zzstoatzz.io
atproto relay implementation in zig
zlay.waow.tech
add malloc arena metrics to prometheus endpoint
mallinfo2() exposes in-use vs free-but-held-by-malloc bytes,
letting us distinguish real leaks from glibc fragmentation.
also adds VmHWM and RssAnon from /proc/self/status.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
+43
-12
src/broadcaster.zig
+43
-12
src/broadcaster.zig
···
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return fbs.getWritten();
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}
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const malloc_h = @cImport(@cInclude("malloc.h"));
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+
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fn appendProcMetrics(w: anytype) void {
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// RSS from /proc/self/statm (field[1] * page_size)
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if (std.fs.openFileAbsolute("/proc/self/statm", .{})) |f| {
···
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}
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} else |_| {}
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-
// thread count from /proc/self/status
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// thread count + memory detail from /proc/self/status
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if (std.fs.openFileAbsolute("/proc/self/status", .{})) |f| {
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defer f.close();
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var status_buf: [4096]u8 = undefined;
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const n = f.readAll(&status_buf) catch 0;
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if (n > 0) {
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const content = status_buf[0..n];
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if (std.mem.indexOf(u8, content, "Threads:")) |pos| {
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const rest = content[pos + "Threads:".len ..];
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const trimmed = std.mem.trimLeft(u8, rest, " \t");
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const end = std.mem.indexOfScalar(u8, trimmed, '\n') orelse trimmed.len;
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if (std.fmt.parseInt(u64, trimmed[0..end], 10)) |threads| {
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std.fmt.format(w,
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\\# TYPE relay_threads_total gauge
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\\relay_threads_total {d}
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\\
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, .{threads}) catch {};
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} else |_| {}
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const fields = .{
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.{ "Threads:", "relay_threads_total" },
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.{ "VmHWM:", "relay_vm_hwm_kb" },
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.{ "RssAnon:", "relay_rss_anon_kb" },
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};
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inline for (fields) |entry| {
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if (std.mem.indexOf(u8, content, entry[0])) |pos| {
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const rest = content[pos + entry[0].len ..];
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const trimmed = std.mem.trimLeft(u8, rest, " \t");
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const end = std.mem.indexOfScalar(u8, trimmed, ' ') orelse
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(std.mem.indexOfScalar(u8, trimmed, '\n') orelse trimmed.len);
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if (std.fmt.parseInt(u64, trimmed[0..end], 10)) |val| {
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std.fmt.format(w,
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\\# TYPE {s} gauge
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\\{s} {d}
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\\
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, .{ entry[1], entry[1], val }) catch {};
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} else |_| {}
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}
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}
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}
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} else |_| {}
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// glibc malloc arena stats — distinguishes in-use heap from fragmentation
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const mi = malloc_h.mallinfo2();
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std.fmt.format(w,
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\\# TYPE relay_malloc_arena_bytes gauge
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\\# HELP relay_malloc_arena_bytes total bytes claimed from OS by malloc
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\\relay_malloc_arena_bytes {d}
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\\
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\\# TYPE relay_malloc_in_use_bytes gauge
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\\# HELP relay_malloc_in_use_bytes bytes actively allocated (in-use heap)
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\\relay_malloc_in_use_bytes {d}
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\\
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\\# TYPE relay_malloc_free_bytes gauge
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\\# HELP relay_malloc_free_bytes free bytes held by malloc (fragmentation)
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\\relay_malloc_free_bytes {d}
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\\
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\\# TYPE relay_malloc_mmap_bytes gauge
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\\# HELP relay_malloc_mmap_bytes bytes allocated via mmap (large blocks)
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\\relay_malloc_mmap_bytes {d}
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\\
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, .{ mi.arena, mi.uordblks, mi.fordblks, mi.hblkhd }) catch {};
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}
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const posix_vfs = @cImport(@cInclude("sys/statvfs.h"));