Gain insights into Docker fundamentals, delve into advanced concepts like database connectivity and Docker Compose, and discover how to monitor and scale services with Docker Swarm.

course_final_image.tar.gz

Flask App_new

docker-compose

Docker_build

flask_venv

Flask_demo_test

add db to container

Exercise

Exercise 2

exercise 3

exercise_4

Bonus Section - Flask

exercise 3-copy

docker-compose-copy

Docker_build-copy

add db to container-copy

Exercise 2-copy

exercise_4-copy

Bonus Section - Flask-copy

Docker_build-copy-copy

Whether you are a DevOps beginner or just a developer who wants to start working with containers, you’re in the right place. Docker is an in-demand technology that you will be exposed to frequently while on the job.

 

Docker is used for setting up, deploying, and running applications, at scale, by containerizing them. More on that later. Docker also provides developers with a consistent environment for product development, and along with Kubernetes, makes managing the development lifecycle a breeze.

 

In this course, you will learn the fundamentals of Docker such as containers, images, and commands. You’ll then progress to more advanced concepts like connecting to a database container and how to simplify workflows with Docker Compose. At the end, you’ll learn how to monitor clusters and scale Docker services with Swarm.

Working with Containers: Docker & Docker Compose

Here, we will see how to access application logs from the container.

# Container logs

When we run our app in Docker, we might need to access logs of the server. If your container is running in daemon mode or in the background, type `docker ps` to list all running containers.

```
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
64dcb356b5e4        flask_app:1.0       "flask run"         12 hours ago        Up 12 hours                             charming_solomon
```

Now, on the command line, type

`docker logs <CONTAINER ID>`

This should show all the logs our application server has created so far. Below is a snapshot of my logs:

```
 * Serving Flask app "app.py" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 310-087-588
 * Detected change in '/code/app.py', reloading
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 310-087-588
 * Detected change in '/code/app.py', reloading
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 310-087-588
```

You can further save these logs in any file by redirecting stdout to a file.

`docker logs <CONTAINER ID> >output.log`


# Real-time logs

Although in production, the log management strategy will be different, for startups or a small case project, there might be 
a situation where you have to watch real-time logs rather than access old logs.

There are two ways to do that:
1. This is a little bit critical. You can attach a daemon container directly to a command prompt. In short, you will bring the container foreground from a daemon mode.

Open a new terminal window like so:
* `docker ps` to check running containers
* `docker attach <CONTAINER ID>`

This will show a blank line with the cursor at the starting position if no one is accessing your app.

Next, refresh the app in the browser.

You should see an entry for the log is now generated.

```
Venkateshs-MacBook-Air:Online_Projects venkateshachintalwar$ docker attach 204df32b9504
172.17.0.1 - - [03/Apr/2020 15:49:39] "POST / HTTP/1.1" 200 -
```

>Why is this critical and not recommended? If you accidentally press ctrl+c or any kill signal to get back to the shell, the application will stop.

2. In this method, we will use the earlier-used command to see container logs. 

`docker logs -f <CONTAINER ID>`

This code above will print all the logs and listen for new activity.

```
 * Serving Flask app "app.py"
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
172.17.0.1 - - [03/Apr/2020 18:13:39] "POST / HTTP/1.1" 200 -
```

This is safe because when you exit and get back to the shell, the app will continue running. 

Accessing Application Logs in Docker

Introduction to Course

Why Docker?

Getting Started With Docker

Docker Fundamentals

Automation using Dockerfile

Advance Docker

Introduction to Docker-Compose

Exposure to Docker Swarm

Bonus Section

Accessing Application Logs in Docker