Starts data persistence integration

The difference between master and the old data-persistence branch was huge, seems more effective to manually cherry pick the changes and integrate them

pisa/db_manager.py

@@ -0,0 +1,81 @@
+import json
+import plyvel
+
+from pisa.logger import Logger
+from pisa.conf import WATCHER_PREFIX, RESPONDER_PREFIX, WATCHER_LAST_BLOCK_KEY, RESPONDER_LAST_BLOCK_KEY
+
+logger = Logger("Daemon")
+
+
+class DBManager:
+    def __init__(self, db_path):
+        try:
+            self.db = plyvel.DB(db_path)
+
+        except plyvel.Error as e:
+            if 'create_if_missing is false' in str(e):
+                logger.info("No db found. Creating a fresh one")
+                self.db = plyvel.DB(db_path, create_if_missing=True)
+
+    def load_appointments_db(self, prefix):
+        data = {}
+
+        for k, v in self.db.iterator(prefix=prefix):
+            # Get uuid and appointment_data from the db
+            uuid = k[1:].decode('utf-8')
+            data[uuid] = json.loads(v)
+
+        return data
+
+    def get_last_known_block(self, prefix):
+        last_block = self.db.get(prefix)
+
+        if last_block:
+            last_block = last_block.decode('utf-8')
+
+        return last_block
+
+    def create_entry(self, key, value, prefix=None):
+        if isinstance(prefix, str):
+            key = prefix + key
+
+        key = key.encode('utf-8')
+        value = value.encode('utf-8')
+
+        self.db.put(key, value)
+
+    def delete_entry(self, key,  prefix=None):
+        if isinstance(prefix, str):
+            key = prefix + key
+
+        key = key.encode('utf-8')
+
+        self.db.delete(key)
+
+    def load_watcher_appointments(self):
+        return self.load_appointments_db(prefix=WATCHER_PREFIX)
+
+    def load_responder_jobs(self):
+        return self.load_appointments_db(prefix=RESPONDER_PREFIX)
+
+    def store_watcher_appointment(self, uuid, appointment):
+        self.create_entry(uuid, appointment, prefix=WATCHER_PREFIX)
+        logger.info("Adding appointment to Watchers's db", uuid=uuid)
+
+    def store_responder_job(self, uuid, job):
+        self.create_entry(uuid, job, prefix=RESPONDER_PREFIX)
+        logger.info("Adding appointment to Responder's db", uuid=uuid)
+
+    def delete_watcher_appointment(self, uuid):
+        self.delete_entry(uuid, prefix=WATCHER_PREFIX)
+        logger.info("Deleting appointment from Watcher's db", uuid=uuid)
+
+    def delete_responder_job(self, uuid):
+        self.delete_entry(uuid, prefix=RESPONDER_PREFIX)
+        logger.info("Deleting appointment from Responder's db", uuid=uuid)
+
+    def store_last_block_watcher(self, block_hash):
+        self.create_entry(WATCHER_LAST_BLOCK_KEY, block_hash)
+
+    def store_last_block_responder(self, block_hash):
+        self.create_entry(RESPONDER_LAST_BLOCK_KEY, block_hash)