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)