'
+        password_file = placeholders.get(password_file_key)
+        if not password_file:
+            continue
+
+        try:
+            with open(password_file) as f:
+                placeholders[password_key] = f.read().rstrip('\r\n')
+        except Exception as e:
+            raise ValueError('Failed to read {0}: {1}'.format(password_file_key, e))
+
+
 def get_placeholders(provider):
     placeholders = {}
     for key, value in os.environ.items():
@@ -541,6 +558,9 @@ def get_placeholders(provider):
         else:
             placeholders[key] = value
 
+    set_password_from_file(placeholders, ('ETCD_PASSWORD', 'ETCD3_PASSWORD',
+                                          'PGPASSWORD_STANDBY', 'PGPASSWORD_ADMIN', 'PGPASSWORD_SUPERUSER'))
+
     placeholders.setdefault('PGHOME', os.path.expanduser('~'))
     placeholders.setdefault('APIPORT', '8008')
     placeholders.setdefault('BACKUP_SCHEDULE', '0 1 * * *')