feat: xev Dynamic API + gitignore updates for Shadow support by GrapeBaBa · Pull Request #704 · blockblaz/zeam

GrapeBaBa · 2026-04-02T14:50:28Z

Summary

Switch xev from compile-time backend selection to Dynamic API for runtime io_uring/epoll detection
This makes the binary portable across Linux kernel versions and Shadow-compatible
Add gitignore entries for zig-pkg/ cache, Shadow simulator outputs, and IDE files

Details

xev Dynamic API

All @import("xev") changed to @import("xev").Dynamic, which probes io_uring at runtime and falls back to epoll. A detectBackend() helper in utils.zig is called early in main and in test setup.

gitignore

zig-pkg/ — local Zig package cache (should not be committed)
shadow.yaml, shadow.data/ — generated by lean-quickstart/run-shadow.sh
.idea/ — JetBrains IDE files

Test plan

Verify build passes on CI
Verify existing tests pass
Verify Shadow 4-node devnet works with lean-quickstart/run-shadow.sh

Copilot

Pull request overview

This PR updates the Zig codebase to use libxev’s Dynamic API so the runtime can select the best available I/O backend (io_uring vs epoll), improving portability across Linux kernel versions and compatibility with Shadow. It also updates .gitignore to exclude additional local/tool-generated artifacts.

Changes:

Switched @import("xev") usages to @import("xev").Dynamic across node, network, and CLI code.
Added a detectBackend() helper and invoked it early in CLI startup and node test initialization.
Updated .gitignore to ignore zig-pkg/, Shadow outputs, and .idea/.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pkgs/node/src/utils.zig	Introduces `detectBackend()` and moves node code to `xev.Dynamic`.
pkgs/node/src/testing.zig	Calls backend detection before initializing the event loop in tests.
pkgs/node/src/node.zig	Switches xev import for tests to `xev.Dynamic`.
pkgs/node/src/lib.zig	Re-exports `detectBackend` for external callers (CLI).
pkgs/node/src/clock.zig	Switches xev import to `xev.Dynamic`.
pkgs/network/src/mock.zig	Switches to `xev.Dynamic` and adds backend detection in tests.
pkgs/network/src/interface.zig	Switches xev import to `xev.Dynamic`.
pkgs/network/src/ethlibp2p.zig	Switches xev import to `xev.Dynamic`.
pkgs/cli/src/node.zig	Switches xev import to `xev.Dynamic`.
pkgs/cli/src/main.zig	Calls `node_lib.detectBackend()` early during CLI startup.
build.zig	Notes that xev backend override is no longer needed.
.gitignore	Ignores `zig-pkg/`, Shadow outputs, and JetBrains IDE files.

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pkgs/node/src/utils.zig

Copilot · 2026-04-02T14:54:50Z

pkgs/network/src/mock.zig

+    if (@hasDecl(xev, "detect")) xev.detect() catch @panic("no available xev backend");
    var loop = try xev.Loop.init(.{});


This if (@hasDecl(xev, "detect")) xev.detect() ... backend-detection snippet is duplicated in multiple tests in this file. Consider factoring it into a small local helper (e.g., detectBackendOrPanic()), so the behavior/error handling stays consistent and future changes only need to be made once.

Copilot · 2026-04-02T14:54:51Z

pkgs/network/src/mock.zig

+    if (@hasDecl(xev, "detect")) xev.detect() catch @panic("no available xev backend");
    var loop = try xev.Loop.init(.{});
    defer loop.deinit();


This backend detection line duplicates the same xev.detect() snippet used earlier in this file. To reduce repetition (and keep the panic/error message consistent), consider extracting the detection into a single helper and calling it from each test before xev.Loop.init.

pkgs/cli/src/main.zig

Switch from compile-time xev backend selection to the Dynamic API, which probes io_uring at runtime and falls back to epoll. This is needed for Shadow network simulator (no io_uring support) but also makes the binary portable across Linux kernel versions.

g11tech · 2026-04-07T13:10:31Z

copilot suggestions seem appropriate, can you apply them/resolve them

- Change detectBackend() to return error instead of panicking, so callers get the underlying error name for debugging - Update CLI main.zig to handle the error via ErrorHandler - Update testing.zig to propagate the error - Extract detectBackendOrFail() helper in mock.zig to eliminate duplicated xev.detect() snippets

Copilot

Pull request overview

Copilot reviewed 10 out of 11 changed files in this pull request and generated no new comments.

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GrapeBaBa · 2026-04-08T13:01:07Z

copilot suggestions seem appropriate, can you apply them/resolve them

fixed

Copilot

Pull request overview

Copilot reviewed 10 out of 11 changed files in this pull request and generated 3 comments.

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Copilot · 2026-04-08T13:06:04Z

pkgs/node/src/testing.zig

    pub fn init(allocator: Allocator, opts: NodeTestOptions) !NodeTestContext {
+        const utils = @import("./utils.zig");
+        utils.detectBackend() catch |err| {
+            std.log.err("failed to detect I/O backend: {s}", .{@errorName(err)});
+            return err;
+        };


@import("./utils.zig") is being done inside NodeTestContext.init. In this codebase, file/module imports are typically declared at top-level with the other const ... = @import(...) statements; consider moving this to a top-level const utils = @import("./utils.zig"); to keep imports centralized and avoid function-local compile-time imports.

Copilot · 2026-04-08T13:06:04Z

pkgs/network/src/mock.zig

+/// Detect the best available I/O backend at runtime.
+/// Factored out to avoid duplicating the detection snippet in every test.
+fn detectBackendOrFail() !void {
+    if (@hasDecl(xev, "detect")) {
+        try xev.detect();
+    }
+}


detectBackendOrFail() duplicates the backend-detection logic introduced in pkgs/node/src/utils.zig (and now exported as @zeam/node.detectBackend). To avoid the two implementations drifting if libxev’s Dynamic API changes, consider centralizing this helper in a shared place (e.g. @zeam/utils) and calling it from both node and network tests.

Copilot · 2026-04-08T13:06:04Z

pkgs/node/src/node.zig

+const xev = @import("xev").Dynamic;



This xev import appears unused in this file (no xev. references). If it’s not needed anymore, it should be removed to reduce confusion about where the event loop backend is configured.

Suggested change

const xev = @import("xev").Dynamic;

Copilot AI review requested due to automatic review settings April 2, 2026 14:50

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GrapeBaBa added 2 commits April 3, 2026 11:26

chore: add gitignore entries for zig-pkg cache and Shadow outputs

ddcfd5c

GrapeBaBa force-pushed the shadow-to-main branch from bb009e5 to ddcfd5c Compare April 3, 2026 03:27

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Copilot AI review requested due to automatic review settings April 8, 2026 12:18

Copilot started reviewing on behalf of GrapeBaBa April 8, 2026 12:19 View session

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GrapeBaBa requested review from Copilot and zclawz April 8, 2026 13:00

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g11tech approved these changes Apr 8, 2026

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g11tech merged commit 4b2a711 into main Apr 8, 2026
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g11tech deleted the shadow-to-main branch April 8, 2026 14:25

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feat: xev Dynamic API + gitignore updates for Shadow support#704

feat: xev Dynamic API + gitignore updates for Shadow support#704
g11tech merged 3 commits intomainfrom
shadow-to-main

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		if (@hasDecl(xev, "detect")) xev.detect() catch @panic("no available xev backend");
		var loop = try xev.Loop.init(.{});

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GrapeBaBa commented Apr 2, 2026

Summary

Details

xev Dynamic API

gitignore

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