pipelines

Background

pipelines was created as a simple interface for developing and modifying CI pipelines at Viaduct. Its a lightweight wrapper on Go channels for specifying dependencies between, running, and gracefully shutting down asynchronous processes. pipelines gives developers a intuitive way to declare dependencies amongst concurrent processes to create a pipeline (DAG) and a structured way to add new or modify existing functionality.

Overview

Example

Below is an example pipeline that polls the Github Status API every minute, filters for statuses that indicate degregaded services, then notifies the engineering team via Slack and email.

package main

import (
  "encoding/json"
  "net/http"
  "net/smtp"
  "time"

  "github.com/viaduct-ai/pipelines/processor"
  "github.com/viaduct-ai/pipelines"
)

const (
  githubStatusAPI = "https://kctbh9vrtdwd.statuspage.io/api/v2/status.json"
  // fake webhook
  slackWebhookURL = "https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX"
)

type GithubStatusAPIResp struct {
  Status GithubStatus `json:"status"`
}
type GithubStatus struct {
  Description string `json:"description"`
  Indicator string `json:"indicator"`
}

func main() {
  minuteTicker, err := processor.NewTicker(time.Minute)
  getGithuStatusProc, err := processor.New(getGithubStatus, nil, 0)
  githubOutages, err := processor.New(filterForOutages, nil, 0)
  slackAlertProc, err := processor.New(slackAlert, nil, 0)
  emailAlertProc, err := processor.New(emailAlert, nil, 0)

  pipeline := pipelines.New()

  // Get Github's status every minute
  pipeline.Process(getGithubStatusProc).Consumes(minuteTicker)
  // Check Github status for outages
  pipeline.Process(githubOutages).Consumes(getGithubStatusProc)
  // Slack & Email alerts consume Github outage events
  pipeline.Processes(slackAlert, emailAlert).Consumes(githubOutages)

  // Start the pipeline
  pipeline.Run()

  // Wait for a termination signal
  sigs := make(chan os.Signal, 1)
  signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
  <-sigs

  // Gracefully shutdown all processes in the Pipeline
  pipeline.Shutdown()
}

func getGithubStatus(i interface{}) (interface{}, error) {
  var result GithubStatusAPIResp

  resp, err := http.Get(githubStatusAPI)

  if err != nil {
    return result, error
  }
  defer resp.Body.Close()

  json.NewDecoder(resp.Body).Decode(&result)

  return interface{}(result)
}

func filterForOutages(i interface{}) (interface{}, error) {
  switch v := i.(type) {
    case GithubStatusAPIResp:
      // none, minor, major, or critical
      if indicator := v.Status.Indicator; indicator == "none" {
        return nil, nil
      }
      return i, nil
    default:
      return nil, nil
  }
}

type SlackRequestBody struct {
    Text string `json:"text"`
}


func slackAlert(i interface{}) (interface{}, error) {
  msg := "Heads up! Github is experience issues."
  slackBody, _ := json.Marshal(SlackRequestBody{Text: msg})
  req, err := http.NewRequest(http.MethodPost, webhookUrl, bytes.NewBuffer(slackBody))
  if err != nil {

      return err
  }

  req.Header.Add("Content-Type", "application/json")

  client := &http.Client{Timeout: 10 * time.Second}
  resp, err := client.Do(req)
  if err != nil {
      return nil, err
  }

  buf := new(bytes.Buffer)
  buf.ReadFrom(resp.Body)
  if buf.String() != "ok" {
      return nil, errors.New("Non-ok response returned from Slack")
  }

  return nil, nil
}

func emailAlert(i interface{})(interface{}, error){
	// Choose auth method and set it up
  auth := smtp.PlainAuth(
		"",
		"[email protected]",
		"password",
		"mail.example.com",
	)

  to := []string{"[email protected]"}
  msg := []byte(
	  "Subject: Expect Issues with Github\r\n" +
	  "Github is down. Go home.")
  err := smtp.SendMail("mail.example.com:25", auth, "[email protected]", to, msg)

  return nil, err
}

Filtering

A nil value returned from Processor.Process will be implicitly filtered and not sent to any of its consumers. For example, if you had many Processors that only care about a Github push events, then you could create a upstream Processor that consumes all Github events but returns nil for any non push event.

Error Handling

Currently, all errors returned by Processor.Process will be ignored and logged to stderr. This is subject to change in the future.