** System NOT running to use fully qualified hostnames ** ** Hostname 127.0.0.1 is illegal **

[mhanberg]

Not sure if this is the best place to post or on #174 but I have a similar issue with the lastest expert release.

Expert release: commit: 2c2b7f4 installed via flakes with nix
OS: linux
Elixir: 1.19.
Editor: helix.
Terminal: fish

helix-log:

2025-10-20T14:50:26.695 helix_view::document [WARN] LSP formatting failed: protocol error: InternalError: ** (ErlangError) Erlang error: {:erpc, :noconnection}
    (kernel 10.2.7.2) erpc.erl:1376: :erpc.call/5
    (xp_expert 0.1.0) lib/expert/provider/handlers/formatting.ex:16: XPExpert.Provider.Handlers.Formatting.handle/2
    (xp_expert 0.1.0) lib/expert.ex:94: XPExpert.handle_request/2
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:372: anonymous fn/2 in XPGenLSP.loop/3
    (xp_telemetry 1.3.0) telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:371: anonymous fn/5 in XPGenLSP.loop/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:601: anonymous fn/4 in XPGenLSP.attempt/4
    (elixir 1.17.3) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2

expert-log:

14:50:26.700 [debug] sent notification server -> client window/logMessage
14:50:26.700 [warning] client -> server notification crashed
14:50:26.700 [warning] client -> server notification crashed
14:50:41.748 [error] ** System NOT running to use fully qualified hostnames **
** Hostname 127.0.0.1 is illegal **

14:50:41.749 [error] ** (ErlangError) Erlang error: {:erpc, :noconnection}
    (kernel 10.2.7.2) erpc.erl:1376: :erpc.call/5
    (elixir 1.17.3) lib/enum.ex:987: Enum."-each/2-lists^foreach/1-0-"/2
    (xp_expert 0.1.0) lib/expert/state.ex:196: XPExpert.State.apply/2
    (xp_expert 0.1.0) lib/expert.ex:200: XPExpert.apply_to_state/2
    (xp_expert 0.1.0) lib/expert.ex:139: XPExpert.handle_notification/2
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:528: anonymous fn/2 in XPGenLSP.loop/3
    (xp_telemetry 1.3.0) telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:524: anonymous fn/4 in XPGenLSP.loop/3

14:50:41.749 [debug] sent notification server -> client window/logMessage
14:50:41.749 [warning] client -> server notification crashed
14:50:41.826 [error] ** System NOT running to use fully qualified hostnames **
** Hostname 127.0.0.1 is illegal **

14:50:41.827 [error] ** (ErlangError) Erlang error: {:erpc, :noconnection}
    (kernel 10.2.7.2) erpc.erl:1376: :erpc.call/5
    (elixir 1.17.3) lib/enum.ex:987: Enum."-each/2-lists^foreach/1-0-"/2
    (xp_expert 0.1.0) lib/expert/state.ex:196: XPExpert.State.apply/2
    (xp_expert 0.1.0) lib/expert.ex:200: XPExpert.apply_to_state/2
    (xp_expert 0.1.0) lib/expert.ex:139: XPExpert.handle_notification/2
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:528: anonymous fn/2 in XPGenLSP.loop/3
    (xp_telemetry 1.3.0) telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:524: anonymous fn/4 in XPGenLSP.loop/3

14:50:41.827 [debug] sent notification server -> client window/logMessage
14:50:41.827 [warning] client -> server notification crashed

Originally posted by @tcoopman in #59 (comment)

[Terbium-135]

Still testing Zed for Windows since the last weekend and can confirm:
Same error and neither formatting works using Zed and Expert

OS: Windows - with remote connecting to a Debian WSL
Elixir: 1.19-otp28
Erlang: OTP28.1
Editor: Zed
Terminal: zsh

[Terbium-135]

Format is working again after switching to
Elixir: 1.19.1-otp28
Erlang: OTP28.1.1

[Terbium-135]

After some more testing:
Format is working only a few times after deleting _build (not sure about index) then Expert is bugging out.

Sorry for the false positive

[doorgan]

I think this may be related to EPMDless deployments, the ETS backend's WAL may be panicking because there's more than one writer for it

[mhanberg]

I think this message happens when you try to start a node with a fully qualified name but you're using short names (we are and should).

I think we can maybe switch to always using localhost instead of trying to find the machines hostname.

[nineluj]

Same error here, using the nix flake to run the latest commit.

14:56:34.261 [info] Application logger started at :plain@balrog
14:56:34.261 [info] Application xp_mime started at :plain@balrog
14:56:34.261 [info] Application xp_hpax started at :plain@balrog
14:56:34.261 [info] Application crypto started at :plain@balrog
14:56:34.261 [info] Application asn1 started at :plain@balrog
14:56:34.261 [info] Application public_key started at :plain@balrog

Later followed by:

14:56:56.913 [error] ** System NOT running to use fully qualified hostnames **
** Hostname 127.0.0.1 is illegal **

14:56:56.914 [error] ** (ErlangError) Erlang error: {:erpc, :noconnection}
    (kernel 10.2.7.2) erpc.erl:1376: :erpc.call/5
    (xp_expert 0.1.0) lib/expert/provider/handlers/code_action.ex:16: XPExpert.Provider.Handlers.CodeAction.handle/2
    (xp_expert 0.1.0) lib/expert.ex:99: XPExpert.handle_request/2
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:372: anonymous fn/2 in XPGenLSP.loop/3
    (xp_telemetry 1.3.0) /build/telemetry-1.3.0/src/telemetry.erl:324: :xp_telemetry.span/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:371: anonymous fn/5 in XPGenLSP.loop/3
    (xp_gen_lsp 0.11.0) lib/gen_lsp.ex:601: anonymous fn/4 in XPGenLSP.attempt/4
    (elixir 1.17.3) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2

Host info:

$ hostname -f
balrog
$ cat /etc/hosts | grep balrog
127.0.0.2 balrog
$ elixir -v
Erlang/OTP 27 [erts-15.2.7.2] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]

Elixir 1.17.3 (compiled with Erlang/OTP 27)

[doorgan]

This should no longer be reproducible since after #205 we're only using longnames