Initial commit for pg-ping

Co-authored-by: prabhu43 <j.prabhu91@gmail.com>

Author: aswinkarthik

.gitignore

@@ -0,0 +1,36 @@
+
+# Created by https://www.gitignore.io/api/go,visualstudiocode
+# Edit at https://www.gitignore.io/?templates=go,visualstudiocode
+
+### Go ###
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+### Go Patch ###
+/vendor/
+/Godeps/
+
+### VisualStudioCode ###
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+
+### VisualStudioCode Patch ###
+# Ignore all local history of files
+.history
+
+# End of https://www.gitignore.io/api/go,visualstudiocode
+.env
+pg-ping

go.mod

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+module pg-ping
+
+go 1.12
+
+require (
+	github.com/kelseyhightower/envconfig v1.3.0
+	github.com/lib/pq v1.0.0
+)

go.sum

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+github.com/kelseyhightower/envconfig v1.3.0 h1:IvRS4f2VcIQy6j4ORGIf9145T/AsUB+oY8LyvN8BXNM=
+github.com/kelseyhightower/envconfig v1.3.0/go.mod h1:cccZRl6mQpaq41TPp5QxidR+Sa3axMbJDNb//FQX6Gg=
+github.com/lib/pq v1.0.0 h1:X5PMW56eZitiTeO7tKzZxFCSpbFZJtkMMooicw2us9A=
+github.com/lib/pq v1.0.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=

main.go

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+package main
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/kelseyhightower/envconfig"
+	_ "github.com/lib/pq"
+)
+
+// PGConfig contains configurations to connect to a PG database
+type PGConfig struct {
+	Username      string
+	Password      string
+	Host          string
+	DBName        string
+	Query         string
+	FrequencyInMS int32
+}
+
+// ConnStr returns a connection string to connect to postgres
+func (c *PGConfig) ConnStr() string {
+	return fmt.Sprintf("postgres://%s:%s@%s/%s?sslmode=disable", c.Username, c.Password, c.Host, c.DBName)
+}
+
+// GetQuery returns the query to use to ping
+func (c *PGConfig) GetQuery() string {
+	if c.Query == "" {
+		return "select 1"
+	}
+
+	return c.Query
+}
+
+// GetFrequency returns the frequence in MS in which the query should be run
+func (c *PGConfig) GetFrequency() time.Duration {
+	if c.FrequencyInMS == 0 {
+		return time.Second
+	}
+
+	return time.Duration(c.FrequencyInMS) * time.Millisecond
+}
+
+func main() {
+	var conf PGConfig
+	err := envconfig.Process("PGPING", &conf)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	json.NewEncoder(os.Stdout).Encode(conf)
+
+	db, err := sql.Open("postgres", conf.ConnStr())
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	ticker := time.NewTicker(conf.GetFrequency())
+	encoder := json.NewEncoder(os.Stdout)
+	for range ticker.C {
+		encoder.Encode(executeQuery(db, conf.GetQuery()))
+	}
+}
+
+// SQLResult  tracks sql response and time taken
+type SQLResult struct {
+	Value          string
+	TimeTakenInMS  float64
+	Failed         bool
+	FailureMessage string
+}
+
+func executeQuery(db *sql.DB, query string) SQLResult {
+	res := SQLResult{}
+
+	ctx, cancelFunc := context.WithCancel(context.Background())
+	tenSecondTimer := time.NewTimer(10 * time.Second)
+	go func() {
+		<-tenSecondTimer.C
+		cancelFunc()
+	}()
+
+	start := time.Now()
+	rows, err := db.QueryContext(ctx, query)
+	res.TimeTakenInMS = time.Since(start).Seconds() * 1000
+
+	if err != nil {
+		res.Failed = true
+		res.FailureMessage = err.Error()
+		return res
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			res.Failed = true
+			res.FailureMessage = err.Error()
+			return res
+		}
+
+		res.Value = name
+	}
+
+	return res
+}