43fc3c6d34
Add automatic reconnect (with exponential back-off) to the socket backend. If the connection is lost while pusing a change, try to reconnect. Handle edge-cases that might come up depending on when the disconnect happaned. Currently the parameters are hardcoded: it will retry 5 times, on the first retry it will wait 5 seconds before reconnecting. There is an exponential backoff of 1.5, so on the fifth try it will wait about 25 seconds. This is particularly useful when conencting over Tor, as transient interruptions are fairly common there.
A simple and reliable backup plugin
This version only supports the default SQLite3 database
This plugin will maintain clean database backups to another location. It uses
the db_write hook to make sure to always have a backup that is not missing any
state updates and is not potentially harmful.
Related info about backup solutions: https://github.com/ElementsProject/lightning/blob/master/doc/BACKUP.md
Installation
There are some Python dependencies. You can install them using pip3:
pip3 install --user -r requirements.txt
Setup
Before the backup plugin can be used it has to be initialized once. The following
command will create /mnt/external/location/file.sql as backup file and reference it
in backup.lock in the lightning directory that stores the internal state, and
which makes sure no two instances are using the same backup.
./backup-cli init --lightning-dir ~/.lightning/bitcoin file:///mnt/external/location/file.bkp
Notes:
- If you are not using the default lightning directory you'll need to
change
~/.lightning/bitcoinin the command line to point to that directory instead. - You should use some non-local SSH or NFS mount as destination, otherwise any failure of the disk may result in both the original as well as the backup being corrupted.
- Currently only the
file:///URL scheme is supported.
IMPORTANT note about hsm_secret
You need to secure ~/.lightning/bitcoin/hsm_secret once! This
file will not change, but without this file, the database backup will be
unusable!
Make sure it has user read only permissions, otherwise lightningd will refuse
to work: chmod 0400 hsm_secret
Running
In order to tell lightningd to use the plugin you either need to tell it
via the startup option --plugin /path/to/backup.py or by placing it (or a
symlink to it) in the lightning plugin directory (~/.lightning/plugins).
On daemon startup the plugin will check the integrity of the existing backup and complain if there is a version mismatch.
Performing backup compaction
A backup compaction incorporates incremental updates into a single snapshot.
This will reduce the size of the backup file and reduce the time needed to
restore the backup. This can be done through the plugin command backup-compact:
lightning-cli backup-compact
Be aware that this can take a long time depending on the size of the backup and I/O speeds, during which the daemon will not be reachable.
Restoring a backup
If things really messed up and you need to reinstall clightning, you can
restore the database backup by using the backup-cli utility:
./backup-cli restore file:///mnt/external/location ~/.lightning/bitcoin/lightningd.sqlite3