How to Handle Panic in Go's MGO DialWithTimeout() Failure?

Handling Panic in Go's MGO: DialWithTimeout() Failure

Consider the following situation: you have a Go function that connects to a MongoDB instance using the mgo library. However, you want to handle the case where MongoDB is unavailable without crashing the program.

The original code attempts to achieve this by using a defer/recover mechanism. However, the panic still causes the program to exit. Let's explore a revised approach:

package main

import (
    "fmt"
    "time"
)

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

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

    // Handle panic
    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")
    }
}

In this revised code:

• The defer block now explicitly calls recover() and handles the recovered value (panic) as an error. This panic recovery prevents the program from exiting.
• The DialWithTimeout function is called with the correct MongoDB host and port (in this example, localhost:27017).
• The program prints a message to indicate whether it successfully connected to MongoDB or not.

By implementing this error handling mechanism, you can gracefully handle the situation where MongoDB is unavailable without crashing your program. This allows your application to continue processing other tasks or gracefully fail with a descriptive error message.

The above is the detailed content of How to Handle Panic in Go's MGO DialWithTimeout() Failure?. For more information, please follow other related articles on the PHP Chinese website!