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feat(multiService): Add service option to modify underlying process settings #617

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e852b77
feat: Provide granular control to modify the process from the service…
shivaraj-bh Oct 31, 2025
62ce133
chore: processSettings
shivaraj-bh Oct 31, 2025
e8b176d
chore: ah
shivaraj-bh Oct 31, 2025
ac14bb3
chore: discard lib.hasAttr
shivaraj-bh Nov 2, 2025
0f22ac7
docs: add
shivaraj-bh Nov 2, 2025
1c18198
docs: fix render
shivaraj-bh Nov 2, 2025
722ca7b
fix: don't enforce defining `processSettings.<name>` for all processe…
shivaraj-bh Nov 4, 2025
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48 changes: 48 additions & 0 deletions doc/custom-service.md
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,54 @@ Now that we have defined the multi-instance service, we can import it in our fla
And finally, `nix run`:
![[multi-instance-hello.png]]

> [!TIP]
> Do not introduce new options to configure underlying process-compose settings of a process, use the default `processSettings.<name>` option.
> Examples:
> - Bad:
> ```nix
> # Definition
> { config, ... }:
> {
> options = {
> ...
> extraEnvironment = lib.mkOption {
> type = lib.types.attrs;
> default = { };
> };
> };
> config = {
> outputs.settings = {
> processes.<name> = {
> environment = <defaults> // config.extraEnvironment;
> };
> };
> };
>
> }
>
> # Usage
> {
> services.<name>.<name> = {
> extraEnvironment = ...
> };
> }
> ```
> - Good:
> ```nix
>
> # No change in definition
>
> # Usage
> {
> services.<name>.<name> = {
> processSettings.<name> = {
> environment = ...;
> };
> };
> }
> ```


## See also

- [Postgres with replica](https://github.com/nammayatri/nammayatri/blob/main/Backend/nix/services/postgres-with-replica.nix)
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8 changes: 5 additions & 3 deletions example/llm/flake.nix
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Expand Up @@ -68,12 +68,14 @@
# RAG_RERANKING_MODEL_AUTO_UPDATE = "True";
# DEVICE_TYPE = "cpu";
};
processSettings."open-webui1" = {
# Modify the process-compose setting
# Start the Open WebUI service after the Ollama service has finished initializing and loading the models
depends_on.ollama1-models.condition = "process_completed_successfully";
};
};
};

# Start the Open WebUI service after the Ollama service has finished initializing and loading the models
settings.processes.open-webui1.depends_on.ollama1-models.condition = "process_completed_successfully";

# Open the browser after the Open WebUI service has started
settings.processes.open-browser = {
command =
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25 changes: 16 additions & 9 deletions nix/lib.nix
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Expand Up @@ -21,12 +21,13 @@
default = "./data/${name}";
description = "The directory where all data for `${service}.<name>` is stored";
};
namespace = lib.mkOption {
description = ''
Namespace for the ${service} service
'';
default = "${service}.${name}";
type = lib.types.str;
processSettings = lib.mkOption {
type = lib.types.lazyAttrsOf lib.types.deferredModule;
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@shivaraj-bh shivaraj-bh Oct 31, 2025

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lazyAttrsOf because a service can define multiple processes (postgres, postgres-init for example)

description = "Settings for a process-compose process defined in this service";
default = { };
apply = v: {
processes = v;
};
};
outputs = {
defaultProcessSettings = lib.mkOption {
Expand All @@ -37,7 +38,7 @@
Default settings for all processes under the ${service} service
'';
default = {
namespace = lib.mkDefault config.namespace;
namespace = lib.mkDefault "${service}.${name}";
};
};
settings = lib.mkOption {
Expand All @@ -48,7 +49,12 @@
'';
apply = v: v // {
processes = lib.flip lib.mapAttrs v.processes (_: cfg:
{ imports = [ config.outputs.defaultProcessSettings cfg ]; }
{
imports = [
config.outputs.defaultProcessSettings
cfg
];
}
);
};
};
Expand Down Expand Up @@ -77,7 +83,8 @@
imports =
lib.pipe config.services.${service} [
(lib.filterAttrs (_: cfg: cfg.enable))
(lib.mapAttrsToList (_: cfg: cfg.outputs.settings))
(lib.mapAttrsToList (_: cfg: [ cfg.outputs.settings cfg.processSettings ]))
lib.concatLists
];
};
};
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