Tag Archives: Python

A trick to see what causes Python error Unindent does not match any outer indentation level with PyCharm

That’s one of the problems with Python. Blocks of code are defined by their indentation position.

That’s a pain when you copy and past and the IDE reindents the code thinking that is doing great, or generate a new inner class instead of replacing all the code.

Well, this error is very annoying cause it means that you mixed spaces and Tabs as indent separators.

But you can go crazy trying to find a tab in your code, so there is a trick that I came with:

Basically go to Menu Edit > Find and then type 4 times space. PyCharm will highlight all the places were this indentation (4 spaces) is present, so you’ll find the impostor without going blind or losing to many time.

As you can see, in front of def execute_command_without_waiting we don’t have 4 spaces. And in this case the impostor was not a camouflaged tab \t but 3 spaces instead of four.

News from the blog 2020-08-19

  • I assisted to the OpenZFS leadership meeting.

I tried to continue following it since I left Sanmina. ZFS is really an amazing Software and it’s lead by an amazing Community of super cool Engineers and companies. I would like to continue contributing ASAP.

I bought some new hard drives in order to work a bit on this. You don’t need to have dedicated hardware if you want to test features. You can run in a VirtualBox or VMWare Workstation.

  • I received more books about DevOps and Python

None is perfect. I see flaws in all of them and bad architecture practices*, however from all I learn interesting things.

*I guess that’s why I wrote my own book :)

You know, I study every day. At least 30 minutes, after work. As part of my healthy routines.

But I also study and learn during the work, as we have time available for this.

I’m very fortunate that Blizzard gives me time every day to study. That’s amazing. They also send us to events paying the ticket, travel, hotel, expenses… now with covid-19 we only go to virtual events, but the company still pay for this and give free days. Is a very nice company.

I use a lot Linux Academy too:

I continue having purchases of my book, and I’m very happy about that. I’m working on improving it and providing more contents and samples going from the scratch, with step by step code samples. From spaghetti code reading CSV files, to OOP with Full Coverage.

  • My application for a Higher degree Computer Science Cloud Computing (Level 8) has been accepted. The Irish government pays me 90% of the degree, and Blizzard will pay me the other 10% after I pass the first year course.

I’m really grateful to this beautiful country, Ireland.

Having an Irish degree is something that brings me an special illusion.

  • I have updated CTOP.py with some interesting features

It allows to pass a fixed width and height for the terminal render. That’s very useful when you run CTOP in a Docker non interactive session, or from a Cron, with the –iterations=1 so the output can be captured programmatically.

  • Jetbrains has provided me with a Free License of all their products, in order to support my work in Open Source projects. That’s very nice. I’m using now mainly PyCharm and PhpStorm.
  • At the beginning of the covid-19 I wrote a simulator in Python. That’s why I was able to anticipate that the number of cases and deaths would be very much higher when nobody around me knew what was going to happen. My first simulations were simple, and the algorithms were growing in complexity until I had a full rich Object Oriented modeler. Maybe I’ll write an article about this someday.
    • I based my data in https://www.worldometers.info/coronavirus/#countries
    • I studied the evolution of several countries and I was working with simulations in Spain until their government started blocking the information and stop providing transparent and accurate metrics.
  • I’m seeing how the covid is affecting and transforming several kind of business:
    • Meetup.com I see meetups with more than 1,000 users closing, as they are no meeting anymore
    • Airlines, obviously
    • Hotels, offering less services
    • Metasearchers and OTAs (Online travel agencies)
    • I can imagine the impact on airbnb
    • Discos, nightclubs are closing doors
    • Restaurants, they will lose the Christmas season (with families and companies doing lunch and dinners)
  • At the same time, other companies are hitting records in sales
  • After doing a Masterclass to some colleagues about Refactor, Code Reliability, Quality, The non-happy path and Unit Testing, I’m preparing some contents that I’ll publish to the Community soon. So far I created this repo, where I added the source code for lesson 0: starting to program in Python videos that I created few months ago to help beginners.

https://gitlab.com/carles.mateo/teach-unit-testing/-/tree/master/lesson0

I also added some contents to lesson 1, where we refactor pure spaghetti code with no error control, to something more elaborated with unit testing and full code coverage. Still procedural, but I will jump to next class in two weeks, where we will move to OOP and Dependency Injection.

  • Here my “Harley” assembled :)

A simple trick to find your Git Submodules imports in Python by adding to Syspath

If you are using Git Submodules, is very probable that at some point you will create you own libraries. Probably those libraries will have their own structure, even with their own tests/ folder and you’re adding into a subfolder into your new project and maybe you have problems using relative imports.

This is a trick you can use to add the relevant root folder of your project to the System Path, so the libraries are found, specially when you call by command line from anywhere in the filesystem. This works for Python2 and Python3.

#!/usr/bin/env python3

import sys
import os

s_path_program = os.path.dirname(__file__)
sys.path.append(s_path_program + '../../')

from clib.src.argsutils import ArgsUtils
from clib.src.datetimeutils import DateTimeUtils
from clib.src.fileutils import FileUtils

This sample can be found in my book Pythom Combat Guide.

LDAPGUI a LDAP GUI program in Python and Tkinter

I wanted to automate certain operations that we do very often, and so I decided to do a PoC of how handy will it be to create GUI applications that can automate tasks.

As locating information in several repositories of information (ldap, databases, websites, etc…) can be tedious I decided to create a small program that queries LDAP for the information I’m interested, in this case a Location. This small program can very easily escalated to launch the VPN, to query a Database after querying LDAP if no results are found, etc…

I share with you the basic application as you may find interesting to create GUI applications in Python, compatible with Windows, Linux and Mac.

I’m super Linux fan but this is important, as many multinationals still use Windows or Mac even for Engineers and SRE positions.

With the article I provide a Dockerfile and a docker-compose.yml file that will launch an OpenLDAP Docker Container preloaded with very basic information and a PHPLDAPMIN Container.

Installation of the dependencies

Ubuntu:

sudo apt-get install python3.8 python3-tk
pip install ldap3

Windows and Mac:

Install Python3.6 or greater and from command line.

For Mac install pip if you don’t have it.

pip install ldap3

Python Code

#!/bin/env python3

import tkinter as tk
from ldap3 import Server, Connection, MODIFY_ADD, MODIFY_REPLACE, ALL_ATTRIBUTES, ObjectDef, Reader
from ldap3.utils.dn import safe_rdn
from lib.fileutils import FileUtils

# sudo apt-get install python3.8 python3-tk
# pip install ldap3


class LDAPGUI:

    s_config_file = "config.cfg"

    s_ldap_server = "ldapslave01"
    s_connection = "uid=%USERNAME%, cn=users, cn=accounts, dc=demo1, dc=carlesmateo, dc=com"
    s_username = "carlesmateo"
    s_password = "Secret123"
    s_query = "location=%LOCATION%,dc=demo1,dc=carlesmateo,dc=com"

    i_window_width = 610
    i_window_height = 650
    i_frame_width = i_window_width-5
    i_frame_height = 30
    i_frame_results_height = 400

    # Graphical objects
    o_window = None
    o_entry_ldap = None
    o_entry_connection = None
    o_entry_results = None
    o_entry_username = None
    o_entry_location = None
    o_button_search = None

    def __init__(self, o_fileutils):
        self.o_fileutils = o_fileutils

    def replace_connection_with_username(self):
        s_connection_raw = self.o_entry_username.get()
        s_connection = self.s_connection.replace("%USERNAME%", s_connection_raw)
        return s_connection

    def replace_query_with_location(self):
        s_query_raw = self.o_entry_location.get()
        s_query = self.s_query.replace("%LOCATION%", s_query_raw)
        return s_query

    def clear_results(self):
        self.o_entry_results.delete("1.0", tk.END)

    def enable_button(self):
        self.o_button_search["state"] = tk.NORMAL

    def disable_button(self):
        self.o_button_search["state"] = tk.DISABLED

    def ldap_run_query(self):

        self.disable_button()
        self.clear_results()

        s_ldap_server = self.o_entry_ldap.get()
        self.o_entry_results.insert(tk.END, "Connecting to: " + s_ldap_server + "...\n")
        try:

            o_server = Server(s_ldap_server)
            o_conn = Connection(o_server,
                                self.replace_connection_with_username(),
                                self.s_password,
                                auto_bind=False)
            o_conn.bind()

            if isinstance(o_conn.last_error, str):
                s_last_error = o_conn.last_error
                self.o_entry_results.insert(tk.END, "Last error: " + s_last_error + "\n")

            if isinstance(o_conn.result, str):
                s_conn_result = o_conn.result
                self.o_entry_results.insert(tk.END, "Connection result: " + s_conn_result + "\n")

            s_query = self.replace_query_with_location()
            self.o_entry_results.insert(tk.END, "Performing Query: " + s_query + "\n")

            obj_location = ObjectDef('organizationalUnit', o_conn)
            r = Reader(o_conn, obj_location, s_query)
            r.search()
            self.o_entry_results.insert(tk.END, "Results: \n" + str(r) + "\n")
            #print(r)

            #print(0, o_conn.extend.standard.who_am_i())
            # https://github.com/cannatag/ldap3/blob/master/tut1.py
            # https://github.com/cannatag/ldap3/blob/master/tut2.py

        except:
            self.o_entry_results.insert(tk.END, "There has been a problem" + "\n")

            if isinstance(o_conn.last_error, str):
                s_last_error = o_conn.last_error
                self.o_entry_results.insert(tk.END, "Last error: " + s_last_error + "\n")

        try:
            self.o_entry_results.insert(tk.END, "Closing connection\n")
            o_conn.unbind()
        except:
            self.o_entry_results.insert(tk.END, "Problem closing connection" + "\n")

        self.enable_button()

    def create_frame_location(self, o_window, i_width, i_height):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_lbl_location = tk.Label(master=o_frame,
                                  text="Location:",
                                  width=10,
                                  height=1)
        o_lbl_location.place(x=0, y=0)

        o_entry = tk.Entry(master=o_frame, fg="yellow", bg="blue", width=50)
        o_entry.insert(tk.END, "")
        o_entry.place(x=100, y=0)

        return o_frame, o_entry

    def create_frame_results(self, o_window, i_width, i_height):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_entry = tk.Text(master=o_frame, fg="grey", bg="white", width=75, height=20)
        o_entry.insert(tk.END, "")
        o_entry.place(x=0, y=0)

        return o_frame, o_entry

    def create_frame_username(self, o_window, i_width, i_height, s_username):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_lbl_location = tk.Label(master=o_frame,
                                  text="Username:",
                                  width=10,
                                  height=1)
        o_lbl_location.place(x=0, y=0)

        o_entry_username = tk.Entry(master=o_frame, fg="yellow", bg="blue", width=50)
        o_entry_username.insert(tk.END, s_username)
        o_entry_username.place(x=100, y=0)

        return o_frame, o_entry_username

    def create_frame_ldapserver(self, o_window, i_width, i_height, s_server):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_lbl_ldapserver = tk.Label(master=o_frame,
                                    text="LDAP Server:",
                                    width=10,
                                    height=1)
        o_lbl_ldapserver.place(x=0, y=0)
        # We don't need to pack the label, as it is inside a Frame, packet
        # o_lbl_ldapserver.pack()

        o_entry = tk.Entry(master=o_frame, fg="yellow", bg="blue", width=50)
        o_entry.insert(tk.END, s_server)
        o_entry.place(x=100, y=0)

        return o_frame, o_entry

    def create_frame_connection(self, o_window, i_width, i_height, s_connection):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_lbl_connection = tk.Label(master=o_frame,
                                    text="Connection:",
                                    width=10,
                                    height=1)
        o_lbl_connection.place(x=0, y=0)
        # We don't need to pack the label, as it is inside a Frame, packet
        # o_lbl_ldapserver.pack()

        o_entry_connection = tk.Entry(master=o_frame, fg="yellow", bg="blue", width=50)
        o_entry_connection.insert(tk.END, s_connection)
        o_entry_connection.place(x=100, y=0)

        return o_frame, o_entry_connection

    def create_frame_query(self, o_window, i_width, i_height, s_query):
        o_frame = tk.Frame(master=o_window, width=i_width, height=i_height)
        o_frame.pack()

        o_lbl_query = tk.Label(master=o_frame,
                                    text="Connection:",
                                    width=10,
                                    height=1)
        o_lbl_query.place(x=0, y=0)

        o_entry_query = tk.Entry(master=o_frame, fg="yellow", bg="blue", width=50)
        o_entry_query.insert(tk.END, s_query)
        o_entry_query.place(x=100, y=0)

        return o_frame, o_entry_query

    def create_button(self):
        o_button = tk.Button(
            text="Search",
            width=25,
            height=1,
            bg="blue",
            fg="yellow",
            command=self.ldap_run_query
        )

        o_button.pack()

        return o_button

    def render_screen(self):
        o_window = tk.Tk()
        o_window.title("LDAPGUI by Carles Mateo")
        self.o_window = o_window
        self.o_window.geometry(str(self.i_window_width) + 'x' + str(self.i_window_height))

        o_frame_ldap, o_entry_ldap = self.create_frame_ldapserver(o_window=o_window,
                                                                  i_width=self.i_frame_width,
                                                                  i_height=self.i_frame_height,
                                                                  s_server=self.s_ldap_server)
        self.o_entry_ldap = o_entry_ldap
        o_frame_connection, o_entry_connection = self.create_frame_connection(o_window=o_window,
                                                                              i_width=self.i_frame_width,
                                                                              i_height=self.i_frame_height,
                                                                              s_connection=self.s_connection)
        self.o_entry_connection = o_entry_connection

        o_frame_user, o_entry_user = self.create_frame_username(o_window=o_window,
                                                                i_width=self.i_frame_width,
                                                                i_height=self.i_frame_height,
                                                                s_username=self.s_username)
        self.o_entry_username = o_entry_user

        o_frame_query, o_entry_query = self.create_frame_query(o_window=o_window,
                                                               i_width=self.i_frame_width,
                                                               i_height=self.i_frame_height,
                                                               s_query=self.s_query)
        self.o_entry_query = o_entry_query


        o_frame_location, o_entry_location = self.create_frame_location(o_window=o_window,
                                                                        i_width=self.i_frame_width,
                                                                        i_height=self.i_frame_height)

        self.o_entry_location = o_entry_location

        o_button_search = self.create_button()
        self.o_button_search = o_button_search

        o_frame_results, o_entry_results = self.create_frame_results(o_window=o_window,
                                                                     i_width=self.i_frame_width,
                                                                     i_height=self.i_frame_results_height)
        self.o_entry_results = o_entry_results

        o_window.mainloop()

    def load_config_values(self):
        b_success, d_s_config = self.o_fileutils.read_config_file_values(self.s_config_file)
        if b_success is True:
            if 'server' in d_s_config:
                self.s_ldap_server = d_s_config['server']
            if 'connection' in d_s_config:
                self.s_connection = d_s_config['connection']
            if 'username' in d_s_config:
                self.s_username = d_s_config['username']
            if 'password' in d_s_config:
                self.s_password = d_s_config['password']
            if 'query' in d_s_config:
                self.s_query = d_s_config['query']


def main():
    o_fileutils = FileUtils()

    o_ldapgui = LDAPGUI(o_fileutils=o_fileutils)
    o_ldapgui.load_config_values()

    o_ldapgui.render_screen()


if __name__ == "__main__":
    main()

Dockerfile

FROM osixia/openldap

# Note: Docker compose will generate the Docker Image.
# Run:  sudo docker-compose up -d

LABEL maintainer="Carles Mateo"

ENV LDAP_ORGANISATION="Carles Mateo Test Org" \
    LDAP_DOMAIN="carlesmateo.com"

COPY bootstrap.ldif /container/service/slapd/assets/config/bootstrap/ldif/50-bootstrap.ldif

docker-compose.yml

version: '3.3'
services:
  ldap_server:
      build:
        context: .
        dockerfile: Dockerfile
      environment:
        LDAP_ADMIN_PASSWORD: test1234
        LDAP_BASE_DN: dc=carlesmateo,dc=com
      ports:
        - 389:389
      volumes:
        - ldap_data:/var/lib/ldap
        - ldap_config:/etc/ldap/slapd.d
  ldap_server_admin:
      image: osixia/phpldapadmin:0.7.2
      ports:
        - 8090:80
      environment:
        PHPLDAPADMIN_LDAP_HOSTS: ldap_server
        PHPLDAPADMIN_HTTPS: 'false'
volumes:
  ldap_data:
  ldap_config:

config.cfg

# Config File for LDAPGUI by Carles Mateo
# https://blog.carlesmateo.com
#

# Configuration for working with the prepared Docker
server=127.0.0.1:389
connection=cn=%USERNAME%,dc=carlesmateo,dc=com
username=admin_gh
password=admin_gh_pass
query=cn=%LOCATION%,dc=carlesmateo,dc=com

# Carles other tests
#server=ldapslave.carlesmateo.com
#connection=uid=%USERNAME%, cn=users, cn=accounts, dc=demo1, dc=carlesmateo, dc=com
#username=carlesmateo
#password=Secret123
#query=location=%LOCATION%,dc=demo1,dc=carlesmateo,dc=com

bootstrap.ldif

In order to bootstrap the Data on the LDAP Server I use a bootstrap.ldif file copied into the Server.

Credits, I learned this trick in this page: https://medium.com/better-programming/ldap-docker-image-with-populated-users-3a5b4d090aa4

dn: cn=developer,dc=carlesmateo,dc=com
changetype: add
objectclass: Engineer
cn: developer
givenname: developer
sn: Developer
displayname: Developer User
mail: developer@carlesmateo.com
userpassword: developer_pass

dn: cn=maintainer,dc=carlesmateo,dc=com
changetype: add
objectclass: Engineer
cn: maintainer
givenname: maintainer
sn: Maintainer
displayname: Maintainer User
mail: maintainer@carlesmateo.com
userpassword: maintainer_pass

dn: cn=admin,dc=carlesmateo,dc=com
changetype: add
objectclass: Engineer
cn: admin
givenname: admin
sn: Admin
displayname: Admin
mail: admin@carlesmateo.com
userpassword: admin_pass

dn: ou=Groups,dc=carlesmateo,dc=com
changetype: add
objectclass: organizationalUnit
ou: Groups

dn: ou=Users,dc=carlesmateo,dc=com
changetype: add
objectclass: organizationalUnit
ou: Users

dn: cn=Admins,ou=Groups,dc=carlesmateo,dc=com
changetype: add
cn: Admins
objectclass: groupOfUniqueNames
uniqueMember: cn=admin,dc=carlesmateo,dc=com

dn: cn=Maintaners,ou=Groups,dc=carlesmateo,dc=com
changetype: add
cn: Maintaners
objectclass: groupOfUniqueNames
uniqueMember: cn=maintainer,dc=carlesmateo,dc=com
uniqueMember: cn=developer,dc=carlesmateo,dc=com

lib/fileutils.py

You can download this file from the lib folder in my project CTOP.py

More information about programming with tkinter:

https://realpython.com/python-gui-tkinter/#getting-user-input-with-entry-widgets

https://www.tutorialspoint.com/python/python_gui_programming.htm

https://effbot.org/tkinterbook/entry.htm

About LDAP:

https://ldap3.readthedocs.io/en/latest/

Refreshing settings in a Docker immutable image with Python and Flask

This is a trick to restart a Service that is running on a immutable Docker, with some change, and you need to refresh the values very quickly without having to roll the CI/CD Jenkins Pipeline and uploading a new image.

So why would you need to do that?.

I can think about possible scenarios like:

  • Need to roll out an urgent fix in a time critical manner
  • Jenkins is broken
  • Somebody screw it on the git master branch
  • Docker Hub is down
  • GitHub is down
  • Your artifactory is down
  • The lines between your jumpbox or workstation and the secure Server are down and you have really few bandwidth
  • You have to fix something critical and you only have a phone with you and SSH only
  • Maybe the Dockerfile had latest, and the latest image has changed
FROM os:latest

The ideal is that if you work with immutable images, you roll out a new immutable image and that’s it.

But if for whatever reason you need to update this super fast, this trick may become really handy.

Let’s go for it!.

Normally you’ll start your container with a command similar to this:

docker run -d --rm -p 5000:5000 api_carlesmateo_com:v7 prod 

The first thing we have to do is to stop the container.

So:

docker ps

Locate your container across the list of running containers and stop it, and then restart without the –rm:

docker stop container_name
docker run -d -p 5000:5000 api_carlesmateo_com:v7 prod

the –rm makes the container to cleanup. By default a container’s file system persists even after the container exits. So don’t start it with –rm.

Ok, so login to the container:

docker exec -it container_name /bin/sh 

Edit the config you require to change, for example config.yml

If what you have to update is a password, and is encoded in base64, encode it:

echo -n "ThePassword" | base64
VGhlUGFzc3dvcmQ=

Stop the container. You can do it by stopping the container with docker stop or from inside the container, killing the listening process, probably a Python Flask.

If your Dockerfile ends with something like:

ENTRYPOINT ["./webservice.py"]

And webservice.py has Python Flask code similar to this:

#!/usr/bin/python3
#
# webservice.py
#
# Author: Carles Mateo
# Creation Date: 2020-05-10 20:50 GMT+1
# Description: A simple Flask Web Application
#              Part of the samples of https://leanpub.com/pythoncombatguide
#              More source code for the book at https://gitlab.com/carles.mateo/python_combat_guide
#


from flask import Flask, request
import logging

# Initialize Flask
app = Flask(__name__)


# Sample route so http://127.0.0.1/carles
@app.route('/carles', methods=['GET'])
def carles():
    logging.critical("A connection was established")
    return "200"

logging.info("Initialized...")

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5000, debug=True)

Then you can kill the process, and so ending the container, from inside the container by doing:

ps -ax | grep webservice
 5750 root     56:31 {webservice.py} /usr/bin/python /opt/webservice/webservice.py
kill -9 5790

This will finish the container the same way as docker stop container_name.

Then start the container (not run)

docker start container_name

You can now test from outside or from inside the container. If from insise:

/opt/webservice # wget localhost:5000/carles
Connecting to localhost:5000 (127.0.0.1:5000)
carles               100% |**************************************************************************************************************|     3  0:00:00 ETA
/opt/webservice # cat debug.log
2020-05-06 20:46:24,349 Initialized...
2020-05-06 20:46:24,359  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
2020-05-06 20:46:24,360  * Restarting with stat
2020-05-06 20:46:24,764 Initialized...
2020-05-06 20:46:24,771  * Debugger is active!
2020-05-06 20:46:24,772  * Debugger PIN: 123-456-789
2020-05-07 13:18:43,890 127.0.0.1 - - [07/May/2020 13:18:43] "GET /carles HTTP/1.1" 200 -

if you don’t use YAML files or what you need is to change the code, all this can be avoided as when you update the Python code, Flash realizes that and reloads. See this line in the logs:

2020-05-07 13:18:40,431  * Detected change in '/opt/webservice/wwebservice.py', reloading

You can also start a container with shell directly:

sudo docker run -it ctop /bin/bash

Python Combat Guide published

After some work reviewing it and ensuring it has the expected quality, I finally published my book Python Combat Guide.

Is an atypical creation. Is more a Master Class to my best friend, it could be a SDM, TL leading a small Software Development department, a Coder or a Scientist wanting to join IT as programmer and to learn a lot of stuff very quickly, than rather a formal Python Book for learning. Absolutely is not for beginners.

If you want to buy it, to explore the TOC, extended description…

https://leanpub.com/pythoncombatguide

Lesson 0, learning to code in Python for non programmers

Ok, so you can take a look at my video, and hopefully it makes spark your motivation to learn by yourself. :)

So all the people that are at home, closed down for coronavirus, you have a chance now to start learning Python and from there get a live as programmer.

You can download the code for this lesson 0, from:

https://gitlab.com/carles.mateo/teach-unit-testing/-/blob/master/lesson0/tree.py

I’m teaching Unit Testing, Refactors, Quality Code and moving from Procedural to OOP to some colleagues, you can find source code for our classes here (please, be aware that there are some error made on purpose to show why and why not do things and hot to apply proper unit testing)

https://gitlab.com/carles.mateo/teach-unit-testing/-/tree/master

There are many free useful resources to learn Python:

Resources for Microservices and Business Domain Solutions for the Cloud Architect / Microservices Architect

First you have to understand that Python, Java and PHP are worlds completely different.

In Python you’ll probably use Flask, and listen to the port you want, inside Docker Container.

In PHP you’ll use a Frameworks like Laravel, or Symfony, or Catalonia Framework (my Framework) :) and a repo or many (as the idea is that the change in one microservice cannot break another it is recommended to have one git repo per Service) and split the requests with the API Gateway and Filters (so /billing/ goes to the right path in the right Server, is like rewriting URLs). You’ll rely in Software to split your microservices. Usually you’ll use Docker, but you have to add a Web Server and any other tools, as the source code is not packet with a Web Server and other Dependencies like it is in Java Spring Boot.

In Java you’ll use Spring Cloud and Spring Boot, and every Service will be auto-contained in its own JAR file, that includes Apache Tomcat and all other Dependencies and normally running inside a Docker. Tcp/Ip listening port will be set at start via command line, or through environment. You’ll have many git repositories, one per each Service.

Using many repos, one per Service, also allows to deploy only that repository and to have better security, with independent deployment tokens.

It is not unlikely that you’ll use one language for some of your Services and another for other, as well as a Database or another, as each Service is owner of their data.

In any case, you will be using CI/CD and your pipeline will be something like this:

  1. Pull the latest code for the Service from the git repository
  2. Compile the code (if needed)
  3. Run the Unit and Integration Tests
  4. Compile the service to an executable artifact (f.e. Java JAR with Tomcat server and other dependencies)
  5. Generate a Machine image with your JAR deployed (for Java. Look at Spotify Docker Plugin to Docker build from Maven), or with Apache, PHP, other dependencies, and the code. Normally will be a Docker image. This image will be immutable. You will probably use Dockerhub.
  6. Machine image will be started. Platform test are run.
  7. If platform tests pass, the service is promoted to the next environment (for example Dev -> Test -> PreProd -> Prod), the exact same machine is started in the next environment and platform tests are repeated.
  8. Before deploying to Production the new Service, I recommend running special Application Tests / Behavior-driven. By this I mean, to conduct tests that really test the functionality of everything, using a real browser and emulating the acts of a user (for example with BeHat, Cucumber or with JMeter).
    I recommend this specially because Microservices are end-points, independent of the implementation, but normally they are API that serve to a whole application. In an Application there are several components, often a change in the Front End can break the application. Imagine a change in Javascript Front End, that results in a call a bit different, for example, with an space before a name. Imagine that the Unit Tests for the Service do not test that, and that was not causing a problem in the old version of the Service and so it will crash when the new Service is deployed. Or another example, imagine that our Service for paying with Visa cards generates IDs for the Payment Gateway, and as a result of the new implementation the IDs generated are returned. With the mocked objects everything works, but when we deploy for real is when we are going to use the actual Bank Payment. This is also why is a good idea to have a PreProduction environment, with PreProduction versions of the actual Services we use (all banks or the GDS for flights/hotel reservation like Galileo or Amadeus have a Test, exactly like Production, Gateway)

If you work with Microsoft .NET, you’ll probably use Azure DevOps.

We IT Engineers, CTOs and Architects, serve the Business. We have to develop the most flexible approaches and enabling the business to release as fast as their need.

Take in count that Microservices is a tool, a pattern. We will use it to bring more flexibility and speed developing, resilience of the services, and speed and independence deploying. However this comes at a cost of complexity.

Microservices is more related to giving flexibility to the Business, and developing according to the Business Domains. Normally oriented to suite an API. If you have an API that is consumed by third party you will have things like independence of Services (if one is down the others will still function), gradual degradation, being able to scale the Services that have more load only, being able to deploy a new version of a Service which is independent of the rest of the Services, etc… the complexity in the technical solution comes from all this resilience, and flexibility.

If your Dev Team is up to 10 Developers or you are writing just a CRUD Web Application, a PoC, or you are an Startup with a critical Time to Market you probably you will not want to use Microservices approach. Is like killing flies with laser cannons. You can use typical Web services approach, do everything in one single Https request, have transactions, a single Database, etc…

But if your team is 100 Developer, like a big eCommerce, you’ll have multiple Teams between 5 and 10 Developers per Business Domain, and you need independence of each Service, having less interdependence. Each Service will own their own Data. That is normally around 5 to 7 tables. Each Service will serve a Business Domain. You’ll benefit from having different technologies for the different needs, however be careful to avoid having Teams with different knowledge that can have hardly rotation and difficult to continue projects when the only 2 or 3 Devs that know that technology leave. Typical benefit scenarios can be having MySql for the Billing Services, but having NoSQL Database for the image catalog, or to store logs of account activity. With Microservices, some services will be calling other Services, often asynchronously, using Queues or Streams, you’ll have Callbacks, Databases for reading, you’ll probably want to have gradual and gracefully failure of your applications, client load balancing, caches and read only databases/in-memory databases… This complexity is in order to protect one Service from the failure of others and to bring it the necessary speed under heavy load.

Here you can find a PDF Document of the typical resources I use for Microservice Projects.

You can also download it from my github repository:

https://github.com/carlesmateo/awesome-microservices

Do you use other solutions that are not listed?. Leave a message. I’ll investigate them and update the Document, to share with the Community.

Update 2020-03-06: I found this very nice article explaining the same. Microservices are not for everybody and not the default option: https://www.theregister.co.uk/AMP/2020/03/04/microservices_last_resort/

Update 2020-03-11: Qcom with 1,600 microservices says that microservices architecture is the las resort: https://www.theregister.co.uk/AMP/2020/03/09/monzo_microservices/

A handy trick command line to get the usages of our Python Methods in the code

We all use powerful code analysis tool, but sometimes you’re presented with a problem and you have just… the terminal.

This Bash code is handy.

grep "def " /home/carles/code/gitlab/cloud/terraform/src/scale/lib/iscsi.py | tr "()" "  " | awk '{ print $2; }' |  grep -v "__init" | sort > ./function_names_iscsi.txt

So this basically will get all the methods (“def ” whatever), strip the parenthesis with tr, and get the second column with awk, so basically the method name, sort it and write it to the file.

Then I will cd to the src directory and execute the seconds part:

cd /home/carles/code/gitlab/cloud/terraform/src/
for fname in $(cat ~/function_names_iscsi.txt); do printf "%s: %s\n" "$fname" "$(grep -r $fname *|grep -v 'def ' -c)"; done > ~/functions_being_used.txt

That will produce a nice list with the number of times of the method being called, in the form of:

method_name: occurrences

That’s the equivalent to doing Find Usages is PyCharm.

It’s easy to identify dead code then, with method_name: 0.

You can also run this to your Jenkins to warn when there is Dead Code in your repository.

Curiosity Python string.strip() removes just more than white spaces

Another Python curiosity.

If you see the Official Python3 documentation for strip(), it says that strip without parameters will return the string without the leading and trailing white spaces.
Optionally you can pass a string with the characters you want to eliminate.

The official documentation for Python 2 says:

string.strip(s[, chars])

Return a copy of the string with leading and trailing characters removed. If chars is omitted or None, whitespace characters are removed. If given and not None, chars must be a string; the characters in the string will be stripped from the both ends of the string this method is called on.

Changed in version 2.2.3: The chars parameter was added. The chars parameter cannot be passed in earlier 2.2 versions.

https://docs.python.org/2/library/string.html

A white space is a white space. Is not an Enter.
But strip() without parameters will remove white spaces (space), and Enter \n and Tabs \t.

Probably you will not realize that unless you read from a file that has empty lines at the end for a reason, and you use strip().

You can see a demonstration following this small program, that runs the same for Python2 and Python3.

And the corresponding output for python2 and python3:

The [ ] characters where added to show that there are no hidden tabs or similar after.

Here I paste the code so you can try yourself:

import sys


def print_bar():
    print("-----------------------------------------------------")


def print_between_brackets(s_test):
    print("[" + s_test + "]")


s_string_with_enters = "  Testing strip not only removing white spaces, but Enter and Tabs s well\n\t\n\n"

print("Testing .strip()")
print("You are running Python " + sys.version)
print("This is the original string")
print_bar()
print_between_brackets(s_string_with_enters)
print_bar()
print("Now after strip()...")
print_bar()
print_between_brackets(s_string_with_enters.strip())
print_bar()
print("As you can see the Enters and the Tabs have been removed, not just the spaced")

I think this should be disambiguate so I decided to take action. Is very easy to blame and never contribute. Not me. I went to Python to fix that and I located a bug reporting this issue:

https://bugs.python.org/issue25433

The issue was registed and made specially interesting contributions by Dimitri Papadopoulos Orfanos.

The thread is really interesting to read. I recommend it.

At a glance:

“Python heavily relies on isspace() to detect “whitespace” characters.”

* Lib/string.py near line 23:
  whitespace = ' \t\n\r\v\f'

So all those characters will be stripped in Python2.7 if you use just string.strip()

The ticket was opened the 2015-10-18 12:15. So it’s a shame the documentation has not been updated yet, more than 3 years later. Those are the kind of things, lack of care, that I can’t understand. Not looking for the excellence.

Please, do note that Python3 supports Unicode natively and things are always a bit different than with Python2 and AscII.