Sunday, February 28, 2021

Raspberry Pi display problems

Having successfully installed a new Raspberry Pi with Raspbian OS, it is common that the next reboot the screen display just leaves a blank screen. You just know its the display setting run when at the boot screen the system messages can be seen.

Firstly, the most important file you must know is the /boot/config.txt

This contains many configuration, that require the file to be save and RPi to be restarted. 

If your display is working, but the resolution is wrong, then access the start menu And look for Configuration, or directly access the resolution setting, type 

raspi-config


When the display is a touch screen, it would be a good idea to install a virtual keyboard. Do this by

sudo apt install florence

Back to troubleshooting a display that's not showing. Always check your display is powered, and that system messages appear at boot before proceeding here.


Step 1.

Ensure RPi is connected to your local network, then SSH to your RPi. On MS Windows there is a software named Putty. 


Step 2. 

Determine your device supported resolutions. Use either of following commands;

tvservice -m CEA

tvservice -m DMT

Depending on whether you are connected to a TV (CEA) or computer monitor (DMT). Generally, a TV with VGA cable will use CEA. 


Step 3.

Edit the file /boot/config.txt

Use the settings identified in Step 2. If you are using CEA then the value of hdmi_group=1,

if its DMT then hdmi_group=2. 


Eg 1. when connected to a monitor with resolution 1280×720 and frequency 60Hz, these are the settings;

hdmi_safe=1

hdmi_group=2

hdmi_mode=85

Eg 2. when connected to a TV through HDMI with resolution 640x480 and frequency 60Hz. Since the TV have a standard HDMI connector, hdmi_safe will be commented out. These are the settings;

#hdmi_safe=1

hdmi_group=2

hdmi_mode=4


Reference: Raspberry site

Thursday, February 18, 2021

How to alter Postgresql table owner

 All this while I have been changing table owners individually in a specific schema. One fine day, there was a requirement to transfer all tables to another owner without changing the database ownership.


The existing tables where having owner as "postgres", but to allow other application to access, a separate user is created and allowed access. Here is how its done to assign the user;

\c mydatabase;

ALTER TABLE public.users OWNER TO contractors;


In the case where ALL tables are to have a new owner, then following can be done

select 'ALTER TABLE ' || table_name || ' OWNER TO contractors;' from information_schema.tables where table_schema = 'public' \gexec ;

Wednesday, February 10, 2021

Select Query with JSON column in Postgresql

 Recently I encountered a problem to use JSONB type column with Reportserver and log it in their forum. Since I have made the example, why not post it here? 

Here is an example to use JSONB type column in Postgresql 10 and newer.

Step 1: Create the sample database


CREATE TABLE public.products (
    id int4 NOT NULL PRIMARY KEY,
    "name" varchar NOT NULL,
    "product" jsonb NULL
);


Step 2: Add sample data


id|name       |product                                                               |
--|-----------|----------------------------------------------------------------------|
1|Orange bod |[{"id": 18, "name": "Orange Gala", "value": "1Bll-1-99-aaa"}]         |
2|Chicken Pie|[{"id": 4, "name": "Downtown Chicken Pie", "value": "1Bll-1-201-aaa"}]|
3|Apple Pie  |[{"id": 5, "name": "Apple Pie", "value": "1All-1-1000-xzp"}]          |


Step 3: Run an SQL query

SELECT name, jsonb_agg(t->'name') AS brand, jsonb_agg(t->'value') AS code 

FROM products, jsonb_array_elements(products.product) t

GROUP BY name;


The results
name       |brand                   |code               |
-----------|------------------------|-------------------|
Apple Pie  |["Apple Pie"]           |["1All-1-1000-xzp"]|
Orange bod |["Orange Gala"]         |["1Bll-1-99-aaa"]  |
Chicken Pie|["Downtown Chicken Pie"]|["1Bll-1-201-aaa"] |


Another method is to include a WHERE clause as shown below;

SELECT name, jsonb_agg(t->'name') AS brand, jsonb_agg(t->'value') AS code 

FROM products, jsonb_array_elements(products.product) t

WHERE t->>'name'='Orange Gala'

GROUP BY name;


I hope this simple example will benefit you. 

Friday, January 22, 2021

SQL to replace username field with user id

The scenario is, a table called assets was loaded through a script, but the column updated_by which should contain the user id, is stored with the user name instead. How to replace the updated_by field with the user id?


Here is an example of the table structure;

assets(id, name, description, updated_by)

users(id, name)


Solution 

Through the SQL command;

UPDATE assets t2

SET    updated_by = t1.id

FROM   users t1

WHERE  t2.updated_by = t1.user_id;

Wednesday, January 13, 2021

How to install Docker ReportServer Community

 ReportServer for Community is a Java based application that is available through Docker. There are options to install manually but some knowledge on Tomcat and Java is required.

The Docker (version 20.10.1) option installs on an image with Debian release 10 (Buster) with ReportServer version 3.3.0. 

The ReportServer for community image is available at https://bitnami.com/stack/reportserver/containers

Pre-requisite:

  • Installed Docker version 20+
  • You have create an account with docker and Docker is running with your signin.




On Windows, open powershell and go to your install folder. In my case its C:\users\tboxmy

Retrieve from the server required image

docker pull bitnami/reportserver

Yet to know if this line was useful, as I did not run docker-compose up -d

curl https://raw.githubusercontent.com/bitnami/bitnami-docker-reportserver-community/master/docker-compose.yml > docker-compose.yml


Configure network and database

docker network create reportserver-tier

docker run -d --name mariadb -e ALLOW_EMPTY_PASSWORD=yes -e MARIADB_USER=bn_reportserver -e MARIADB_DATABASE=bitnami_reportserver --net reportserver-tier --volume C:\Users\nasbo\mariadb-persistence:/bitnami bitnami/mariadb:latest


List the images

docker images


Start ReportServer

docker run -d --name reportserver-community -p 80:8080 -e ALLOW_EMPTY_PASSWORD=yes -e REPORTSERVER_DATABASE_USER=bn_reportserver -e REPORTSERVER_DATABASE_NAME=bitnami_reportserver --net reportserver-tier bitnami/reportserver:latest


Access ReportServer from a web browser

http://localhost/reportserver

Use default username user and password as bitnami


Friday, November 13, 2020

Laravel quick commands for Artisan

 Laravel utilise Artisan to help make working with development faster. This allow programmers to focus more on the development than the management of packages and some repeated workflows.



Here I list the top few commands that I use;

For scaffolding

  • make:controller
    • Create a controller file in app/Http/Controllers
    • php artisan make:controller ArticleController
  • Create a default model
    • php artisan make:model Article
  • Create a model along with migration and factory
    • php artisan make:model Article -crmf
  • Create migration file
    • php artisan make:migration create_articles_table
  • Process all the migration file that haven't been run before
    • php artisan migrate
  • Create Seeder file
    • php artisan make:seeder CustomerTableSeeder
  • Process seeder file
    • php artisan db:seed
    • php artisan db:seed --class=CustomerTableSeeder
  • List command help
    • php artisan list
  • Routing
    • php artisan route:list
  • Debugging
    • php artisan tinker
  • Front-end user interface
    • php artisan ui bootstrap|vue|react
  • Remove Front-end user interface
    • php artisan preset none
  • Create front-end with user authentication
    • php artisan ui vue --auth
  • A stand alone server start, maintenance mode, normal mode
    • php artisan serve
    • php artisan down
    • php artisan up
  • Refresh laravel optimisation files
    • php artisan dump-autoload

Tuesday, November 10, 2020

Laravel and logging of errors

During the course of development, there are many tools and approaches to debug a programme. In Laravel there is a default logging that supports RFC 5424 and here is how to apply it in a Laravel 7 based application.

As a point of reference, this article is for default Laravel 7 on a Apache2 webserver. Which means, if PHP-FPM is used, check the webserver log files. Additionally, there are many more advanced logging by Laravel, for example use of Rollbar, if you have time to explore.

What is Laravel logging? 

Withing Laravel framework, its config/app.php determines classes that does logging. Monolog logging library is used to provide the classes that can be called from the framework. Its flexibility allows logging across different files and even disk. 

The default logging uses a channel known as stack and is configured as

 'default' => env('LOG_CHANNEL', 'stack'),

This provides logging in several levels of severity that range from in the following order;

  • info
  • debug
  • notice
  • warning
  • error
  • critical
  • emergency

Context data is provided for a more consistent format as described in PSR-3.

How to enable default logging? 

Edit the file .env and have this line to enable debug mode;

APP_DEBUG=true

Where is the default logging done? It all in the file laravel.log found in <project_folder>/storage/logs. Ensure the application have correct permission to write app/storage and all its subfolders. When using Selinux, also ensure its allowed to write.

When is logging done?

This can be done practically any where, such as within the controller, views and any other executable.

How to do the logging? 

Taking that you have by now enabled debug mode.

Lets look at how its done within a Controller.

  1. Ensure top of the controller file contains the line
    • use Illuminate\Support\Facades\Log;
  2. Write the code to log your message
    • Log::info('This is where the code runs');

Once when you run the application and the Log::info( ) gets triggered, have a look at the end of file storage/logs/laravel.log to find the message.

Will consider to write further on formatting of the log in order for logging tools to pull data and generate reports or monitoring

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