88 lines
2.8 KiB
Go
88 lines
2.8 KiB
Go
// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package transactions
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import (
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"sync"
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"time"
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"github.com/matrix-org/util"
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)
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// DefaultCleanupPeriod represents the default time duration after which cacheCleanService runs.
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const DefaultCleanupPeriod time.Duration = 30 * time.Minute
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type txnsMap map[string]*util.JSONResponse
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// Cache represents a temporary store for response entries.
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// Entries are evicted after a certain period, defined by cleanupPeriod.
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// This works by keeping two maps of entries, and cycling the maps after the cleanupPeriod.
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type Cache struct {
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sync.RWMutex
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txnsMaps [2]txnsMap
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cleanupPeriod time.Duration
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}
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// New is a wrapper which calls NewWithCleanupPeriod with DefaultCleanupPeriod as argument.
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func New() *Cache {
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return NewWithCleanupPeriod(DefaultCleanupPeriod)
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}
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// NewWithCleanupPeriod creates a new Cache object, starts cacheCleanService.
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// Takes cleanupPeriod as argument.
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// Returns a reference to newly created Cache.
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func NewWithCleanupPeriod(cleanupPeriod time.Duration) *Cache {
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t := Cache{txnsMaps: [2]txnsMap{make(txnsMap), make(txnsMap)}}
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t.cleanupPeriod = cleanupPeriod
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// Start clean service as the Cache is created
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go cacheCleanService(&t)
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return &t
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}
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// FetchTransaction looks up an entry for txnID in Cache.
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// Looks in both the txnMaps.
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// Returns (JSON response, true) if txnID is found, else the returned bool is false.
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func (t *Cache) FetchTransaction(txnID string) (*util.JSONResponse, bool) {
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t.RLock()
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defer t.RUnlock()
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for _, txns := range t.txnsMaps {
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res, ok := txns[txnID]
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if ok {
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return res, true
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}
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}
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return nil, false
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}
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// AddTransaction adds an entry for txnID in Cache for later access.
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// Adds to the front txnMap.
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func (t *Cache) AddTransaction(txnID string, res *util.JSONResponse) {
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t.Lock()
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defer t.Unlock()
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t.txnsMaps[0][txnID] = res
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}
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// cacheCleanService is responsible for cleaning up entries after cleanupPeriod.
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// It guarantees that an entry will be present in cache for at least cleanupPeriod & at most 2 * cleanupPeriod.
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// This cycles the txnMaps forward, i.e. back map is assigned the front and front is assigned an empty map.
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func cacheCleanService(t *Cache) {
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ticker := time.Tick(t.cleanupPeriod)
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for range ticker {
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t.Lock()
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t.txnsMaps[1] = t.txnsMaps[0]
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t.txnsMaps[0] = make(txnsMap)
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t.Unlock()
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}
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}
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