feat(messaging): add BackendInstallProgressEvent wire type and subject

New NATS subject nodes.<nodeID>.backend.install.<opID>.progress lets the
worker publish transient progress events (file, current/total bytes,
percentage, phase) while a long-running install pulls its OCI image.
BackendInstallRequest gains an optional OpID field so the worker knows
which subject to publish on.

Transient pub/sub (not JetStream): the install reply remains ground
truth for success/failure; dropped progress events are tolerable.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/services/messaging/backend_install_progress.go

@@ -0,0 +1,23 @@
+package messaging
+
+// BackendInstallProgressEvent is the wire payload published by a worker to
+// nodes.<nodeID>.backend.install.<opID>.progress while a long-running install
+// is in flight. Transient: dropped events are acceptable, the master relies
+// on BackendInstallReply for ground truth on success/failure.
+type BackendInstallProgressEvent struct {
+	OpID       string  `json:"op_id"`
+	NodeID     string  `json:"node_id"`
+	Backend    string  `json:"backend"`
+	FileName   string  `json:"file_name,omitempty"`
+	Current    string  `json:"current,omitempty"` // human-readable size, e.g. "412 MB"
+	Total      string  `json:"total,omitempty"`   // human-readable size, e.g. "2.1 GB"
+	Percentage float64 `json:"percentage"`
+	Phase      string  `json:"phase,omitempty"` // "resolving" | "downloading" | "extracting" | "starting"
+}
+
+// SubjectNodeBackendInstallProgress returns the NATS subject for transient
+// progress events emitted by a worker during a single backend.install run.
+// Per-op so multiple concurrent installs on the same node never alias.
+func SubjectNodeBackendInstallProgress(nodeID, opID string) string {
+	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.install." + sanitizeSubjectToken(opID) + ".progress"
+}

core/services/messaging/backend_install_progress_test.go

@@ -0,0 +1,51 @@
+package messaging_test
+
+import (
+	"encoding/json"
+	"strings"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	"github.com/mudler/LocalAI/core/services/messaging"
+)
+
+var _ = Describe("BackendInstallProgress", func() {
+	Context("SubjectNodeBackendInstallProgress", func() {
+		It("composes the per-op progress subject", func() {
+			Expect(messaging.SubjectNodeBackendInstallProgress("node-abc", "op-123")).
+				To(Equal("nodes.node-abc.backend.install.op-123.progress"))
+		})
+
+		It("sanitizes NATS-reserved characters in node and op tokens", func() {
+			// '.' is the NATS hierarchy delimiter, '*' and '>' are wildcards,
+			// and whitespace must be stripped — sanitizeSubjectToken replaces
+			// all of them with '-'. The resulting subject must still parse as
+			// exactly six hierarchy segments: nodes/<node>/backend/install/<op>/progress.
+			subj := messaging.SubjectNodeBackendInstallProgress("a.b c", "x.y z")
+			Expect(subj).ToNot(ContainSubstring(" "))
+			Expect(strings.Count(subj, ".")).To(Equal(5))
+		})
+	})
+
+	Context("BackendInstallProgressEvent", func() {
+		It("JSON round-trips with all known fields", func() {
+			ev := messaging.BackendInstallProgressEvent{
+				OpID:       "op-123",
+				NodeID:     "node-abc",
+				Backend:    "vllm",
+				FileName:   "vllm-cpu.tar.zst",
+				Current:    "412 MB",
+				Total:      "2.1 GB",
+				Percentage: 19.6,
+				Phase:      "downloading",
+			}
+			raw, err := json.Marshal(ev)
+			Expect(err).ToNot(HaveOccurred())
+
+			var got messaging.BackendInstallProgressEvent
+			Expect(json.Unmarshal(raw, &got)).To(Succeed())
+			Expect(got).To(Equal(ev))
+		})
+	})
+})

core/services/messaging/subjects.go

@@ -144,6 +144,12 @@ type BackendInstallRequest struct {
 	// worker still works (the master's install fallback path also uses this
 	// when backend.upgrade returns nats.ErrNoResponders).
 	Force bool `json:"force,omitempty"`
+	// OpID identifies the admin-side operation. When non-empty the worker
+	// publishes BackendInstallProgressEvent values to
+	// SubjectNodeBackendInstallProgress(nodeID, OpID) while the install is
+	// running, debounced to roughly 250ms. Empty means the caller is a
+	// reconciler-driven retry that does not need progress streamed.
+	OpID string `json:"op_id,omitempty"`
 }
 
 // BackendInstallReply is the response from a backend.install NATS request.