Pass Cassandra session reference to http handlers

Question

I'm building a golang backend using gorilla/mux and gocql. My objective is to create a session to a remote cassandra and share the very same session to a serie of handlers.

I came out with this implementation:

server.go:

package main

import (
    "fmt"
    "net/http"
    "os"

    "github.com/andream16/price-probe-go/api/item/rest"
    "github.com/andream16/price-probe-go/cassandra"
    "github.com/gorilla/mux"
)

func main() {

    fmt.Println("Initializing Cassandra connection . . .")
    s, err := cassandra.InitCassandraClient()
    if err != nil {
        fmt.Println("Unable to set up Cassandra client!")
        os.Exit(1)
    }
    fmt.Println("Successfully initialized Cassandra connection . . .")

    fmt.Println("Starting server . . .")
    router := mux.NewRouter()
    router.HandleFunc("/item", itemrest.ItemHandler(&s))

    . . .

}

I create a new HandleFunc for each route and pass it &s.

And each handler is like:

func ItemHandler(session *gocql.Session) func(w http.ResponseWriter, r *http.Request) { }

Is there a more elegant way to achieve this?

Answer 1

Yes, there definitely is a better way to do this. The easiest way would be to use reciever functions (aka methods) as handler functions. Rather than returning a handler from the ItemHandler func (bad name BTW), simple declare a handler directly.

Here's an example of how you could acchieve this:

type MyServer struct {
    cql *gocql.Session
}

func (s *MyServer) ItemHandler(w http.ResponseWriter, r *http.Request) {
    // use s.cql here
}

func New(cql *gocql.Session) (*MyServer, error) {
    s := &MyServer{
        cql: cql,
    }
    // more stuff here
    return s, nil
}

Then, in your main package, simply write this:

s, err := cassandra.InitCassandraClient()
if err != nil {
    fmt.Println("Unable to set up Cassandra client!")
    os.Exit(1)
}
// assume package name server
srv, _ := server.New(&s)
// now ItemHandler with srv as receiver is the handler
router.HandleFunc("/item", srv.ItemHandler)