upstream: an unnamed connect errno fails over, local-resource exchanges are counted, doh faults carry the http status

src/web/metrics.zig

@@ -186,6 +186,9 @@ pub const Sample = struct {
     /// label and cannot live in `UpstreamSample`. Absent while no pool is
     /// wired, like every other collaborator.
     upstream_budget_exhausted_total: ?u64 = null,
+    /// Exchanges the pool ended on this process's own resources. Pool-wide for
+    /// the same reason as `upstream_budget_exhausted_total`.
+    upstream_local_resource_total: ?u64 = null,
     peaks: PeakSample = .{},
 };
 
@@ -300,6 +303,7 @@ pub fn collect(state: *server.WebState, io: std.Io, arena: Allocator) Allocator.
         if (generation.pool) |pool| {
             sample.upstreams = try upstreams(pool, io, arena);
             sample.upstream_budget_exhausted_total = pool.budgetExhaustedTotal();
+            sample.upstream_local_resource_total = pool.localResourceTotal();
         }
     }
 
@@ -512,6 +516,15 @@ pub fn render(w: *std.Io.Writer, sample: Sample) std.Io.Writer.Error!void {
         );
         try w.print("nxdns_upstream_budget_exhausted_total {d}\n", .{total});
     }
+    if (sample.upstream_local_resource_total) |total| {
+        try labeledHead(
+            w,
+            "nxdns_upstream_local_resource_total",
+            "Exchanges this process ended on its own resources (memory, descriptors, an unnamed system error) before any upstream answered.",
+            "counter",
+        );
+        try w.print("nxdns_upstream_local_resource_total {d}\n", .{total});
+    }
 }
 
 fn renderPeaks(w: *std.Io.Writer, peaks: PeakSample) std.Io.Writer.Error!void {
@@ -1788,3 +1801,20 @@ test "the budget-exhausted counter renders pool-wide, without a url label" {
     defer testing.allocator.free(absent);
     try testing.expect(!std.mem.containsAtLeast(u8, absent, 1, "nxdns_upstream_budget_exhausted_total"));
 }
+
+test "the local-resource counter renders pool-wide, without a url label" {
+    const text = try renderToString(testing.allocator, .{ .upstream_local_resource_total = 4 });
+    defer testing.allocator.free(text);
+
+    try testing.expect(std.mem.containsAtLeast(
+        u8,
+        text,
+        1,
+        "# TYPE nxdns_upstream_local_resource_total counter\n",
+    ));
+    try testing.expect(std.mem.containsAtLeast(u8, text, 1, "nxdns_upstream_local_resource_total 4\n"));
+
+    const absent = try renderToString(testing.allocator, .{});
+    defer testing.allocator.free(absent);
+    try testing.expect(!std.mem.containsAtLeast(u8, absent, 1, "nxdns_upstream_local_resource_total"));
+}