milestone 31: concurrent upstream exchanges, dot session reuse, queue metrics

src/server/resolver_integration_test.zig

@@ -155,15 +155,32 @@ const FaultyUpstream = struct {
     }
 };
 
-fn testEntry(url: []const u8, upstream_client: transport.Client, priority: i32) pool.Entry {
-    return .{
-        .endpoint = transport.Endpoint.parse(url) catch unreachable,
-        .client = upstream_client,
-        .priority = priority,
-        .enabled = true,
-        .health = .init,
-    };
-}
+/// One-slot entry storage: the slot the entry points at and the recovery
+/// counter it borrows, declared by the test so both outlive the pool. These
+/// tests drive failover and deadlines, not concurrency within one upstream, so
+/// one slot per entry is the whole story here.
+const EntryStorage = struct {
+    slots: [1]pool.Slot = undefined,
+    recoveries: std.atomic.Value(u64) = .init(0),
+
+    fn entry(
+        self: *EntryStorage,
+        url: []const u8,
+        upstream_client: transport.Client,
+        priority: i32,
+    ) pool.Entry {
+        self.slots[0] = .{ .client = upstream_client };
+        return .{
+            .endpoint = transport.Endpoint.parse(url) catch unreachable,
+            .slots = &self.slots,
+            .priority = priority,
+            .enabled = true,
+            .health = .init,
+            .sem = .{ .permits = self.slots.len },
+            .reuse_recoveries = &self.recoveries,
+        };
+    }
+};
 
 const Outcome = union(enum) {
     work: anyerror!void,
@@ -250,9 +267,11 @@ test "the whole resolver answers over udp and tcp and fails over to a healthy up
         .fail_first = std.math.maxInt(u64),
     };
     var good: GoodUpstream = .{};
+    var bad_storage: EntryStorage = .{};
+    var good_storage: EntryStorage = .{};
     var entries = [_]pool.Entry{
-        testEntry("https://bad.example/dns-query", bad.client(), 10),
-        testEntry("tls://good.example", good.client(), 20),
+        bad_storage.entry("https://bad.example/dns-query", bad.client(), 10),
+        good_storage.entry("tls://good.example", good.client(), 20),
     };
     var upstreams: pool.Pool = .init(&entries, test_cfg, pool_timeouts, 1);