open-consul/agent/service_manager.go

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package agent
import (
"fmt"
"sync"
"github.com/hashicorp/consul/agent/cache"
cachetype "github.com/hashicorp/consul/agent/cache-types"
"github.com/hashicorp/consul/agent/structs"
"github.com/imdario/mergo"
"github.com/mitchellh/copystructure"
"golang.org/x/net/context"
)
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// The ServiceManager is a layer for service registration in between the agent
// and the local state. Any services must be registered with the ServiceManager,
// which then maintains a long-running watch of any globally-set service or proxy
// configuration that applies to the service in order to register the final, merged
// service configuration locally in the agent state.
type ServiceManager struct {
services map[string]*serviceConfigWatch
agent *Agent
lock sync.Mutex
}
func NewServiceManager(agent *Agent) *ServiceManager {
return &ServiceManager{
services: make(map[string]*serviceConfigWatch),
agent: agent,
}
}
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// AddService starts a new serviceConfigWatch if the service has not been registered, and
// updates the existing registration if it has. For a new service, a call will also be made
// to fetch the merged global defaults that apply to the service in order to compose the
// initial registration.
func (s *ServiceManager) AddService(service *structs.NodeService, chkTypes []*structs.CheckType, persist bool, token string, source configSource) error {
// For now only sidecar proxies have anything that can be configured
// centrally. So bypass the whole manager for regular services.
if !service.IsSidecarProxy() {
return s.agent.addServiceInternal(service, chkTypes, persist, token, source)
}
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s.lock.Lock()
defer s.lock.Unlock()
reg := serviceRegistration{
service: service,
chkTypes: chkTypes,
persist: persist,
token: token,
source: source,
}
// If a service watch already exists, update the registration. Otherwise,
// start a new config watcher.
watch, ok := s.services[service.ID]
if ok {
if err := watch.updateRegistration(&reg); err != nil {
return err
}
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s.agent.logger.Printf("[DEBUG] agent.manager: updated local registration for service %q", service.ID)
} else {
// This is a new entry, so get the existing global config and do the initial
// registration with the merged config.
watch := &serviceConfigWatch{
registration: &reg,
readyCh: make(chan error),
updateCh: make(chan cache.UpdateEvent, 1),
agent: s.agent,
}
// Start the config watch, which starts a blocking query for the resolved service config
// in the background.
if err := watch.Start(); err != nil {
return err
}
// Call ReadyWait to block until the cache has returned the initial config and the service
// has been registered.
if err := watch.ReadyWait(); err != nil {
watch.Stop()
return err
}
s.services[service.ID] = watch
s.agent.logger.Printf("[DEBUG] agent.manager: added local registration for service %q", service.ID)
}
return nil
}
func (s *ServiceManager) RemoveService(serviceID string) {
s.lock.Lock()
defer s.lock.Unlock()
serviceWatch, ok := s.services[serviceID]
if !ok {
return
}
serviceWatch.Stop()
delete(s.services, serviceID)
}
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// serviceRegistration represents a locally registered service.
type serviceRegistration struct {
service *structs.NodeService
chkTypes []*structs.CheckType
persist bool
token string
source configSource
}
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// serviceConfigWatch is a long running helper for composing the end config
// for a given service from both the local registration and the global
// service/proxy defaults.
type serviceConfigWatch struct {
registration *serviceRegistration
defaults *structs.ServiceConfigResponse
agent *Agent
// readyCh is used for ReadyWait in order to block until the first update
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// for the resolved service config is received from the cache.
readyCh chan error
// ctx and cancelFunc store the overall context that lives as long as the
// Watch instance is needed, possibly spanning multiple cache.Notify
// lifetimes.
ctx context.Context
cancelFunc func()
// cacheKey stores the key of the current request, when registration changes
// we check to see if a new cache watch is needed.
cacheKey string
// updateCh receives changes from cache watchers or registration changes.
updateCh chan cache.UpdateEvent
// notifyCancel, if non-nil it the cancel func that will stop the currently
// active Notify loop. It does not cancel ctx and is used when we need to
// switch to a new Notify call because cache key changed.
notifyCancel func()
lock sync.Mutex
}
// Start starts the config watch and a goroutine to handle updates over
// the updateCh. This is not safe to call more than once.
func (s *serviceConfigWatch) Start() error {
s.ctx, s.cancelFunc = context.WithCancel(context.Background())
if err := s.ensureConfigWatch(); err != nil {
return err
}
go s.runWatch()
return nil
}
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func (s *serviceConfigWatch) Stop() {
s.cancelFunc()
}
// ReadyWait blocks until the readyCh is closed, which means the initial
// registration of the service has been completed. If there was an error
// with the initial registration, it will be returned.
func (s *serviceConfigWatch) ReadyWait() error {
err := <-s.readyCh
return err
}
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// runWatch handles any update events from the cache.Notify until the
// config watch is shut down.
func (s *serviceConfigWatch) runWatch() {
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firstRun := true
for {
select {
case <-s.ctx.Done():
return
case event := <-s.updateCh:
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if err := s.handleUpdate(event, false, firstRun); err != nil {
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s.agent.logger.Printf("[ERR] agent.manager: error handling service update: %v", err)
}
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firstRun = false
}
}
}
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// handleUpdate receives an update event about either the service registration or the
// global config defaults, updates the local state and re-registers the service with
// the newly merged config. This function takes the serviceConfigWatch lock to ensure
// only one update can be happening at a time.
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func (s *serviceConfigWatch) handleUpdate(event cache.UpdateEvent, locked, firstRun bool) error {
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// Take the agent state lock if needed. This is done before the local config watch
// lock in order to prevent a race between this config watch and others - the config
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// watch lock is the inner lock and the agent stateLock is the outer lock. If this is the
// first run we also don't need to take the stateLock, as this is being waited on
// synchronously by a caller that already holds it.
if !locked && !firstRun {
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s.agent.stateLock.Lock()
defer s.agent.stateLock.Unlock()
}
s.lock.Lock()
defer s.lock.Unlock()
// If we got an error, log a warning if this is the first update; otherwise return the error.
// We want the initial update to cause a service registration no matter what.
if event.Err != nil {
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if firstRun {
s.agent.logger.Printf("[WARN] could not retrieve initial service_defaults config for service %q: %v",
s.registration.service.ID, event.Err)
} else {
return fmt.Errorf("error watching service config: %v", event.Err)
}
} else {
switch res := event.Result.(type) {
case *serviceRegistration:
s.registration = res
// We may need to restart watch if upstreams changed
if err := s.ensureConfigWatch(); err != nil {
return err
}
case *structs.ServiceConfigResponse:
// Sanity check this even came from the currently active watch to ignore
// rare races when switching cache keys
if event.CorrelationID != s.cacheKey {
// It's a no-op. The new watcher will deliver (or may have already
// delivered) the correct config so just ignore this old message.
return nil
}
s.defaults = res
default:
return fmt.Errorf("unknown update event type: %T", event)
}
}
// Merge the local registration with the central defaults and update this service
// in the local state.
service, err := s.mergeServiceConfig()
if err != nil {
return err
}
if err := s.updateAgentRegistration(service); err != nil {
// If this is the initial registration, return the error through the readyCh
// so it can be passed back to the original caller.
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if firstRun {
s.readyCh <- err
}
return fmt.Errorf("error updating service registration: %v", err)
}
// If this is the first registration, set the ready status by closing the channel.
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if firstRun {
close(s.readyCh)
}
return nil
}
// updateAgentRegistration updates the service (and its sidecar, if applicable) in the
// local state.
func (s *serviceConfigWatch) updateAgentRegistration(ns *structs.NodeService) error {
return s.agent.addServiceInternal(ns, s.registration.chkTypes, s.registration.persist, s.registration.token, s.registration.source)
}
// ensureConfigWatch starts a cache.Notify goroutine to run a continuous
// blocking query on the resolved service config for this service. If the
// registration has changed in a way that requires a new blocking query, it will
// cancel any current watch and start a new one. It is a no-op if there is an
// existing watch that is sufficient for the current registration. It is not
// thread-safe and must only be called from the Start method (which is only safe
// to call once as documented) or from inside the run loop.
func (s *serviceConfigWatch) ensureConfigWatch() error {
ns := s.registration.service
name := ns.Service
var upstreams []string
// Note that only sidecar proxies should even make it here for now although
// later that will change to add the condition.
if ns.IsSidecarProxy() {
// This is a sidecar proxy, ignore the proxy service's config since we are
// managed by the target service config.
name = ns.Proxy.DestinationServiceName
// Also if we have any upstreams defined, add them to the request so we can
// learn about their configs.
for _, us := range ns.Proxy.Upstreams {
if us.DestinationType == "" || us.DestinationType == structs.UpstreamDestTypeService {
upstreams = append(upstreams, us.DestinationName)
}
}
}
req := &structs.ServiceConfigRequest{
Name: name,
Datacenter: s.agent.config.Datacenter,
QueryOptions: structs.QueryOptions{Token: s.agent.config.ACLAgentToken},
Upstreams: upstreams,
}
if s.registration.token != "" {
req.QueryOptions.Token = s.registration.token
}
// See if this request is different from the current one
cacheKey := req.CacheInfo().Key
if cacheKey == s.cacheKey {
return nil
}
// If there is an existing notify running, stop it first. This may leave a
// blocking query running in the background but the Notify loop will swallow
// the response and exit when it next unblocks so we can consider it stopped.
if s.notifyCancel != nil {
s.notifyCancel()
}
// Make a new context just for this Notify call
ctx, cancel := context.WithCancel(s.ctx)
s.notifyCancel = cancel
s.cacheKey = cacheKey
// We use the cache key as the correlationID here. Notify in general will not
// respond on the updateCh after the context is cancelled however there could
// possible be a race where it has only just got an update and checked the
// context before we cancel and so might still deliver the old event. Using
// the cacheKey allows us to ignore updates from the old cache watch and makes
// even this rare edge case safe.
err := s.agent.cache.Notify(ctx, cachetype.ResolvedServiceConfigName, req,
s.cacheKey, s.updateCh)
return err
}
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// updateRegistration does a synchronous update of the local service registration and
// returns the result. The agent stateLock should be held when calling this function.
func (s *serviceConfigWatch) updateRegistration(registration *serviceRegistration) error {
return s.handleUpdate(cache.UpdateEvent{
Result: registration,
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}, true, false)
}
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// mergeServiceConfig returns the final effective config for the watched service,
// including the latest known global defaults from the servers.
func (s *serviceConfigWatch) mergeServiceConfig() (*structs.NodeService, error) {
if s.defaults == nil || (!s.registration.service.IsSidecarProxy() && !s.registration.service.IsMeshGateway()) {
return s.registration.service, nil
}
// We don't want to change s.registration in place since it is our source of
// truth about what was actually registered before defaults applied. So copy
// it first.
nsRaw, err := copystructure.Copy(s.registration.service)
if err != nil {
return nil, err
}
// Merge proxy defaults
ns := nsRaw.(*structs.NodeService)
if err := mergo.Merge(&ns.Proxy.Config, s.defaults.ProxyConfig); err != nil {
return nil, err
}
if ns.Proxy.MeshGateway.Mode == structs.MeshGatewayModeDefault {
ns.Proxy.MeshGateway.Mode = s.defaults.MeshGateway.Mode
}
// Merge upstream defaults if there were any returned
for i := range ns.Proxy.Upstreams {
// Get a pointer not a value copy of the upstream struct
us := &ns.Proxy.Upstreams[i]
if us.DestinationType != "" && us.DestinationType != structs.UpstreamDestTypeService {
continue
}
// default the upstreams gateway mode if it didn't specify one
if us.MeshGateway.Mode == structs.MeshGatewayModeDefault {
us.MeshGateway.Mode = ns.Proxy.MeshGateway.Mode
}
usCfg, ok := s.defaults.UpstreamConfigs[us.DestinationName]
if !ok {
// No config defaults to merge
continue
}
if err := mergo.Merge(&us.Config, usCfg); err != nil {
return nil, err
}
}
return ns, err
}