Golang Service Helpers

• Log Structured logging
• Handlers http request middleware to add logging (healthd, context, statsd, structured logs)
• Metrics send monitoring metrics to collectors (currently: stats)
• NetTest helpers for use when testing networks
• Validation to ensure the user input is correct

Log

Handle global logging with context. Based on logrus incorporating golang's context.context

It uses logfmt by default but can also output json using a &logrus.JSONFormatter()

$ go get github.com/graze/golang-service/log

Set global properties

Setting these will mean any use of the global logging context or log.New() will use these properties

log.SetFormatter(&logrus.TextFormatter()) // default
log.SetOutput(os.Stderr) // default
log.SetLevel(log.InfoLevel) // default
log.AddFields(log.KV{"service":"super_service"}) // apply `service=super_service` to each log message

logging using the global logger

log.With(log.KV{
    "module": "request_handler",
    "tag":    "received_request"
    "method": "GET",
    "path":   "/path"
}).Info("Received request");

Example:

time="2016-10-28T10:51:32Z" level=info msg="Received request" module="request_handler" tag="received_request" method=GET path=/path service="super_service"

Log using a local field store

logger := log.New()
logger.Add(log.KV{
    "module": "request_handler"
})
logger.With(log.KV{
    "tag":    "received_request",
    "method": "GET",
    "path":   "/path"
}).Info("Received GET /path")
logger.Err(err).Error("Failed to handle input request")

time="2016-10-28T10:51:32Z" level=info msg="Received GET /path" tag="received_request" method=GET path=/path module="request_handler"

Log using a context

The logger can use golang's context to pass around fields

logger := log.New()
logger.Add(log.KV{"module": "request_handler"})
ctx := logger.NewContext(context.Background())
log.Ctx(ctx).
    With(log.KV{"tag": "received_request"}).
    Info("Received request")

time="2016-10-28T10:51:32Z" level=info msg="Received request" tag="received_request" module="request_handler"

The context can be applied to another local logger

logger := log.New()
logger.Add(log.KV{"module": "request_handler"})
ctx := logger.NewContext(context.Background())

logger2 := log.New()
logger2.SetOutput(os.Stderr)
logger2.Add(log.KV{"tag": "received_request"})
logger2.Ctx(ctx).Info("Received request")

time="2016-10-28T10:51:32Z" level=info msg="Received request" tag="received_request" module="request_handler"

Modifying a loggers properties

logger := log.New()
logger.SetFormatter(&logrus.JSONFormatter{})
logger.SetLevel(log.DebugLevel)
logger.SetOutput(os.Stdout)

logger.Debug("some debug output printed")

logger implements the log.Logger interface which includes SetFormatter, SetLevel, SetOutput, Level and AddHook

{"time":"2016-10-28T10:51:32Z","level":"debug","msg":"some debug output printed"}

Handlers

Collection of middleware handlers for use by HTTP services

$ go get github.com/graze/golang-service/handlers

Context Adder

log a logging context is stored within the request context.

r := mux.NewRouter()
r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    ctx := r.Context()

    log.Ctx(ctx).With(log.KV{"module":"get"}).Info("logging GET")
}

http.ListenAndServe(":1234", handlers.LogContextHandler(r))

Output:

time="2016-10-28T10:51:32Z" level=info msg="Logging GET" dur=0.00881 http.host="localhost:1234" http.method=GET http.path="/" http.protocol="HTTP/1.1" http.uri="/" module=get transaction=8ba382cc-5c42-441c-8f48-11029d806b9a

Healthd Logger

• Support the healthd logs from AWS Elastic Beanstalk logs: AWS

By default it writes entries to the location: /var/log/nginx/healthd/application.log.<year>-<month>-<day>-<hour>. Using the handlers.HealthdIoHandler(io.Writer, http.Handler) will write to a custom path

see http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/health-enhanced-serverlogs.html

Example:

r := mux.NewRouter()
r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("This is a catch-all route"))
})
loggedRouter := handlers.HealthdHandler(r)
http.ListenAndServe(":1123", loggedRouter)

Statsd Logger

• Output response_time and count statistics for each request to a statsd host

This will output to StatsD using the following variables

Environment Variables:

    STATSD_HOST: The host of the statsd server
    STATSD_PORT: The port of the statsd server
    STATSD_NAMESPACE: The namespace to prefix to every metric name
    STATSD_TAGS: A comma separared list of tags to apply to every metric reported

Example:

    STATSD_HOST: localhost
    STATSD_PORT: 8125
    STATSD_NAMESPACE: app.live.
    STATSD_TAGS: env:live,version:1.0.2

Usage:

r := mux.NewRouter()
r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
   w.Write([]byte("This is a catch-all route"))
})
loggedRouter := handlers.StatsdHandler(r)
http.ListenAndServe(":1123", loggedRouter)

To use a manually created statsd client:

c, _ := statsd.New("127.0.0.1:8125")
loggedRouter := handlers.StatsdHandler(c, r)

Structured Request Logger

This outputs a structured log entry for each request send to the http server

r := mux.NewRouter()
r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("This is a catch-all route"))
})
loggedRouter := handlers.StructuredLogHandler(
    log.With(log.KV{"module":"request.handler"}),
    r)
http.ListenAndServe(":1123", loggedRouter)

Default Output:

time="2016-10-28T10:51:32Z" level=info msg="GET / HTTP/1.1" dur=0.003200881 http.bytes=80 http.host="localhost:1123" http.method=GET http.path="/" http.protocol="HTTP/1.1" http.ref= http.status=200 http.uri="/" http.user= module=request.handler tag="request_handled" ts="2016-10-28T10:51:31.542424381Z"

Metrics

Provides statsd metrics sending

Manually create a client

client, _ := metrics.GetStatsd(StatdClientConf{host,port,namespace,tags})
client.Incr("metric", []string{}, 1)

Create a client using environment variables. see above

client, _ := metrics.GetStatsdFromEnv()
client.Incr("metric", []string{}, 1)

NetTest

Network helpers when for testing against networks

$ go get github.com/graze/golang-service/nettest

done := make(chan string)
addr, sock, srvWg := nettest.CreateServer(t, "tcp", ":0", done)
defer srvWg.Wait()
defer os.Remove(addr.String())
defer sock.Close()

s, err := net.Dial("tcp", addr.String())
fmt.Fprintf(s, msg + "\n")
if msg = "\n" != <-done {
    panic("message mismatch")
}

Validation

A very simple validation for user input

$ go get github.com/graze/golang-service/validate

It uses the interface: Validator containing the method Validate which will return an error if the item is not valid

type Validator interface {
    Validate(ctx context.Context) error
}

type Item struct {
    Name        string `json:"name"`
    Description string `json:"description"`
    Winning     bool   `json:"winning"`
}
func (i Item) Validate(ctx context.Context) error {
    if utf8.RuneCountInString(i.Name) <= 3 {
        return fmt.Errorf("field: name must have more than 3 characters")
    }
    return nil
}

func CreateItem(w http.ResponseWriter, r *http.Request) {
    item := &Item{}
    if err := validate.JsonRequest(ctx, r, item); err != nil {
        w.WriteHeader(400)
        return
    }

    // item.Name, item.Description, item.Winning etc...
}

Development

Testing

To run tests, run this on your host machine:

$ make install
$ make test

License

• General code: MIT License
• some code: Copyright (c) 2013 The Gorilla Handlers Authors. All rights reserved.