Simple reporting server in Go

server.go

package main

import (
  "log"
  "flag"
  "fmt"
  "database/sql"
  _ "github.com/go-sql-driver/mysql"
)

var (
  reportName = flag.String("name", "", "Name of the report to generate.")
)

type reportInstructions struct {
  query string
  scan []string
}

func main() {
  flag.Parse()

  var instructions reportInstructions

  switch *reportName {
    case "users":
    instructions = reportInstructions{
      query: "SELECT DATE(date_joined) date, COUNT(id) total FROM auth_user WHERE 1=1 GROUP BY 1",
      scan: []string{"%s ", "%d"},
    }
  }

  if instructions.query == "" {
    log.Fatal("No query")
    return
  }

  db, err := sql.Open("mysql", "prod_user:prod_password@/prod")
  if err != nil {
    log.Fatal("Could not connect to database:", err)
  }
  rows, err := db.Query(instructions.query)
  if err != nil {
    log.Println("Query Error:", err)
  }

  columns, err := rows.Columns()
  if err != nil {
    log.Fatal("Columns Error:", err)
  }

  valueColumn := make(map[string]*interface{})
  pointers := make([]interface{}, len(columns))

  for i, column := range columns {
    var value interface{}
    valueColumn[column] = &value
    pointers[i] = &value
  }

  for rows.Next() {
    if err := rows.Scan(pointers...); err != nil {
      log.Fatal("Scan Error:", err)
    }
    for i, scan := range instructions.scan {
      fmt.Printf(scan, *pointers[i].(*interface{}))
    }
    fmt.Printf("\n")
  }
  if err := rows.Err(); err != nil {
    log.Fatal(err)
  }
}

Simple reporting cli/service/server in Go, could be easily extended as an RPC service using net/rpc/jsonrpc or expose via HTTP using net/http.

You can also play by the command line using github.com/holman/spark !

Future work:

• HTTP Frontend
• CRUD For reportInstructions
• Filtering of reports
• Cursor for reports
• Async for cursors