Peterbe.com

A blog and website by Peter Bengtsson

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hashin 0.15.0 now copes nicely with under_scores

15 June 2020 0 comments   Python

https://github.com/peterbe/hashin/pull/119


tl;dr hashin 0.15.0 makes package comparison agnostic to underscore or hyphens

See issue #116 for a fuller story. Basically, now it doesn't matter if you write...

hashin python_memcached

...or...

hashin python-memcached

And the same can be said about the contents of your requirements.txt file. Suppose it already had something like this:

python_memcached==1.59 \
    --hash=sha256:4dac64916871bd35502 \
    --hash=sha256:a2e28637be13ee0bf1a8

and you type hashin python-memcached it will do the version comparison on these independent of the underscore or hyphen.

Thank @caphrim007 who implemented this for the benefit of Renovate.

./bin/huey-isnt-running.sh - A bash script to prevent lurking ghosts

10 June 2020 0 comments   Python, Linux, Bash


tl;dr; Here's a useful bash script to avoid starting something when its already running as a ghost process.

Huey is a great little Python library for doing background tasks. It's like Celery but much lighter, faster, and easier to understand.

What cost me almost an hour of hair-tearing debugging today was that I didn't realize that a huey daemon process had gotten stuck in the background with code that wasn't updating as I made changes to the tasks.py file in my project. I just couldn't understand what was going on.

The way I start my project is with honcho which is a Python Foreman clone. The Procfile looks something like this:

elasticsearch: cd /Users/peterbe/dev/PETERBECOM/elasticsearch-7.7.0 && ./bin/elasticsearch -q
web: ./bin/run.sh web
minimalcss: cd minimalcss && PORT=5000 yarn run start
huey: ./manage.py run_huey --flush-locks --huey-verbose
adminui: cd adminui && yarn start
pulse: cd pulse && yarn run dev

And you start that with simply typing:

honcho start

When you Ctrl-C , it kills all those processes but somehow somewhere it doesn't always kill everything. Restarting the computer isn't a fun alternative.

So, to prevent my sanity from draining I wrote this script:

#!/usr/bin/env bash
set -eo pipefail

# This is used to make sure that before you start huey, 
# there isn't already one running the background.
# It has happened that huey gets lingering stuck as a 
# ghost and it's hard to notice it sitting there 
# lurking and being weird.

bad() {
    echo "Huey is already running!"
    exit 1
}

good() {
    echo "Huey is NOT already running"
    exit 0
}

ps aux | rg huey | rg -v 'rg huey' | rg -v 'huey-isnt-running.sh' && bad || good

(If you're wondering what rg is; it's short for ripgrep)

And I change my Procfile accordingly:

-huey: ./manage.py run_huey --flush-locks --huey-verbose
+huey: ./bin/huey-isnt-running.sh && ./manage.py run_huey --flush-locks --huey-verbose

There really isn't much rocket science or brain surgery about this blog post but I hope it inspires someone who's been in similar trenches that a simple bash script can make all the difference.

Check your email addresses in Python, as a whole

22 May 2020 0 comments   Python, MDN


So recently, in MDN, we changed the setting WELCOME_EMAIL_FROM. Seems harmless right? Wrong, it failed horribly in runtime and we didn't notice until it was in production. Here's the traceback:

SMTPSenderRefused: (552, b"5.1.7 The sender's address was syntactically invalid.\n5.1.7 see : http://support.socketlabs.com/kb/84 for more information.", '=?utf-8?q?Janet?=')
(8 additional frame(s) were not displayed)
...
  File "newrelic/api/function_trace.py", line 151, in literal_wrapper
    return wrapped(*args, **kwargs)
  File "django/core/mail/message.py", line 291, in send
    return self.get_connection(fail_silently).send_messages([self])
  File "django/core/mail/backends/smtp.py", line 110, in send_messages
    sent = self._send(message)
  File "django/core/mail/backends/smtp.py", line 126, in _send
    self.connection.sendmail(from_email, recipients, message.as_bytes(linesep='\r\n'))
  File "python3.8/smtplib.py", line 871, in sendmail
    raise SMTPSenderRefused(code, resp, from_addr)

SMTPSenderRefused: (552, b"5.1.7 The sender's address was syntactically invalid.\n5.1.7 see : http://support.socketlabs.com/kb/84 for more information.", '=?utf-8?q?Janet?=')

Yikes!

So, to prevent this from happening every again we're putting this check in:

from email.utils import parseaddr

WELCOME_EMAIL_FROM = config("WELCOME_EMAIL_FROM", ...)

# If this fails, SMTP will probably also fail.
assert parseaddr(WELCOME_EMAIL_FROM)[1].count('@') == 1, parseaddr(WELCOME_EMAIL_FROM)

You could go to town even more on this. Perhaps use the email validator within django but for now I'd call that overkill. This is just a decent check before anything gets a chance to go wrong.

Build pyenv Python versions on macOS Catalina 10.15

19 February 2020 0 comments   Python, MacOSX

https://github.com/pyenv/pyenv/issues/1348#issuecomment-588001367


I'm still working on getting pyenv in my bloodstream. It seems like totally the right tool for having different versions of Python available on macOS that don't suddenly break when you run brew upgrade periodically. But every thing I tried failed with an error similar to this:

python-build: use openssl from homebrew
python-build: use readline from homebrew
Installing Python-3.7.0...
python-build: use readline from homebrew

BUILD FAILED (OS X 10.15.x using python-build 20XXXXXX)

Inspect or clean up the working tree at /var/folders/mw/0ddksqyn4x18lbwftnc5dg0w0000gn/T/python-build.20190528163135.60751
Results logged to /var/folders/mw/0ddksqyn4x18lbwftnc5dg0w0000gn/T/python-build.20190528163135.60751.log

Last 10 log lines:
./Modules/posixmodule.c:5924:9: warning: this function declaration is not a prototype [-Wstrict-prototypes]
    if (openpty(&master_fd, &slave_fd, NULL, NULL, NULL) != 0)
        ^
./Modules/posixmodule.c:6018:11: error: implicit declaration of function 'forkpty' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    pid = forkpty(&master_fd, NULL, NULL, NULL);
          ^
./Modules/posixmodule.c:6018:11: warning: this function declaration is not a prototype [-Wstrict-prototypes]
2 warnings and 2 errors generated.
make: *** [Modules/posixmodule.o] Error 1
make: *** Waiting for unfinished jobs....

I read through the Troubleshooting FAQ and the "Common build problems" documentation. xcode was up to date and I had all the related brew packages upgraded. Nothing seemed to work.

Until I saw this comment on an open pyenv issue: "Unable to install any Python version on MacOS"

All I had to do was replace the 10.14 for 10.15 and now it finally worked here on Catalina 10.15. So, the magical line was this:

SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk \
MACOSX_DEPLOYMENT_TARGET=10.15 \
PYTHON_CONFIGURE_OPTS="--enable-framework" \
pyenv install -v 3.7.6

Hopefully, by blogging about it you'll find this from Googling and I'll remember the next time I need it because it did eat 2 hours of precious evening coding time.

redirect-chain - Getting a comfortable insight input URL redirects history

14 February 2020 0 comments   Python

https://pypi.org/project/redirect-chain/


You can accomplish the same with curl -L but I've had this as a little personal hack script in my ~/bin folder on my computer. Thought I'd make it a public tool. Also, from here, a lot more can be done to this script if you wanna help out with ideas.

▶ redirect-chain http://developer.mozilla.org/en-US/docs/xpcshell
0  http://developer.mozilla.org/en-US/docs/xpcshell 301
1 > https://developer.mozilla.org/en-US/docs/xpcshell 301
2 >> https://developer.mozilla.org/docs/en/XPConnect/xpcshell 302
3 >>> https://developer.mozilla.org/en-US/docs/en/XPConnect/xpcshell 301
4 >>>> https://developer.mozilla.org/en-US/docs/XPConnect/xpcshell 301
5 >>>>> https://developer.mozilla.org/en-US/docs/Mozilla/XPConnect/xpcshell 301
6 >>>>>> https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Language_bindings/XPConnect/xpcshell 200

It basically gives you a pretty summary of redirects from a starting URL.

To install it on your system run:

pipx install redirect-chain

Happy Friday!

How to resolve a git conflict in poetry.lock

07 February 2020 0 comments   Python


We use poetry in MDN Kuma. That means there's a pyproject.toml and a poetry.lock file. To add or remove dependencies, you don't touch either file in an editor. For example, to add a package:

poetry add --dev black

It changes pyproject.toml and poetry.lock for you. (Same with yarn add somelib which edits package.json and yarn.lock).

Suppose that you make a pull request to add a new dependency, but someone sneaks a new pull request in before you and have theirs landed in master before. Well, that's how you end up in this place:

Conflicting files

So how do you resolve that?

So, you go back to your branch and run something like:

git checkout master 
git pull origin master
git checkout my-branch
git merge master

Now you get this in git status:

Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   poetry.lock

And the contents of poetry.lock looks something like this:

Conflict

I wish there just was a way poetry itself could just figure fix this.

What you need to do is to run:

# Get poetry.lock to look like it does in master
git checkout --theirs poetry.lock
# Rewrite the lock file
poetry lock

Now, your poetry.lock file should correctly reflect the pyproject.toml that has been merged from master.

To finish up, resolve the conflict:

git add poetry.lock
git commit -a -m "conflict resolved"

# and most likely needed
poetry install

content-hash

Inside the poetry.lock file there's the lock file's hash. It looks like this:

[metadata]
content-hash = "875b6a3628489658b323851ce6fe8dafacd5f69e5150d8bb92b8c53da954c1be"

So, as can be seen in my screenshot, when git conflicted on this it looks like this:

 [metadata]
+<<<<<<< HEAD
+content-hash = "6658b1379d6153dd603bbc27d04668e5e93068212c50e76bd068e9f10c0bec59"
+=======
 content-hash = "5c00dce18ddffd5d6f797dfa14e4d56bf32bbc3769d7b761a2b1b3ff14bce287"
+>>>>>>> master

Basically, the content-hash = "5c00dce1... is what you'd find in master and content-hash = "6658b137... is what you would see in your branch before the conflict.

When you run that poetry lock you can validate that the new locking worked because it should be a hash. One that is neither 5c00dce1... or 6658b137....

Notes

I'm still new to poetry and I'm learning. This was just some loud note-to-self so I can remember for next time.

I don't yet know what else can be automated if there's a conflict in pyproject.toml too. And what do you do if there are serious underlying conflicts in Python packages, like they added a package that requires somelib<=0.99 and you added something that requires somelib>=1.11.

Also, perhaps there are ongoing efforts within the poetry project to help out with this.

UPDATE Feb 12, 2020

My colleague informed me that this change was actually NOT what I wanted. poetry lock actually updates some dependencies as it makes a completely new lock file. I didn't immediately notice that in my case because the lock file is large. See this open issue which is about the ability to update the lock file without upgrading any other dependencies.