working on harmonia

tests/harmonia/configuration.nix

@@ -0,0 +1,72 @@
+{ pkgs, lib, config, modulesPath, ... }:
+let
+  moduleList = import "${modulesPath}/module-list.nix";
+
+  dynixFromSearchPath = let
+    res = builtins.tryEval <dynix>;
+  in lib.optional res.success res.value;
+in
+{
+  imports = [
+    "${modulesPath}/testing/test-instrumentation.nix"
+    ./hardware-configuration.nix
+  ] ++ lib.concatLists [
+    dynixFromSearchPath
+    moduleList
+  ];
+
+  dynamicism.for.harmonia.enable = true;
+  services.harmonia = {
+    enable = true;
+    settings = {
+      # Default.
+      workers = 4;
+      # Default.
+      max_connection_rate = 256;
+    };
+  };
+
+  system.switch.enable = true;
+  documentation.enable = false;
+
+  networking.hostName = "harmonia-machine";
+
+  boot.loader.grub = {
+    enable = true;
+    device = "/dev/vda";
+    forceInstall = true;
+  };
+
+  nix = {
+    package = pkgs.lixPackageSets.latest.lix;
+    nixPath = [
+      "nixpkgs=${pkgs.path}"
+      "/nix/var/nix/profiles/per-user/root/profile/share/nixos/modules"
+    ];
+
+    settings = {
+      experimental-features = [ "nix-command" "pipe-operator" ];
+      substituters = lib.mkForce [ ];
+      hashed-mirrors = null;
+      connect-timeout = 1;
+      # For my debugging purposes.
+      show-trace = true;
+    };
+  };
+
+  environment.pathsToLink = [ "/share" ];
+  environment.extraOutputsToInstall = [ "modules" ];
+  environment.variables = {
+    "NIXOS_CONFIG" = "/etc/nixos/configuration.nix";
+  };
+
+  environment.shellAliases = {
+    ls = "eza --long --header --group --group-directories-first --classify --binary";
+  };
+
+  environment.systemPackages = with pkgs; [
+    eza
+    fd
+    ripgrep
+  ];
+}

tests/harmonia/hardware-configuration.nix

@@ -0,0 +1,4 @@
+{ ... }:
+{
+
+}

tests/harmonia/test-script.py

@@ -0,0 +1,125 @@
+import functools
+from pathlib import Path
+from pprint import pformat
+import shlex
+import textwrap
+import tomllib
+from typing import Any, cast, TYPE_CHECKING
+
+from beartype import beartype
+
+from test_driver.machine import Machine
+from test_driver.errors import RequestedAssertionFailed
+
+if TYPE_CHECKING:
+    global machine
+    machine = cast(Machine, ...)
+    assert machine.shell is not None
+
+ls = "eza -lah --color=always --group-directories-first"
+
+indent = functools.partial(textwrap.indent, prefix='  ')
+
+@beartype
+def run_log(machine: Machine, *commands: str, timeout: int | None = 60) -> str:
+    output = ""
+    for command in commands:
+        with machine.nested(f"must succeed: {command}"):
+            (status, out) = machine.execute(f"{command} | tee /dev/stderr", timeout=timeout)
+            if status != 0:
+                machine.log(f"output: {out}")
+                raise RequestedAssertionFailed(
+                    f"command `{command}` failed (exit code {status})",
+                )
+            output += out
+
+    return output
+
+@beartype
+def get_config_file() -> dict[str, Any]:
+    machine.wait_for_unit("harmonia.service")
+    pid = int(machine.get_unit_property("harmonia.service", "MainPID"))
+    env_lines: list[str] = machine.succeed(f"cat /proc/{pid}/environ").replace("\0", "\n").splitlines()
+    pairs: list[list[str]] = [line.split("=", maxsplit=1) for line in env_lines]
+    env = dict(pairs)
+
+    config_file = Path(env["CONFIG_FILE"])
+
+    machine.log(f"copying from VM: {config_file=}")
+    machine.copy_from_vm(config_file.as_posix())
+
+    config_file_path = machine.out_dir / config_file.name
+    with open(config_file_path, "rb") as f:
+        config_data = tomllib.load(f)
+
+    config_file_path.unlink()
+    return config_data
+
+machine.wait_for_unit("default.target")
+assert "lix" in machine.succeed("nix --version").lower()
+machine.log("INIT")
+
+# Config should have our initial values.
+config_toml = get_config_file()
+machine.log(f"config.toml BEFORE first rebuild (initial): {indent(pformat(config_toml))}")
+assert int(config_toml['workers']) == 4, f"{config_toml['workers']=} != 4"
+assert int(config_toml['max_connection_rate']) == 256, f"{config_toml['max_connection_rate']=} != 256"
+
+with machine.nested("must succeed: initial nixos-rebuild switch"):
+    machine.succeed("nixos-generate-config")
+    machine.succeed("mkdir -vp /etc/nixos")
+    # Dereference is required since that configuration.nix is probably a symlink to the store.
+    machine.succeed("cp -rv --dereference /run/current-system/sw/share/nixos/configuration.nix /etc/nixos/")
+    machine.succeed("env PAGER= nixos-rebuild switch --log-format raw-with-logs --fallback")
+
+# Config should not have changed.
+config_toml = get_config_file()
+machine.log(f"config.toml after first rebuild: {indent(pformat(config_toml))}")
+assert int(config_toml['workers']) == 4, f"{config_toml['workers']=} != 4"
+assert int(config_toml['max_connection_rate']) == 256, f"{config_toml['max_connection_rate']=} != 256"
+
+new_workers = 20
+expr = textwrap.dedent(f"""
+    let
+        nixos = import <nixpkgs/nixos> {{ }};
+    in nixos.config.dynamicism.doChange {{
+        option = "services.harmonia.settings.workers";
+        value = {new_workers};
+    }}
+""").strip()
+machine.succeed(rf"""
+    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
+""".strip())
+
+# Workers, but not max connection rate, should have changed.
+config_toml = get_config_file()
+machine.log(f"config.toml after DYNAMIC ACTIVATION: {indent(pformat(config_toml))}")
+assert int(config_toml['workers']) == new_workers, f"{config_toml['workers']=} != {new_workers}"
+assert int(config_toml['max_connection_rate']) == 256, f"{config_toml['max_connection_rate']=} != 256"
+
+new_max_connection_rate = 100
+expr = textwrap.dedent(f"""
+    let
+        nixos = import <nixpkgs/nixos> {{ }};
+    in nixos.config.dynamicism.doChange {{
+        option = [ "services" "harmonia" "settings" "max_connection_rate" ];
+        value = {new_max_connection_rate};
+    }}
+""").strip()
+machine.succeed(rf"""
+    nix run --show-trace --log-format raw-with-logs --impure -E {shlex.quote(expr)}
+""".strip())
+
+# Max connection rate should have changed, but workers should have reverted.
+config_toml = get_config_file()
+machine.log(f"config_toml after SECOND dynamic activation: {indent(pformat(config_toml))}")
+assert int(config_toml['max_connection_rate']) == new_max_connection_rate, f"{config_toml['max_connection_rate']=} != {new_max_connection_rate}"
+
+# And this should set everything back.
+machine.succeed("env PAGER= nixos-rebuild switch --log-format raw-with-logs --fallback")
+machine.systemctl("restart harmonia.service")
+machine.wait_for_unit("harmonia.service")
+config_toml = get_config_file()
+machine.log(f"config_toml after NORMAL activation: {indent(pformat(config_toml))}")
+assert int(config_toml['max_connection_rate']) == 256, f'{config_toml["max_connection_rate"]=} != 256'
+assert int(config_toml['workers']) == 4, f'{config_toml["workers"]=} != 4'

tests/harmonia/test.nix

@@ -0,0 +1,23 @@
+{ ... }:
+{
+  name = "nixos-test-dynamicism-harmonia";
+
+  defaults = { ... }: { };
+
+  extraPythonPackages = p: [ p.beartype ];
+
+  nodes.machine = { name, pkgs, ... }: {
+    imports = [ ./configuration.nix ];
+
+    environment.systemPackages = let
+      configFileTree = pkgs.runCommand "${name}-configuration-dot-nix" { } ''
+        set -euo pipefail
+        install -Dm a=r ${./configuration.nix} "$out/share/nixos/configuration.nix"
+      '';
+    in [
+      configFileTree
+    ];
+  };
+
+  testScript = builtins.readFile ./test-script.py;
+}