Fix backend db session leak, pass session to filter

chainsyncer/backend.py

@@ -32,7 +32,8 @@ class SyncerBackend:
     def connect(self):
         """Loads the state of the syncer session with the given id.
         """
-        self.db_session = SessionBase.create_session()
+        if self.db_session == None:
+            self.db_session = SessionBase.create_session()
         q = self.db_session.query(BlockchainSync)
         q = q.filter(BlockchainSync.id==self.object_id)
         self.db_object = q.first()
@@ -46,6 +47,7 @@ class SyncerBackend:
         self.db_session.add(self.db_object)
         self.db_session.commit()
         self.db_session.close()
+        self.db_session = None
        
 
     def chain(self):

chainsyncer/driver.py

@@ -28,7 +28,7 @@ class Syncer:
         self.cursor = None
         self.running = True
         self.backend = backend
-        self.filter = SyncFilter()
+        self.filter = SyncFilter(backend)
         self.progress_callback = progress_callback
 
 

chainsyncer/error.py

@@ -6,3 +6,7 @@ class LoopDone(Exception):
 
 class RequestError(Exception):
     pass
+
+
+class BackendError(Exception):
+    pass

chainsyncer/filter.py

@@ -1,13 +1,17 @@
 # standard imports
 import logging
 
+# local imports
+from .error import BackendError
+
 logg = logging.getLogger(__name__)
 
 class SyncFilter:
 
-    def __init__(self, safe=True):
+    def __init__(self, backend, safe=True):
         self.safe = safe
         self.filters = []
+        self.backend = backend
 
 
     def add(self, fltr):
@@ -19,15 +23,21 @@ class SyncFilter:
    
 
     def apply(self, conn, block, tx):
+        session = None
+        try:
+            session = self.backend.connect()
+        except sqlalchemy.exc.TimeoutError as e:
+            self.backend.disconnect()
+            raise BackendError('database connection fail: {}'.format(e))
         for f in self.filters:
             logg.debug('applying filter {}'.format(str(f)))
-            f.filter(conn, block, tx)
+            f.filter(conn, block, tx, self.backend.db_session)
+        self.backend.disconnect()
 
-
-class NoopFilter(SyncFilter):
+class NoopFilter:
     
-    def filter(self, conn, block, tx):
-        logg.debug('noop filter :received\n{} {}'.format(block, tx))
+    def filter(self, conn, block, tx, db_session=None):
+        logg.debug('noop filter :received\n{} {} {}'.format(block, tx, id(db_session)))
 
 
     def __str__(self):