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nix component: build hook: refactor
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@dermetfan
dermetfan committed Jul 15, 2024
1 parent 52aaaed commit 97b4274
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Showing 5 changed files with 183 additions and 118 deletions.
48 changes: 39 additions & 9 deletions src/build.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,14 +29,21 @@ pub fn build(b: *Build) !void {
cizero_exe.root_module.addImport("cizero", cizero_mod);
b.installArtifact(cizero_exe);

{
const nix_build_hook_exe = b.addExecutable(.{
.name = "build-hook",
.root_source_file = b.path("components/nix/build-hook/main.zig"),
.target = opts.target,
.optimize = opts.optimize,
});
const nix_build_hook_mod = b.addModule("nix-build-hook", .{
.root_source_file = b.path("components/nix/build-hook/root.zig"),
.target = opts.target,
.optimize = opts.optimize,
});

const nix_build_hook_exe = b.addExecutable(.{
.name = "build-hook",
.root_source_file = b.path("components/nix/build-hook/main.zig"),
.target = opts.target,
.optimize = opts.optimize,
});
nix_build_hook_exe.root_module.addImport("nix-build-hook", nix_build_hook_mod);

{
const install_nix_build_hook_exe = b.addInstallArtifact(nix_build_hook_exe, .{ .dest_dir = .{ .override = .{ .custom = "libexec/cizero/components/nix" } } });
b.getInstallStep().dependOn(&install_nix_build_hook_exe.step);
}
Expand All @@ -53,7 +60,7 @@ pub fn build(b: *Build) !void {
const test_step = b.step("test", "Run unit tests");
{
const cizero_mod_test = b.addTest(.{
.name = "cizero",
.name = "cizero (mod)",
.root_source_file = cizero_mod.root_source_file.?,
.target = opts.target,
.optimize = opts.optimize,
Expand All @@ -66,7 +73,7 @@ pub fn build(b: *Build) !void {
}
{
const cizero_exe_test = b.addTest(.{
.name = "exe",
.name = "cizero (exe)",
.root_source_file = cizero_exe.root_module.root_source_file.?,
.target = opts.target,
.optimize = opts.optimize,
Expand All @@ -77,6 +84,29 @@ pub fn build(b: *Build) !void {
const run_cizero_exe_test = b.addRunArtifact(cizero_exe_test);
test_step.dependOn(&run_cizero_exe_test.step);
}
{
const nix_build_hook_mod_test = b.addTest(.{
.name = "nix-build-hook (mod)",
.root_source_file = nix_build_hook_mod.root_source_file.?,
.target = opts.target,
.optimize = opts.optimize,
});

const run_nix_build_hook_mod_test = b.addRunArtifact(nix_build_hook_mod_test);
test_step.dependOn(&run_nix_build_hook_mod_test.step);
}
{
const nix_build_hook_exe_test = b.addTest(.{
.name = "nix-build-hook (exe)",
.root_source_file = nix_build_hook_exe.root_module.root_source_file.?,
.target = opts.target,
.optimize = opts.optimize,
});
nix_build_hook_exe_test.root_module.addImport("nix-build-hook", nix_build_hook_mod);

const run_nix_build_hook_exe_test = b.addRunArtifact(nix_build_hook_exe_test);
test_step.dependOn(&run_nix_build_hook_exe_test.step);
}

_ = lib.addCheckTls(b);
}
Expand Down
4 changes: 0 additions & 4 deletions src/components/Nix.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1182,7 +1182,3 @@ fn build(allocator: std.mem.Allocator, installables: []const []const u8) !BuildR

return .{ .outputs = try outputs.toOwnedSlice(allocator) };
}

test {
_ = @import("nix/build-hook/main.zig");
}
130 changes: 25 additions & 105 deletions src/components/nix/build-hook/main.zig
View file
Original file line number Diff line number Diff line change
@@ -1,18 +1,17 @@
const std = @import("std");

const log = @import("log.zig");
const protocol = @import("protocol.zig");
const build_hook = @import("nix-build-hook");

const stdin = std.io.getStdIn().reader();
const stderr = std.io.getStdErr().writer();

pub const std_options = .{
.logFn = log.logFn,
.logFn = build_hook.log.logFn,
};

pub fn main() void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer if (gpa.deinit() == .leak) (log.Action{ .error_info = .{
defer if (gpa.deinit() == .leak) (build_hook.log.Action{ .error_info = .{
.level = .warn,
.msg = "leaked memory",
.raw_msg = @tagName(.leak),
Expand All @@ -21,7 +20,7 @@ pub fn main() void {
const allocator = gpa.allocator();

innerMain(allocator) catch |err|
log.logErrorInfo(allocator, .@"error", err, "error: {s}", .{@errorName(err)}) catch |err|
build_hook.log.logErrorInfo(allocator, .@"error", err, "error: {s}", .{@errorName(err)}) catch |err|
std.debug.panic("could not log error: {}\n", .{err});
}

Expand All @@ -33,36 +32,31 @@ fn innerMain(allocator: std.mem.Allocator) !void {
var args = try std.process.argsWithAllocator(allocator);
defer args.deinit();

_ = args.next();

const verbosity: log.Action.Verbosity = @enumFromInt(std.fmt.parseUnsigned(std.meta.Tag(log.Action.Verbosity), args.next().?, 10) catch |err| switch (err) {
error.Overflow => @intFromEnum(log.Action.Verbosity.vomit),
else => return err,
});
const verbosity = try build_hook.parseArgs(&args);
std.log.debug("log verbosity: {s}", .{@tagName(verbosity)});
}

var settings = try protocol.readStringStringMap(allocator, stdin);
defer settings.deinit();
var nix_config, var connection = try build_hook.start(allocator, stdin, stderr);
defer nix_config.deinit();

if (std.log.defaultLogEnabled(.debug)) {
var settings_msg = std.ArrayList(u8).init(allocator);
defer settings_msg.deinit();
var nix_config_msg = std.ArrayList(u8).init(allocator);
defer nix_config_msg.deinit();

var iter = settings.iterator();
var iter = nix_config.iterator();
while (iter.next()) |entry| {
try settings_msg.appendNTimes(' ', 2);
try settings_msg.appendSlice(entry.key_ptr.*);
try settings_msg.appendSlice(" = ");
try settings_msg.appendSlice(entry.value_ptr.*);
try settings_msg.append('\n');
try nix_config_msg.appendNTimes(' ', 2);
try nix_config_msg.appendSlice(entry.key_ptr.*);
try nix_config_msg.appendSlice(" = ");
try nix_config_msg.appendSlice(entry.value_ptr.*);
try nix_config_msg.append('\n');
}

std.log.debug("nix config: \n{s}", .{settings_msg.items});
std.log.debug("nix config: \n{s}", .{nix_config_msg.items});
}

var ifds_file = ifds_file: {
const builders = settings.get("builders").?;
const builders = nix_config.get("builders").?;
if (builders.len == 0) {
std.log.err("expected path to write IFDs to in nix config entry `builders` but it is empty", .{});
return error.NoBuilders;
Expand All @@ -80,23 +74,7 @@ fn innerMain(allocator: std.mem.Allocator) !void {

const ifds_writer = ifds_file.writer();

const Drv = struct {
am_willing: bool,
needed_system: []const u8,
drv_path: []const u8,
required_features: []const []const u8,

pub fn deinit(self: @This(), alloc: std.mem.Allocator) void {
alloc.free(self.needed_system);

alloc.free(self.drv_path);

for (self.required_features) |feature| alloc.free(feature);
alloc.free(self.required_features);
}
};

var drvs = std.StringHashMapUnmanaged(Drv){};
var drvs = std.StringHashMapUnmanaged(build_hook.Derivation){};
defer {
// No need to free the keys explicitly
// because `Drv.drv_path` is used as the key
Expand All @@ -109,21 +87,8 @@ fn innerMain(allocator: std.mem.Allocator) !void {
}

while (true) {
{
const command = protocol.readPacket(allocator, stdin) catch |err| switch (err) {
error.EndOfStream => return,
else => return err,
};
defer allocator.free(command);

if (!std.mem.eql(u8, command, "try")) {
std.log.debug("received unexpected command \"{s}\", expected \"try\"", .{std.fmt.fmtSliceEscapeLower(command)});
return;
}
}

const drv = blk: {
const drv = try protocol.readStruct(Drv, allocator, stdin);
const drv = try connection.readDerivation(allocator);

const gop = try drvs.getOrPut(allocator, drv.drv_path);

Expand Down Expand Up @@ -154,66 +119,21 @@ fn innerMain(allocator: std.mem.Allocator) !void {
try ifds_writer.writeAll(drv.drv_path);
try ifds_writer.writeByte('\n');

try decline();
try connection.decline();
}

// The rest of this function is only implemented to demonstrate
// how a build hook would be expected to behave in principle.
// In practice we will never get here
// because we do not intend to accept any build.

const accepted = try accept(allocator, "ssh://example.com");
defer accepted.deinit(allocator);
const build_io = try connection.accept(allocator, "ssh://example.com");
defer build_io.deinit(allocator);

{
const accepted_json = try std.json.stringifyAlloc(allocator, accepted, .{});
defer allocator.free(accepted_json);
const build_io_json = try std.json.stringifyAlloc(allocator, build_io, .{});
defer allocator.free(build_io_json);

std.log.debug("accepted: {s}", .{accepted_json});
std.log.debug("accepted: {s}", .{build_io_json});
}
}

fn decline() !void {
try stderr.print("# decline\n", .{});
}

/// The nix daemon will immediately kill the build hook after we decline permanently
/// so make sure to clean up all resources before calling this function.
///
/// This is because (if I interpret nix' code correctly)
/// [`worker.hook = 0`](https://github.com/NixOS/nix/blob/5fe2accb754249df6cb8f840330abfcf3bd26695/src/libstore/build/derivation-goal.cc#L1160)
/// invokes the [destructor](https://github.com/NixOS/nix/blob/5fe2accb754249df6cb8f840330abfcf3bd26695/src/libstore/build/hook-instance.cc#L82)
/// which sends SIGKILL [by default](https://github.com/NixOS/nix/blob/5fe2accb754249df6cb8f840330abfcf3bd26695/src/libutil/processes.cc#L54) (oof).
fn declinePermanently() !void {
try stderr.print("# decline-permanently\n", .{});
}

fn postpone() !void {
try stderr.print("# postpone\n", .{});
}

const Accepted = struct {
inputs: []const []const u8,
wanted_outputs: []const []const u8,

pub fn deinit(self: @This(), alloc: std.mem.Allocator) void {
for (self.inputs) |input| alloc.free(input);
alloc.free(self.inputs);

for (self.wanted_outputs) |output| alloc.free(output);
alloc.free(self.wanted_outputs);
}
};

/// The nix daemon will close stdin and wait for EOF from the build hook.
/// Therefore we can only accept once.
/// The nix daemon will start another instance of the build hook for the remaining derivations.
fn accept(allocator: std.mem.Allocator, store_uri: []const u8) !Accepted {
try stderr.print("# accept\n{s}\n", .{store_uri});
return protocol.readStruct(Accepted, allocator, stdin);
}

test {
_ = log;
_ = protocol;
}
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