Merge pull request 'A mesh seat's holder elsewhere answers before this machine's own provider (hq issue 258)' (#59) from fix/a-mesh-seat-answers-before-the-machines-own into main

internal/catalogue/resolve.go

@@ -341,7 +341,7 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 		// trust boundary the moment both ends are containers**, and treating it as one gave the
 		// commonest arrangement of all — a service and its database on one node — the weakest
 		// handling, silently.
-		if satisfied[want] && !isModule(catalogue, want) {
+		if satisfied[want] && !isModule(catalogue, want) && !answeredElsewhere(want, node, world, brokered) {
 			here := func(name string) bool { return chosen[name] || assignedHere[name] }
 			local := providersHere(catalogue, here, want)
 			// Which of them it matters to choose between. A plain capability — a shell, a display
@@ -1134,3 +1134,28 @@ func machineReachRemedy(catalogue map[string]Manifest, want, node string) string
 	}
 	return fmt.Sprintf("assign one to %s: %s", node, strings.Join(named, "; "))
 }
+
+// answeredElsewhere says that a mesh-wide provision this machine could answer itself is answered by
+// another machine all the same: one this machine was pinned to, or the holder of the mesh seat that
+// delivers it (novox/hq ADR 0110, ADR 0194).
+//
+// **A provider on the machine was taken before either was asked.** The branch for a provision
+// answered here bound the consumer to the local provider and consulted a pin only between two local
+// ones, and the seat's holder never; both were read only for a provider on another machine. So when
+// every machine ran a provider of `wildcard-resolution` — each machine's own resolver, still assigned
+// while the mesh moved to one — every machine bound its resolver configuration to itself, with the
+// mesh's one resolver recorded, held and pinned (novox/hq issue 258). The seat is the mesh's choice of
+// who answers, made once; a provider that merely runs here does not overrule it, and neither does it
+// overrule a pin somebody set on this machine.
+//
+// Not in the first pass, which asks only what this machine offers and has no providers to read.
+func answeredElsewhere(want string, node Node, world World, brokered map[string]bool) bool {
+	if world.Unchecked || !brokered[want] {
+		return false
+	}
+	if c, pinned := world.Pinned[want]; pinned {
+		return c.Node != node.Name
+	}
+	holder, held := HolderAmong(want, world.Offered[want], world.Held)
+	return held && holder.Node != node.Name
+}

internal/catalogue/resolver_manifests_test.go

@@ -15,7 +15,8 @@ import (
 // same arrangement, and to the two things a resolver here must never do — read resolv.conf for
 // its upstreams, or take an address systemd-resolved holds.
 
-// resolverShelf is the three resolver modules beside something that answers `mesh-addressing`.
+// resolverShelf is the three resolver modules and the container runtime beside something that
+// answers `mesh-addressing`.
 // The networking module that really does is composed in the controller and cannot be imported
 // here, so a stand-in offers the same word; what is under test is the manifests, not the network.
 func resolverShelf(t *testing.T) map[string]Manifest {
@@ -23,7 +24,7 @@ func resolverShelf(t *testing.T) map[string]Manifest {
 	shelf := map[string]Manifest{
 		"net": {Module: "net", Version: "1", Provides: []Offer{{Name: "mesh-addressing"}}},
 	}
-	for _, name := range []string{"dnsmasq", "resolv-conf", "resolved-split-dns"} {
+	for _, name := range []string{"dnsmasq", "resolv-conf", "resolved-split-dns", "docker"} {
 		shelf[name] = catalogueManifest(t, name)
 	}
 	return shelf
@@ -117,8 +118,9 @@ func TestTheResolverForwardsToFixedUpstreamsAndNeverReadsResolvConf(t *testing.T
 // that file, the machine pointed at the resolver by address, and the runtime given no resolver of
 // its own but kept running across a restart (ADR 0196).
 func TestTheResolverAndWhatAsksItComposeOnOneMachine(t *testing.T) {
-	got, err := Resolve(resolverShelf(t), []string{"dnsmasq", "resolv-conf"},
+	got, err := Resolve(resolverShelf(t), []string{"dnsmasq", "resolv-conf", "docker"},
-		Node{Name: "anchor", At: "anchor.internal"}, World{})
+		Node{Name: "anchor", At: "anchor.internal", Capabilities: map[string]bool{
+			"package-manager": true, "service-manager": true, "privileged": true}}, World{})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -167,13 +169,19 @@ func TestTheResolverAndWhatAsksItComposeOnOneMachine(t *testing.T) {
 		t.Errorf("the resolver was not told to forward the zone to its answerer:\n%s", z)
 	}
 
-	// The runtime's own file, written into (novox/hq ADR 0102) with one key, by what decides how the
+	// The runtime's own file, written into (novox/hq ADR 0102) with one key, by the runtime's own
-	// machine resolves: a restart keeps every container running. No `dns` — a container copies its
+	// module — a module does not write another software's configuration (issue 190): a restart keeps
-	// machine's resolvers (ADR 0196), and the mesh's resolver is not written into the runtime twice.
+	// every container running. No `dns` — a container copies its machine's resolvers (ADR 0196), and
+	// neither the resolver nor what decides how the machine resolves writes the runtime's file.
 	if ids["dnsmasq.runtime-dns"] != nil {
 		t.Errorf("the resolver still writes the runtime's dns: %v", ids["dnsmasq.runtime-dns"])
 	}
-	runtime := ids["resolv-conf.runtime-config"]
+	for id := range ids {
+		if strings.HasPrefix(id, "resolv-conf.runtime") {
+			t.Errorf("what the machine asks still writes the runtime's file: %s", id)
+		}
+	}
+	runtime := ids["docker.daemon"]
 	if runtime == nil || runtime["path"] != "/etc/docker/daemon.json" || runtime["into"] != "json" {
 		t.Fatalf("live-restore is not written into the runtime's file: %v", runtime)
 	}
@@ -195,7 +203,7 @@ func TestTheResolverAndWhatAsksItComposeOnOneMachine(t *testing.T) {
 			t.Errorf("the runtime is ordered restarted, which stops every container (ADR 0102): %v", r)
 		}
 		for _, on := range asStrings(r["reload-on"]) {
-			if on == "resolv-conf.runtime-config" {
+			if on == "docker.daemon" {
 				reloaded = true
 			}
 		}

internal/catalogue/seat_answers_before_local_test.go

@@ -0,0 +1,67 @@
+package catalogue
+
+import "testing"
+
+// A mesh-wide provision whose seat is held on another machine is answered by that holder, even on a
+// machine that runs a provider of its own (novox/hq issue 258). Every machine ran its own resolver
+// while the mesh moved to one; each bound its resolver configuration to itself, with the mesh's
+// resolver held elsewhere and pinned.
+func resolverMesh() map[string]Manifest {
+	return map[string]Manifest{
+		"resolver": {Module: "resolver", Version: "1",
+			Provides: []Offer{{Name: "wildcard-resolution", Scope: ScopeMesh}},
+			Claims:   []Claim{{Name: "mesh-dns-resolver", Scope: ScopeMesh}}},
+		"asker": {Module: "asker", Version: "1", Requires: []string{"wildcard-resolution"}},
+	}
+}
+
+func resolverWorld(held string, pin *Chosen) World {
+	w := World{
+		Offered: map[string][]Provider{"wildcard-resolution": {
+			{Node: "anchor", At: "anchor.internal", Module: "resolver"},
+			{Node: "laptop", At: "laptop.internal", Module: "resolver"},
+		}},
+	}
+	// Held is who holds it across the mesh; Holdings is the same holder on record, which lets this
+	// machine's own claimant stand beside it (ADR 0131).
+	w.Held = []Held{{Claim: "mesh-dns-resolver", Scope: ScopeMesh, Node: held, Module: "resolver"}}
+	w.Holdings = w.Held
+	if pin != nil {
+		w.Pinned = map[string]Chosen{"wildcard-resolution": *pin}
+	}
+	return w
+}
+
+func answeredFrom(t *testing.T, world World) string {
+	t.Helper()
+	laptop := Node{Name: "laptop", At: "laptop.internal"}
+	got, err := Resolve(resolverMesh(), []string{"resolver", "asker"}, laptop, world)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, n := range got.Needs {
+		if n.Name == "wildcard-resolution" {
+			return n.From
+		}
+	}
+	t.Fatalf("no binding for wildcard-resolution: %+v", got.Needs)
+	return ""
+}
+
+func TestTheSeatsHolderElsewhereAnswersBeforeThisMachinesOwnProvider(t *testing.T) {
+	if from := answeredFrom(t, resolverWorld("anchor", nil)); from != "anchor" {
+		t.Fatalf("bound to %s; the seat is held on anchor", from)
+	}
+}
+
+func TestAPinElsewhereAnswersBeforeThisMachinesOwnProvider(t *testing.T) {
+	if from := answeredFrom(t, resolverWorld("laptop", &Chosen{Node: "anchor", Module: "resolver"})); from != "anchor" {
+		t.Fatalf("bound to %s; this machine was pinned to anchor", from)
+	}
+}
+
+func TestTheHolderOnThisMachineStillAnswersHere(t *testing.T) {
+	if from := answeredFrom(t, resolverWorld("laptop", nil)); from != "laptop" {
+		t.Fatalf("bound to %s; the seat is held here", from)
+	}
+}