Add script wait_db.py to Django

scripts/start.sh

@@ -3,30 +3,9 @@
 # Exporting all environment variables to use in crontab
 env | sed 's/^\(.*\)$/ \1/g' > /root/env
 
-function_postgres_ready() {
-python << END
-import socket
-import time
-import os
-
-port = int(os.environ["POSTGRES_PORT"])
-
-s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-
-s.connect(('slave-db', port))
-s.close()
-END
-}
-
 echo '======= CHECKING FOR UNINSTALLED PKGs AND INSTALLING'
 pip freeze || pip install -r requirements.txt
 
-until function_postgres_ready; do
-  >&2 echo "======= POSTGRES IS UNAVAILABLE, WAITING"
-  sleep 1
-done
-echo "======= POSTGRES IS UP, CONNECTING"
-
 echo '======= MAKING MIGRATIONS'
 python3 manage.py makemigrations
 

smi/settings.py

@@ -12,6 +12,7 @@
 
 import os
 import environ
+from .wait_db import start_services
 
 env = environ.Env()
 
@@ -103,6 +104,8 @@
     }
 }
 
+start_services()
+
 # DATABASES = {
 #     'default': {
 #         'ENGINE': 'django.db.backends.sqlite3',

smi/wait_db.py

@@ -0,0 +1,56 @@
+import importlib
+import os
+import time
+
+import logging
+
+SERVICES_STARTED = False
+
+def start_services():
+    global SERVICES_STARTED
+
+    if SERVICES_STARTED:
+        return
+
+    start_postgres()
+
+    SERVICES_STARTED = True
+
+
+log = logging.getLogger()
+
+
+def start_postgres():
+    settings_path = os.environ['DJANGO_SETTINGS_MODULE']
+    settings = importlib.import_module(settings_path)
+
+    db = settings.DATABASES['default']
+    dbname = db['NAME']
+    user = db['USER']
+    password = db['PASSWORD']
+    host = db['HOST']
+
+    for _ in range(100):
+        if can_connect(dbname, user, password, host):
+            log.info("======= POSTGRES IS UP, CONNECTING")
+            return
+        log.warning('======= POSTGRES IS UNAVAILABLE, WAITING 0.5 Seconds')
+        time.sleep(0.5)
+
+    log.critical('Maximum number of attempts connecting to postgres database')
+    raise RuntimeError('could not connect to database')
+
+
+def can_connect(dbname, user, password, host):
+    import psycopg2
+
+    try:
+        psycopg2.connect(
+            dbname=dbname,
+            user=user,
+            password=password,
+            host=host
+        )
+    except psycopg2.OperationalError:
+        return False
+    return True