server: a query that finds every permit taken waits for one instead of failing, the budget is 64, permit and upstream turns wait on a futex with one thread each, the thread pool has no task limit, and transparent huge pages are off for the process

src/server/dot_server.zig

@@ -60,7 +60,6 @@ pub const StatsSnapshot = struct {
     tls_handshake_failures: u64,
     idle_timeouts: u64,
     connection_errors: u64,
-    dropped_no_permit: u64,
 };
 
 pub const DotServer = struct {
@@ -83,6 +82,7 @@ pub const DotServer = struct {
         pub const Owner = DotServer;
         pub const ConnPayload = Payload;
         pub const serveConn = serveOne;
+        pub const closing = wakeBudgetWaiters;
         pub const read_buffer_len = stream_buffer_len;
         pub const write_buffer_len = stream_buffer_len;
         pub const log = std.log.scoped(.dot_server);
@@ -121,6 +121,10 @@ pub const DotServer = struct {
         self.core.serve(io);
     }
 
+    fn wakeBudgetWaiters(self: *DotServer, io: std.Io) void {
+        self.budget.wakeWaiters(io);
+    }
+
     pub fn deinit(self: *DotServer, io: std.Io) void {
         self.core.deinit(io);
         self.* = undefined;
@@ -138,7 +142,6 @@ pub const DotServer = struct {
             .tls_handshake_failures = self.stats.tls_handshake_failures.load(.monotonic),
             .idle_timeouts = core.idle_timeouts.load(.monotonic),
             .connection_errors = core.connection_errors.load(.monotonic),
-            .dropped_no_permit = core.dropped_no_permit.load(.monotonic),
         };
     }
 
@@ -219,11 +222,11 @@ pub const DotServer = struct {
                 },
             }
 
-            // There is no framing for "no answer", so the connection ends.
-            const work = self.budget.tryAcquire(io) orelse {
-                listener.bump(&stats.dropped_no_permit);
-                return;
-            };
+            // Bounded like a read: a query still waiting when the idle budget
+            // runs out ends the connection, with the timeout counted by the
+            // budget. There is no framing for "no answer".
+            const permit_deadline: std.Io.Clock.Timestamp = .fromNow(io, budget);
+            const work = self.budget.acquire(io, permit_deadline, &self.core.run_state) catch return;
             defer self.budget.release(io, work);
 
             const outcome = self.handler.handle(