Go中的“明确关闭” mgo MongoDB

Question

I have a Docker cluster running 10 web services (of the same kind). They are all using MongoDB, among other things for data persistence.

This is the code that gets called from main(), when the service is booting up:

// Init establishes a connection with MongoDB instance.
func Init(mongoURL string) *mgo.Session {
    mongo, err := mgo.Dial(mongoURL)
    misc.PanicIf(err)

    // make sure we are strongly consistent
    mongo.SetMode(mgo.Strong, true)

    // update global state
    db = mongo
    Entries = db.DB("").C("entries")
    Channels = db.DB("").C("channels")
    Settings = db.DB("").C("settings")
    Metadata = db.DB("").C("metadata")

    // only use this on first load, to confirm the settings are there
    // every refresh should be done via UpdateGlobalSettings (thread-safe)
    GlobalSettings = &GlobalSettingsStruct{}
    GlobalSettings.Init()

    return mongo
}

So basically the API and the workers just use global variables such as Entries, Settings, etc.

After running for a while, the service stopped working properly. Every mongo action, such as Entries.find(...) returns an err of: Closed Explicitly.

What does that mean? Should I be refreshing the mongoDB connection periodically or should I make it close and re-establish connection with each request?

The app is performance oriented, so despite mongo connection being down, everything is still up and running as everything operates on in-memory or cluster cache. I don't want to do something stupid that delays processing.

Answer 1

First of all try enabling debug mode in mgo in order to get some more info about what's happening.

I suppose the server is dropping the connection after some inactivity time. In any case, usually the approach is to do a mgo Dial and then Copy the connection at the beginning of every request handling(using a middleware).

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