Files
mattermost/store/local_cache_supplier.go
Jesse Hallam 4286456077 MM-10856: deduplicate posts with the same pending post id (#10006)
* MM-10856: deduplicate posts with the same pending post id

Leverage a fixed size cache with a window of 30 seconds to deduplicate posts received by a single app server. Clients that duplicate the same pending post id will see one request potentially delayed until the first finishes, after which the same payload should be returned by both.  Duplicate posts outside the 30 second window will not be de-duplicated.

Note that the cache is not synchronized between app servers. In an HA cluster consisting of more than one app server, sticky load balancing (e.g. hashing by IP or Session ID) is required to route the users to the same app instance for multiple requests.

Other options considered for this feature:
* adding a column to the `Posts` table: rejected as being too heavyweight
* maintaining a `PendingPostIds` table: similarly rejected for the database impact
* using the pending post id as the post id and relying on the unique constraints on the Post table: rejected for being difficult to show that it's safe to use a client-provided value as the row identifier

* utils/lru: simplify to ttl internally and for new methods

* move seenPendingPostIdsCache to App.Server

* just fail concurrent post requests, vs. trying to wait

* add debug log when create post is deduplicated
2018-12-17 15:16:57 -08:00

132 lines
3.7 KiB
Go

// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.
package store
import (
"context"
"github.com/mattermost/mattermost-server/einterfaces"
"github.com/mattermost/mattermost-server/model"
"github.com/mattermost/mattermost-server/utils"
)
const (
REACTION_CACHE_SIZE = 20000
REACTION_CACHE_SEC = 30 * 60
ROLE_CACHE_SIZE = 20000
ROLE_CACHE_SEC = 30 * 60
SCHEME_CACHE_SIZE = 20000
SCHEME_CACHE_SEC = 30 * 60
CLEAR_CACHE_MESSAGE_DATA = ""
)
type LocalCacheSupplier struct {
next LayeredStoreSupplier
reactionCache *utils.Cache
roleCache *utils.Cache
schemeCache *utils.Cache
metrics einterfaces.MetricsInterface
cluster einterfaces.ClusterInterface
}
// Caching Interface
type ObjectCache interface {
AddWithExpiresInSecs(key, value interface{}, expireAtSecs int64)
AddWithDefaultExpires(key, value interface{})
Purge()
Get(key interface{}) (value interface{}, ok bool)
Remove(key interface{})
Len() int
Name() string
GetInvalidateClusterEvent() string
}
func NewLocalCacheSupplier(metrics einterfaces.MetricsInterface, cluster einterfaces.ClusterInterface) *LocalCacheSupplier {
supplier := &LocalCacheSupplier{
reactionCache: utils.NewLruWithParams(REACTION_CACHE_SIZE, "Reaction", REACTION_CACHE_SEC, model.CLUSTER_EVENT_INVALIDATE_CACHE_FOR_REACTIONS),
roleCache: utils.NewLruWithParams(ROLE_CACHE_SIZE, "Role", ROLE_CACHE_SEC, model.CLUSTER_EVENT_INVALIDATE_CACHE_FOR_ROLES),
schemeCache: utils.NewLruWithParams(SCHEME_CACHE_SIZE, "Scheme", SCHEME_CACHE_SEC, model.CLUSTER_EVENT_INVALIDATE_CACHE_FOR_SCHEMES),
metrics: metrics,
cluster: cluster,
}
if cluster != nil {
cluster.RegisterClusterMessageHandler(model.CLUSTER_EVENT_INVALIDATE_CACHE_FOR_REACTIONS, supplier.handleClusterInvalidateReaction)
cluster.RegisterClusterMessageHandler(model.CLUSTER_EVENT_INVALIDATE_CACHE_FOR_ROLES, supplier.handleClusterInvalidateRole)
}
return supplier
}
func (s *LocalCacheSupplier) SetChainNext(next LayeredStoreSupplier) {
s.next = next
}
func (s *LocalCacheSupplier) Next() LayeredStoreSupplier {
return s.next
}
func (s *LocalCacheSupplier) doStandardReadCache(ctx context.Context, cache ObjectCache, key string, hints ...LayeredStoreHint) *LayeredStoreSupplierResult {
if hintsContains(hints, LSH_NO_CACHE) {
if s.metrics != nil {
s.metrics.IncrementMemCacheMissCounter(cache.Name())
}
return nil
}
if cacheItem, ok := cache.Get(key); ok {
if s.metrics != nil {
s.metrics.IncrementMemCacheHitCounter(cache.Name())
}
result := NewSupplierResult()
result.Data = cacheItem
return result
}
if s.metrics != nil {
s.metrics.IncrementMemCacheMissCounter(cache.Name())
}
return nil
}
func (s *LocalCacheSupplier) doStandardAddToCache(ctx context.Context, cache ObjectCache, key string, result *LayeredStoreSupplierResult, hints ...LayeredStoreHint) {
if result.Err == nil && result.Data != nil {
cache.AddWithDefaultExpires(key, result.Data)
}
}
func (s *LocalCacheSupplier) doInvalidateCacheCluster(cache ObjectCache, key string) {
cache.Remove(key)
if s.cluster != nil {
msg := &model.ClusterMessage{
Event: cache.GetInvalidateClusterEvent(),
SendType: model.CLUSTER_SEND_BEST_EFFORT,
Data: key,
}
s.cluster.SendClusterMessage(msg)
}
}
func (s *LocalCacheSupplier) doClearCacheCluster(cache ObjectCache) {
cache.Purge()
if s.cluster != nil {
msg := &model.ClusterMessage{
Event: cache.GetInvalidateClusterEvent(),
SendType: model.CLUSTER_SEND_BEST_EFFORT,
Data: CLEAR_CACHE_MESSAGE_DATA,
}
s.cluster.SendClusterMessage(msg)
}
}
func (s *LocalCacheSupplier) Invalidate() {
s.doClearCacheCluster(s.reactionCache)
s.doClearCacheCluster(s.roleCache)
s.doClearCacheCluster(s.schemeCache)
}