Added support for dict/json environment variables for docker image

configs/docker_config.py

@@ -27,6 +27,7 @@ legal_envvars = (
     'SALT',
     'SQLALCHEMY_TRACK_MODIFICATIONS',
     'SQLALCHEMY_DATABASE_URI',
+    'SQLALCHEMY_ENGINE_OPTIONS',
     'MAIL_SERVER',
     'MAIL_PORT',
     'MAIL_DEBUG',
@@ -98,14 +99,25 @@ legal_envvars_bool = (
     'CAPTCHA_ENABLE',
 )
 
+legal_envvars_dict = (
+    'SQLALCHEMY_ENGINE_OPTIONS',
+)
+
 # import everything from environment variables
 import os
 import sys
-
+import json
 
 def str2bool(v):
     return v.lower() in ("true", "yes", "1")
 
+def dictfromstr(v,ret):
+    try:
+        return json.loads(ret)
+    except Exception as e:
+        print('Cannot parse json {} for variable {}'.format(ret, v))
+        print(e)
+        raise ValueError
 
 for v in legal_envvars:
 
@@ -129,4 +141,6 @@ for v in legal_envvars:
             ret = str2bool(ret)
         if v in legal_envvars_int:
             ret = int(ret)
+        if v in legal_envvars_dict:
+            ret = dictfromstr(v, ret)
         sys.modules[__name__].__dict__[v] = ret

docs/wiki/configuration/Environment-variables.md

@@ -58,5 +58,7 @@
 | SIGNUP_ENABLED | 
 | SQLALCHEMY_DATABASE_URI | SQL Alchemy URI to connect to database | N | no default |
 | SQLALCHEMY_TRACK_MODIFICATIONS |
+| SQLALCHEMY_ENGINE_OPTIONS | json string. e.g. '{"pool_recycle":600,"echo":1}' [^2] |
 
 [^1]: Flask secret key (see https://flask.palletsprojects.com/en/1.1.x/config/#SECRET_KEY for how to generate)
+[^2]: See Flask-SQLAlchemy Documentation for all engine options.