Monday, September 2, 2013

Twistd upload FTP server

How to fix "Failed to retrieve directory listing"

I was trying to get a quick ftp server up and running, and it seems liked `twistd` is getting to be installed just about everywhere these days so it seemed simple enough:

twistd -n ftp -r .

Got a twistd up and serving ftp out of the current working directly for anonymous download.

But I actually wanted the server to let me upload (side note: people hate windows because it's terrible, what a wasteland, it's a terrible chore to get even the most basic things done without tools like scp?).

So I started with the simple example.

But nothing is ever "simple" in Twisted.  It turns out the FTPRealm blah blah blah - no body cares.

I was getting an error doing the first directory listing when I connected to the server as an authenticated user, anonymous listing worked fine.  Here was the not helpful at all traceback:

2013-09-02 13:03:54-0700 [FTP (ProtocolWrapper),0,] DTPFactory.setTimeout set to 10 seconds
2013-09-02 13:03:54-0700 [FTP (ProtocolWrapper),0,] DTPFactory starting on 62816
2013-09-02 13:03:54-0700 [FTP (ProtocolWrapper),0,] Starting factory
2013-09-02 13:03:54-0700 [twisted.protocols.ftp.DTPFactory] DTPFactory.buildProtocol
2013-09-02 13:03:54-0700 [twisted.protocols.ftp.DTPFactory] cancelling DTP timeout

Oh of course!  The DTPFactory/ProtcolWrapper blah blah - no body cares!

Silly thing was trying to read `/home/` - which while probably useful in on a Linux machine wasn't so helpful on my MacBook.

Here's what I ended up with:

"simple" FTP server on a Mac

#! /usr/bin/env python
import os

from twisted.internet import reactor
from twisted.protocols.ftp  import FTPFactory
from twisted.protocols.ftp  import FTPRealm 
from twisted.cred.portal    import Portal
from twisted.cred.checkers  import AllowAnonymousAccess
from twisted.cred.checkers import InMemoryUsernamePasswordDatabaseDontUse as \


users = {
    os.environ['USER']: PASSWORD

p = Portal(FTPRealm('./', userHome='/Users'), 
    (   AllowAnonymousAccess(),

f = FTPFactory(p)

reactor.listenTCP(2121, f)

^ login with your username and blank password; it's not secure, duh.

Wednesday, March 13, 2013

Short commit SHA in Jenkins jobs' build name

I always forget this, and spend way too much time looking it up.  This is the part I'm looking for:
Hi future me.

If you're not me, you probably already have the GitHub Plugin installed, which pulls in the base Git Plugin.  And if you started reading on the wiki page for the git plugin you may have noticed a reference to a environment variable available as GIT_COMMIT.  After some bit of searching you bump into the Build Name Setter Plugin, and try adding some stuff in the "Build Name" field on the job configuration maybe like:
Which doesn't work, so you go back to more important stuff.

Or maybe you get lucky and realize the Token Macro Plugin is involved and stumble across the example there.  Which is hidden in-between some Java you can barely look at, is the small blurb at the end of a paragraph which mentions "${GIT_REVISION,length=8}".

What was interesting there for me was that the build name setter relies completely on the token macro plugin for the string expansion, and pulling strings out of the ENV is not it's primary purpose.  There's a special syntax even:
Which if you discovered, probably frustrated you, since can't seem to use the ENV vars you export during the build script, or even do basic bash variable manipulation like ${GIT_COMMIT:0:8}.

At this point you're realizing the fact that the token macro expansion only looks like bash variable expansion to confuse you.

Jenkins plugins can and do internally in their java guts define and export sometimes parameterized "tokens" which are exported for the specific purpose of being available to the token macro plugin which the build name setter users.

I honestly had no idea how anyone was supposed to know how this stuff worked together short of trolling through the git plugin's source like I did and reading GitRevisionTokenMacro.  But when I looked at the commit, my eyes were opened!

Jenkin's plugin system allows authors to write these html snippets which will be inlined into the job configuration page!?  This is why I can never seem to find "the docs" for a plugin - they're just added in all over the place whenever you install them - wherever it seems relevant to the author who wrote them!

So my new plan is to "always click the ? first" - why wasn't that my old plan?