This repository contains two Golang templates for OpenFaaS which give additional control over the HTTP request and response. They will both handle higher throughput than the classic watchdog due to the process being kept warm.
Using the templates:
faas-cli template store pull golang-http
faas-cli template store pull golang-middleware
Or:
$ faas template pull https://github.com/openfaas-incubator/golang-http-template
$ faas new --list
Languages available as templates:
- golang-http
- golang-middleware
The two templates are equivalent with golang-http
using a structured request/response object and the alternative implementing a Golang http.HandleFunc
from the Golang stdlib. golang-http
is more "conventional" for a Golang serverless template but this is a question of style/taste.
You can manage dependencies in one of the following ways:
- To use Go modules without vendoring, the default already is set
GO111MODULE=on
but you also can make that explicit by adding--build-arg GO111MODULE=on
tofaas-cli up
, you can also use--build-arg GOPROXY=https://
if you want to use your own mirror for the modules - You can also Go modules with vendoring, run
go mod vendor
in your function folder and add--build-arg GO111MODULE=off --build-arg GOFLAGS='-mod=vendor'
tofaas-cli up
- If you have a private module dependency, we recommend using the vendoring technique from above.
If a folder named static
is found in the root of your function's source code, it will be copied into the final image published for your function.
To read this back at runtime, you can do the following:
package function
import (
"io/ioutil"
"net/http"
)
func Handle(w http.ResponseWriter, r *http.Request) {
data, err := ioutil.ReadFile("./static/file.txt")
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
w.Write(data)
}
This template provides additional context and control over the HTTP response from your function.
This template is the most performant and recent Golang template for OpenFaaS which also provides a function-style request and response for the user.
$ faas template store pull golang-http
# Or
$ faas template pull https://github.com/openfaas-incubator/golang-http-template
$ faas new --lang golang-http <fn-name>
Example writing a successful message:
package function
import (
"fmt"
"net/http"
"github.com/openfaas-incubator/go-function-sdk"
)
// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
var err error
message := fmt.Sprintf("Hello world, input was: %s", string(req.Body))
return handler.Response{
Body: []byte(message),
}, err
}
Example writing a custom status code
package function
import (
"fmt"
"net/http"
"github.com/openfaas-incubator/go-function-sdk"
)
// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
var err error
return handler.Response{
Body: []byte("Your workload was accepted"),
StatusCode: http.StatusAccepted,
}, err
}
Example writing an error / failure.
package function
import (
"fmt"
"net/http"
"github.com/openfaas-incubator/go-function-sdk"
)
// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
var err error
return handler.Response{
Body: []byte("the input was invalid")
}, fmt.Errorf("invalid input")
}
The error will be logged to stderr
and the body
will be written to the client along with a HTTP 500 status code.
Example reading a header.
package function
import (
"log"
"github.com/openfaas-incubator/go-function-sdk"
)
// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
var err error
log.Println(req.Header) // Check function logs for the request headers
return handler.Response{
Body: []byte("This is the response"),
Header: map[string][]string{
"X-Served-By": []string{"My Awesome Function"},
},
}, err
}
Example responding to an aborted request.
The Request
object provides access to the request context. This allows you to check if the request has been cancelled by using the context's done channel req.Context().Done()
or the context's error req.Context().Err()
package function
import (
"fmt"
"net/http"
handler "github.com/openfaas-incubator/go-function-sdk"
)
// Handle a function invocation
func Handle(req handler.Request) (handler.Response, error) {
var err error
for i := 0; i < 10000; i++ {
if req.Context().Err() != nil {
return handler.Response{}, fmt.Errorf("request cancelled")
}
fmt.Printf("count %d\n", i)
}
message := fmt.Sprintf("Hello world, input was: %s", string(req.Body))
return handler.Response{
Body: []byte(message),
StatusCode: http.StatusOK,
}, err
}
This context can also be passed to other methods so that they can respond to the cancellation as well, for example db.ExecContext(req.Context())
This template uses the http.HandlerFunc as entry point.
Like the golang-http template, this is one of the fastest templates available, but takes a more service-orientated approach to its signature. Instead of looking like a traditional function, the user has complete control over the HTTP request and response.
$ faas template store pull golang-middleware
# Or
$ faas template pull https://github.com/openfaas-incubator/golang-http-template
$ faas new --lang golang-middleware <fn-name>
Example writing a JSON response:
package function
import (
"encoding/json"
"fmt"
"io"
"net/http"
"os"
)
func Handle(w http.ResponseWriter, r *http.Request) {
var input []byte
if r.Body != nil {
defer r.Body.Close()
// read request payload
reqBody, err := io.ReadAll(r.Body)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
input = reqBody
}
}
// log to stdout
fmt.Printf("request body: %s", string(input))
response := struct {
Payload string `json:"payload"`
Headers map[string][]string `json:"headers"`
Environment []string `json:"environment"`
}{
Payload: string(input),
Headers: r.Header,
Environment: os.Environ(),
}
resBody, err := json.Marshal(response)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
// write result
w.WriteHeader(http.StatusOK)
w.Write(resBody)
}
Example persistent database connection pool between function calls:
package function
import (
"database/sql"
"fmt"
"io"
"net/http"
"strings"
_ "github.com/go-sql-driver/mysql"
)
// db pool shared between function calls
var db *sql.DB
func init() {
var err error
db, err = sql.Open("mysql", "user:password@/dbname")
if err != nil {
panic(err.Error())
}
err = db.Ping()
if err != nil {
panic(err.Error())
}
}
func Handle(w http.ResponseWriter, r *http.Request) {
var query string
ctx := r.Context()
if r.Body != nil {
defer r.Body.Close()
// read request payload
body, err := io.ReadAll(r.Body)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
query = string(body)
}
// log to stdout
fmt.Printf("Executing query: %s", query)
rows, err := db.QueryContext(ctx, query)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
defer rows.Close()
ids := make([]string, 0)
for rows.Next() {
if e := ctx.Err(); e != nil {
http.Error(w, e, http.StatusBadRequest)
return
}
var id int
if err := rows.Scan(&id); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
ids = append(ids, string(id))
}
if err := rows.Err(); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
result := fmt.Sprintf("ids %s", strings.Join(ids, ", "))
// write result
w.WriteHeader(http.StatusOK)
w.Write([]byte(result))
}
Example retrieving request query strings
package function
import (
"fmt"
"net/http"
)
func Handle(w http.ResponseWriter, r *http.Request) {
// Parses RawQuery and returns the corresponding
// values as a map[string][]string
// for more info https://golang.org/pkg/net/url/#URL.Query
query := r.URL.Query()
w.WriteHeader(http.StatusOK)
w.Write([]byte(fmt.Sprintf("id: %s", query.Get("id"))))
}
It is often natural to organize your code into sub-packages, for example you may have a function with the following structure
./echo
├── go.mod
├── go.sum
├── handler.go
└── pkg
└── version
└── version.go
Now if you want to reference theversion
sub-package, import it as
import "handler/function/pkg/version"
This works like any local Go project.
Sub-modules (meaning sub-folders with a go.mod
) are not supported.