Add param for Dry run to use a DB file instead of memory (#182)

README.md

@@ -140,14 +140,16 @@ changes, it will suffice to edit `config.json` and restart the container.
 
 ### Usage
 ```
-usage: freqtrade [-h] [-c PATH] [-v] [--version] [--dynamic-whitelist]
+usage: main.py [-h] [-c PATH] [-v] [--version] [--dynamic-whitelist [INT]]
-                 {backtesting} ...
+               [--dry-run-db]
+               {backtesting,hyperopt} ...
 
 Simple High Frequency Trading Bot for crypto currencies
 
 positional arguments:
-  {backtesting}
+  {backtesting,hyperopt}
     backtesting         backtesting module
+    hyperopt            hyperopt module
 
 optional arguments:
   -h, --help            show this help message and exit
@@ -155,9 +157,12 @@ optional arguments:
                         specify configuration file (default: config.json)
   -v, --verbose         be verbose
   --version             show program's version number and exit
-  --dynamic-whitelist INT   dynamically generate and update whitelist based on 24h
+  --dynamic-whitelist [INT]
+                        dynamically generate and update whitelist based on 24h
                         BaseVolume (Default 20 currencies)
-
+  --dry-run-db          Force dry run to use a local DB
+                        "tradesv3.dry_run.sqlite" instead of memory DB. Work
+                        only if dry_run is enabled.
 ```
 
 #### Dynamic whitelist example

freqtrade/main.py

@@ -325,6 +325,14 @@ def main() -> None:
     if args.dynamic_whitelist:
         logger.info('Using dynamically generated whitelist. (--dynamic-whitelist detected)')
 
+    # If the user ask for Dry run with a local DB instead of memory
+    if args.dry_run_db:
+        if _CONF.get('dry_run', False):
+            _CONF.update({'dry_run_db': True})
+            logger.info('Dry_run will use the DB file: "tradesv3.dry_run.sqlite". (--dry_run_db detected)')
+        else:
+            logger.info('Dry run is disabled. (--dry_run_db ignored)')
+
     try:
         init(_CONF)
         old_state = None

freqtrade/misc.py

@@ -119,6 +119,13 @@ def parse_args(args: List[str]):
         metavar='INT',
         nargs='?',
     )
+    parser.add_argument(
+        '--dry-run-db',
+        help='Force dry run to use a local DB "tradesv3.dry_run.sqlite" instead of memory DB. Work only if dry_run is \
+             enabled.',
+        action='store_true',
+        dest='dry_run_db',
+    )
     build_subcommands(parser)
     parsed_args = parser.parse_args(args)
 

freqtrade/persistence.py

@@ -29,6 +29,11 @@ def init(config: dict, engine: Optional[Engine] = None) -> None:
     _CONF.update(config)
     if not engine:
         if _CONF.get('dry_run', False):
+            # the user wants dry run to use a DB
+            if _CONF.get('dry_run_db', False):
+                engine = create_engine('sqlite:///tradesv3.dry_run.sqlite')
+            # Otherwise dry run will store in memory
+            else:
                 engine = create_engine('sqlite://',
                                        connect_args={'check_same_thread': False},
                                        poolclass=StaticPool,