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I’ve added an ActivityPub plugin so content here will easily be shared on the fediverse, hopefully.
You can follow me @uda@x59.co
If you aren’t familiar with Python, FastAPI or Timezones, this might not be the post for you, sorry.
For the rest of you geeks (like me), here is an example how to validate supported timezones in an input (Query, Path etc.). Scratch that, this is about how to validate dynamic lists of values in FastAPI by using timezones as an example.
As you know, in FastAPI you can validate predefined values by using String Enums (A class sub-classed from str
and Enum
), so how do you validate dynamic lists of values?
According to the docs, this is how you create a dynamic Enum
:
>>> from datetime import timedelta
>>> class Period(timedelta, Enum):
... "different lengths of time"
... _ignore_ = 'Period i'
... Period = vars()
... for i in range(367):
... Period['day_%d' % i] = i
The _ignore_
part is to remove the variable generated by the property Period
and the for
loop, of course.
Back to Timezones, according to the docs you can get the list of timezones supported by the locally installed IANA timezone DB:
import zoneinfo
zoneinfo.available_timezones()
And to our mini validation example:
import zoneinfo
from datetime import datetime
from enum import Enum
from fastapi import FastAPI, Query
app = FastAPI()
class Timezone(str, Enum):
_ignore_ = 'Timezone z'
Timezone = vars()
for z in zoneinfo.available_timezones():
Timezone[z] = z
@app.get('/')
def get_time(zone: Timezone = Query(Timezone.UTC)):
return {'now': datetime.now(tz=zoneinfo.ZoneInfo(zone))}
This way you can accept a timezone string, but not inserting it into any function without validating it is a string you can trust, and in the same time you don’t have to maintain that list on your own.
Remember #1: that the timezone list is recalculated every time the function is called (app start in this case), so if you run this directly on a machine, remember to restart the app after updating the timezone DB.
Remember #2: that most of the Enum
items aren’t accessible in the class instance notation, Timezone.America/New_York
, but you can access it using the dict notation Timezone['America/New_York']
, The common names of course are accessible, like Timezone.UTC
and Timezone.EST
.
This is an update on Journey to new DNS servers, which I am now calling op-nslookup
I was playing around with PowerDNS on one of my existing servers, using a separate port, then ran simple dig queries and wanted to see what the difference would be. TL;DR: I wasn’t impressed.
What did I try:
In both cases (bind or gsqlite3 as backends) the performance was the same, I managed to tune the performance so the average of the query time was on par with the existing bind.
The bad part here was that while the minimum was the same (120-124ms) the maximum was way higher for PowerDNS (400ms 600ms while Bind was usually up to 300ms) so I think my numbers are not very scientific and if I want to be sure I’ll need to benchmark using a reliable tool and not simply run and copy-paste into calc…
But this isn’t all and I will definitely need to invest more time in comparing features, since I am sure there are configurations at which I can get more out of it, even in speed wise.
The fact this is a hobby project does not mean I need to lower my standards.
I have been managing my own DNS servers for a long time now, most of the time using ISPConfig to manage two to three BIND instances. It has been fun, but I got tired of ISPConfig’s limitations in some areas, and I want to have my own definition of servers.
I have tried that before, several times, but I did the mistake so many did before, trying to solve everything in one shot. And learning from my paid work experience, it isn’t worth the time. So I am going on a new journey to build my own infrastructure, starting with my self-hosted DNS servers, one piece of the infrastructure at a time.
It might take time, and I am aware that sometimes it’ll be days and weeks between progresses, but it is a journey of learning and sharing. So let’s begin.
If I am in the US and the server is in Europe, a 100ms response time in the server itself is really slow. The server must respond very quickly to each request.
When a change is introduced, a 60 seconds to update is slow, think about APIs updating DNS records for verification purposes, it needs to go to the next step within that timeframe. So my goal is up to 20 seconds to implement record changes.
I expect the server to support most of the RR types, namely support:
It should fully support DNSSEC with the latest practices
The program I will choose should be actively maintained, otherwise any bug report, feature request or merge request might just remain in limbo, and I will either have to fork it or move to another solution.
These are the only two after filtering the common available options, given that I already use IPv6 in both serving and records, wild card records and want to use DNSSEC.
I’ll state the obvious, I need the software to be open and free source, be tested and run smoothly on Linux server (I can manage with BSD if that will become a requirement).
Well, a lovely idea, I always like to consider it in every project, but this isn’t on the table for now, sorry me.
Bu, as a consolation, I will be working on all integration and admin interfaces, and with the slightest hint of trouble using available solutions I’ll just write up my own.
That’s it for now, hitting the road for new DNS servers.
Lately I needed to run tcpdump
on several servers for a given time, and then download the pcap
fiels, all in a programmatic way.
So I got to know the useful timeout
command, simple and straight-forward.
timeout 120s tcpdump -s 0 -A dst port 80
Remember that if you are not running as root
and using sudo
, you will need to put sudo
before the timeout
command, so it can actually send the SIGTERM
without getting Permission denied
.
sudo timeout 120s tcpdump -s 0 -A dst port 80
If you want to learn more about timeout:
https://explainshell.com/explain?cmd=timeout+120s+tcpdump+-s+0+-A+dst+port+80
In my previous post re. nginx dynamic settings, I’ve put an example of using variables in the index directive for serving a dynamic main file. This time I want to talk about try_files directive.
In the official examples, linked above, there is a one showing how to provide default place holder image, which is nice, and useful for hard set configurations. Most of the other examples are around internal rewrites to language interpreters.
Now say you host a Drupal multi-site, or WordPress multi-site and want to provide different favicon.ico files or robots.txt per domain, this can come handy. Here is an example:
location /favicon.ico { try_files $http_host.favicon.ico favicon.ico =404; log_not_found off; access_log off; }
This way you can provide a default file for all, and specify a unique one for some.
Notice that for favicon.ico this doesn’t really cover it, since themes provide “shortcut icon” tags that override the default favicon. But for robots.txt this is very useful.
Looking through solutions on the internet, I found that for nginx there are plenty solution for dynamic root directories, headers and environment variables out there.
Today I was asked about using the same application directory with various cached index files, in this case, the determination is based on the domain accessed.
The previous solution used was to create spearate root directories with copies of the same system, which is wrong, just a waste of deployment time and configuration.
A more elegant solution, is to use the $http_host variable, and define a dynamic index file, like this:
index index.$http_host.php index.php index.html;
Now, be aware, this might not always be the best solution. also, most of the times, this will not be the specific setting or variable to use, but the idea is there.
Following this great old post from David Walsh’s post Tweet for Code #2, here is a PHP adaptation for this JavaScript Var Swap tweet:
$b = [$a, $a = $b][0];
Works on PHP 5.4 and up.
I know this is not very practical, for daily work, but it can come handy in a job interview.
♦ ♦ ♦
[Update:June 16, 2016]
In PHP 7.1.x it will finally be possible to use a cleaner swap short-code:
[$a, $b] = [$b, $a];
[/Update]
When using Gitlab / Github for development with large development groups, with or without branch per feature, you probably would want to use a development branch, and setting it as a default is a good idea. so when making a new clone you will automatically be in the development branch.
You need to keep in mind that deploying will now require the usage of -b master in the clone command (unless you are using tags, which is really a better idea, but just to be fair, in old installations you can’t clone into tags, so you can… no, just upgrade)
I attached screenshots from both Gitlab and Github’s settings page, just change the “Default branch”.
Gitlab:
Github:
For the bad guy, contempt feeds his actions, penalty fits them.
But the narrow-minded guy, punishment feeds his narrowness, shame fits him.