ivermac

A colleague and I were using Jedis and wanted to delete multiple keys at once without using a loop. The version of Jedis we were using has 2 del functions and the one we wanted use is a java vararg function and can be found here. We understood a Java vararg function as a variadic function in Clojure which simply means a function with infinite arity. Assuming b1 and a1 are keys in redis, the following is what we attempted initially:

(.del jedis "a1" "b1")

The above failed with the following error: IllegalArgumentException No matching method found: del for class redis.clients.jedis.Jedis clojure.lang.Reflector.invokeMatchingMethod (Reflector.java:80)

ivermac

If you are using redis and wanted to check how many open connections are there at the moment, use the client list command in your redis terminal.

127.0.0.1:6379> client list
id=936 addr=127.0.0.1:61277 fd=8 name= age=3 idle=0 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=32768 obl=0 oll=0 omem=0 events=r cmd=client

This is a powerful debugging tool especially when you have an app that's using redis and seems to be opening connections without closing them, meaning you run out of memory in your redis host server.

Before getting to this stage, a colleague in the SRE team had used the following command to identify the redis problem

ivermac

To generate random values for secret keys

import os
os.urandom(24).encode('hex')

To view hidden attribute of an object

object._className__attrName

ivermac

Inspired by this url. From this page, the input.rc file is used to map the keyboard to specific situations.

"\e[A": history-search-backward
"\e[B": history-search-forward
"\e[C": forward-char
"\e[D": backward-char

ivermac

search for a file

find / -name <file-name>

search for a directory

find / -type d -name "<directory-name>"

ivermac

I included a non-Clojurescript directory in the checkout of a clojurescript project and started getting the following error:

Compiling ClojureScript...
WARNING: no :cljsbuild entry found in project definition.
--------------------------------------------------------------------------------
WARNING: your :cljsbuild configuration is in a deprecated format.  It has been
automatically converted it to the new format, which will be printed below.
It is recommended that you update your :cljsbuild configuration ASAP.
--------------------------------------------------------------------------------
:cljsbuild

ivermac

ABOUT

about:config settings to harden the Firefox browser. Privacy and performance enhancements.
To change these settings type 'about:config' in the url bar. Then search the setting you would like to change and modify the value. Some settings may break certain websites from functioning and rendering normally. Some settings may also make firefox unstable.

I am not liable for any damages/loss of data.

Not all these changes are necessary and will be dependent upon your usage and hardware. Do some research on settings if you don't understand what they do. These settings are best combined with your standard privacy extensions (HTTPS Everywhere, NoScript/Request Policy, uBlock origin, agent spoofing, Privacy Badger etc), and all plugins set to "Ask To Activate".

ivermac

(defn get-query-params-str [query-params-map & [query-param-str]]
  "Converts a hash-map to a query param string containing the keys and values
   in the hash-map
   Note: this function assumes the values have already been url-encoded"
  (let [query-param-str (str query-param-str)
        query-param-str-blank? (string/blank? query-param-str)
        key (first (keys query-params-map))
        query-param-key (name (or key ""))
        query-param-val (and key (key query-params-map))]

ivermac

Found clojure type reflection useful when using java objects in clojure. Especially in the repl

(use 'clojure.pprint 'clojure.reflect)
(def object-members (:members (reflect <object>)))
(print-table [:name :type :flags] (sort-by :name object-members))

The official documentation is here

ivermac

I use brew's postgresql service and after cold reboot on the mac I was using, I got the following when I tried to access psql on the command line:

psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

I got my fix from here. In a nutshell, the postmaster.pid file already exists and has to be removed. Removing file that file fixed it for me i.e.

rm -f /usr/local/var/postgres/postmaster.pid

You might also want to to checkout the postgres log file (tail -n 10 /usr/local/var/log/postgres.log) for any errors and bugs.