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source.go
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// Copyright 2019 Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package source
import (
"context"
"fmt"
"io"
"strconv"
"sync/atomic"
"time"
"github.com/gogo/status"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/peer"
mcp "istio.io/api/mcp/v1alpha1"
"istio.io/istio/pkg/log"
"istio.io/istio/pkg/mcp/internal"
"istio.io/istio/pkg/mcp/monitoring"
)
var scope = log.RegisterScope("mcp", "mcp debugging", 0)
// Request is a temporary abstraction for the MCP node request which can
// be used with the mcp.MeshConfigRequest and mcp.RequestResources. It can
// be removed once we fully cutover to mcp.RequestResources.
type Request struct {
Collection string
// Most recent version was that ACK/NACK'd by the sink
VersionInfo string
SinkNode *mcp.SinkNode
// hidden
incremental bool
}
// WatchResponse contains a versioned collection of pre-serialized resources.
type WatchResponse struct {
Collection string
// Version of the resources in the response for the given
// type. The node responses with this version in subsequent
// requests as an acknowledgment.
Version string
// Resourced resources to be included in the response.
Resources []*mcp.Resource
// The original request for triggered this response
Request *Request
}
type (
// CancelWatchFunc allows the consumer to cancel a previous watch,
// terminating the watch for the request.
CancelWatchFunc func()
// PushResponseFunc allows the consumer to push a response for the
// corresponding watch.
PushResponseFunc func(*WatchResponse)
)
// Watcher requests watches for configuration resources by node, last
// applied version, and type. The watch should send the responses when
// they are ready. The watch can be canceled by the consumer.
type Watcher interface {
// Watch returns a new open watch for a non-empty request.
//
// Cancel is an optional function to release resources in the
// producer. It can be called idempotently to cancel and release resources.
Watch(*Request, PushResponseFunc) CancelWatchFunc
}
// CollectionOptions configures the per-collection updates.
type CollectionOptions struct {
// Name of the collection, e.g. istio/networking/v1alpha3/VirtualService
Name string
// When true, the source is allowed to push incremental updates to the sink.
// Incremental updates are only used if the sink requests it (per request)
// and the source decides to make use of it.
Incremental bool
}
// CollectionOptionsFromSlice returns a slice of collection options from
// a slice of collection names.
func CollectionOptionsFromSlice(names []string) []CollectionOptions {
options := make([]CollectionOptions, 0, len(names))
for _, name := range names {
options = append(options, CollectionOptions{
Name: name,
})
}
return options
}
// Options contains options for configuring MCP sources.
type Options struct {
Watcher Watcher
CollectionOptions []CollectionOptions
Reporter monitoring.Reporter
}
// Stream is for sending Resource messages and receiving RequestResources messages.
type Stream interface {
Send(*mcp.Resources) error
Recv() (*mcp.RequestResources, error)
Context() context.Context
}
// Sources implements the resource source message exchange for MCP. It can be instantiated by client and server
// source implementations to manage the MCP message exchange.
type Source struct {
watcher Watcher
collections []CollectionOptions
nextStreamID int64
reporter monitoring.Reporter
connections int64
}
// watch maintains local push state of the most recent watch per-type.
type watch struct {
// only accessed from connection goroutine
cancel func()
ackedVersionMap map[string]string // resources that exist at the sink; by name and version
pending *mcp.Resources
incremental bool
}
// connection maintains per-stream connection state for a
// node. Access to the stream and watch state is serialized
// through request and response channels.
type connection struct {
peerAddr string
stream Stream
id int64
// unique nonce generator for req-resp pairs per xDS stream; the server
// ignores stale nonces. nonce is only modified within send() function.
streamNonce int64
requestC chan *mcp.RequestResources // a channel for receiving incoming requests
reqError error // holds error if request channel is closed
watches map[string]*watch // per-type watch state
watcher Watcher
reporter monitoring.Reporter
queue *internal.UniqueQueue
}
const DefaultRetryPushDelay = 10 * time.Millisecond
// New creates a new resource source.
func New(options *Options) *Source {
s := &Source{
watcher: options.Watcher,
collections: options.CollectionOptions,
reporter: options.Reporter,
}
return s
}
func (s *Source) newConnection(stream Stream) *connection {
peerAddr := "0.0.0.0"
peerInfo, ok := peer.FromContext(stream.Context())
if ok {
peerAddr = peerInfo.Addr.String()
} else {
scope.Warnf("No peer info found on the incoming stream.")
peerInfo = nil
}
con := &connection{
stream: stream,
peerAddr: peerAddr,
requestC: make(chan *mcp.RequestResources),
watches: make(map[string]*watch),
watcher: s.watcher,
id: atomic.AddInt64(&s.nextStreamID, 1),
reporter: s.reporter,
queue: internal.NewUniqueScheduledQueue(len(s.collections)),
}
var collections []string
for i := range s.collections {
collection := s.collections[i]
w := &watch{
ackedVersionMap: make(map[string]string),
incremental: collection.Incremental,
}
con.watches[collection.Name] = w
collections = append(collections, collection.Name)
}
s.reporter.SetStreamCount(atomic.AddInt64(&s.connections, 1))
scope.Infof("MCP: connection %v: NEW (ResourceSource), supported collections: %#v", con, collections)
return con
}
func (s *Source) processStream(stream Stream) error {
con := s.newConnection(stream)
defer s.closeConnection(con)
go con.receive()
for {
select {
case <-con.queue.Ready():
collection, item, ok := con.queue.Dequeue()
if !ok {
break
}
resp := item.(*WatchResponse)
w, ok := con.watches[collection]
if !ok {
scope.Errorf("unknown collection in dequeued watch response: %v", collection)
break // bug?
}
// the response may have been cleared before we got to it
if resp != nil {
if err := con.pushServerResponse(w, resp); err != nil {
return err
}
}
case req, more := <-con.requestC:
if !more {
return con.reqError
}
if err := con.processClientRequest(req); err != nil {
return err
}
case <-con.queue.Done():
scope.Debugf("MCP: connection %v: stream done", con)
return status.Error(codes.Unavailable, "server canceled watch")
case <-stream.Context().Done():
scope.Debugf("MCP: connection %v: stream done, err=%v", con, stream.Context().Err())
return stream.Context().Err()
}
}
}
func (s *Source) closeConnection(con *connection) {
con.close()
s.reporter.SetStreamCount(atomic.AddInt64(&s.connections, -1))
}
// String implements Stringer.String.
func (con *connection) String() string {
return fmt.Sprintf("{addr=%v id=%v}", con.peerAddr, con.id)
}
// Queue the response for sending in the dispatch loop. The caller may provide
// a nil response to indicate that the watch should be closed.
func (con *connection) queueResponse(resp *WatchResponse) {
if resp == nil {
con.queue.Close()
} else {
con.queue.Enqueue(resp.Collection, resp)
}
}
func calculateDelta(current []*mcp.Resource, acked map[string]string) (added []mcp.Resource, removed []string) {
// TODO - consider storing desired state as a map to make this faster
desired := make(map[string]*mcp.Resource, len(current))
// compute diff
for _, envelope := range current {
prevVersion, exists := acked[envelope.Metadata.Name]
if !exists {
// new
added = append(added, *envelope)
} else if prevVersion != envelope.Metadata.Version {
// update
added = append(added, *envelope)
}
// tracking for delete
desired[envelope.Metadata.Name] = envelope
}
for name := range acked {
if _, exists := desired[name]; !exists {
removed = append(removed, name)
}
}
return added, removed
}
func (con *connection) pushServerResponse(w *watch, resp *WatchResponse) error {
var (
added []mcp.Resource
removed []string
)
// send an incremental update if enabled for this collection and the most
// recent request from the sink requested it.
var incremental bool
if w.incremental && resp.Request.incremental {
incremental = true
}
if incremental {
added, removed = calculateDelta(resp.Resources, w.ackedVersionMap)
} else {
for _, resource := range resp.Resources {
added = append(added, *resource)
}
}
msg := &mcp.Resources{
SystemVersionInfo: resp.Version,
Collection: resp.Collection,
Resources: added,
RemovedResources: removed,
Incremental: incremental,
}
// increment nonce
con.streamNonce = con.streamNonce + 1
msg.Nonce = strconv.FormatInt(con.streamNonce, 10)
if err := con.stream.Send(msg); err != nil {
con.reporter.RecordSendError(err, status.Code(err))
return err
}
scope.Debugf("MCP: connection %v: SEND collection=%v version=%v nonce=%v inc=%v",
con, resp.Collection, resp.Version, msg.Nonce, msg.Incremental)
w.pending = msg
return nil
}
func (con *connection) receive() {
defer close(con.requestC)
for {
req, err := con.stream.Recv()
if err != nil {
code := status.Code(err)
if code == codes.Canceled || err == io.EOF {
scope.Infof("MCP: connection %v: TERMINATED %q", con, err)
return
}
con.reporter.RecordRecvError(err, code)
scope.Errorf("MCP: connection %v: TERMINATED with errors: %v", con, err)
// Save the stream error prior to closing the stream. The caller
// should access the error after the channel closure.
con.reqError = err
return
}
select {
case con.requestC <- req:
case <-con.queue.Done():
scope.Debugf("MCP: connection %v: stream done", con)
return
case <-con.stream.Context().Done():
scope.Debugf("MCP: connection %v: stream done, err=%v", con, con.stream.Context().Err())
return
}
}
}
func (con *connection) close() {
scope.Infof("MCP: connection %v: CLOSED", con)
for _, w := range con.watches {
if w.cancel != nil {
w.cancel()
}
}
}
func (con *connection) processClientRequest(req *mcp.RequestResources) error {
collection := req.Collection
con.reporter.RecordRequestSize(collection, con.id, req.Size())
w, ok := con.watches[collection]
if !ok {
return status.Errorf(codes.InvalidArgument, "unsupported collection %q", collection)
}
// nonces can be reused across streams; we verify nonce only if it initialized
if req.ResponseNonce == "" || w.pending.GetNonce() == req.ResponseNonce {
versionInfo := ""
if w.pending == nil {
scope.Infof("MCP: connection %v: inc=%v WATCH for %v", con, req.Incremental, collection)
} else {
versionInfo = w.pending.SystemVersionInfo
if req.ErrorDetail != nil {
scope.Warnf("MCP: connection %v: NACK collection=%v version=%q with nonce=%q error=%#v inc=%v", // nolint: lll
con, collection, req.ResponseNonce, versionInfo, req.ErrorDetail, req.Incremental)
con.reporter.RecordRequestNack(collection, con.id, codes.Code(req.ErrorDetail.Code))
} else {
scope.Infof("MCP: connection %v ACK collection=%v with version=%q nonce=%q inc=%v",
con, collection, versionInfo, req.ResponseNonce, req.Incremental)
con.reporter.RecordRequestAck(collection, con.id)
internal.UpdateResourceVersionTracking(w.ackedVersionMap, w.pending)
}
// clear the pending request after we finished processing the corresponding response.
w.pending = nil
}
if w.cancel != nil {
w.cancel()
}
sr := &Request{
SinkNode: req.SinkNode,
Collection: collection,
VersionInfo: versionInfo,
incremental: req.Incremental,
}
w.cancel = con.watcher.Watch(sr, con.queueResponse)
} else {
// This error path should not happen! Skip any requests that don't match the
// latest watch's nonce. These could be dup requests or out-of-order
// requests from a buggy node.
if req.ErrorDetail != nil {
scope.Errorf("MCP: connection %v: STALE NACK collection=%v with nonce=%q (expected nonce=%q) error=%+v inc=%v", // nolint: lll
con, collection, req.ResponseNonce, w.pending.GetNonce(), req.ErrorDetail, req.Incremental)
con.reporter.RecordRequestNack(collection, con.id, codes.Code(req.ErrorDetail.Code))
} else {
scope.Errorf("MCP: connection %v: STALE ACK collection=%v with nonce=%q (expected nonce=%q) inc=%v", // nolint: lll
con, collection, req.ResponseNonce, w.pending.GetNonce(), req.Incremental)
con.reporter.RecordRequestAck(collection, con.id)
}
}
return nil
}