101 lines
2.6 KiB
Go
101 lines
2.6 KiB
Go
// Copyright 2016 PingCAP, Inc.
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//
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// 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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// See the License for the specific language governing permissions and
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// limitations under the License.
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package domain
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import (
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"sync"
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"time"
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)
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// SchemaValidator is the interface for checking the validity of schema version.
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type SchemaValidator interface {
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// Update the schema validator, add a new item, delete the expired items.
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// The schemaVer is valid within leaseGrantTime plus lease duration.
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Update(leaseGrantTime uint64, schemaVer int64)
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// Check is it valid for a transaction to use schemaVer, at timestamp txnTS.
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Check(txnTS uint64, schemaVer int64) bool
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// Latest returns the latest schema version it knows, but not necessary a valid one.
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Latest() int64
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}
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type schemaValidator struct {
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mux sync.RWMutex
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lease time.Duration
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items map[int64]time.Time
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latestSchemaVer int64
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}
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func newSchemaValidator(lease time.Duration) SchemaValidator {
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return &schemaValidator{
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lease: lease,
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items: make(map[int64]time.Time),
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}
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}
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func (s *schemaValidator) Update(leaseGrantTS uint64, schemaVer int64) {
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s.mux.Lock()
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s.latestSchemaVer = schemaVer
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leaseGrantTime := extractPhysicalTime(leaseGrantTS)
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leaseExpire := leaseGrantTime.Add(s.lease - time.Millisecond)
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// Renewal lease.
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s.items[schemaVer] = leaseExpire
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// Delete expired items, leaseGrantTime is server current time, actually.
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for k, expire := range s.items {
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if leaseGrantTime.After(expire) {
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delete(s.items, k)
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}
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}
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s.mux.Unlock()
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}
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// Check checks schema validity, returns true if use schemaVer at txnTS is legal.
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func (s *schemaValidator) Check(txnTS uint64, schemaVer int64) bool {
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s.mux.RLock()
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defer s.mux.RUnlock()
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if s.lease == 0 {
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return true
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}
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expire, ok := s.items[schemaVer]
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if !ok {
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// Can't find schema version means it's already expired.
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return false
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}
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t := extractPhysicalTime(txnTS)
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if t.After(expire) {
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return false
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}
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return true
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}
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// Latest returns the latest schema version it knows.
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func (s *schemaValidator) Latest() int64 {
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s.mux.RLock()
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ret := s.latestSchemaVer
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s.mux.RUnlock()
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return ret
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}
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func extractPhysicalTime(ts uint64) time.Time {
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t := int64(ts >> 18) // 18 for physicalShiftBits
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return time.Unix(t/1e3, (t%1e3)*1e6)
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}
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