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Golang / MGO —恐慌:没有可访问的服务器

go

我有以下连接到Mongo的功能。为了进行测试,我关闭了mongod,并希望允许该程序在w / 0
mongo不可用的情况下继续运行。如果无法连接服务器,MGO似乎会引发紧急情况,因此我在下面编写了一个延迟/恢复操作,但是紧急情况仍然导致程序退出。从中恢复的正确方法是什么?

func connectToMongo(sess *mgo.Session, coll *mgo.Collection, sessionErr error) bool {
    fmt.Println("enter main - connecting to mongo")

    // tried doing this - doesn't work as intended
    defer func() {
        if r := recover(); r != nil {
            var ok bool
            err, ok := r.(error)
            if !ok {
                fmt.Printf("pkg:  %v,  error: %s", r, err)
            }
        }
        return false
    }()

    maxWait := time.Duration(5 * time.Second)
    sess, sessionErr = mgo.DialWithTimeout("localhost", maxWait)
    if sessionErr == nil {
        session.SetMode(mgo.Monotonic, true)
        coll = session.DB("MyDB").C("MyCollection")
    } else { // never gets here
        fmt.Println("Unable to connect to local mongo instance!")
    }
    return true
}

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2020-07-02

共1个答案

小编典典

运行您发布的代码的以下版本。尽量不要修改代码,至少不要更改行号的位置。这样,如果您发布堆栈跟踪,则数字将匹配。

package main

import (
    "fmt"
    "time"
)

import (
    "labix.org/v2/mgo"
)

func connectToMongo() bool {
    ret := false
    fmt.Println("enter main - connecting to mongo")

    // tried doing this - doesn't work as intended
    defer func() {
        if r := recover(); r != nil {
            fmt.Println("Detected panic")
            var ok bool
            err, ok := r.(error)
            if !ok {
                fmt.Printf("pkg:  %v,  error: %s", r, err)
            }
        }
    }()

    maxWait := time.Duration(5 * time.Second)
    session, sessionErr := mgo.DialWithTimeout("localhost:27017", maxWait)
    if sessionErr == nil {
        session.SetMode(mgo.Monotonic, true)
        coll := session.DB("MyDB").C("MyCollection")
        if ( coll != nil ) {
            fmt.Println("Got a collection object")
            ret = true
        }
    } else { // never gets here
        fmt.Println("Unable to connect to local mongo instance!")
    }
    return ret
}

func main() {
    if ( connectToMongo() ) {
        fmt.Println("Connected")
    } else {
        fmt.Println("Not Connected")
    }
}

当MongoDB启动时,我看到:

enter main - connecting to mongo
Got a collection object
Connected

当MongoDB关闭时,我看到:

enter main - connecting to mongo
Unable to connect to local mongo instance!
Not Connected

如果您没有看到相同的行为,请发布输出,包括看到的恐慌。

2020-07-02