September 20, 2016

How do I know when my docker mysql container is up and mysql is ready for taking queries?

Haren’s Question:

I am deploying a few different docker containers, mysql being the first one. I want to run scripts as soon as database is up and proceed to building other containers. The script has been failing because it was trying to run when the entrypoint script, which sets up mysql (from this official mysql container), was still running.

sudo docker run --name mysql -e MYSQL_ROOT_PASSWORD=MY_ROOT_PASS -p 3306:3306 -d mysql
[..] wait for mysql to be ready [..]
mysql -h -P 3306 -u root --password=MY_ROOT_PASS < MY_SQL_SCRIPT.sql

Is there a way to wait for a signal of an entrypoiny mysql setup script finishing inside the docker container? Bash sleep seems like a suboptimal solution.

EDIT: Went for a bash script like this. Not the most elegant and kinda brute force but works like a charm. Maybe someone will find that useful.

OUTPUT="Can't connect"
while [[ $OUTPUT == *"Can't connect"* ]]
OUTPUT=$(mysql -h $APP_IP -P :$APP_PORT -u yyy --password=xxx < ./my_script.sql 2>&1)

On your ENTRYPOINT script, you have to check if you have a valid MySQL connection or not.

This solution does not require you to install a MySQL Client on the container and while running the container with php:7.0-fpm running nc was not an option, because it had to be installed as well. Also, checking if the port is open does not necessarily mean that the service is running and exposed correctly. [more of this]

So in this solution, I will show you how to run a PHP script to check if a MySQL Container is able to take connection. If you want to know why I think this is a better approach check my comment here.


cat << EOF > /tmp/wait_for_mysql.php
$connected = false;
while(!$connected) {
        $dbh = new pdo( 
            'mysql:host=mysql:3306;dbname=db_name', 'db_user', 'db_pass',
        $connected = true;
    catch(PDOException $ex){
        error_log("Could not connect to MySQL");
        error_log("Waiting for MySQL Connection.");
php /tmp/wait_for_mysql.php
# Rest of entry point bootstrapping

By running this, you are essentially blocking any bootstrapping logic of your container UNTIL you have a valid MySQL Connection.

June 30, 2016

How to run Witter app from Udacity “Offline Web Applications” course using docker?

This blog post shows how you can run the Wittr application from a Udacity course called ‘Offline Web Applications’ using docker. This is helpful if your development stack does not run on localhost and you want to overcome `insecure origin` issue of the browsers.

Note: This is blog post, so I have written a bit back story as well. If you don’t want to read about that clone run docker-compose up -d Done!

I was trying a course from udacity called “Offline Web Applications” and I got stuck in the point where I was trying to register the service worker. That was because the request to register the service worker was coming form an insecure origin. Nowadays, modern browser browswer have started to deprecate powerful web feature on insecure origin (more here)) and the course fails to address this issue because the developer’s stack can vary. So the question is What is secure origin?

In chrome “Secure origins” are origins that match at least one of the following (scheme, host, port) patterns: more here

(https, *, *)
(wss, *, *)
(*, localhost, *)
(*, 127/8, *)
(*, ::1/128, *)
(file, *, —)
(chrome-extension, *, —) 

So it still supports developer in a way that is does not restrict request from localhost 127... or ::1. Which was another thing to fix because my development stack is not be the most common one as I don’t use localhost to test my work. I do these through vms, vagrant and nowadays from docker as well. This means that most of the time the test url is anything but localhost. So stuck on this for a while I tries several things, like trying to turn off insecure origin flag on flag, proxy, trying to point localhost to another ip is windows 10 bunch of bullshit which is just lost time. So I created a docker configuration to run the witter project.

file: Dockerfile

FROM node:latest

# Create app directory
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

# Install app dependencies
COPY ./* /usr/src/app/
RUN npm install

# Bundle app source
COPY . /usr/src/app

EXPOSE 8888 8889
CMD [ "npm run serve" ]

Simple enough for those who know docker basics. It binds with the ports in the host, so the project will run as localhost:8888 and localhost:8889 as the course wants. But if you want to know what it does, I am happy to explain it.

I have forked the course repo and have added this (with a docker-compose.yml as well) to the project itself at:

Clone rather than the one provided in the course and run docker-compose up -d and continue with the course. I have also have created a pull request to help others but there is already 2 previous pull request pending without any comments, So I doubt it will be pulled.

Comments appreciated.


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