Find an exact match of a nested field
(note that .keyword has to be added to string fields)
{
"query": {
"bool": {
"must": [
{
"term": {
"filemetadata.title.keyword": "File test.pdf"
}
}
]
}
},
"size": 200
}
Data generated and used by Docker containers does not persist after restarts. We use Docker volumes to manage data to solve this issue. We use it to persist data in a container or share data between containers.
Volumes are the preferred mechanism for persisting data generated and user by Docker containers. Volumes are easier to back up or migrate.
Volumes are often a better choice than persisting data in a container’s writable layer, because a volume does not increase the size of the containers using it. The volume’s contents exist outside the lifecycle of a given container.
We have 3 volume types:
Helpful to persist data temporarily. If we restart our container data is still visible. It doesn’t persist when we remove the container. Not accessible by other containers. They’re created inside /var/lib/docker/volume.
Example file:
version: '3.8'
services:
db:
image: mysql
restart: always
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: test_db
ports:
- "3306:3306"
volumes:
- /var/lib/mysql
Steps to go from a docker-compose file, to build an Image out of the file, upload it to DockerHub, and run it with Kubernetes (minikube).
# linux
curl -L https://github.com/kubernetes/kompose/releases/download/v1.22.0/kompose-linux-amd64 -o kompose
chmod +x kompose
sudo mv ./kompose /usr/local/bin/kompose
Clone the files, go to the directory where your Dockerfile is and run:
# mariocodes is my DockerHub username
# kubernetes-custom-java-maven-app is the name of the repo I created at DockerHub
docker build -f Dockerfile -t mariocodes/kubernetes-custom-java-maven-app .
See logs:
kubectl logs <pod-name>
Modifiers:
-c If you have multiple containers in your Pod, you can choose the container to view.-f continuously stream logs back to the terminal without exiting.You can also use the exec command to execute commands in running containers:
# attach to bash
kubectl exec -it <pod-name> -- bash
# attach to running process
kubectl attach -it <pod-name>
CrashLoopBackOff and no log appears. This happens as the container has no command to run so it start up and then immediately exits.
Give your image a command.
apiVersion: v1
kind: Pod
metadata:
name: twocontainers
spec:
containers:
- name: container1
image: python:3.6-alpine
command: ['sh', '-c', 'echo cont1 > index.html && python -m http.server 8082']
- name: container2
image: python:3.6-alpine
command: ['sh', '-c', 'echo cont1 > index.html && python -m http.server 8083']
This are my databases notes for both Relational (MySQL and MariaDB) and no relational (MongoDB).
1. MySQL Administration
2. SQL Experience
3. MySQL User Privileges
This details various ways that you can interact with the code and data running inside your pod.
If you want access to a specific pod, even if it’s not serving traffic on the internet. To achieve this, Kubernetes has support built into it.
kubectl port-forward kuard 8080:8080
A secure tunnel is created from your local machine, though the K8s master, to the instance of the Pod running on one of the worker nodes.
When you need to debug.
# downloads the current logs from the running instance
kubectl logs kuard
# continuously streams logs
kubectl logs -f kuard
# get logs from a previous instance of the container. Useful if your containers are continuously restarting at startup.
kubectl logs kuard --previous
i18n is just a nomenclature for Internationalization. i18n involves, among other things, the ability to display translated content. It prepares a digital product for localization by for example, separate the content into strings so they are ready to be translated and delivered.
The same goes for L10n. This is a nomenclature for Localization. L10n involves translating content, adapting graphics and finalizing the producto for each regional market.
https://www.oneskyapp.com/blog/i18n-need-to-know-internationalization/
(Oficial Doc: https://minikube.sigs.k8s.io/docs/start/)
Technology to quickly set up a Kubernetes cluster locally to learn how to use Kubernetes.
How to install on a fresh Ubuntu installation:
Install prerrequisites and kubectl
sudo apt-get update && sudo apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee -a /etc/apt/sources.list.d/kubernetes.list
sudo apt-get update
sudo apt-get install -y kubectl
Don’t create indexes in every column. This slows things down on insert, delete or update operations.
You may create an index for columns that are common in WHERE, ORDER BY or GROUP BY clauses. You may also consider adding an index in columns that are used to relate other tables JOIN.
Index are best used for big domain fields such as ids, names, surnames. Don’t use them for male/female fields.
A good recommendation is to measure performance time before and after the creation of that index. If your index doesn’t improve performance remove it as it causes overhead.
The union sentence is used to accumulate results for two SELECT sentences.
SELECT column1, column2 FROM table1
UNION
SELECT column1, column2 FROM table2
We have the following tables
company1
| per | name | surname |
|---|---|---|
| 1 | ANTONIO | PEREZ |
| 2 | PEDRO | RUIZ |
company2
| per | name | surname |
|---|---|---|
| 1 | LUIS | LOPEZ |
| 2 | ANTONIO | PEREZ |