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December 1, 2015 21:24
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Connect to a PostgreSQL instance through an SSH tunnel.
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#!/usr/bin/guile \ | |
-e main -s | |
!# | |
;;; pg-tunnel.scm -- Connect to a PostgreSQL instance through an SSH tunnel. | |
;; Copyright (C) 2015 Artyom V. Poptsov <poptsov.artyom@gmail.com> | |
;; | |
;; This program is free software: you can redistribute it and/or | |
;; modify it under the terms of the GNU General Public License as | |
;; published by the Free Software Foundation, either version 3 of the | |
;; License, or (at your option) any later version. | |
;; | |
;; This program is distributed in the hope that it will be useful, but | |
;; WITHOUT ANY WARRANTY; without even the implied warranty of | |
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
;; General Public License for more details. | |
;; | |
;; You should have received a copy of the GNU General Public License | |
;; along with this program. If not, see <http://www.gnu.org/licenses/>. | |
;;; Commentary: | |
;; An example of using Guile-SSH [1] tunnels and Guile-PG [2] to access a | |
;; remote PostgreSQL database. | |
;; | |
;; This program is known to work with the 'master' branch of Guile-SSH, commit | |
;; '1673d06'. | |
;; | |
;; Example: | |
;; ./pg-tunnel.scm --host=example.org --dbname=example --user=alice \ | |
;; 'select * from people' | |
;; | |
;; References: | |
;; | |
;; [1] https://github.com/artyom-poptsov/guile-ssh | |
;; [2] http://www.nongnu.org/guile-pg/ | |
;;; Code: | |
(use-modules (ice-9 getopt-long) | |
;; PostgreSQL adapter from Guile-PG | |
(database postgres) | |
;; Guile-SSH | |
(ssh session) | |
(ssh auth) | |
(ssh tunnel)) | |
(setlocale LC_ALL "") | |
(define *mtx* (make-mutex 'allow-external-unlock 'unchecked-unlock)) | |
(lock-mutex *mtx* 0 #f) | |
(define (start-postgres-tunnel host) | |
"Start an SSH tunnel to a postgres server running on a HOST." | |
(let ((session (make-session #:host host #:config #t))) | |
(connect! session) | |
(format #t "Session with a server: ~a~%" session) | |
(authenticate-server session) | |
(userauth-agent! session) | |
(let ((tunnel (make-tunnel session | |
#:host "localhost" | |
#:port 5432))) | |
(format #t "Starting the tunnel ~a ...~%" tunnel) | |
(unlock-mutex *mtx*) | |
(start-forward tunnel)))) | |
;;; Helper procedures for processing of a result of a query | |
;; Taken from Guile-PG tutorial | |
;; <http://www.nongnu.org/guile-pg/doc/Processing-Results.html#Processing-Results> | |
(define (field-names result) | |
(map (lambda (field) | |
(pg-fname result field)) | |
(iota (pg-nfields result)))) | |
(define (get-values result tuple) | |
(map (lambda (field) | |
(pg-getvalue result tuple field)) | |
(iota (pg-nfields result)))) | |
(define (tuple->alist result tuple) | |
(map (lambda (n v) (cons (string->symbol n) v)) | |
(field-names result) | |
(get-values result tuple))) | |
;;; | |
(define (print-help-and-exit) | |
(display "\ | |
Usage: pg-tunnel [options] query | |
Options: | |
--host Name of the host on which DB is running. | |
--dbname Name of a database. | |
--user Database user name. | |
--help Print this message and exit. | |
Example: | |
./pg-tunnel.scm --host=example.org --dbname=example --user=alice \\ | |
'select * from people' | |
") | |
(exit 0)) | |
(define (main args) | |
"Entry point." | |
(let* ((option-spec '((host (value #t) (required? #t)) | |
(dbname (value #t) (required? #t)) | |
(user (value #t) (required? #t)) | |
(help (value #f)))) | |
(options (getopt-long args option-spec)) | |
(dbname (option-ref options 'dbname #f)) | |
(user (option-ref options 'user #f)) | |
(host (option-ref options 'host #f)) | |
(help-needed? (option-ref options 'help #f)) | |
(args (option-ref options '() #f)) | |
;; Start an SSH tunnel. | |
(thread (call-with-new-thread | |
(lambda () | |
(start-postgres-tunnel host))))) | |
(and (or help-needed? | |
(null? args)) | |
(print-help-and-exit)) | |
;; Wait for tunnel to be established. | |
(lock-mutex *mtx*) | |
(let ((db (pg-connectdb (format #f "dbname=~a user=~a host=localhost port=5432" | |
dbname user)))) | |
(format #t "DB connection created: ~a~%" db) | |
(format #t "Query: ~a~%" args) | |
(let ((result (pg-exec db (car args)))) | |
(format #t "Response: ~a~%" (tuple->alist result 0)) | |
(cancel-thread thread) | |
(set! db #f))))) | |
;;; pg-tunnel.scm ends here. |
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