fix(server): listing linked environments no longer waits out an asleep peer

apps/server/src/peer/PeerLinks.test.ts

@@ -12,6 +12,7 @@ import * as Effect from "effect/Effect";
 import * as Fiber from "effect/Fiber";
 import * as Layer from "effect/Layer";
 import * as Option from "effect/Option";
+import * as Queue from "effect/Queue";
 import * as Ref from "effect/Ref";
 import * as Schema from "effect/Schema";
 import * as HttpRouter from "effect/http/HttpRouter";
@@ -389,6 +390,62 @@ it.effect("never sends a link's token to an address that stops answering as that
   ).pipe(Effect.provide(NodeHttpServer.layerTest)),
 );
 
+it.effect("lists a peer asleep at every address as unreachable within one probe budget", () =>
+  Effect.scoped(
+    Effect.gen(function* () {
+      const b = yield* serveB(box);
+      // Another address of the same machine, asleep too.
+      const wake = yield* Deferred.make<void>();
+      const elsewhere = yield* serveRaw(() =>
+        Deferred.await(wake).pipe(Effect.as(HttpServerResponse.empty({ status: 503 }))),
+      );
+      yield* Effect.addFinalizer(() => Deferred.succeed(wake, undefined));
+      const a = yield* makeA(laptop);
+      const pairing = yield* b.auth.issuePairingCredential();
+      yield* a.links.link({
+        url: b.url,
+        alternateUrls: [elsewhere],
+        pairingCode: pairing.credential,
+        access: "auto",
+      });
+
+      yield* Ref.set(b.asleep, true);
+      const listing = yield* a.links.list.pipe(Effect.forkScoped);
+      yield* Queue.take(b.unanswered);
+      yield* TestClock.adjust(Duration.seconds(3));
+      const listed = yield* Fiber.join(listing);
+      expect(listed.map((link) => link.status)).toEqual(["unreachable"]);
+    }),
+  ).pipe(Effect.provide(NodeHttpServer.layerTest)),
+);
+
+it.effect("lists a peer as reachable at another address while its first one sleeps", () =>
+  Effect.scoped(
+    Effect.gen(function* () {
+      const b = yield* serveB(box);
+      const described = yield* HttpClient.get(`${b.url}/.well-known/t3/environment`).pipe(
+        Effect.flatMap((response) => response.text),
+        Effect.provide(FetchHttpClient.layer),
+      );
+      // Another address of the same machine that answers.
+      const elsewhere = yield* serveRaw(() =>
+        Effect.succeed(HttpServerResponse.text(described, { contentType: "application/json" })),
+      );
+      const a = yield* makeA(laptop);
+      const pairing = yield* b.auth.issuePairingCredential();
+      yield* a.links.link({
+        url: b.url,
+        alternateUrls: [elsewhere],
+        pairingCode: pairing.credential,
+        access: "auto",
+      });
+
+      yield* Ref.set(b.asleep, true);
+      expect((yield* a.links.list).map((link) => link.status)).toEqual(["reachable"]);
+    }),
+  ).pipe(Effect.provide(NodeHttpServer.layerTest)),
+);
+
 it.effect("cancelling a descriptor probe aborts its request and leaves later resolves fresh", () =>
   Effect.scoped(
     Effect.gen(function* () {

apps/server/src/peer/PeerLinks.testkit.ts

@@ -7,8 +7,10 @@ import {
   type ExecutionEnvironmentDescriptor,
 } from "@t3tools/contracts";
 import * as Context from "effect/Context";
+import * as Deferred from "effect/Deferred";
 import * as Effect from "effect/Effect";
 import * as Layer from "effect/Layer";
+import * as Queue from "effect/Queue";
 import * as Ref from "effect/Ref";
 import * as FetchHttpClient from "effect/http/FetchHttpClient";
 import * as HttpRouter from "effect/http/HttpRouter";
@@ -70,6 +72,9 @@ export const servePeer = <E, R>(
     const descriptor = yield* Ref.make(initial);
     const bearers = yield* Ref.make<ReadonlyArray<string>>([]);
     const probes = yield* Ref.make(0);
+    const asleep = yield* Ref.make(false);
+    const unanswered = yield* Queue.unbounded<void>();
+    const wake = yield* Deferred.make<void>();
     const layerEnvironment = Layer.succeed(ServerEnvironment.ServerEnvironment, {
       getEnvironmentId: Ref.get(descriptor).pipe(Effect.map((current) => current.environmentId)),
       getDescriptor: Ref.get(descriptor),
@@ -91,6 +96,11 @@ export const servePeer = <E, R>(
           const request = yield* HttpServerRequest.HttpServerRequest;
           if (request.url.startsWith("/.well-known/t3/environment")) {
             yield* Ref.update(probes, (count) => count + 1);
+            if (yield* Ref.get(asleep)) {
+              yield* Queue.offer(unanswered, undefined);
+              yield* Deferred.await(wake);
+              return yield* Effect.die("the peer was closed while asleep");
+            }
           }
           const authorization = request.headers.authorization;
           if (authorization !== undefined) {
@@ -141,6 +151,8 @@ export const servePeer = <E, R>(
       Layer.fresh,
       Layer.build,
     );
+    // An unanswered request would hold the server open past the test.
+    yield* Effect.addFinalizer(() => Deferred.succeed(wake, undefined));
     const address = (yield* HttpServer.HttpServer).address;
     if (address._tag === "UnixPathAddress") return yield* Effect.die("expected a TCP address");
     const url = `http://127.0.0.1:${address.port}`;
@@ -154,6 +166,10 @@ export const servePeer = <E, R>(
       bearers,
       /** How often its descriptor was asked for, as a probe of whether it answers. */
       probes,
+      /** While set, its descriptor never answers, as a machine that is asleep. */
+      asleep,
+      /** One entry per descriptor request it left unanswered while asleep. */
+      unanswered,
       /** The sessions linking created there, which its Connections lists. */
       linkedSessions: auth
         .listSessions()

apps/server/src/peer/PeerLinks.ts

@@ -51,6 +51,8 @@ const LINK_REDIRECT_URI = "http://127.0.0.1/t3code-peer-link";
  */
 const probeTimeout = (origin: string) =>
   isLocalLoopbackHost(new URL(origin).hostname) ? Duration.seconds(3) : Duration.seconds(10);
+/** How long a listing waits on a link's addresses; a real call still gives a waking peer `probeTimeout`. */
+const LIST_PROBE_TIMEOUT = Duration.seconds(3);
 
 /** Node's TLS verification code in a failed request's cause chain, if any. */
 export const certificateErrorCode = (error: unknown) => {
@@ -567,18 +569,15 @@ const make = Effect.gen(function* () {
     now: DateTime.Utc,
   ): Effect.fn.Return<PeerLinkSummary> {
     if (DateTime.isLessThanOrEqualTo(link.expiresAt, now)) return { ...link, status: "expired" };
-    let label = link.label;
-    const answered = yield* Effect.findFirst(link.urls, (url) =>
-      answersAs(url, link.environmentId).pipe(
-        Effect.map((found) => {
-          if (Option.isNone(found)) return false;
-          label = found.value.label;
-          return true;
-        }),
+    // A race over no addresses never settles.
+    if (link.urls.length === 0) return { ...link, status: "unreachable" };
+    const answered = yield* Effect.raceAll(
+      link.urls.map((url) =>
+        answersAs(url, link.environmentId).pipe(Effect.flatMap(Effect.fromOption)),
       ),
-    );
+    ).pipe(Effect.timeoutOption(LIST_PROBE_TIMEOUT), Effect.orElseSucceed(Option.none));
     if (Option.isNone(answered)) return { ...link, status: "unreachable" };
-    return { ...(yield* withLabel(link, label)), status: "reachable" };
+    return { ...(yield* withLabel(link, answered.value.label)), status: "reachable" };
   });
 
   const list: PeerLinks["Service"]["list"] = Effect.gen(function* () {