Month: March 2022

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Cassandra – tablestats

How to produce a digest of tables using nodetool

$ nodetool tablestats | awk ‘ /Keyspace/ || /Latency/ {print $0} /Table:/ {gsub(/^[ ][ ]/,””);table=”–> “$0} /Space used/ && $NF > 0 {gsub(/^[ ][ ]/,””);space=space “|” $0} /used by snapshots/ {printf(“%-30s\t%-30s\n”,table,space);table=””;space=””} ‘

Keyspace : system_traces
Read Latency: NaN ms
Write Latency: NaN ms
–> Table: events
–> Table: sessions
Keyspace : system
Read Latency: 4.279434782608696 ms
Write Latency: 0.3454382659499075 ms
–> Table: IndexInfo
–> Table: available_ranges
–> Table: batches
–> Table: batchlog
–> Table: built_views
–> Table: compaction_history |Space used (live): 13424|Space used (total): 13424
–> Table: hints
–> Table: local |Space used (live): 15977|Space used (total): 15977
–> Table: paxos
–> Table: peer_events
–> Table: peers |Space used (live): 14912|Space used (total): 14912
–> Table: prepared_statements
–> Table: range_xfers
–> Table: size_estimates |Space used (live): 94270|Space used (total): 94270
–> Table: sstable_activity |Space used (live): 11098|Space used (total): 11098
–> Table: transferred_ranges
–> Table: views_builds_in_progress
Keyspace : system_distributed
Read Latency: NaN ms
Write Latency: NaN ms
–> Table: parent_repair_history
–> Table: repair_history
–> Table: view_build_status
Keyspace : system_schema
Read Latency: 1.7939485294117647 ms
Write Latency: 2.188590909090909 ms
–> Table: aggregates
–> Table: columns |Space used (live): 18096|Space used (total): 18096
–> Table: dropped_columns
–> Table: functions
–> Table: indexes
–> Table: keyspaces |Space used (live): 10828|Space used (total): 10828
–> Table: tables |Space used (live): 16857|Space used (total): 16857
–> Table: triggers
–> Table: types
–> Table: views
Keyspace : system_auth
Read Latency: 0.241 ms
Write Latency: 0.123 ms
–> Table: resource_role_permissons_index
–> Table: role_members
–> Table: role_permissions
–> Table: roles |Space used (live): 5134|Space used (total): 5134

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Python Lesson #2

One of the first things you are probably going to want to do is use modules.

For example to print out pi, we use the math module as below

import math
math.pi

3.141592653589793

When we import modules they generally come with same namespace, i.e. calling pi function with prefix namespace of math. For performance, etc we can also just import the specific functions we want to use. This puts the function in the global name space. For example:

from math import pi
pi

It is also possible to use a alias – such as

import math as m
m.pi

You can also create your own modules simply by storing functions in filenames with .py extension. So for example we create a file called mymodule.py with following content

# mymodule.py
def double(number):
—>return 2 * number

Then we invoke with following .. if you get an error try import sys;print sys.path for folders searched for modules. Also you can use PYTHONPATH system variable to include other paths

import mymodle
double(65)
>> 130

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R – Quickly Graph

How to quickly paste into R and get some results on a Mac (just change pipe/paste for diff OS)

df<-read.table(pipe("pbpaste"),sep=" ")
names(df)<-c("date","time","count")
df$dtg<-strptime(paste(df$date,df$time,sep=" "),"%Y-%m-%d %H:%M:%S")
plot(df$dtg,df$count,las=2)

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Python Intro

I have been working with Python and spent many hours of study, but best way to learn is to teach 🙂

As per my other guides into PHP, Perl, etc .. I will gradually write some intro, intermediate and advanced topics.

As a quick warm up 🙂

$ python -c 'print("Hi World")'
Hi World

$ python -c 'print(type("test"))'
<type 'str'>

$ python -c 'print(3**7)'
2187

Quick bit of OO – defining method

class Car:      # class attrib     category = "Vehicle"      # instance attrib     def __init__(self,name,make,model):         self.name=name         self.make=make         self.model=model      # instance method     def desc(self):         return "Name: {} is made by {} and is the {} body shape".format(self.name,self.make,self.model)

Then creating an object from this class and calling methods

fordLaser=Car("Ford Laser","Ford","Hatchback")
print(fordLaser.desc())

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Datascience – Ruby

Just having a play with ruby and thought I’d try to simulate summary(x):

irb(main):001:0> y=[]
irb(main):002:0> def x();rand(9999);end;
=> :x
irb(main):003:0> def summary(x=0); puts "min: #{x.min} max: #{x.max} mean: #{(x.sum(0.0)/x.size).round(2)}"; end
=> :summary
irb(main):004:0> 99.times do; y<<x;end
=> 99
irb(main):005:0> summary(y)
min: 23 max: 9851 mean: 5127.23

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Git clone – gitlab docker

HowTo: clone from a gitlab server running inside a docker container

  1. Ensure SSH pubkey is setup by following https://docs.gitlab.com/ee/ssh/
  2. Check source port for SSH here:

docker inspect gitlab | jq '.[0].NetworkSettings.Ports."22/tcp"'

  1. This .ssh/config worked for me

Host git
Hostname 127.0.0.1
User git
Identityfile ~/.ssh/id_ed25519
Port 922

  1. Then clone like this:

git clone git@git:root/my-awesome-project.git