open-consul/agent/rpc/subscribe/subscribe.go

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package subscribe
import (
"errors"
"fmt"
"github.com/hashicorp/go-hclog"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"github.com/hashicorp/consul/acl"
"github.com/hashicorp/consul/agent/consul/state"
"github.com/hashicorp/consul/agent/consul/stream"
"github.com/hashicorp/consul/proto/pbservice"
"github.com/hashicorp/consul/proto/pbsubscribe"
)
// Server implements a StateChangeSubscriptionServer for accepting SubscribeRequests,
// and sending events to the subscription topic.
type Server struct {
Backend Backend
Logger Logger
}
func NewServer(backend Backend, logger Logger) *Server {
return &Server{Backend: backend, Logger: logger}
}
type Logger interface {
Trace(msg string, args ...interface{})
With(args ...interface{}) hclog.Logger
}
var _ pbsubscribe.StateChangeSubscriptionServer = (*Server)(nil)
type Backend interface {
// TODO(streaming): Use ResolveTokenAndDefaultMeta instead once SubscribeRequest
// has an EnterpriseMeta.
ResolveToken(token string) (acl.Authorizer, error)
Forward(dc string, f func(*grpc.ClientConn) error) (handled bool, err error)
Subscribe(req *stream.SubscribeRequest) (*stream.Subscription, error)
}
func (h *Server) Subscribe(req *pbsubscribe.SubscribeRequest, serverStream pbsubscribe.StateChangeSubscription_SubscribeServer) error {
logger := h.newLoggerForRequest(req)
handled, err := h.Backend.Forward(req.Datacenter, forwardToDC(req, serverStream, logger))
if handled || err != nil {
return err
}
logger.Trace("new subscription")
defer logger.Trace("subscription closed")
// Resolve the token and create the ACL filter.
authz, err := h.Backend.ResolveToken(req.Token)
if err != nil {
return err
}
sub, err := h.Backend.Subscribe(toStreamSubscribeRequest(req))
if err != nil {
return err
}
defer sub.Unsubscribe()
ctx := serverStream.Context()
elog := &eventLogger{logger: logger}
for {
event, err := sub.Next(ctx)
switch {
case errors.Is(err, stream.ErrSubForceClosed):
logger.Trace("subscription reset by server")
return status.Error(codes.Aborted, err.Error())
case err != nil:
return err
}
var ok bool
event, ok = filterByAuth(authz, event)
if !ok {
continue
}
elog.Trace(event)
e := newEventFromStreamEvent(req.Topic, event)
if err := serverStream.Send(e); err != nil {
return err
}
}
}
// TODO: can be replaced by mog conversion
func toStreamSubscribeRequest(req *pbsubscribe.SubscribeRequest) *stream.SubscribeRequest {
return &stream.SubscribeRequest{
Topic: req.Topic,
Key: req.Key,
Token: req.Token,
Index: req.Index,
}
}
func forwardToDC(
req *pbsubscribe.SubscribeRequest,
serverStream pbsubscribe.StateChangeSubscription_SubscribeServer,
logger Logger,
) func(conn *grpc.ClientConn) error {
return func(conn *grpc.ClientConn) error {
logger.Trace("forwarding to another DC")
defer logger.Trace("forwarded stream closed")
client := pbsubscribe.NewStateChangeSubscriptionClient(conn)
streamHandle, err := client.Subscribe(serverStream.Context(), req)
if err != nil {
return err
}
for {
event, err := streamHandle.Recv()
if err != nil {
return err
}
if err := serverStream.Send(event); err != nil {
return err
}
}
}
}
// filterByAuth to only those Events allowed by the acl token.
func filterByAuth(authz acl.Authorizer, event stream.Event) (stream.Event, bool) {
// authz will be nil when ACLs are disabled
if authz == nil {
return event, true
}
fn := func(e stream.Event) bool {
return enforceACL(authz, e) == acl.Allow
}
return event.Filter(fn)
}
func newEventFromStreamEvent(topic pbsubscribe.Topic, event stream.Event) *pbsubscribe.Event {
e := &pbsubscribe.Event{
Topic: topic,
Key: event.Key,
Index: event.Index,
}
switch {
case event.IsEndOfSnapshot():
e.Payload = &pbsubscribe.Event_EndOfSnapshot{EndOfSnapshot: true}
return e
case event.IsNewSnapshotToFollow():
e.Payload = &pbsubscribe.Event_NewSnapshotToFollow{NewSnapshotToFollow: true}
return e
}
setPayload(e, event.Payload)
return e
}
func setPayload(e *pbsubscribe.Event, payload interface{}) {
switch p := payload.(type) {
case []stream.Event:
e.Payload = &pbsubscribe.Event_EventBatch{
EventBatch: &pbsubscribe.EventBatch{
Events: batchEventsFromEventSlice(p),
},
}
case state.EventPayloadCheckServiceNode:
e.Payload = &pbsubscribe.Event_ServiceHealth{
ServiceHealth: &pbsubscribe.ServiceHealthUpdate{
Op: p.Op,
// TODO: this could be cached
CheckServiceNode: pbservice.NewCheckServiceNodeFromStructs(p.Value),
},
}
default:
panic(fmt.Sprintf("unexpected payload: %T: %#v", p, p))
}
}
func batchEventsFromEventSlice(events []stream.Event) []*pbsubscribe.Event {
result := make([]*pbsubscribe.Event, len(events))
for i := range events {
event := events[i]
result[i] = &pbsubscribe.Event{Key: event.Key, Index: event.Index}
setPayload(result[i], event.Payload)
}
return result
}