myhosts: manage transient local DNS mapping via simple CLI

Note: mh is not yet released and provides no guarantee about command line or switches or the way it handles duplicates.

Problem

As a developer I need to test frontend Javascript code dealing with more domains as easy as possible.

This expects

1. Easy to start/stop various services. Solved by Docker/Postman
2. Assign transient local DNS names.
3. Delete them once containers are not running or by the end of the test.

And last two points are why I wrote mh, it will change local DNS (via /etc/hosts) and point it to local containers. And drop all the changes on test stop (or when server is turned off).

License

MIT, see LICENSE file

Running a server

go get github.com/vyskocilm/mh
sudo mh server
# or via systemd to daemonize it
sudo systemd-run --name mh mh server

Manipulate with entries

mh add ip name
mh del ip-or-name
mh list

Groups

mh stores entries by the group allowing one to easilly drop all added entries from one group

mh add --group integration_project_1 ip name
mh add --group integration_project_1 ip2 name2
...
mh delgrp integration_project_1

if not specified, entries goes into $default group.

It is possible to export MH_GROUP variable to ensure add and del commands stays indide group.

export MH_GROUP=integration_project_1

mh add ip1 name1
mh add ip2 name2
mh del ip1

...
mh delgrp

Use with docker

Creates DNS mapping api.test to apimoc_api_1 container

mh add $(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' apimock_api_1) api.test

Garbage collect!

mh restores original /etc/hosts upon completion.

^Ctrl+C
# or systemctl stop mh
# check that ALL written entries are removed and /etc/hosts is restored

Communication method

mh use unix socket /vat/run/mh.sock by default on unix systems and port :3003 on Windows by default. Can be changes via -H/--host command line flag.

# listen on /tmp/mh.sock
mh --host unix:///tmp/mh.sock server
# listen on port 1234
mh --host 1234 server

If unix socket is specified and mh started as a root user, socket is assigned under docker group. This is for convenience as most potential users would have docker installed and configured.

TODO

8. drop all other capabilities!!!
9. how to deal with duplicates? should it be smart?
10. drop data from memory on commit fail!
11. allow usage of different group for unix socket
12. remove socket begore server start
13. socket activation
14. HTTPS/TLS/CA/certificates support - browsers will treat http as insecure soonish so there must be a way to create TLS ready infrastructure

Alternatives

Prior to writing mh I did experiment with a following methods, however did not like any of those.

1. sudo vim /etc/hosts: slow, can't be automated, leaves garbage inside
2. LD_PRELOAD tricks: cumbersome, works only for code using glibc
3. unshare tricks: still involve root, hard to automate
4. nss_wrapper: same LD_PRELOAD trick