Merge pull request 'A container's mesh names are part of what it is' (#44) from fix/a-containers-mesh-names-are-part-of-what-it-is into main

internal/apply/apply.go

@@ -1501,6 +1501,20 @@ func containerSpecReading(r *declaration.Container, declares, reads map[string]s
 	for _, a := range r.Args {
 		b.WriteString("arg " + a + "\n")
 	}
+	// **The mesh's names are part of what a container is** (novox/hq 04-ISSUES/135). A container
+	// resolves every other machine and every public name through the entries the mesh gives it at
+	// creation, and nothing re-reads them afterwards — so a container left alone when the roster
+	// moved is one that cannot reach anything by name, for ever, while every check reports it
+	// running. That is exactly what happened when this mesh's overlay range changed: one container
+	// whose image and files never changed kept an address five days out of date and restarted
+	// 2286 times against a database it could no longer find.
+	//
+	// Sorted, so the digest does not move for a reordering nobody made.
+	hosts := append([]string(nil), r.Hosts...)
+	sort.Strings(hosts)
+	for _, h := range hosts {
+		b.WriteString("host " + h + "\n")
+	}
 	// The resolver and address are part of what was declared: a container whose dns or ip moved
 	// is a different container, or the fields could never reach one that already ran — which is
 	// exactly how their first deployment silently changed nothing.

internal/apply/mesh_names_test.go

@@ -0,0 +1,54 @@
+package apply
+
+import (
+	"testing"
+
+	"github.com/novox/mesh-host/internal/declaration"
+)
+
+// **A container's mesh names are part of what it is** (novox/hq 04-ISSUES/135).
+//
+// A container resolves every machine and every public name through the entries it was given when it
+// was created, and nothing re-reads them. So a container the host leaves alone because nothing else
+// about it changed is a container that cannot reach anything by name — for ever, while every check
+// reports it running. That is what happened when this mesh's overlay range moved: one container kept
+// an address five days out of date and restarted 2286 times against a database it could no longer
+// find, and the host compared everything about it except that.
+func TestAContainersMeshNamesAreComparedLikeTheRestOfIt(t *testing.T) {
+	was := &declaration.Container{
+		Name: "umami", Image: "ghcr.io/example/umami@sha256:" + zeros(64),
+		Hosts: []string{"novox.internal:10.42.0.1", "umami.novox.be:10.42.0.1"},
+	}
+	moved := &declaration.Container{
+		Name: was.Name, Image: was.Image,
+		Hosts: []string{"novox.internal:10.10.0.1", "umami.novox.be:10.10.0.1"},
+	}
+	if containerSpecReading(was, nil, nil) == containerSpecReading(moved, nil, nil) {
+		t.Fatal("a container whose mesh names moved compares equal, so it is never recreated")
+	}
+
+	// And the order they arrive in is not a change: the digest must not move for a reordering
+	// nobody made.
+	reordered := &declaration.Container{
+		Name: moved.Name, Image: moved.Image,
+		Hosts: []string{moved.Hosts[1], moved.Hosts[0]},
+	}
+	if containerSpecReading(moved, nil, nil) != containerSpecReading(reordered, nil, nil) {
+		t.Fatal("the same names in another order read as a different container")
+	}
+
+	// A container the mesh gives no names is unaffected, so nothing is recreated for a field it
+	// does not set.
+	plain := &declaration.Container{Name: "plex", Image: was.Image}
+	if containerSpecReading(plain, nil, nil) == containerSpecReading(was, nil, nil) {
+		return // different for other reasons, which is fine
+	}
+}
+
+func zeros(n int) string {
+	out := make([]byte, n)
+	for i := range out {
+		out[i] = '0'
+	}
+	return string(out)
+}