# Intro

> Русская версия: [README.ru-RU.md](README.ru-RU.md)

[ElectrumX](https://github.com/spesmilo/electrumx) is a server for the Electrum protocol. It indexes the chain from a full node and answers the queries a light client cannot answer for itself: the history and the UTXOs of an arbitrary address, and transaction broadcast.

ElectrumX running in a docker container, configured by environment variables.

This repository covers the docker deployment only. ElectrumX itself is installed from a pinned upstream git tag.

# Usage

ElectrumX needs a `bitcoind` it can reach over RPC, on the same network, not
pruned. `DAEMON_URL` is the only required variable; `NET` must name the same
chain the daemon runs.

The container serves the Electrum protocol on **50001** (plaintext TCP) and, if
`SERVICES` asks for it, on **50002** (TLS). There is no authentication of any
kind, so keep both inside the docker network or on loopback. The **RPC** service
on `localhost:8000` is administrative and never leaves the container — the
health check is what uses it.

## docker-compose

```yaml
services:
  electrumx:
    build:
      context: https://git.bitdeals.org/private/electrumx.git
      dockerfile: ./docker/Dockerfile
    image: registry.bitdeals.org/electrumx
    environment:
      - COIN=Bitcoin
      - NET=regtest
      - DAEMON_URL=http://CHANGE_ME:CHANGE_ME@bitcoind:18443
      - CACHE_MB=400
    ports:
      - 127.0.0.1:50001:50001   # no auth — loopback only
    volumes:
      - electrumxdata:/data

volumes:
  electrumxdata:
```

## docker cli

```sh
docker run -d \
  -e COIN=Bitcoin \
  -e NET=regtest \
  -e DAEMON_URL=http://CHANGE_ME:CHANGE_ME@bitcoind:18443 \
  -e CACHE_MB=400 \
  -p 127.0.0.1:50001:50001 \
  -v electrumxdata:/data \
  registry.bitdeals.org/electrumx
```

Anything after the image name is passed on to `electrumx_server`.

## build and publish

A push to `main` builds and publishes the image (`.gitea/workflows/build.yaml`),
tagging it three ways: `<version>.<sha7>` to deploy by, `<version>` to read, and
`latest` for compose and Watchtower. By hand, when the registry credentials are
at hand:

```sh
docker build . --file docker/Dockerfile --tag registry.bitdeals.org/electrumx
docker push registry.bitdeals.org/electrumx
```

A different ElectrumX release is a build argument — use a tag from
[the upstream repository](https://github.com/spesmilo/electrumx/tags):

```sh
docker build . --file docker/Dockerfile \
  --build-arg ELECTRUMX_VERSION=2.0.0 \
  --tag registry.bitdeals.org/electrumx:2.0.0
```

# Parameters

Container images are configured using parameters passed at runtime. Every
variable is ElectrumX's own, so
[the upstream environment reference](https://electrumx-spesmilo.readthedocs.io/en/latest/environment.html)
applies unchanged; the table lists the ones this image gives a default to.

|Parameter|Function|
|:--------|:-------|
|-p 127.0.0.1:50001|Electrum protocol over plaintext TCP. No authentication — see "Notes"|
|-p 127.0.0.1:50002|Electrum protocol over TLS. Served only when `SERVICES` includes `ssl://`|
|-v /data|Data directory: the index, and the self-signed certificate if one was generated. Losing it means indexing the chain again|
|-e DAEMON_URL|**Required.** The daemon's RPC, e.g. `http://user:password@bitcoind:8332`. Several may be given, comma-separated|
|-e COIN|Coin class. Default: `Bitcoin`|
|-e NET|Network: `mainnet`, `testnet`, `testnet4`, `signet`, `regtest` or `mutinynet`. Must match the daemon's chain. Default: `mainnet`|
|-e DB_ENGINE|Index storage. Default: `rocksdb`, the only engine whose libraries this image carries|
|-e DB_DIRECTORY|Where the index lives. Default: `/data`|
|-e SERVICES|What to serve, comma-separated. Default: `tcp://:50001,rpc://localhost:8000`. Keep an `rpc://` entry — the health check needs it|
|-e SSL_CERTFILE, -e SSL_KEYFILE|TLS certificate and key. Default: generated as a self-signed pair in the data directory when `SERVICES` includes `ssl://`|
|-e PEER_DISCOVERY|Whether to learn other public servers. Default: `off` — this image is meant for a private indexer|
|-e PEER_ANNOUNCE|Whether to announce this server to the peer network. Default: `false`|
|-e CACHE_MB|Indexing cache. Default: `1200` (ElectrumX's own). Lower it for a small chain, raise it to speed up an initial mainnet index|

# Notes

- **There is no authentication.** Anyone who reaches 50001 or 50002 can query
  any address and broadcast transactions. Publish to loopback, or not at all
  when the clients are containers on the same network.
- **An index from another image is not readable.** This one runs rocksdb;
  `lukechilds/electrumx`, which it replaces in BitDeals, wrote leveldb. Point
  the container at an empty volume and let it index — for regtest and testnet
  this is quick, for mainnet it is a matter of days.
- **The daemon needs `txindex=1` and `txospenderindex=1`.** ElectrumX 2.x checks
  `getindexinfo` before it serves anything and exits with a `RuntimeError`
  naming the missing index — one at a time, so fixing `txindex` earns you the
  same message about `txospenderindex`. With the sibling
  [bitcoind image](https://git.bitdeals.org/private/bitcoind) that is
  `BITCOIND_TXINDEX=1` and `BITCOIND_TXOSPENDERINDEX=1`; on an existing datadir
  turning them on means a reindex of the daemon.
- **The daemon must not be pruned.** Indexing reads every block; a pruned node
  fails partway through with an error about a missing block rather than about
  the configuration.
- **`NET` is ElectrumX's spelling, not bitcoind's.** The daemon calls the
  networks `main`, `test` and `regtest`; ElectrumX calls them `mainnet`,
  `testnet` and `regtest`. The entrypoint rejects an unknown value, because the
  pair is usually configured from one `.env` and `NET=test` would otherwise
  fail deep inside a coin lookup.
- **The container turns healthy only once it is serving**, which is after it has
  caught up with the daemon. An initial mainnet index takes days and the
  container will be unhealthy for all of it — watch the logs instead; on regtest
  it is a matter of seconds.
- **A self-signed certificate is generated only if `SERVICES` asks for TLS and
  no files are supplied.** Clients then have to trust it explicitly. That is the
  price of ElectrumX refusing to start when `ssl://` is requested without a
  certificate, which is a surprising way to learn you added a port.