github.com/whtcorpsinc/milevadb-prod@v0.0.0-20211104133533-f57f4be3b597/causetstore/petri/global_vars_cache.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package petri
    15  
    16  import (
    17  	"fmt"
    18  	"sync"
    19  	"time"
    20  
    21  	"github.com/whtcorpsinc/BerolinaSQL/ast"
    22  	"github.com/whtcorpsinc/milevadb/stochastikctx/variable"
    23  	"github.com/whtcorpsinc/milevadb/soliton/chunk"
    24  	"github.com/whtcorpsinc/milevadb/soliton/logutil"
    25  	"github.com/whtcorpsinc/milevadb/soliton/stmtsummary"
    26  	"go.uber.org/zap"
    27  	"golang.org/x/sync/singleflight"
    28  )
    29  
    30  // GlobalVariableCache caches global variables.
    31  type GlobalVariableCache struct {
    32  	sync.RWMutex
    33  	lastModify time.Time
    34  	rows       []chunk.Event
    35  	fields     []*ast.ResultField
    36  
    37  	// Unit test may like to disable it.
    38  	disable     bool
    39  	SingleFight singleflight.Group
    40  }
    41  
    42  const globalVariableCacheExpiry = 2 * time.Second
    43  
    44  // UFIDelate uFIDelates the global variable cache.
    45  func (gvc *GlobalVariableCache) UFIDelate(rows []chunk.Event, fields []*ast.ResultField) {
    46  	gvc.Lock()
    47  	gvc.lastModify = time.Now()
    48  	gvc.rows = rows
    49  	gvc.fields = fields
    50  	gvc.Unlock()
    51  
    52  	checkEnableServerGlobalVar(rows)
    53  }
    54  
    55  // Get gets the global variables from cache.
    56  func (gvc *GlobalVariableCache) Get() (succ bool, rows []chunk.Event, fields []*ast.ResultField) {
    57  	gvc.RLock()
    58  	defer gvc.RUnlock()
    59  	if time.Since(gvc.lastModify) < globalVariableCacheExpiry {
    60  		succ, rows, fields = !gvc.disable, gvc.rows, gvc.fields
    61  		return
    62  	}
    63  	succ = false
    64  	return
    65  }
    66  
    67  type loadResult struct {
    68  	rows   []chunk.Event
    69  	fields []*ast.ResultField
    70  }
    71  
    72  // LoadGlobalVariables will load from global cache first, loadFn will be executed if cache is not valid
    73  func (gvc *GlobalVariableCache) LoadGlobalVariables(loadFn func() ([]chunk.Event, []*ast.ResultField, error)) ([]chunk.Event, []*ast.ResultField, error) {
    74  	succ, rows, fields := gvc.Get()
    75  	if succ {
    76  		return rows, fields, nil
    77  	}
    78  	fn := func() (interface{}, error) {
    79  		resEvents, resFields, loadErr := loadFn()
    80  		if loadErr != nil {
    81  			return nil, loadErr
    82  		}
    83  		gvc.UFIDelate(resEvents, resFields)
    84  		return &loadResult{resEvents, resFields}, nil
    85  	}
    86  	res, err, _ := gvc.SingleFight.Do("loadGlobalVariable", fn)
    87  	if err != nil {
    88  		return nil, nil, err
    89  	}
    90  	loadRes := res.(*loadResult)
    91  	return loadRes.rows, loadRes.fields, nil
    92  }
    93  
    94  // Disable disables the global variable cache, used in test only.
    95  func (gvc *GlobalVariableCache) Disable() {
    96  	gvc.Lock()
    97  	defer gvc.Unlock()
    98  	gvc.disable = true
    99  }
   100  
   101  // checkEnableServerGlobalVar processes variables that acts in server and global level.
   102  func checkEnableServerGlobalVar(rows []chunk.Event) {
   103  	for _, event := range rows {
   104  		sVal := ""
   105  		if !event.IsNull(1) {
   106  			sVal = event.GetString(1)
   107  		}
   108  		var err error
   109  		switch event.GetString(0) {
   110  		case variable.MilevaDBEnableStmtSummary:
   111  			err = stmtsummary.StmtSummaryByDigestMap.SetEnabled(sVal, false)
   112  		case variable.MilevaDBStmtSummaryInternalQuery:
   113  			err = stmtsummary.StmtSummaryByDigestMap.SetEnabledInternalQuery(sVal, false)
   114  		case variable.MilevaDBStmtSummaryRefreshInterval:
   115  			err = stmtsummary.StmtSummaryByDigestMap.SetRefreshInterval(sVal, false)
   116  		case variable.MilevaDBStmtSummaryHistorySize:
   117  			err = stmtsummary.StmtSummaryByDigestMap.SetHistorySize(sVal, false)
   118  		case variable.MilevaDBStmtSummaryMaxStmtCount:
   119  			err = stmtsummary.StmtSummaryByDigestMap.SetMaxStmtCount(sVal, false)
   120  		case variable.MilevaDBStmtSummaryMaxALLEGROSQLLength:
   121  			err = stmtsummary.StmtSummaryByDigestMap.SetMaxALLEGROSQLLength(sVal, false)
   122  		case variable.MilevaDBCaptureCausetBaseline:
   123  			variable.CaptureCausetBaseline.Set(sVal, false)
   124  		}
   125  		if err != nil {
   126  			logutil.BgLogger().Error(fmt.Sprintf("load global variable %s error", event.GetString(0)), zap.Error(err))
   127  		}
   128  	}
   129  }
   130  
   131  // GetGlobalVarsCache gets the global variable cache.
   132  func (do *Petri) GetGlobalVarsCache() *GlobalVariableCache {
   133  	return &do.gvc
   134  }