Running lightwalletd with zebra

Zebra's RPC methods can support a lightwalletd service backed by zebrad. We recommend using zcash/lightwalletd because we use it in testing. Other lightwalletd forks have limited support, see the Sync lightwalletd section for more info.

Contents:

Configure zebra for lightwalletd

We need a zebra configuration file. First, we create a file with the default settings:

zebrad generate -o ~/.config/zebrad.toml

The above command places the generated zebrad.toml config file in the default preferences directory of Linux. For other OSes default locations see here.

Tweak the following option in order to prepare for lightwalletd setup.

JSON-RPC

We need to configure Zebra to behave as an RPC endpoint. The standard RPC port for Zebra is:

  • 8232 for Mainnet, and
  • 18323 for Testnet.

For example, to use Zebra as a lightwalletd backend on Mainnet, give it this ~/.config/zebrad.toml:

[rpc]
# listen for RPC queries on localhost
listen_addr = '127.0.0.1:8232'

# automatically use multiple CPU threads
parallel_cpu_threads = 0

WARNING: This config allows multiple Zebra instances to share the same RPC port. See the RPC config documentation for details.

Sync Zebra

With the configuration in place you can start synchronizing Zebra with the Zcash blockchain. This may take a while depending on your hardware.

zebrad start

Zebra will display information about sync process:

...
zebrad::commands::start: estimated progress to chain tip sync_percent=10.783 % 
...

Until eventually it will get there:

...
zebrad::commands::start: finished initial sync to chain tip, using gossiped blocks sync_percent=100.000 % 
...

You can interrupt the process at any time with ctrl-c and Zebra will resume the next time at around the block you were downloading when stopping the process.

When deploying for production infrastructure, the above command can/should be implemented as a server service or similar configuration.

For implementing zebra as a service please see here.

Download and build lightwalletd

While you synchronize Zebra you can install lightwalletd.

Before installing, you need to have go in place. Please visit the go install page with download and installation instructions.

With go installed and in your path, download and install lightwalletd:

git clone https://github.com/zcash/lightwalletd
cd lightwalletd
make
make install

If everything went good you should have a lightwalletd binary in ~/go/bin/.

Sync lightwalletd

Please make sure you have zebrad running (with RPC endpoint and up to date blockchain) to synchronize lightwalletd.

  • lightwalletd requires a zcash.conf file, however this file can be empty if you are using the default Zebra rpc endpoint (127.0.0.1:8232) and the zcash/lightwalletd fork.

    • Some lightwalletd forks also require a rpcuser and rpcpassword, but Zebra ignores them if it receives them from lightwalletd
    • When using a non-default port, use rpcport=28232 and rpcbind=127.0.0.1
    • When using testnet, use testnet=1

  • For production setups lightwalletd requires a cert.pem. For more information on how to do this please see here.

  • lightwalletd can run without the certificate (with the --no-tls-very-insecure flag) however this is not recommended for production environments.

With the cert in ./ and an empty zcash.conf we can start the sync with:

lightwalletd --zcash-conf-path ~/.config/zcash.conf --data-dir ~/.cache/lightwalletd --log-file /dev/stdout

By default lightwalletd service will listen on 127.0.0.1:9067

Lightwalletd will do its own synchronization, while it is doing you will see messages as:

...
{"app":"lightwalletd","level":"info","msg":"Ingestor adding block to cache: 748000","time":"2022-05-28T19:25:49-03:00"}
{"app":"lightwalletd","level":"info","msg":"Ingestor adding block to cache: 749540","time":"2022-05-28T19:25:53-03:00"}
{"app":"lightwalletd","level":"info","msg":"Ingestor adding block to cache: 751074","time":"2022-05-28T19:25:57-03:00"}
...

Wait until lightwalletd is in sync before connecting any wallet into it. You will know when it is in sync as those messages will not be displayed anymore.

Run tests

The Zebra team created tests for the interaction of zebrad and lightwalletd.

To run all the Zebra lightwalletd tests:

  1. install lightwalletd
  2. install protoc
  3. build Zebra with --features=lightwalletd-grpc-tests

Please refer to acceptance tests documentation in the Lightwalletd tests section.

Connect a wallet to lightwalletd

The final goal is to connect wallets to the lightwalletd service backed by Zebra.

For demo purposes we used zecwallet-cli with the adityapk00/lightwalletd fork. We didn't test zecwallet-cli with zcash/lightwalletd yet.

Make sure both zebrad and lightwalletd are running and listening.

Download and build the cli-wallet

cargo install --locked --git https://github.com/adityapk00/zecwallet-light-cli

zecwallet-cli binary will be at ~/.cargo/bin/zecwallet-cli.

Run the wallet

$ zecwallet-cli --server 127.0.0.1:9067
Lightclient connecting to http://127.0.0.1:9067/
{
  "result": "success",
  "latest_block": 1683911,
  "total_blocks_synced": 49476
}
Ready!
(main) Block:1683911 (type 'help') >>