Add flyadmin commands

Author: Shaun Davis

Dockerfile

@@ -6,7 +6,8 @@ FROM golang:1.16 as flyutil
 WORKDIR /go/src/github.com/fly-examples/fly-postgres
 COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -v -o /fly/bin/start ./cmd
+RUN CGO_ENABLED=0 GOOS=linux go build -v -o /fly/bin/flyadmin ./cmd/flyadmin
+RUN CGO_ENABLED=0 GOOS=linux go build -v -o /fly/bin/start ./cmd/start
 
 FROM postgres:${PG_VERSION}
 ENV PGDATA=/data/pg_data

cmd/flyadmin/main.go

@@ -0,0 +1,252 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/jackc/pgx/v4"
+)
+
+type cmd func(pg *pgx.Conn, input map[string]interface{}) (result interface{}, err error)
+
+func main() {
+	app := os.Getenv("FLY_APP_NAME")
+	hostname := fmt.Sprintf("%s.internal:5432", app)
+	conn, err := openConnection(hostname)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error connecting to postgres: %s\n", err)
+		os.Exit(1)
+	}
+	defer conn.Close(context.Background())
+
+	if len(os.Args) == 1 {
+		fmt.Fprintln(os.Stderr, "subcommand required")
+		os.Exit(1)
+	}
+
+	command := os.Args[1]
+	input := map[string]interface{}{}
+
+	if len(os.Args) > 2 && os.Args[2] != "" {
+		if err := json.Unmarshal([]byte(os.Args[2]), &input); err != nil {
+			fmt.Fprintf(os.Stderr, "error decoding json input: %s\n", err)
+			os.Exit(1)
+		}
+	}
+
+	commands := map[string]cmd{
+		"database-list":    listDatabases,
+		"database-create":  createDatabase,
+		"database-delete":  deleteDatabase,
+		"user-list":        listUsers,
+		"user-create":      createUser,
+		"user-delete":      deleteUser,
+		"grant-access":     grantAccess,
+		"revoke-access":    revokeAccess,
+		"grant-superuser":  grantSuperuser,
+		"revoke-superuser": revokeSuperuser,
+	}
+
+	cmd := commands[command]
+	if cmd == nil {
+		fmt.Fprintf(os.Stderr, "unknown command '%s'\n", command)
+		os.Exit(1)
+	}
+
+	output, err := cmd(conn, input)
+	resp := response{
+		Result: output,
+	}
+	if err != nil {
+		resp.Error = err.Error()
+	}
+
+	if err := json.NewEncoder(os.Stdout).Encode(resp); err != nil {
+		fmt.Fprintf(os.Stderr, "error marshaling response '%s'\n", err)
+		os.Exit(1)
+	}
+}
+
+type response struct {
+	Result interface{} `json:"result"`
+	Error  string      `json:"error,omitempty"`
+}
+
+func listDatabases(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := `
+		SELECT d.datname,
+					(SELECT array_agg(u.usename::text order by u.usename) 
+						from pg_user u 
+						where has_database_privilege(u.usename, d.datname, 'CONNECT')) as allowed_users
+		from pg_database d where d.datistemplate = false
+		order by d.datname;
+		`
+
+	rows, err := pg.Query(context.Background(), sql)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	values := []dbInfo{}
+
+	for rows.Next() {
+		di := dbInfo{}
+		if err := rows.Scan(&di.Name, &di.Users); err != nil {
+			return nil, err
+		}
+		values = append(values, di)
+	}
+
+	return values, nil
+}
+
+type userInfo struct {
+	Username  string   `json:"username"`
+	SuperUser bool     `json:"superuser"`
+	Databases []string `json:"databases"`
+}
+
+type dbInfo struct {
+	Name  string   `json:"name"`
+	Users []string `json:"users"`
+}
+
+func listUsers(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := `
+		select u.usename,
+			usesuper as superuser,
+      (select array_agg(d.datname::text order by d.datname)
+				from pg_database d
+				WHERE datistemplate = false
+				AND has_database_privilege(u.usename, d.datname, 'CONNECT')
+			) as allowed_databases
+			from pg_user u
+			order by u.usename
+			`
+
+	rows, err := pg.Query(context.Background(), sql)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	values := []userInfo{}
+
+	for rows.Next() {
+		ui := userInfo{}
+		if err := rows.Scan(&ui.Username, &ui.SuperUser, &ui.Databases); err != nil {
+			return nil, err
+		}
+		values = append(values, ui)
+	}
+
+	return values, nil
+}
+
+func createUser(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf(`CREATE USER %s WITH LOGIN PASSWORD '%s'`, input["username"], input["password"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	if val, ok := input["superuser"]; ok && val == true {
+		return grantSuperuser(pg, input)
+	}
+
+	return true, nil
+}
+
+func deleteUser(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf(`DROP USER IF EXISTS %s`, input["username"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func createDatabase(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("CREATE DATABASE %s;", input["name"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func deleteDatabase(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("DROP DATABASE %s;", input["name"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func grantAccess(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("GRANT ALL PRIVILEGES ON DATABASE %s TO %s", input["database"], input["username"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func revokeAccess(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("REVOKE ALL PRIVILEGES ON DATABASE %s FROM %s", input["database"], input["username"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func grantSuperuser(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("ALTER USER %s WITH SUPERUSER;", input["username"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func revokeSuperuser(pg *pgx.Conn, input map[string]interface{}) (interface{}, error) {
+	sql := fmt.Sprintf("ALTER USER %s WITH NOSUPERUSER;", input["username"])
+
+	_, err := pg.Exec(context.Background(), sql)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func openConnection(hostname string) (*pgx.Conn, error) {
+	url := fmt.Sprintf("postgres://%s/postgres", hostname)
+	conf, err := pgx.ParseConfig(url)
+
+	if err != nil {
+		return nil, err
+	}
+	conf.User = "flypgadmin"
+	conf.Password = os.Getenv("SU_PASSWORD")
+
+	return pgx.ConnectConfig(context.Background(), conf)
+}