调试卡死程序

Question

I wrote the following ETL tool which gets data from Mysql, convert into JSON & print it on the screen

package main

import (
    "bytes"
    "database/sql"
    "encoding/json"
    "fmt"
    "log"
    "strconv"
    "strings"
    "time"

    _ "github.com/go-sql-driver/mysql"
)

const dbformat = "2006-01-02 15:04:05"

type MysqlReceipt struct {
    Id               int
    Amount           sql.NullFloat64
    Cc_last4         sql.NullString
    Employee_id      sql.NullString
    Employee_name    sql.NullString
    Is_test          byte
    Menu_items       sql.NullString
    Payable          sql.NullFloat64
    Pos_type         sql.NullString
    Pos_version      sql.NullString
    Punchh_key       string
    Receipt_datetime sql.NullString
    Subtotal_amount  sql.NullFloat64
    Transaction_no   sql.NullString
    Business_id      int
    Location_id      int
    Created_at       string
    Updated_at       sql.NullString
    Revenue_code     sql.NullString
    Revenue_id       sql.NullString
    Status           sql.NullString
    Ipv4_addr        sql.NullString
}

type Menu_item struct {
    id, name, family, major_group, item_type string
    qty                                      int
    amount                                   float64
}

type BigReceipt struct {
    Id                       int
    Amount                   float64
    Cc_last4                 string
    Employee_id              string `json:",omitempty"`
    Employee_name            string `json:",omitempty"`
    Is_test                  byte
    Menu_item_name           string
    Menu_item_id             string
    Menu_item_amount         float64
    Menu_item_family         string
    Menu_item_major_group    string
    Menu_item_type           string
    Menu_item_qty            int
    Payable                  float64
    Pos_type                 string `json:",omitempty"`
    Pos_version              string `json:",omitempty"`
    Punchh_key               string
    Receipt_datetime         string
    Subtotal_amount          float64
    Transaction_no           string `json:",omitempty"`
    Business_id, Location_id int
    Created_at               time.Time
    Updated_at               time.Time `json:",omitempty"`
    Revenue_code             string    `json:",omitempty"`
    Revenue_id               string    `json:",omitempty"`
    Status                   string    `json:",omitempty"`
    Ipv4_addr                string    `json:",omitempty"`
    Stored_at                int64
}

func (m Menu_item) ValidItem() bool {
    if m.item_type == "M" || m.item_type == "D" {
        return true
    } else {
        return false
    }
}

func main() {
    db, err := sql.Open("mysql", "root:password@tcp(xxxxxxx.us-east-1.rds.amazonaws.com:3306)/db_name_goes_here")
    if err != nil {
        log.Fatal(err)
    }
    err = db.Ping()
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()
    rows, err := db.Query(`select id,amount,cc_last4,employee_id,employee_name,is_test,menu_items,payable,pos_type,
    pos_version,punchh_key,receipt_datetime,subtotal_amount,transaction_no,business_id,location_id,created_at,
    updated_at,revenue_code,revenue_id,status,ipv4_addr from receipts`)
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()
    for rows.Next() {
        var mr MysqlReceipt
        err = rows.Scan(&mr.Id, &mr.Amount, &mr.Cc_last4, &mr.Employee_id, &mr.Employee_name, &mr.Is_test, &mr.Menu_items,
            &mr.Payable, &mr.Pos_type, &mr.Pos_version, &mr.Punchh_key, &mr.Receipt_datetime, &mr.Subtotal_amount, &mr.Transaction_no,
            &mr.Business_id, &mr.Location_id, &mr.Created_at, &mr.Updated_at, &mr.Revenue_code, &mr.Revenue_id, &mr.Status, &mr.Ipv4_addr)
        if err != nil {
            log.Fatal(err)
        }
        if !mr.Menu_items.Valid {
            continue
        }
        r := BigReceipt{Id: mr.Id,
            Amount:           mr.Amount.Float64,
            Cc_last4:         mr.Cc_last4.String,
            Employee_id:      mr.Employee_id.String,
            Employee_name:    mr.Employee_name.String,
            Is_test:          mr.Is_test,
            Payable:          mr.Payable.Float64,
            Pos_type:         mr.Pos_type.String,
            Pos_version:      mr.Pos_version.String,
            Punchh_key:       mr.Punchh_key,
            Receipt_datetime: mr.Receipt_datetime.String,
            Subtotal_amount:  mr.Subtotal_amount.Float64,
            Transaction_no:   mr.Transaction_no.String,
            Business_id:      mr.Business_id,
            Location_id:      mr.Location_id,
            Revenue_code:     mr.Revenue_code.String,
            Revenue_id:       mr.Revenue_id.String,
            Status:           mr.Status.String,
            Ipv4_addr:        mr.Ipv4_addr.String,
            Stored_at:        time.Now().Unix(),
        }
        r.Created_at = datetimeParse(mr.Created_at)
        if mr.Updated_at.Valid {
            r.Updated_at = datetimeParse(mr.Updated_at.String)
        }
        menuItems := strings.Split(mr.Menu_items.String, "^")
        items := parseMenuItems(menuItems)
        for _, v := range items {
            r.Menu_item_name = v.name
            r.Menu_item_id = v.id
            r.Menu_item_amount = v.amount
            r.Menu_item_family = v.family
            r.Menu_item_major_group = v.major_group
            r.Menu_item_type = v.item_type
            r.Menu_item_qty = v.qty
            b, err := json.Marshal(r)
            if err != nil {
                log.Fatal(err)
            }
            fmt.Println(r.Id)
            var out bytes.Buffer
            json.Compact(&out, b)
            fmt.Println(string(b))
        }
    }
    err = rows.Err()
    if err != nil {
        log.Fatal(err)
    }
}

func datetimeParse(dateStr string) time.Time {
    datetime, err := time.Parse(dbformat, dateStr)
    if err != nil {
        log.Fatal(err)
    }
    return datetime
}

func parseMenuItems(menuItems []string) []Menu_item {
    var items []Menu_item
    var item Menu_item
    for _, v := range menuItems {
        itemParts := strings.Split(v, "|")

        item.name = itemParts[0]
        item.qty, _ = strconv.Atoi(itemParts[1])
        item.amount, _ = strconv.ParseFloat(itemParts[2], 64)
        item.item_type = strings.ToUpper(itemParts[3])
        item.id = itemParts[4]
        item.family = itemParts[5]
        item.major_group = itemParts[6]
        if item.ValidItem() {
            items = append(items, item)
        } else {
            continue
        }
    }
    return items
}

Now, This works fine for test database but in production database where there are millions of rows, it gets stuck after fetching 1,000 rows & stops printing on screen. I left it running for the night.

In morning, I sent it QUIT signal & got the following stack trace

SIGQUIT: quit
PC=0x5fecb m=0

goroutine 0 [idle]:
runtime.mach_semaphore_wait(0xe03, 0x0, 0x0, 0x0, 0x0, 0x407520, 0x52db9, 0xffffffffffffffff, 0x0, 0x7fff5fbff0fc, ...)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/sys_darwin_amd64.s:407 +0xb
runtime.semasleep1(0xffffffffffffffff, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/os1_darwin.go:385 +0xe5
runtime.semasleep.func1()
    /usr/local/Cellar/go/1.5/libexec/src/runtime/os1_darwin.go:401 +0x29
runtime.systemstack(0x7fff5fbff100)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/asm_amd64.s:278 +0xab
runtime.semasleep(0xffffffffffffffff, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/os1_darwin.go:402 +0x36
runtime.notesleep(0x407970)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/lock_sema.go:169 +0x100
runtime.stopm()
    /usr/local/Cellar/go/1.5/libexec/src/runtime/proc1.go:1128 +0x112
runtime.findrunnable(0xc82001d500, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/proc1.go:1530 +0x69e
runtime.schedule()
    /usr/local/Cellar/go/1.5/libexec/src/runtime/proc1.go:1639 +0x267
runtime.park_m(0xc820000180)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/proc1.go:1698 +0x18b
runtime.mcall(0x7fff5fbff280)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/asm_amd64.s:204 +0x5b

goroutine 1 [IO wait]:
net.runtime_pollWait(0x7a1000, 0x72, 0xc82000a2d0)
    /usr/local/Cellar/go/1.5/libexec/src/runtime/netpoll.go:157 +0x60
net.(*pollDesc).Wait(0xc8200a4060, 0x72, 0x0, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/net/fd_poll_runtime.go:73 +0x3a
net.(*pollDesc).WaitRead(0xc8200a4060, 0x0, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/net/fd_poll_runtime.go:78 +0x36
net.(*netFD).Read(0xc8200a4000, 0xc820372077, 0x3f89, 0x3f89, 0x0, 0x760050, 0xc82000a2d0)
    /usr/local/Cellar/go/1.5/libexec/src/net/fd_unix.go:232 +0x23a
net.(*conn).Read(0xc8200a6000, 0xc820372077, 0x3f89, 0x3f89, 0x0, 0x0, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/net/net.go:172 +0xe4
github.com/go-sql-driver/mysql.(*buffer).fill(0xc820080080, 0x102, 0x0, 0x0)
    /Users/gaurish/golang/src/github.com/go-sql-driver/mysql/buffer.go:57 +0x2b5
github.com/go-sql-driver/mysql.(*buffer).readNext(0xc820080080, 0x102, 0x0, 0x0, 0x0, 0x0, 0x0)
    /Users/gaurish/golang/src/github.com/go-sql-driver/mysql/buffer.go:86 +0x55
github.com/go-sql-driver/mysql.(*mysqlConn).readPacket(0xc820080080, 0x0, 0x0, 0x0, 0x0, 0x0)
    /Users/gaurish/golang/src/github.com/go-sql-driver/mysql/packets.go:57 +0x47a
github.com/go-sql-driver/mysql.(*mysqlConn).readUntilEOF(0xc820080080, 0x0, 0x0)
    /Users/gaurish/golang/src/github.com/go-sql-driver/mysql/packets.go:698 +0x2d
github.com/go-sql-driver/mysql.(*mysqlRows).Close(0xc8200a0120, 0x0, 0x0)
    /Users/gaurish/golang/src/github.com/go-sql-driver/mysql/rows.go:67 +0x73
database/sql.(*Rows).Close(0xc8200aa060, 0x0, 0x0)
    /usr/local/Cellar/go/1.5/libexec/src/database/sql/sql.go:1710 +0x92
main.parseMenuItems(0xc82036e480, 0x44, 0x44, 0x0, 0x0, 0x0)
    /Users/gaurish/code/practice/mysql2json/mysql2json.go:186 +0x468
main.main()
    /Users/gaurish/code/practice/mysql2json/mysql2json.go:142 +0xf2e

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
    /usr/local/Cellar/go/1.5/libexec/src/runtime/asm_amd64.s:1696 +0x1

goroutine 5 [chan receive]:
database/sql.(*DB).connectionOpener(0xc820088960)
    /usr/local/Cellar/go/1.5/libexec/src/database/sql/sql.go:634 +0x45
created by database/sql.Open
    /usr/local/Cellar/go/1.5/libexec/src/database/sql/sql.go:481 +0x336

rax    0xe
rbx    0xe03
rcx    0x7fff5fbff088
rdx    0x7fff5fbff100
rdi    0xe03
rsi    0x407520
rbp    0x407860
rsp    0x7fff5fbff088
r8     0x407860
r9     0x0
r10    0x0
r11    0x286
r12    0x2c
r13    0x4fc3ed4b8b0
r14    0x14059837c8b46200
r15    0x38
rip    0x5fecb
rflags 0x286
cs     0x7
fs     0x0
gs     0x0
exit status 2

Further, I tried debugging it further by commenting out the defer rows.Close() call. now after 1,000 rows or so, instead of stalling, it immediately returns the following error:

panic: runtime error: index out of range

goroutine 1 [running]:
main.parseMenuItems(0xc820366900, 0x44, 0x44, 0x0, 0x0, 0x0)
    /Users/gaurish/code/practice/mysql2json/mysql2json.go:186 +0x468
main.main()
    /Users/gaurish/code/practice/mysql2json/mysql2json.go:142 +0xf03

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
    /usr/local/Cellar/go/1.5/libexec/src/runtime/asm_amd64.s:1696 +0x1

goroutine 5 [runnable]:
database/sql.(*DB).connectionOpener(0xc820088780)
    /usr/local/Cellar/go/1.5/libexec/src/database/sql/sql.go:634 +0x45
created by database/sql.Open
    /usr/local/Cellar/go/1.5/libexec/src/database/sql/sql.go:481 +0x336
exit status 2

Questions:

1. Why does it get stuck immediately after fetching 1,000(appox) rows?
2. How does commenting out defer rows.Close() stops from getting stuck & panics immediately?
3. Is there is a better way to write this program?

Lastly, I am sorry if any of the above these are stupid questions or question is too long. I am new to Go & trying to learn.

Answer 1

This was a issue with the driver. Fixed it by removing the defer call & checking the array bounds.