fix: don't spam nodes with updates and instead pull the registry on keepalive

TODO.md

@@ -1,3 +1,56 @@
+# Background
+Some background first:
+the node can have multiple roles
+this includes (but not limited to)
+* Host (can generate events)
+* DNS (can consume the events and act on them)
+* Something else that I might come up with (the architecture has to be expandable)
+
+# Control pane (3+ nodes)
+* Quorum
+    * Consists of $n / 2 + 1$ nodes
+    * Cluster is considered "degraded" if no quorum can be created
+* Stores an event log
+    * **Only** leader can append to the log (with quorum permission)
+* Membership authority
+    * No joins without quorum approval
+    * Leaves are not propagated without quorum
+* Manages epoch (useful for GC)
+    * Node $N$ with $N.epoch != cluster.epoch$ can **not** join the cluster, and has to re-join (bootstrap)
+* Can (but doesn't have to) be a bootstrap point
+
+# Membership
+* Membership is managed though SWIM
+* Each node contains a small slice of the entire network
+## Joining
+Each node has an array of roles:
+1. That it performs
+2. That it requires to operate (can be moved out to the master, or the shared type)
+3. That it needs for bootstrapping (analogous to 2.)
+
+Node can join via a master or via other nodes
+When a node requests to join, the responder makes a request to the CP and asks for a permission to add this node
+* If master allows
+    1. The node gets a membership digest from the CP.
+    2. The node *can* be brought up to speed using it's neighbors from 1.
+    3. Node join event gets broadcasted over SWIM gossiping
+* Otherwise, nothing happens
+
+# Host node
+## Bootstrap
+Host node requests `dns` nodes on join (and other node types, such as `ns`, `nginx`, etc... They should really be called something like `dns_processor`, and the internals (how it processes the dns) should not be visible to the cluster, but that's a task for a future me)
+When a new update occurs, it sends the update to *some* `dns` hosts.
+
+# DNS node
+## Bootstrap
+First, it gets all the available `hosts` from the CP
+Then it requests their configs and sets map[hostName]seq accordingly
+## Simple join (when other nodes exist)
+It requests it's config from other nodes and that's it
+
+<!-- TODO: finish the TODO file lol -->
+
+# Minor To-Do
 - auth middleware lol
 - move request logging out of the request handling into a middleware
 - nginx role

go.mod

@@ -2,10 +2,12 @@ module git.wzray.com/homelab/hivemind
 
 go 1.25.5
 
-require github.com/rs/zerolog v1.34.0
+require (
+	github.com/rs/zerolog v1.34.0
+	github.com/BurntSushi/toml v1.6.0
+)
 
 require (
-	github.com/BurntSushi/toml v1.6.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/pkg/errors v0.9.1 // indirect

internal/roles/master/master.go

@@ -9,6 +9,7 @@ import (
 	"git.wzray.com/homelab/hivemind/internal/state"
 	"git.wzray.com/homelab/hivemind/internal/types"
 	"git.wzray.com/homelab/hivemind/internal/web/client"
+	"github.com/rs/zerolog/log"
 )
 
 type Role struct {
@@ -36,7 +37,7 @@ func New(state *state.RuntimeState, config config.MasterConfig) *Role {
 func (r *Role) OnStartup(ctx context.Context) error {
 	r.tasksGroup.Go(func() {
 		r.observer.Start(ctx, func(n types.Node) error {
-			_, err := r.onLeave(n)
+			_, err := r.onLeave(n, true)
 			return err
 		})
 	})
@@ -50,7 +51,7 @@ func (r *Role) OnShutdown() error {
 }
 
 func (r *Role) notify(path types.Path, v any) {
-	for _, n := range r.state.Registry.Nodes() {
+	for _, n := range r.state.Registry.ByRole(types.MasterRole) {
 		addr := n.Endpoint
 		r.tasksGroup.Go(func() {
 			client.Post[any](addr, path, v)
@@ -58,39 +59,58 @@ func (r *Role) notify(path types.Path, v any) {
 	}
 }
 
-func (r *Role) onJoin(node types.Node) (map[string]types.Node, error) {
+func (r *Role) onJoin(node types.Node, notify bool) (map[string]types.Node, error) {
 	if err := r.state.Registry.AddNode(node); err != nil {
 		return nil, err
 	}
 
-	r.notify(types.PathNodeJoin, node)
+	if notify {
+		r.notify(types.PathMasterEventJoin, node)
+	}
 
 	return r.state.Registry.AllNodes(), nil
 }
 
-func (r *Role) onLeave(node types.Node) (bool, error) {
+func (r *Role) onLeave(node types.Node, notify bool) (bool, error) {
 	if err := r.state.Registry.RemoveNode(node); err != nil {
 		return false, err
 	}
 
-	r.notify(types.PathNodeLeave, node)
+	if notify {
+		r.notify(types.PathMasterEventLeave, node)
+	}
 
 	return true, nil
 }
 
-func (r *Role) onKeepAlive(node types.Node) (bool, error) {
+func (r *Role) onKeepAlive(node types.Node, notify bool) (map[string]types.Node, error) {
 	r.observer.onKeepAlive(node)
 
 	if ok := r.state.Registry.Exists(node.Hostname); !ok {
-		_, err := r.onJoin(node)
+		// TODO: i don't like this side effect
-		return true, err
+		if _, err := r.onJoin(node, true); err != nil {
+			log.Warn().Err(err).Msg("unable to add node to the registry from keepalive")
+		}
 	}
 
-	return false, nil
+	if notify {
+		r.notify(types.PathMasterEventKeepalive, node)
+	}
+
+	return r.state.Registry.AllNodes(), nil
+}
+
+func eventFunc[R any](fn func(types.Node, bool) (R, error), notify bool) func(types.Node) (R, error) {
+	return func(n types.Node) (R, error) {
+		return fn(n, notify)
+	}
 }
 
 func (c *Role) RegisterHandlers(r types.Registrator) {
-	r.Register(types.PostEndpoint(types.PathMasterJoin, c.onJoin))
+	r.Register(types.PostEndpoint(types.PathMasterKeepalive, eventFunc(c.onKeepAlive, true)))
-	r.Register(types.PostEndpoint(types.PathMasterLeave, c.onLeave))
+	r.Register(types.PostEndpoint(types.PathMasterEventKeepalive, eventFunc(c.onKeepAlive, false)))
-	r.Register(types.PostEndpoint(types.PathMasterKeepalive, c.onKeepAlive))
+	r.Register(types.PostEndpoint(types.PathMasterJoin, eventFunc(c.onJoin, true)))
+	r.Register(types.PostEndpoint(types.PathMasterLeave, eventFunc(c.onLeave, true)))
+	r.Register(types.PostEndpoint(types.PathMasterEventJoin, eventFunc(c.onJoin, false)))
+	r.Register(types.PostEndpoint(types.PathMasterEventLeave, eventFunc(c.onLeave, false)))
 }

internal/roles/node/node.go

@@ -92,7 +92,6 @@ func (r *Role) Leave() error {
 
 func (r *Role) OnStartup(ctx context.Context) error {
 	r.keepaliveGroup.Go(r.keepaliveFunc(ctx))
-
 	return nil
 }
 
@@ -107,11 +106,20 @@ func (r *Role) keepaliveFunc(ctx context.Context) func() {
 			logger := log.With().Str("name", m.Hostname).Logger()
 			logger.Debug().Msg("sending keepalive packet")
 
-			if _, err := client.Post[any](m.Endpoint, types.PathMasterKeepalive, r.state.Self); err != nil {
+			nodes, err := client.Post[map[string]types.Node](m.Endpoint, types.PathMasterKeepalive, r.state.Self)
+			if err != nil {
 				logger.Info().Err(err).Msg("unable to send keepalive packet")
-			} else {
+				continue
-				logger.Debug().Msg("keepalive packet sent")
 			}
+
+			logger.Debug().Msg("keepalive packet sent")
+
+			if err := r.state.Registry.Set(*nodes); err != nil {
+				logger.Warn().Err(err).Msg("unable to set masters nodes")
+				continue
+			}
+
+			break
 		}
 	}
 
@@ -127,26 +135,10 @@ func (r *Role) keepaliveFunc(ctx context.Context) func() {
 	}
 }
 
-func (r *Role) onJoin(node types.Node) (bool, error) {
-	if err := r.state.Registry.AddNode(node); err != nil {
-		return false, err
-	}
-	return true, nil
-}
-
-func (r *Role) onLeave(node types.Node) (bool, error) {
-	if err := r.state.Registry.RemoveNode(node); err != nil {
-		return false, err
-	}
-	return true, nil
-}
-
 func healthcheck() (string, error) {
 	return "OK", nil
 }
 
 func (n *Role) RegisterHandlers(r types.Registrator) {
 	r.Register(types.GetEndpoint(types.PathNodeHealthcheck, healthcheck))
-	r.Register(types.PostEndpoint(types.PathNodeJoin, n.onJoin))
-	r.Register(types.PostEndpoint(types.PathNodeLeave, n.onLeave))
 }

internal/types/web.go

@@ -15,13 +15,14 @@ func (p Path) String() string {
 }
 
 const (
-	PathMasterJoin      Path = "/master/join"
+	PathMasterJoin           Path = "/master/join"
-	PathMasterLeave     Path = "/master/leave"
+	PathMasterLeave          Path = "/master/leave"
-	PathMasterKeepalive Path = "/master/keepalive"
+	PathMasterKeepalive      Path = "/master/keepalive"
+	PathMasterEventJoin      Path = "/master/event_join"
+	PathMasterEventLeave     Path = "/master/event_leave"
+	PathMasterEventKeepalive Path = "/master/event_keepalive"
 
 	PathNodeHealthcheck Path = "/node/healthcheck"
-	PathNodeJoin        Path = "/node/join"
-	PathNodeLeave       Path = "/node/leave"
 
 	PathDnsCallback Path = "/dns/callback"