Golang, PostgreSQL and array_agg

If you have SQL like this:

Microservice architecture patterns

Why do you need a microservice architecture? Decrease blast radius of problems and increase flexibility. You want technology diversity in your company. You want to scale your app more granular according to consumer needs. You want newcomers to be productive earlier. You want your company structure to be mirrored with technical responsibilities (it’s mainly about …

Postgresql: style guide for DataGrip

Place it into xml file and import into DataGrip or another jetbrains’ product

PostgreSQL: using indices on json fields

It’s obviously a really bad idea. But if you really need it, that’s what you can do.

Postgresql: show all locked queries

WITH RECURSIVE l AS (
 SELECT pid, locktype, mode, granted,
ROW(locktype,database,relation,page,tuple,virtualxid,transactionid,classid,objid,objsubid) obj
 FROM pg_locks
), pairs AS (
 SELECT w.pid waiter, l.pid locker, l.obj, l.mode
 FROM l w
 JOIN l ON l.obj IS NOT DISTINCT FROM w.obj AND l.locktype=w.locktype AND NOT l.pid=w.pid AND l.granted
 WHERE NOT w.granted
), tree AS (
 SELECT l.locker pid, l.locker root, NULL::record obj, NULL AS mode, 0 lvl, locker::text path, array_agg(l.locker) OVER () all_pids
 FROM ( SELECT DISTINCT locker FROM pairs l WHERE NOT EXISTS (SELECT 1 FROM pairs WHERE waiter=l.locker) ) l
 UNION ALL
 SELECT w.waiter pid, tree.root, w.obj, w.mode, tree.lvl+1, tree.path||'.'||w.waiter, all_pids || array_agg(w.waiter) OVER ()
 FROM tree JOIN pairs w ON tree.pid=w.locker AND NOT w.waiter = ANY ( all_pids )
)
SELECT (clock_timestamp() - a.xact_start)::interval(3) AS ts_age,
      replace(a.state, 'idle in transaction', 'idletx') state,
      (clock_timestamp() - state_change)::interval(3) AS change_age,
      a.datname,tree.pid,a.usename,a.client_addr,lvl,
      (SELECT count(*) FROM tree p WHERE p.path ~ ('^'||tree.path) AND NOT p.path=tree.path) blocked,
      repeat(' .', lvl)||' '||left(regexp_replace(query, '\s+', ' ', 'g'),100) query
FROM tree
JOIN pg_stat_activity a USING (pid)
ORDER BY path;

WITH RECURSIVE l AS (

SELECT pid, locktype, mode, granted,

ROW(locktype,database,relation,page,tuple,virtualxid,transactionid,classid,objid,objsubid) obj

FROM pg_locks

), pairs AS (

SELECT w.pid waiter, l.pid locker, l.obj, l.mode

FROM l w

JOIN l ON l.obj IS NOT DISTINCT FROM w.obj AND l.locktype=w.locktype AND NOT l.pid=w.pid AND l.granted

WHERE NOT w.granted

), tree AS (

SELECT l.locker pid, l.locker root, NULL::record obj, NULL AS mode, 0 lvl, locker::text path, array_agg(l.locker) OVER () all_pids

FROM ( SELECT DISTINCT locker FROM pairs l WHERE NOT EXISTS (SELECT 1 FROM pairs WHERE waiter=l.locker) ) l

UNION ALL

SELECT w.waiter pid, tree.root, w.obj, w.mode, tree.lvl+1, tree.path||'.'||w.waiter, all_pids || array_agg(w.waiter) OVER ()

FROM tree JOIN pairs w ON tree.pid=w.locker AND NOT w.waiter = ANY ( all_pids )

)

SELECT (clock_timestamp() - a.xact_start)::interval(3) AS ts_age,

replace(a.state, 'idle in transaction', 'idletx') state,

(clock_timestamp() - state_change)::interval(3) AS change_age,

a.datname,tree.pid,a.usename,a.client_addr,lvl,

(SELECT count(*) FROM tree p WHERE p.path ~ ('^'||tree.path) AND NOT p.path=tree.path) blocked,

repeat(' .', lvl)||' '||left(regexp_replace(query, '\s+', ' ', 'g'),100) query

FROM tree

JOIN pg_stat_activity a USING (pid)

ORDER BY path;

Smart Home systems

There are quite a lot of that systems: MajorDoMo OpenHab Iobroker Domoticz HomeAssistant The most interesting ones are: Iobroker (Node.js-based) HomeAssistant (based on Python 3)

Install exact version via brew

For instance, we’re looking for kubernetes-helm@2.9 helm 2.9

git -C "$(brew --repo homebrew/core)" fetch --unshallow
cd "$(brew --repo homebrew/core)"
git log Formula/kubernetes-helm.rb
# searching for 2.9.0 with a command /2\.9\.0 and copying hash like "7ade79f13b4bbcc6126803245594d97b2abbe2fa"
git checkout -b kubernetes-helm@2.9.0 7ade79f13b4bbcc6126803245594d97b2abbe2fa
HOMEBREW_NO_AUTO_UPDATE=1 brew install kubernetes-helm

git -C "$(brew --repo homebrew/core)" fetch --unshallow

cd "$(brew --repo homebrew/core)"

git log Formula/kubernetes-helm.rb

# searching for 2.9.0 with a command /2\.9\.0 and copying hash like "7ade79f13b4bbcc6126803245594d97b2abbe2fa"

git checkout -b kubernetes-helm@2.9.0 7ade79f13b4bbcc6126803245594d97b2abbe2fa

HOMEBREW_NO_AUTO_UPDATE=1 brew install kubernetes-helm

Now we have needed version of helm. If you see an error message like Error: go: unknown version :mountain_lion, you should make a little hack (as it said here). Check all the files depending on

grep 'depends_on :macos => :mountain_lion' Formula/*
# you'll see something like
Formula/bashdb.rb:  depends_on :macos => :mountain_lion
Formula/chrome-cli.rb:  depends_on :macos => :mountain_lion
Formula/clipsafe.rb:  depends_on :macos => :mountain_lion
Formula/go.rb:  depends_on :macos => :mountain_lion
Formula/go@1.8.rb:  depends_on :macos => :mountain_lion
Formula/go@1.9.rb:  depends_on :macos => :mountain_lion
Formula/ios-sim.rb:  depends_on :macos => :mountain_lion
Formula/mesos.rb:  depends_on :macos => :mountain_lion
Formula/mongodb.rb:  depends_on :macos => :mountain_lion
Formula/mongodb@3.0.rb:  depends_on :macos => :mountain_lion
Formula/mongodb@3.2.rb:  depends_on :macos => :mountain_lion
Formula/mongodb@3.4.rb:  depends_on :macos => :mountain_lion
...

grep 'depends_on :macos => :mountain_lion' Formula/*

# you'll see something like

Formula/bashdb.rb: depends_on :macos => :mountain_lion

Formula/chrome-cli.rb: depends_on :macos => :mountain_lion

Formula/clipsafe.rb: depends_on :macos => :mountain_lion

Formula/go.rb: depends_on :macos => :mountain_lion

Formula/go@1.8.rb: depends_on :macos => :mountain_lion

Formula/go@1.9.rb: depends_on :macos => :mountain_lion

Formula/ios-sim.rb: depends_on :macos => :mountain_lion

Formula/mesos.rb: depends_on :macos => :mountain_lion

Formula/mongodb.rb: depends_on :macos => :mountain_lion

Formula/mongodb@3.0.rb: depends_on :macos => :mountain_lion

Formula/mongodb@3.2.rb: depends_on :macos => :mountain_lion

Formula/mongodb@3.4.rb: depends_on :macos => :mountain_lion

...

In each file just comment a string saying depends_on :macos …

docker-compose example for ceph, kafka, postgres cluster

That is how it can be done:

Setting zsh on you mac

This gist is great: https://gist.github.com/kevin-smets/8568070 I just added these line at the bottom:

plugins=(zsh-autosuggestions git)

DEFAULT_USER=...

POWERLEVEL9K_SHORTEN_DIR_LENGTH=2

source /usr/local/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh

plugins=(zsh-autosuggestions git)

DEFAULT_USER=...

POWERLEVEL9K_SHORTEN_DIR_LENGTH=2

source /usr/local/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh

List of embedded plugins: https://github.com/robbyrussell/oh-my-zsh/tree/master/plugins Custom plugins are installed here — ~/.oh-my-zsh/custom/plugins (actually, $ZSH_CUSTOM/plugins). Like this:

git clone https://github.com/zsh-users/zsh-autosuggestions ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-autosuggestions

1	git clone https://github.com/zsh-users/zsh-autosuggestions ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-autosuggestions

CO2 sensor DIY

Article says how to make your own CO2 sensor with Arduino and visualize data with Grafana. It’s in Russian. https://ovcharov.me/2018/10/21/co2-sensor-mh-z19b/