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config_source.go
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config_source.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package catalog
import (
"context"
"errors"
"sync"
"github.com/hashicorp/go-hclog"
"github.com/hashicorp/go-memdb"
"github.com/hernad/consul/acl"
"github.com/hernad/consul/agent/configentry"
"github.com/hernad/consul/agent/grpc-external/limiter"
"github.com/hernad/consul/agent/local"
"github.com/hernad/consul/agent/proxycfg"
"github.com/hernad/consul/agent/structs"
)
const source proxycfg.ProxySource = "catalog"
// ConfigSource wraps a proxycfg.Manager to register services with it, from the
// catalog, when they are requested by the xDS server.
type ConfigSource struct {
Config
mu sync.Mutex
watches map[proxycfg.ProxyID]*watch
shutdownCh chan struct{}
}
type watch struct {
numWatchers int // guarded by ConfigSource.mu.
closeCh chan chan struct{}
}
// NewConfigSource creates a ConfigSource with the given configuration.
func NewConfigSource(cfg Config) *ConfigSource {
return &ConfigSource{
Config: cfg,
watches: make(map[proxycfg.ProxyID]*watch),
shutdownCh: make(chan struct{}),
}
}
// Watch wraps the underlying proxycfg.Manager and dynamically registers
// services from the catalog with it when requested by the xDS server.
func (m *ConfigSource) Watch(serviceID structs.ServiceID, nodeName string, token string) (<-chan *proxycfg.ConfigSnapshot, limiter.SessionTerminatedChan, proxycfg.CancelFunc, error) {
// If the service is registered to the local agent, use the LocalConfigSource
// rather than trying to configure it from the catalog.
if nodeName == m.NodeName && m.LocalState.ServiceExists(serviceID) {
return m.LocalConfigSource.Watch(serviceID, nodeName, token)
}
// Begin a session with the xDS session concurrency limiter.
//
// We do this here rather than in the xDS server because we don't want to apply
// the limit to services from the LocalConfigSource.
//
// See: https://github.com/hernad/consul/issues/15753
session, err := m.SessionLimiter.BeginSession()
if err != nil {
return nil, nil, nil, err
}
proxyID := proxycfg.ProxyID{
ServiceID: serviceID,
NodeName: nodeName,
Token: token,
}
// Start the watch on the real proxycfg Manager.
snapCh, cancelWatch := m.Manager.Watch(proxyID)
// Wrap the cancelWatch function with our bookkeeping. m.mu must be held when calling.
var cancelOnce sync.Once
cancel := func() {
cancelOnce.Do(func() {
cancelWatch()
m.cleanup(proxyID)
session.End()
})
}
m.mu.Lock()
defer m.mu.Unlock()
w, ok := m.watches[proxyID]
if ok {
w.numWatchers++
} else {
w = &watch{closeCh: make(chan chan struct{}), numWatchers: 1}
m.watches[proxyID] = w
if err := m.startSync(w.closeCh, proxyID); err != nil {
delete(m.watches, proxyID)
cancelWatch()
session.End()
return nil, nil, nil, err
}
}
return snapCh, session.Terminated(), cancel, nil
}
func (m *ConfigSource) Shutdown() {
close(m.shutdownCh)
}
// startSync fetches a service from the state store's catalog tables and
// registers it with the proxycfg Manager. It spawns a goroutine to watch
// and re-register the service whenever it changes - this goroutine will
// run until a signal is sent on closeCh (at which point the service will
// be deregistered).
//
// If the first attempt to fetch and register the service fails, startSync
// will return an error (and no goroutine will be started).
func (m *ConfigSource) startSync(closeCh <-chan chan struct{}, proxyID proxycfg.ProxyID) error {
logger := m.Logger.With(
"proxy_service_id", proxyID.ServiceID.String(),
"node", proxyID.NodeName,
)
logger.Trace("syncing catalog service")
fetchAndRegister := func() (memdb.WatchSet, error) {
store := m.GetStore()
ws := memdb.NewWatchSet()
// Add the store's AbandonCh to the WatchSet so that if the store is abandoned
// during a snapshot restore we'll unblock and re-register the service.
ws.Add(store.AbandonCh())
_, ns, err := store.NodeService(ws, proxyID.NodeName, proxyID.ID, &proxyID.EnterpriseMeta, structs.DefaultPeerKeyword)
switch {
case err != nil:
logger.Error("failed to read service from state store", "error", err.Error())
return nil, err
case ns == nil:
m.Manager.Deregister(proxyID, source)
logger.Trace("service does not exist in catalog, de-registering it with proxycfg manager")
return ws, nil
case !ns.Kind.IsProxy():
err := errors.New("service must be a sidecar proxy or gateway")
logger.Error(err.Error())
return nil, err
}
_, ns, err = configentry.MergeNodeServiceWithCentralConfig(ws, store, ns, logger)
if err != nil {
logger.Error("failed to merge with central config", "error", err.Error())
return nil, err
}
if err = m.Manager.Register(proxyID, ns, source, proxyID.Token, false); err != nil {
logger.Error("failed to register service", "error", err.Error())
return nil, err
}
return ws, nil
}
syncLoop := func(ws memdb.WatchSet) {
// Cancel the context on return to clean up the goroutine started by WatchCh.
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
for {
select {
case <-ws.WatchCh(ctx):
// Something changed, unblock and re-run the query.
//
// It is expected that all other branches of this select will return and
// cancel the context given to WatchCh (to clean up its goroutine).
case doneCh := <-closeCh:
// All watchers of this service (xDS streams) have gone away, so it's time
// to free its resources.
//
// TODO(agentless): we should probably wait for a short grace period before
// de-registering the service to allow clients to reconnect after a network
// blip.
logger.Trace("de-registering service with proxycfg manager because all watchers have gone away")
m.Manager.Deregister(proxyID, source)
close(doneCh)
return
case <-m.shutdownCh:
// Manager is shutting down, stop the goroutine.
return
}
var err error
ws, err = fetchAndRegister()
if err != nil {
return
}
}
}
ws, err := fetchAndRegister()
if err != nil {
// Currently, only the first attempt's error is returned to the xDS server,
// which terminates the stream immediately.
//
// We don't (yet) have a way to surface subsequent errors to the xDS server.
//
// We could wrap ConfigSnapshot in a sum type (i.e. a struct that contains
// either a snapshot or an error) but given the relative unlikelihood of a
// query that succeeds once failing in the future, it doesn't seem worth it.
//
// Instead, we log the error and leave any watchers hanging. Perhaps another
// solution would be to close any watch channels when de-registering a service?
return err
}
go syncLoop(ws)
return nil
}
// cleanup decrements the watchers counter for the given proxy, and if it has
// reached zero, stops the sync goroutine (and de-registers the service).
func (m *ConfigSource) cleanup(id proxycfg.ProxyID) {
m.mu.Lock()
defer m.mu.Unlock()
h := m.watches[id]
h.numWatchers--
if h.numWatchers == 0 {
// We wait for doneCh to be closed by the sync goroutine, so that the lock is
// held until after the service is de-registered - this prevents a potential
// race where another sync goroutine is started for the service and we undo
// its call to register the service.
//
// This cannot deadlock because closeCh is unbuffered. Sending will only
// succeed if the sync goroutine is ready to receive (which always closes
// doneCh).
doneCh := make(chan struct{})
select {
case h.closeCh <- doneCh:
<-doneCh
case <-m.shutdownCh:
// ConfigSource is shutting down, so the goroutine will be stopped anyway.
}
delete(m.watches, id)
}
}
type Config struct {
// NodeName is the name of the local agent node.
NodeName string
// Manager is the proxycfg Manager with which proxy services will be registered.
Manager ConfigManager
// State is the agent's local state that will be used to check if a proxy is
// registered locally.
LocalState *local.State
// LocalConfigSource is used to configure proxies registered in the agent's
// local state.
LocalConfigSource Watcher
// GetStore is used to access the server's state store.
GetStore func() Store
// Logger will be used to write log messages.
Logger hclog.Logger
// SessionLimiter is used to enforce xDS concurrency limits.
SessionLimiter SessionLimiter
}
//go:generate mockery --name ConfigManager --inpackage
type ConfigManager interface {
Watch(req proxycfg.ProxyID) (<-chan *proxycfg.ConfigSnapshot, proxycfg.CancelFunc)
Register(proxyID proxycfg.ProxyID, service *structs.NodeService, source proxycfg.ProxySource, token string, overwrite bool) error
Deregister(proxyID proxycfg.ProxyID, source proxycfg.ProxySource)
}
type Store interface {
NodeService(ws memdb.WatchSet, nodeName string, serviceID string, entMeta *acl.EnterpriseMeta, peerName string) (uint64, *structs.NodeService, error)
ReadResolvedServiceConfigEntries(ws memdb.WatchSet, serviceName string, entMeta *acl.EnterpriseMeta, upstreamIDs []structs.ServiceID, proxyMode structs.ProxyMode) (uint64, *configentry.ResolvedServiceConfigSet, error)
AbandonCh() <-chan struct{}
}
//go:generate mockery --name Watcher --inpackage
type Watcher interface {
Watch(proxyID structs.ServiceID, nodeName string, token string) (<-chan *proxycfg.ConfigSnapshot, limiter.SessionTerminatedChan, proxycfg.CancelFunc, error)
}
//go:generate mockery --name SessionLimiter --inpackage
type SessionLimiter interface {
BeginSession() (limiter.Session, error)
}