Electrs fails with Bitcoin Knots due to environment variable parsing error

[harbi]

Bug Description:
Electrs app crashes with Error: Failed to resolve address 10.21.21.7:: invalid port value when using Bitcoin Knots instead of Bitcoin Core.

Root Cause:
The app expects Bitcoin Core environment variables APP_BITCOIN_* but Bitcoin Knots uses different variable names APP_BITCOIN_KNOTS_*. When APP_BITCOIN_RPC_PORT is undefined, it creates malformed address 10.21.21.7: instead of 10.21.21.7:8332.

Environment:

• Umbrel Home (2024)
• umbrelOS 1.4.2
• Bitcoin Knots 29.1.knots20250903
• Electrs v0.10.9-1

Steps to Reproduce:

1. Install Bitcoin Knots on Umbrel
2. Install Electrs app
3. Start Electrs
4. Check logs

Logs sample:

electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
electrs_app_1        | Electrum attempting reconnect...
...
Error: Failed to resolve address 10.21.21.7:: invalid port value
Error: Failed to resolve address 10.21.21.7:: invalid port value
Error: Failed to resolve address 10.21.21.7:: invalid port value
Error: Failed to resolve address 10.21.21.7:: invalid port value
Error: Failed to resolve address 10.21.21.7:: invalid port value

[nmfretz]

Thanks for the report @harbi! There's an open PR here getumbrel/umbrel-apps#3619. We're just waiting on the Knots maintainer and will update ASAP.

[ranathan14]

After the latest upgrade to fix this issue, the CPU is heavily used by the process at the end of synchronization.
Is it possible to use the latest version before yesterday’s release? If so, how? Thanks.

[massimodamassa]

After the latest update, I also noticed CPU overload and core temperature increases.
The wallet connection is also unstable.
I also updated Knots, but nothing has changed.

[ranathan14]

After the latest upgrade to fix this issue, the CPU is heavily used by the process at the end of synchronization. Is it possible to use the latest version before yesterday’s release? If so, how? Thanks.

I reinstalled the app by deleting it, and now the CPU usage seems fine and the problem appears to be resolved.

[massimodamassa]

Thanks for the information, I'll try it right away and let you know if I solve the problem.
You're very kind.

[massimodamassa]

After the latest upgrade to fix this issue, the CPU is heavily used by the process at the end of synchronization. Is it possible to use the latest version before yesterday’s release? If so, how? Thanks.

I reinstalled the app by deleting it, and now the CPU usage seems fine and the problem appears to be resolved.

Your advice worked. Thank you so much.