This Week I Learned - 2016 Week 49

Last week post or the whole series.

When a screenshot says a lot. The 14-plus hours uptime is something to be concerned about. Is best to be away from your machine from time to time. As you age, there is no needs to tweak your environment, just use the default settings for almost everything.

Certain unfortunate requirements led me to buy a USB-based high powered 300Mpbs Wifi adapter, TP-Link TL-WN8200ND. Unfortunately, while the driver seems to load properly, I still can't connect through Wifi in Ubuntu 16.10.

Understanding htop. Comprehensive guide to htop and its equivalent console commands. It will make you realize how much htop have aggregate and collect all the necessary information. The same author also wrote another useful guide on HTTP headers.

While we're on HTTP. Encountered this error with Nginx few weeks back where the error log shows that "upstream sent too big header while reading response header from upstream". In other words, your proxy server, Nginx does not like the data sent over from the application server (upstream). Several reasons may cause this like large cookies size, cookies with way old timestamp, or mismatch of response size and content length. Several ways to resolve this, either fix the issue at the upstream , disable proxy buffer, or increase proxy buffer sizes. Example as shown below (do not follow this values, adjust accordingly). Don't understand these settings? You can read details explanation and an excellent guide on these directives.
http {
    proxy_buffers           8 4k;
    proxy_buffer_size         8k;
    proxy_busy_buffers_size   16k;

On Perl. Nothing much pickup for the last two weeks, mostly just test cases and test cases. Interesting behaviour when returning value from subroutine. Being Perl, implicit is better than explicit as compare to Python. For example, there is this rule of do no return `undef`, just use the bareword `return`.
use Dumper;
sub a { return undef; }
sub b { return; }

my @aa = a();
my $a = a();

my @bb = b();
my $b = b();

Dumper(\@aa); # [undef], not false
Dumper($a); # undef, false

Dumper(\@bb); # [], false value because empty array
Dumper($b); # undef, false

How to implement Test-Driven Design (TDD) in Perl? So many good links given in those answers to the questions. Unfortunately, most of the links are quite dated and some may not be that relevant anymore. But since this is Perl, most stuff should be long standardized and stable.

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