本文介绍了模拟对sqlite数据库的多个请求，因为goroutine导致随机恐慌的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我试图模拟来自 http.HandleFunc 的多个请求，以便对sqlite数据库进行更改。我认为由 http.HandleFunc 调用的函数实际上是goroutine。请参阅下面的代码：
I am trying to emulate multiple requests from http.HandleFunc to function which makes changes to sqlite database. I assume that function which is called by http.HandleFunc is actually goroutine. See code below:
package main
import "fmt"
import "time"
import "code.google.com/p/go-sqlite/go1/sqlite3"
import "crypto/rand"
import "encoding/base64"
func getrandomtext() (string) {
b := make([]byte, 12)
rand.Read(b)
en := base64.StdEncoding // or URLEncoding
enclen := en.EncodedLen(len(b))
d := make([]byte, enclen)
en.Encode(d, b)
returntext := string(d[:enclen])
//fmt.Printf("getrandomtext() : '"+returntext+"'\n")
return returntext
}
func main() {
dbname := "multitasking.db"
tablename := "multiwrite"
defer time.Sleep(5000 * time.Millisecond)
db, err := sqlite3.Open("file:"+dbname+"?file:locked.sqlite?cache=shared&mode=rwc")
defer db.Close()
if err != nil {
fmt.Printf("failed to open database, error: " + err.Error() + "\n")
return
}
err = db.Exec("DROP TABLE IF EXISTS "+tablename+";")
if err != nil {
fmt.Printf("error dropping table "+tablename+": "+err.Error()+"\n")
}
err = db.Exec("CREATE TABLE "+tablename+" (id INTEGER PRIMARY KEY AUTOINCREMENT, text VARCHAR(200));")
if err != nil {
fmt.Printf("error creating table "+tablename+": "+err.Error()+"\n")
return
} else {
fmt.Printf("successfully created table "+tablename+"!\n")
}
var insertcount int = 128
fmt.Printf("inserting %d random text rows ...\n", insertcount)
var counter int = 0
insertloop:
if counter < insertcount {
counter++
go func(count int) {
if db.Exec("INSERT INTO "+tablename+"(text) VALUES(\""+getrandomtext()+"\");") !=nil {
fmt.Printf(" -%d", count)
} else {
fmt.Printf(" +%d", count)
}
}(counter)
goto insertloop
}
fmt.Printf("\nExecuted! Waiting some seconds...\n")
time.Sleep(3000 * time.Millisecond)
fmt.Printf("\nRequesting...\n")
ReadTable, err := db.Prepare("SELECT id, text FROM "+tablename+";")
err = ReadTable.Query()
if err != nil {
fmt.Printf("failed to read '"+tablename+"' table, error: " + err.Error() + "\n")
return
}
Readloop:
var RowId int
var RowText string
err = ReadTable.Scan(&RowId, &RowText)
if err == nil {
fmt.Printf("> %d | %s\n", RowId, RowText)
ReadTable.Next()
goto Readloop
}
fmt.Printf("Sqlite3 test done! :)\n")
}
多任务。 db 不存在所有工作正常：
When multitasking.db does not exists all works fine:
C:\Documents and Settings\JekabsR>multitaskingdb
successfully created table multiwrite!
inserting 128 random text rows ...
Executed! Waiting some seconds...
+2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +57 +58 +59 +60 +61 +62 +63 +64 +65 +66 +67 +68
+69 +70 +71 +72 +73 +74 +75 +76 +77 +78 +79 +80 +81 +82 +83 +84 +85 +86 +87 +88
+89 +90 +91 +92 +93 +94 +95 +96 +97 +98 +117 +118 +119 +120 +121 +122 +123 +124
+125 +126 +127 +128 +12 +13 +14 +15 +16 +17 +18 +19 +20 +21 +22 +23 +24 +25 +26
+27 +28 +29 +30 +31 +32 +33 +34 +35 +36 +37 +38 +39 +40 +41 +42 +43 +44 +45 +46
+47 +48 +49 +50 +51 +52 +53 +54 +55 +56 +99 +100 +101 +102 +103 +104 +105 +106
+107 +108 +109 +110 +111 +112 +113 +114 +115 +116 +1
Requesting...
> 1 | ScnK0DScszFPtNgY
> 2 | 8ALa+Dyk48PpJ4em
> 3 | hmEF4yINhg9SxlNy
...
> 127 | AAAAwNCvV/wd0/MR
> 128 | SEbPfK/XuVfgnxPj
Sqlite3 test done! :)
当我再次点击 multitaskingdb 时，这会导致恐慌：
When i hit multitaskingdb again, this causes panic:
C:\Documents and Settings\JekabsR>multitaskingdb
successfully created table multiwrite!
inserting 128 random text rows ...
Executed! Waiting some seconds...
+2 +3 +4 +5 +6 +7 +8 +9 +10panic: invalid memory address or nil pointer derefer
ence
fatal error: panic during malloc
[signal 0xc0000005 code=0x0 addr=0x20 pc=0x41b60a]
runtime stack:
runtime.panic(panic: invalid memory address or nil pointer dereference
+11 -57 -58 -59 -60 -61 -62 -63 -64 -65 -66 -67 -68 -69 -700x520a80, 0x673aaf)
C:/Program Files/Go/src/pkg/runtime/panic.c:233 +0x2b
invalid spdelta 363589 -1
runtime: unexpected return pc for -71 -72 -73 -74 -75 -76 -77 -78 -79 -80 -81 -
82 -83 -84 -85 -86 -87 -88balance called from 0x200
goroutine 48 [syscall]:
runtime.cgocall(0x492817, 0x314476e8)
C:/Program Files/Go/src/pkg/runtime/cgocall.c -89 -90 -91 -92 -93 -94 -9
5 -96 -97 -98 -99 -100 -101 -102 -103 -104 -105 -106:149 +0x10c fp=0x314476dc
code.google.com/p/go-sqlite/go1/sqlite3._Cfunc_sqlite3_exec(0x3d4258, 0x10f47480
, 0x0, 0x0, 0x0, ...)
C:/DOCUME~1/JekabsR/LOCALS~1/Temp/go-build368528647/code.google.com/p/go
-sqlite/go1/sqlite3/_obj/_cgo_defun.c:456 +0x33 fp=0x314476e8
code.google.com/p/go-sqlite/go1/sqlite3.(*Conn).exec(0x10f2d6c0, 0x10f47480, 0x3
8 +13 +14 +15 +16 +17 +18 +19 +20 +21 +22 +23 +24 +25 +26 +27 +28 +29, 0x52f578)
C:/ProgramFiles/Go/src/pkg/code.google.com/p/go-sqlite/go1/sqlite3/sqlit
e3.go:545 +0x4c fp=0x31447704
code.google.com/p/go-sqlite/go1/sqlite3.(*Conn).Exec(0x10f2d6c0, 0x10f47480, +3
0 +31 +32 +33 +34 +35 +36 +37 +38 +39 +40 +41 +42 +43 +44 +47 -48 -490x39, 0x0,
0x0, ...)
C:/ProgramFiles/Go/src/pkg/code.google.com/p/go-sqlite/go1/sqlite3/sqlit
e3.go:231 +0xd2 fp=0x31447764
main.func┬Ę001( -50 -51 -52 -53 -54 -55 -56 +1 -107 -108 -109 -110 -111 -112 -11
3 -114 -115 -1160x2d)
C:/Program Files/Go/src/pkg/development/multitaskingdb/multitaskingdb.go
:52 +0xa2 fp=0x314477c4
runtime.goexit()
C:/Program Files/Go/src/pkg/runtime/proc.c:1394 -117 -118 -119 -120 -121
-122 -123 -124 -125 -126 -127 -128 +12 fp=0x314477c8
created by main.main
C:/Program Files/Go/src/pkg/development/multitaskingdb/multitaskingdb.go
:57 +0x417
goroutine 1 [sleep]:
time.Sleep(0xb2d05e00, 0x0)
C:/Program Files/Go/src/pkg/runtime/time.goc:31 +0x3b
main.main()
C:/Program Files/Go/src/pkg/development/multitaskingdb/multitaskingdb.go
:61 +0x453
goroutine 3 [syscall]:
runtime.goexit()
C:/Program Files/Go/src/pkg/runtime/proc.c:1394
goroutine 49 [syscall]:
code.google.com/p/go-sqlite/go1/sqlite3._Cfunc_sqlite3_exec(0x3d4258, 0x10f47500
, 0x0, 0x0, 0x0, ...)
C:/DOCUME~1/JekabsR/LOCALS~1/Temp/go-build368528647/code.google.com/p/go
-sqlite/go1/sqlite3/_obj/_cgo_defun.c:456 +0x33
code.google.com/p/go-sqlite/go1/sqlite3.(*Conn).exec(0x10f2d6c0, 0x10f47500, 0x3
8, 0x52f578)
C:/ProgramFiles/Go/src/pkg/code.google.com/p/go-sqlite/go1/sqlite3/sqlit
e3.go:545 +0x4c
code.google.com/p/go-sqlite/go1/sqlite3.(*Conn).Exec(0x10f2d6c0, 0x10f47500, 0x3
9, 0x0, 0x0, ...)
C:/ProgramFiles/Go/src/pkg/code.google.com/p/go-sqlite/go1/sqlite3/sqlit
e3.go:231 +0xd2
main.func┬Ę001(0x2e)
C:/Program Files/Go/src/pkg/development/multitaskingdb/multitaskingdb.go
:52 +0xa2
created by main.main
C:/Program Files/Go/src/pkg/development/multitaskingdb/multitaskingdb.go
:57 +0x417
fatal error: panic during malloc
[signal 0xc0000005 code=0x0 addr=0x20 pc=0x41b60a]
runtime stack:
runtime.panic(0x520a80, 0x673aaf)
C:/Program Files/Go/src/pkg/runtime/panic.c:233 +0x2b
invalid spdelta 364736 -1
runtime: unexpected return pc for sqlite3BtreeInsert called from 0x1500
其中问题是什么？
推荐答案
根据sqlite3包的文档，每个goroutine应该有一个连接，而不是一个连接由几个goroutines共享。
According to the documentation of the sqlite3 package, you should have one connection per goroutine and not a single connection shared by several goroutines.
从：
单个连接实例及其所有派生的
对象（预处理语句，备份操作等）
同时来自多个goroutine，无需外部
同步。唯一的例外是Conn.Interrupt（），它可能是另一个goroutine调用的
中止长时间运行的操作。即使
正在访问同一个数据库文件，同时使用不同的连接实例也是
。例如：
A single connection instance and all of its derived objects (prepared statements, backup operations, etc.) may NOT be used concurrently from multiple goroutines without external synchronization. The only exception is Conn.Interrupt(), which may be called from another goroutine to abort a long-running operation. It is safe to use separate connection instances concurrently, even if they are accessing the same database file. For example:
// ERROR (without any extra synchronization)
c, _ := sqlite3.Open("sqlite.db")
go use(c)
go use(c)
// OK
c1, _ := sqlite3.Open("sqlite.db")
c2, _ := sqlite3.Open("sqlite.db")
go use(c1)
go use(c2)
这篇关于模拟对sqlite数据库的多个请求，因为goroutine导致随机恐慌的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！