backup: Add backup-cli tool and use it to initialize the backups

backup/backup-cli

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+from backup import FileBackend
+import os
+import click
+import json
+
+
+@click.command()
+@click.argument("lightning-dir", type=click.Path(exists=True))
+@click.argument("backup-dir", type=click.Path(exists=True))
+def init(lightning_dir, backup_dir):
+    destination = 'file://' + os.path.join(backup_dir, 'backup.dbak')
+    backend = FileBackend(destination)
+    backend.version, backend.prev_version = 0, 0
+    backend.offsets = [512, 0]
+    backend.version_count = 0
+    backend.write_metadata()
+
+    lock_file = os.path.join(lightning_dir, "backup.lock")
+
+    with open(lock_file, "w") as f:
+        f.write(json.dumps({
+            'backend_url': destination,
+        }))
+
+    print("Initialized backup backend {destination}, you can now start c-lightning".format(
+        destination=destination,
+    ))
+
+
+@click.group()
+def cli():
+    pass
+
+
+cli.add_command(init)
+
+if __name__ == "__main__":
+    cli()

backup/backup.py

@@ -1,14 +1,13 @@
 #!/usr/bin/env python3
-from pyln.client import Plugin
-from pprint import pprint
 from collections import namedtuple
+from pyln.client import Plugin
+from typing import Mapping, Type
 from urllib.parse import urlparse
-import struct
+import json
-import os
-from typing import Mapping, Type, Optional
 import logging
+import os
+import struct
 import sys
-from binascii import hexlify
 
 
 plugin = Plugin()
@@ -25,7 +24,8 @@ root.addHandler(handler)
 # A change that was proposed by c-lightning that needs saving to the
 # backup. `version` is the database version before the transaction was
 # applied.
-Change = namedtuple('Change',['version', 'transaction'])
+Change = namedtuple('Change', ['version', 'transaction'])
+
 
 class Backend(object):
     def __init__(self, destination: str):
@@ -40,6 +40,7 @@ class Backend(object):
     def initialize(self) -> bool:
         raise NotImplementedError
 
+
 class FileBackend(Backend):
     def __init__(self, destination: str):
         self.version = None
@@ -116,9 +117,15 @@ class FileBackend(Backend):
         self.prev_version, self.offsets[1] = 0, 0
         return True
 
-backend_map: Mapping[str, Type[Backend]] = {
+
+def resolve_backend_class(backend_url):
+    backend_map: Mapping[str, Type[Backend]] = {
         'file': FileBackend,
-}
+    }
+    p = urlparse(backend_url)
+    backend_cl = backend_map.get(p.scheme, None)
+    return backend_cl
+
 
 def abort(reason: str) -> None:
     plugin.log(reason)
@@ -165,7 +172,7 @@ def on_db_write(writes, data_version, plugin, **kwargs):
     change = Change(data_version, writes)
     if not hasattr(plugin, 'backend'):
         plugin.early_writes.append(change)
-        return True
+        return {"result": "continue"}
     else:
         return apply_write(plugin, change)
 
@@ -175,7 +182,8 @@ def apply_write(plugin, change):
         assert(check_first_write(plugin, change.version))
         plugin.initialized = True
 
-    return plugin.backend.add_entry(change)
+    if plugin.backend.add_change(change):
+        return {"result": "continue"}
 
 
 @plugin.init()
@@ -185,6 +193,17 @@ def on_init(options: Mapping[str, str], plugin: Plugin, **kwargs):
     plugin.db_path = configs['wallet']
     destination = options['backup-destination']
 
+    # Ensure that we don't inadventently switch the destination
+    if os.path.exists("backup.lock"):
+        d = json.load(open("backup.lock", 'r'))
+        if destination is None or destination == 'null':
+            destination = d['backend_url']
+        elif destination != d['backend_url']:
+            abort(
+                "The destination specified as option does not match the one "
+                "specified in backup.lock. Please check your settings"
+            )
+
     if not plugin.db_path.startswith('sqlite3'):
         abort("The backup plugin only works with the sqlite3 database.")
 
@@ -192,8 +211,7 @@ def on_init(options: Mapping[str, str], plugin: Plugin, **kwargs):
         abort("You must specify a backup destination, possibly on a secondary disk.")
 
     # Let's initialize the backed. First we need to figure out which backend to use.
-    p = urlparse(destination)
+    backend_cl = resolve_backend_class(destination)
-    backend_cl = backend_map.get(p.scheme, None)
     if backend_cl is None:
         abort("Could not find a backend for scheme {p.scheme}".format(p=p))
 

backup/test_backup.py

@@ -3,20 +3,23 @@ from pyln.client import RpcError
 from pyln.testing.fixtures import *
 import os
 import time
+import shutil
+import subprocess
+
 
 plugin_dir = os.path.dirname(__file__)
 plugin_path = os.path.join(plugin_dir, "backup.py")
+cli_path = os.path.join(os.path.dirname(__file__), "backup-cli")
 
 
 def test_start(node_factory, directory):
+    bdest = os.path.join(directory, 'backup.dbak')
     opts = {
         'plugin': plugin_path,
-        'backup-destination': 'file://' + os.path.join(directory, 'backup.dbak')
+        'backup-destination': 'file://' + bdest,
         }
-    shutil.copyfile(
+
-        os.path.join(plugin_dir, 'fixtures', "backup.dbak"),
+    subprocess.check_call([cli_path, "init", directory, directory])
-        os.path.join(directory, "backup.dbak")
-    )
     l1 = node_factory.get_node(options=opts)
 
     l1.daemon.wait_for_log(r'backup.py')
@@ -37,14 +40,12 @@ def test_tx_abort(node_factory, directory):
     inbetween the hook call and the DB transaction.
 
     """
+    bdest = os.path.join(directory, 'backup.dbak')
     opts = {
         'plugin': plugin_path,
-        'backup-destination': 'file://' + os.path.join(directory, 'backup.dbak')
+        'backup-destination': 'file://' + bdest,
         }
-    shutil.copyfile(
+    subprocess.check_call([cli_path, "init", directory, directory])
-        os.path.join(plugin_dir, 'fixtures', "backup.dbak"),
-        os.path.join(directory, "backup.dbak")
-    )
     l1 = node_factory.get_node(options=opts)
     l1.stop()
 
@@ -71,10 +72,7 @@ def test_failing_restore(nf, directory):
         'plugin': plugin_path,
         'backup-destination': 'file://' + os.path.join(directory, 'backup.dbak')
         }
-    shutil.copyfile(
+    subprocess.check_call([cli_path, "init", directory, directory])
-        os.path.join(plugin_dir, 'fixtures', "backup.dbak"),
-        os.path.join(directory, "backup.dbak")
-    )
     l1 = node_factory.get_node(options=opts)
     l1.stop()
 
@@ -97,10 +95,7 @@ def test_intermittent_backup(node_factory, directory):
         'plugin': plugin_path,
         'backup-destination': 'file://' + os.path.join(directory, 'backup.dbak')
         }
-    shutil.copyfile(
+    subprocess.check_call([cli_path, "init", directory, directory])
-        os.path.join(plugin_dir, 'fixtures', "backup.dbak"),
-        os.path.join(directory, "backup.dbak")
-    )
     l1 = node_factory.get_node(options=opts)
 
     # Now start without the plugin. This should work fine.