create parent class for sql databases

electrum/sql_db.py

@@ -0,0 +1,51 @@
+import os
+import concurrent
+import queue
+import threading
+
+from sqlalchemy import create_engine
+from sqlalchemy.pool import StaticPool
+from sqlalchemy.orm import sessionmaker
+
+from .util import PrintError
+
+
+def sql(func):
+    """wrapper for sql methods"""
+    def wrapper(self, *args, **kwargs):
+        assert threading.currentThread() != self.sql_thread
+        f = concurrent.futures.Future()
+        self.db_requests.put((f, func, args, kwargs))
+        return f.result(timeout=10)
+    return wrapper
+
+class SqlDB(PrintError):
+    
+    def __init__(self, network, path, base):
+        self.base = base
+        self.network = network
+        self.path = path
+        self.db_requests = queue.Queue()
+        self.sql_thread = threading.Thread(target=self.run_sql)
+        self.sql_thread.start()
+
+    def run_sql(self):
+        engine = create_engine('sqlite:///' + self.path, pool_reset_on_return=None, poolclass=StaticPool)#, echo=True)
+        DBSession = sessionmaker(bind=engine, autoflush=False)
+        self.DBSession = DBSession()
+        if not os.path.exists(self.path):
+            self.base.metadata.create_all(engine)
+        while self.network.asyncio_loop.is_running():
+            try:
+                future, func, args, kwargs = self.db_requests.get(timeout=0.1)
+            except queue.Empty:
+                continue
+            try:
+                result = func(self, *args, **kwargs)
+            except BaseException as e:
+                future.set_exception(e)
+                continue
+            future.set_result(result)
+        # write
+        self.DBSession.commit()
+        self.print_error("SQL thread terminated")