Add slack provider for events

examples/events.md

@@ -27,4 +27,10 @@ sre/provider/grafana.go:127 Annotation 1502808. Annotation added
 
 ## DataDog UO
 ![DataDog](/examples/datadog-events.png)
-![DataDog](/examples/datadog-events2.png)
+![DataDog](/examples/datadog-events2.png)
+
+## Slack UI
+
+Send simple messages from `name` field or structured slack BlockKit json from `attributes["payload"]`(if present) 
+
+![Slack](/examples/slack-events.png)

examples/events_slack.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	_ "embed"
+	"time"
+
+	"github.com/devopsext/sre/common"
+	"github.com/devopsext/sre/provider"
+)
+
+//go:embed slack.json
+var payload []byte
+
+var logs = common.NewLogs()
+var events = common.NewEvents()
+
+func test() {
+
+	events.Now(":exclamation: First", nil)
+
+	m := make(map[string]string)
+	m["payload"] = string(payload)
+
+	events.Now(":grey_exclamation:Second", m)
+	events.Now(":grey_question: *Third*", nil)
+}
+
+func main() {
+
+	defer logs.Stop()   // finalize logs delivery
+	defer events.Stop() // finalize events delivery
+
+	// initialize Stdout logger
+	stdout := provider.NewStdout(provider.StdoutOptions{
+		Format:          "template",
+		Level:           "debug",
+		Template:        "{{.file}} {{.msg}}",
+		TimestampFormat: time.RFC3339Nano,
+		TextColors:      true,
+	})
+	// set caller offset for file:line proper usage
+	stdout.SetCallerOffset(2)
+
+	// add Stdout logger
+	logs.Register(stdout)
+
+	slack := provider.NewSlackEventer(provider.SlackOptions{
+		WebHook: "",
+		Tags:    "",
+		Timeout: 2,
+	}, logs, stdout)
+
+	// add events
+	events.Register(slack)
+
+	test()
+}

examples/slack.json

@@ -0,0 +1,35 @@
+{
+  "blocks": [
+    {
+      "type": "header",
+      "text": {
+        "type": "plain_text",
+        "text": "Daily News",
+        "emoji": true
+      }
+    },
+    {
+      "type": "divider"
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "`06:45 UTC (08:45 ETT)`:\t:grey_exclamation:\t| Germany_Industrial Orders MM"
+      }
+    },
+    {
+      "type": "section",
+      "fields": [
+        {
+          "type": "mrkdwn",
+          "text": "*Symbol*: EUR / EUR,CHF,XAG,XAU"
+        },
+        {
+          "type": "mrkdwn",
+          "text": "*Type*: Industry Sector"
+        }
+      ]
+    }
+  ]
+}

provider/slack.go

@@ -0,0 +1,84 @@
+package provider
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"github.com/devopsext/sre/common"
+	"github.com/devopsext/utils"
+	"io/ioutil"
+	"net/http"
+	"time"
+)
+
+type SlackOptions struct {
+	WebHook string
+	Tags    string
+	Timeout int
+}
+
+type SlackEventer struct {
+	options SlackOptions
+	logger  common.Logger
+	tags    []string
+	client  *http.Client
+	ctx     context.Context
+}
+
+func (se *SlackEventer) Now(name string, attributes map[string]string) {
+	se.At(name, attributes, time.Now())
+}
+
+func (se *SlackEventer) At(name string, attributes map[string]string, when time.Time) {
+	se.Interval(name, attributes, when, when)
+}
+
+func (se *SlackEventer) Interval(name string, attributes map[string]string, begin, end time.Time) {
+	var body string
+
+	body = fmt.Sprintf("{\"text\": \"%s\"}", name)
+	if payload, ok := attributes["payload"]; ok {
+		body = payload
+	}
+
+	resp, err := http.Post(se.options.WebHook, "application/json", bytes.NewBuffer([]byte(body)))
+	if err != nil {
+		se.logger.Error("slack post:", err)
+		return
+	}
+
+	defer resp.Body.Close()
+
+	rBody, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		se.logger.Error("slack post response:", err)
+		return
+	}
+	se.logger.Debug(string(rBody))
+}
+
+func (se *SlackEventer) Stop() {
+	se.client.CloseIdleConnections()
+	se.logger.Info("Slack Eventer stopped.")
+}
+
+func NewSlackEventer(options SlackOptions, logger common.Logger, stdout *Stdout) *SlackEventer {
+	if logger == nil {
+		logger = stdout
+	}
+
+	if utils.IsEmpty(options.WebHook) {
+		logger.Debug("Slack Eventer is disabled")
+		return nil
+	}
+
+	logger.Info("Slack Eventer is up…")
+
+	return &SlackEventer{
+		options: options,
+		logger:  logger,
+		tags:    common.MapToArray(common.GetKeyValues(options.Tags)),
+		client:  common.MakeHttpClient(options.Timeout),
+		ctx:     context.Background(),
+	}
+}