Building Dockerfiles

FROM node:12-stretch

CMD ["node", "-e", "console.log(\"hi lol\")"]

• Start with the node container. This comes from at least at some point, a Debian image.
• There is only one CMD instruction.
• docker build . --tag my-node-app
• docker run my-node-app
• docker images - show the images you built
• You can version them if you want to
• docker ps - see all running Docker processes
• docker stop ${PID} - well, stop it
• Can’t stop with CTRL+C, you have to handle it yourself in the Node.js code, or you can tell Docker to handle it with init flag.
• docker run --init --publish 8000:3000 my-node-app # or you can use -p instead of --publish
  • Run the app that we have in the container (port 3000) and expose it to port 8000 (localhost:8000 locally)

FROM node:12-stretch

USER node

COPY index.js /home/node/code/index.js // Copy current index.js to that directory in the container

CMD ["node", "/home/node/code/index.js"]

• USER instruction let’s us switch from being the root user to different user. The NODE user was already created by the image need to run useradd to add another user.

• WORKDIR - changing directory.

• EXPOSE ???

React-query: Parallel and Dependent Queries

Reference

• Getting both repos and gists: Promise.all

function getReposAndGists(username) {
  return Promise.all([
    fetch(`https://api.github.com/users/${username}/repos`)
      .then((res) => res.json()),
    fetch(`https://api.github.com/users/${username}/gists`)
      .then((res) => res.json())
  ]);
}

• useQueries - used to fetch a variable number of queries.
• Dependent query: Use useQuery third parameter - the configuration object.

Run the issuesQuery only after the labels query has been fetched.

const labelsQuery = useQuery(
  ["repos", owner, repo, "labels"],
  () => fetch(
    `https://api.github.com/repos/${owner}/${repo}/labels`
  ).then((res) => res.json())
);

const labels = labelsQuery.data

const issuesQuery = useQuery(
  ["repos", owner, repo, "issues"],
  () => fetch(
    `https://api.github.com/repos/${owner}/${repo}/issues?labels=${labels[0].name}`
  ).then((res) => res.json()),
  {
    enabled: !!labels
  }
);

• fetch Status - if it’s fetching, idle, or paused.
• Deferred query: Something like when the query immediately makes a request with an empty search query.
• encodeURIComponent()

useQuery API Reference

Reference

• querykey - query will update when the key changes, as long as enabled is not set to false.
• queryFn - required, but only if no default query function has been defined.
• enabled - disable to stop the query from automatically running, used for dependent queries.