зеркало из https://github.com/github/vitess-gh.git
125 строки
3.2 KiB
Go
125 строки
3.2 KiB
Go
// Copyright 2012, Google Inc. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tabletserver
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import (
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"fmt"
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"net/http"
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"sync"
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"sync/atomic"
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"time"
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"github.com/youtube/vitess/go/acl"
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"github.com/youtube/vitess/go/cache"
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"github.com/youtube/vitess/go/mysql/proto"
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)
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var (
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waitError = NewTabletError(ErrFail, "Error waiting for consolidation")
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)
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// Consolidator consolidates duplicate queries from executing simulaneously
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// and shares results between them.
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type Consolidator struct {
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mu sync.Mutex
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queries map[string]*Result
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consolidations *cache.LRUCache
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}
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// NewConsolidator creates a new Consolidator
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func NewConsolidator() *Consolidator {
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co := &Consolidator{queries: make(map[string]*Result), consolidations: cache.NewLRUCache(1000)}
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http.Handle("/debug/consolidations", co)
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return co
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}
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// Result is a wrapper for QueryResult of a query.
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type Result struct {
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executing sync.RWMutex
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consolidator *Consolidator
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sql string
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Result *proto.QueryResult
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Err error
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}
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// Create adds a query to currently executing queries and acquires a
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// lock on its Result if it is not already present. If the query is
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// a duplicate, Create returns false.
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func (co *Consolidator) Create(sql string) (r *Result, created bool) {
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co.mu.Lock()
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defer co.mu.Unlock()
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if r, ok := co.queries[sql]; ok {
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return r, false
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}
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// Preset the error. If there was an unexpected panic during the main
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// query, then all those who waited will return the waitError.
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r = &Result{consolidator: co, sql: sql, Err: waitError}
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r.executing.Lock()
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co.queries[sql] = r
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return r, true
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}
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func (co *Consolidator) ServeHTTP(response http.ResponseWriter, request *http.Request) {
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if err := acl.CheckAccessHTTP(request, acl.DEBUGGING); err != nil {
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acl.SendError(response, err)
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return
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}
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items := co.consolidations.Items()
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response.Header().Set("Content-Type", "text/plain")
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if items == nil {
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response.Write([]byte("empty\n"))
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return
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}
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response.Write([]byte(fmt.Sprintf("Length: %d\n", len(items))))
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for _, v := range items {
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response.Write([]byte(fmt.Sprintf("%v: %s\n", v.Value.(*ccount).Get(), v.Key)))
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}
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}
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func (co *Consolidator) record(sql string) {
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if v, ok := co.consolidations.Get(sql); ok {
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v.(*ccount).Add(1)
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} else {
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c := ccount(1)
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co.consolidations.Set(sql, &c)
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}
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}
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// Broadcast removes the entry from current queries and releases the
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// lock on its Result. Broadcast should be invoked when original
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// query completes execution.
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func (rs *Result) Broadcast() {
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rs.consolidator.mu.Lock()
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defer rs.consolidator.mu.Unlock()
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delete(rs.consolidator.queries, rs.sql)
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rs.executing.Unlock()
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}
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// Wait waits for the original query to complete execution. Wait should
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// be invoked for duplicate queries.
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func (rs *Result) Wait() {
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rs.consolidator.record(rs.sql)
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defer waitStats.Record("Consolidations", time.Now())
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rs.executing.RLock()
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}
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type ccount int64
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func (cc *ccount) Size() int {
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return 1
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}
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func (cc *ccount) Add(n int64) int64 {
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return atomic.AddInt64((*int64)(cc), n)
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}
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func (cc *ccount) Set(n int64) {
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atomic.StoreInt64((*int64)(cc), n)
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}
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func (cc *ccount) Get() int64 {
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return atomic.LoadInt64((*int64)(cc))
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}
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