Eclair (French for Lightning) is a Scala implementation of the Lightning Network.
- Lightning Network Specification Compliance
- JSON API
- Testnet usage
Lightning Network Specification Compliance
Please see the latest release note for detailed information on BOLT compliance.
Eclair offers a feature-rich HTTP API that enables application developers to easily integrate.
For more information please visit the API documentation website.
🚨 Eclair's JSON API should NOT be accessible from the outside world (similarly to Groestlcoin Core API)
You will find detailed guides and frequently asked questions there.
Prerequisite: Groestlcoin Core
Eclair needs a synchronized, segwit-ready, zeromq-enabled, wallet-enabled, non-pruning, tx-indexing Groestlcoin Core node.
You must configure your Groestlcoin node to use
bech32 (segwit) addresses.
If your wallet has "non-segwit UTXOs" (outputs that are neither
bech32), you must send them to a
bech32 address before running eclair.
Run groestlcoind with the following minimal
server=1 rpcuser=foo rpcpassword=bar txindex=1 zmqpubhashblock=tcp://127.0.0.1:29000 zmqpubrawtx=tcp://127.0.0.1:29000
Depending on the actual hardware configuration, it may be useful to provide increased
dbcache parameter value for faster verification and
rpcworkqueue parameter value for better handling of API requests on
# UTXO database cache size, in MiB dbcache=2048 # Number of allowed pending RPC requests (default is 16) rpcworkqueue=128 # How many seconds groestlcoin will wait for a complete RPC HTTP request. # after the HTTP connection is established. rpcclienttimeout=30
Eclair is developed in Scala, a powerful functional language that runs on the JVM, and is packaged as a ZIP archive.
To run Eclair, you first need to install Java, we recommend that you use OpenJDK 11. Other runtimes also work, but we don't recommend using them.
Then download our latest release, unzip the archive and run the following command:
Eclair reads its configuration file, and write its logs, to
~/.eclair by default.
To change your node's configuration, create a file named
~/.eclair. Here's an example configuration file:
Here are some of the most common options:
|eclair.chain||Which blockchain to use: regtest, testnet or mainnet||mainnet|
|eclair.server.port||Lightning TCP port||9735|
|eclair.api.enabled||Enable/disable the API||false. By default the API is disabled. If you want to enable it, you must set a password.|
|eclair.api.port||API HTTP port||8080|
|eclair.api.password||API password (BASIC)||"" (must be set if the API is enabled)|
|eclair.bitcoind.rpcuser||Groestlcoin Core RPC user||foo|
|eclair.bitcoind.rpcpassword||Groestlcoin Core RPC password||bar|
|eclair.bitcoind.zmqblock||Groestlcoin Core ZMQ block address||"tcp://127.0.0.1:29000"|
|eclair.bitcoind.zmqtx||Groestlcoin Core ZMQ tx address||"tcp://127.0.0.1:29000"|
|eclair.bitcoind.wallet||Groestlcoin Core wallet name||""|
Quotes are not required unless the value contains special characters. Full syntax guide here.
→ see here for more configuration options.
Configure Groestlcoin Core wallet
Eclair will use the default loaded Groestlcoin Core wallet to fund any channels you choose to open.
If you want to use a different wallet from the default one, you must set
eclair.bitcoind.wallet accordingly in your
Eclair will return GRS from closed channels to the wallet configured. Any GRS found in the wallet can be used to fund the channels you choose to open.
Java Environment Variables
Some advanced parameters can be changed with java environment variables. Most users won't need this and can skip this section.
However, if you're seeing Java heap size errors, you can try increasing the maximum memory allocated to the JVM with the
You can for example set it to use up to 512 MB (or any value that fits the amount of RAM on your machine) with:
datadir is mandatory if you want to run several instances of eclair on the same machine. You will also have to change ports in
eclair.conf (see above).
|eclair.datadir||Path to the data directory||~/.eclair|
|eclair.printToConsole||Log to stdout (in addition to eclair.log)|
For example, to specify a different data directory you would run the following command:
logback for logging. To use a different configuration, and override the internal logback.xml, run:
You need to backup:
- your groestlcoin core wallet
- your eclair channels
For groestlcoin core, you need to backup the wallet file for the wallet that eclair is using. You only need to this once, when the wallet is created (see https://github.com/Groestlcoin/groestlcoin/blob/master/doc/managing-wallets.md for more information).
For eclair, the files that you need to backup are located in your data directory. You must backup:
- your seeds (
- your channel database (
regtestdepending on which chain you're running on)
Your seeds never change once they have been created, but your channels will change whenever you receive or send payments. Eclair will
create and maintain a snapshot of its database, named
eclair.sqlite.bak, in your data directory, and update it when needed. This file is
always consistent and safe to use even when Eclair is running, and this is what you should back up regularly.
For example, you could configure a
cron task for your backup job. Or you could configure an optional notification script to be called by eclair once a new database snapshot has been created, using the following option:
eclair.file-backup.notify-script = "/absolute/path/to/script.sh"
Make sure your script is executable and uses an absolute path name for
Note that depending on your filesystem, in your backup process we recommend first moving
eclair.sqlite.bak to some temporary file
before copying that file to your final backup location.
You can use the
JAVA_OPTS environment variable to set arguments to
docker run -ti --rm -e "JAVA_OPTS=-Xmx512m -Declair.api.binding-ip=0.0.0.0 -Declair.node-alias=node-pm -Declair.printToConsole" acinq/eclair
If you want to persist the data directory, you can make the volume to your host with the
-v argument, as the following example:
docker run -ti --rm -v "/path_on_host:/data" -e "JAVA_OPTS=-Declair.printToConsole" acinq/eclair
If you enabled the API you can check the status of eclair using the command line tool:
docker exec <container_name> eclair-cli -p foobar getinfo
For advanced usage, Eclair supports plugins written in Scala, Java, or any JVM-compatible language.
A valid plugin is a jar that contains an implementation of the Plugin interface, and a manifest entry for
Main-Class with the FQDN of the implementation.
Here is how to run Eclair with plugins:
eclair-node-<version>-<commit_id>/bin/eclair-node.sh <plugin1.jar> <plugin2.jar> <...>
Non-exhaustive plugins list
Here are some plugins created by the eclair community. If you need support for these plugins, head over to their respective github repository.
Eclair is configured to run on mainnet by default, but you can still run it on testnet (or regtest): start your Groestlcoin Node in
testnet mode (add
groestlcoin.conf or start with
-testnet), and change Eclair's chain parameter and Groestlcoin RPC port:
You may also want to take advantage of the new configuration sections in
groestlcoin.conf to manage parameters that are network specific,
so you can easily run your groestlcoin node on both mainnet and testnet. For example you could use:
server=1 txindex=1 [main] rpcuser=<your-mainnet-rpc-user-here> rpcpassword=<your-mainnet-rpc-password-here> zmqpubhashblock=tcp://127.0.0.1:29000 zmqpubrawtx=tcp://127.0.0.1:29000 [test] rpcuser=<your-testnet-rpc-user-here> rpcpassword=<your-testnet-rpc-password-here> zmqpubhashblock=tcp://127.0.0.1:29001 zmqpubrawtx=tcp://127.0.0.1:29001