Experimental etcd support in LND

With the recent introduction of the kvdb interface LND can support multiple database backends allowing experimentation with the storage model as well as improving robustness trough eg. replicating essential data.

Building on kvdb in v0.11.0 we're adding experimental etcd support to LND. As this is an unstable feature heavily in development, it still has many rough edges for the time being. It is therefore highly recommended to not use LND on etcd in any kind of production environment especially not on bitcoin mainnet.

Building LND with etcd support

To create a dev build of LND with etcd support use the following command:

make tags="kvdb_etcd"

The important tag is the kvdb_etcd, without which the binary is built without the etcd driver.

For development it is advised to set the GOFLAGS environment variable to "-tags=test" otherwise gopls won't work on code in channeldb/kvdb/etcd directory.

Running a local etcd instance for testing

To start your local etcd instance for testing run:

./etcd \
    --auto-tls \
    --advertise-client-urls=https://127.0.0.1:2379 \
    --listen-client-urls=https://0.0.0.0:2379 \
    --max-txn-ops=16384 \
    --max-request-bytes=104857600

The large max-txn-ops and max-request-bytes values are currently required in case of running LND with the full graph in etcd. Upcoming versions will split the database to local and replicated parts and only essential parts will remain in the replicated database, removing the requirement for these additional settings. These parameters have been tested to work with testnet LND.

Configuring LND to run on etcd

To run LND with etcd, additional configuration is needed, specified either through command line flags or in lnd.conf.

Sample command line:

./lnd-debug \
    --db.backend=etcd \
    --db.etcd.host=127.0.0.1:2379 \
    --db.etcd.certfile=/home/user/etcd/bin/default.etcd/fixtures/client/cert.pem \
    --db.etcd.keyfile=/home/user/etcd/bin/default.etcd/fixtures/client/key.pem \
    --db.etcd.insecure_skip_verify

Sample lnd.conf (with other setting omitted):

[db]
backend=etcd
etcd.host=127.0.0.1:2379
etcd.cerfile=/home/user/etcd/bin/default.etcd/fixtures/client/cert.pem
etcd.keyfile=/home/user/etcd/bin/default.etcd/fixtures/client/key.pem
etcd.insecure_skip_verify=true

Optionally users can specifiy db.etcd.user and db.etcd.pass for db user authentication.

Migrating existing channel.db to etcd

This is currently not supported.

Disclaimer

As mentioned before this is an experimental feature, and with that your data may be lost. Use at your own risk!

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