Config: remote Bitcoin Core RPC address not used by bindex REST client

[dskudi]

Config: remote Bitcoin Core RPC address not used by bindex REST client

Have you read the documentation?
Yes. (Please, read usage.md first if you did not.)

How did you configure electrs?

electrs.toml

daemon_p2p_addr = "10.0.0.140:8333"

jsonrpc_import = false

auth = "electrs:<redacted>"

daemon_rpc_addr = "10.0.0.140:8332"

db_dir = "/var/lib/electrs/db"

network = "bitcoin"

electrum_rpc_addr = "0.0.0.0:50001"

log_filters = "INFO"

Environment variables: none

Arguments:

--conf /etc/electrs/config.toml
--daemon-rpc-addr 10.0.0.140:8332
--daemon-dir /var/lib/electrs/bitcoin

Debug output of configuration

Starting electrs 0.11.1 on x86_64 linux with Config {
    network: Bitcoin,
    db_dir: "/var/lib/electrs/db",
    db_log_dir: None,
    db_parallelism: 1,
    daemon_auth: UserPass("electrs", "<sensitive>"),
    daemon_rpc_addr: 10.0.0.140:8332,
    electrum_rpc_addr: 0.0.0.0:50001,
    monitoring_addr: 127.0.0.1:4224,
    wait_duration: 10s,
    jsonrpc_timeout: 15s,
    index_lookup_limit: None,
    reindex_last_blocks: 0,
    auto_reindex: true,
    ignore_mempool: false,
    sync_once: false,
    skip_block_download_wait: false,
    disable_electrum_rpc: false
}

[INFO  bindex::chain] index: Config {
    db_path: "/var/lib/electrs/db/bitcoin",
    url: "http://localhost:8332"
}

Expected behavior

I expected electrs to use the configured Bitcoin Core address:

daemon_rpc_addr = "10.0.0.140:8332"

for all Bitcoin Core communication, including the REST requests used by bindex.

Actual behavior

The JSON-RPC configuration is parsed correctly, but the bindex client uses:

http://localhost:8332

instead.

The resulting requests fail because Bitcoin Core is running on another host:

unavailable http://localhost:8332/rest/blockhashbyheight/0.bin:
Io(Custom { kind: ConnectionRefused, error: "Connection refused" })

I verified that the REST endpoint is available remotely:

curl http://10.0.0.140:8332/rest/blockhashbyheight/0.bin

returns binary output successfully.

I could not find a configuration option in electrs --help for changing the bindex REST URL separately from daemon_rpc_addr.

[dskudi]

Additional debugging

I did some additional investigation after opening this issue.

Using strace, I found that electrs is attempting to access the REST API at http://localhost:8332, even though the startup configuration shows:

daemon_rpc_addr: 10.0.0.140:8332

Example startup output:

Config {
    daemon_rpc_addr: 10.0.0.140:8332,
    ...
}

bindex::chain] index: Config {
    db_path: "/var/lib/electrs/db/bitcoin",
    url: "http://localhost:8332"
}

The strace output confirms it is actually connecting to 127.0.0.1:8332, not 10.0.0.140:8332.

To verify this, I created a local socat proxy forwarding 127.0.0.1:8332 to my Bitcoin node at 10.0.0.140:8332.

After doing that, the previous "Connection refused" errors disappeared, and electrs successfully reached the node. However, it now fails with:

GET http://localhost:8332/rest/blockpart/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f.bin?offset=0&size=285 failed: StatusCode(404)

Error: electrs failed

Caused by:
    0: failed to open index
    1: use https://github.com/bitcoin/bitcoin/pull/33657

The backend node is:

Bitcoin Knots daemon version v29.3.knots20260508

Other REST endpoints such as /rest/blockhashbyheight/0.bin work correctly, but /rest/blockpart/... returns HTTP 404.

So it appears there are two separate issues:

1. The REST client appears to ignore daemon_rpc_addr and instead uses localhost.
2. After working around that, bindex requires the /rest/blockpart endpoint, which is not available on my Bitcoin Knots node.

[dskudi]

I didn't intentionally build a different backend or branch—I simply followed the current build instructions from the repository (git clone, then cargo build --release).

The build I'm running is:

$ git rev-parse HEAD
31c3fc5b398475bd16bda6944a7140a5c37083a4

$ git describe --tags --always
v0.11.1-17-g31c3fc5

So this is the current master branch (17 commits past the v0.11.1 tag), not the tagged release itself.

The configuration appears to be parsed correctly. At startup, electrs reports:

daemon_rpc_addr: 10.0.0.140:8332

However, immediately afterward the bindex backend logs:

index: Config { db_path: "/var/lib/electrs/db/bitcoin", url: "http://localhost:8332" }

Using strace, I confirmed that it actually attempts to connect to 127.0.0.1:8332 rather than 10.0.0.140:8332.

As a workaround, I temporarily forwarded 127.0.0.1:8332 to my remote Bitcoin node. With that in place, electrs no longer failed with "connection refused" and instead progressed to:

GET http://localhost:8332/rest/blockpart/<genesis-hash>.bin?offset=0&size=285 failed: StatusCode(404)

Error: electrs failed

Caused by:
    failed to open index
    use https://github.com/bitcoin/bitcoin/pull/33657

The Bitcoin node I'm connecting to is:

Bitcoin Knots v29.3.knots20260508

At this point it looks like there may be two separate issues:

1. The bindex backend appears to ignore the configured daemon_rpc_addr for REST requests and instead hardcodes localhost.
2. Once connected, it expects the /rest/blockpart endpoint, which is not available on my Bitcoin Knots node and returns HTTP 404.

Please let me know if either of these behaviors is expected with the current master branch, or if I've misunderstood the intended configuration.

[romanz]

Thanks for reporting this issue!

1. it's indeed a bug, will fix. Thanks!
2. new electrs uses https://github.com/romanz/bindex, which requires new REST API endpoints:

• #32540 (index: fetch spent transaction outputs by blockhash) → released in 30.0
• #33657 (rest: allow reading partial block data from storage) → released in 31.0

[sokhapkin]

I use electrs on the same host, but getting 404 error. Bitcoin-core v31:
$ bitcoind -version
Bitcoin Core daemon version v31.0.0 bitcoind
Copyright (C) 2009-2026 The Bitcoin Core developers

But electrs built from current git fails with
Starting electrs 0.11.1 on x86_64 linux with Config { network: Bitcoin, db_dir: "/mnt/bitcoind/electrs-db", db_log_dir: None, db_par
allelism: 1, daemon_auth: CookieFile("/mnt/bitcoind/.cookie"), daemon_rpc_addr: 127.0.0.1:8332, electrum_rpc_addr: 10.38.0.250:50001
, monitoring_addr: 127.0.0.1:4224, wait_duration: 10s, jsonrpc_timeout: 15s, index_lookup_limit: None, reindex_last_blocks: 0, auto_
reindex: true, ignore_mempool: false, sync_once: false, skip_block_download_wait: false, disable_electrum_rpc: false, server_banner:
"Welcome to electrs 0.11.1 (Electrum Rust Server)!" }
[2026-07-11T11:32:02.148Z INFO electrs::server] serving Electrum RPC on 10.38.0.250:50001
[2026-07-11T11:32:02.148Z INFO bindex::chain] index: Config { db_path: "/mnt/bitcoind/electrs-db/bitcoin", url: "http://localhost:8
332" }
[2026-07-11T11:32:02.215Z ERROR bindex::client] GET http://localhost:8332/rest/blockhashbyheight/0.bin failed: StatusCode(404)
Error: electrs failed

Caused by:
0: failed to open index
1: client failed: request failed: http status: 404
2: request failed: http status: 404
3: http status: 404

[sokhapkin]

Nevermind, REST requests were not enabled in bitcoind.conf.

[romanz]

Tested locally with romanz/bindex-rs#118:

$ electrs --network bitcoin --db-dir ./_db --daemon-dir /home/user/.bitcoin --daemon-rpc-addr=::1:8332
...
[2026-07-18T09:52:39.445Z INFO  bindex::chain] index: Config { db_path: "./_db/bitcoin", url: "http://[::1]:8332" }