impress-2020/deploy/playbooks/deploy.yml

---
- name: Deploy impress-2020 from the current local version
  hosts: webserver
  vars:
    skip_build: no # Can override this by running `yarn deploy-skip-build`
    local_app_root: "{{ playbook_dir  }}/../.."
    remote_versions_root: "/srv/impress-2020/versions"
  tasks:
    # For our deployment, our server resources are more constrained than our
    # dev machine, and builds are an expensive uncommon RAM & CPU spike. Let's
    # use our local machine for it! (I found that, running remotely, 2GB RAM
    # was not enough to build impress-2020 😅)
    - name: Run `yarn build` locally to build the current version
      delegate_to: localhost
      command:
        chdir: "{{ local_app_root }}"
        cmd: yarn build
      when: not skip_build

    - name: Generate a version name from the current timestamp
      command: date '+%Y-%m-%d-%s'
      register: new_app_version

    - name: Print out the new version name
      debug:
        msg: "Deploying new version: {{ new_app_version.stdout }}"

    - name: Save new remote folder path to a variable
      set_fact:
        remote_app_root: "{{ remote_versions_root }}/{{ new_app_version.stdout }}"

    - name: Create new remote folder for the new version
      file:
        path: "{{ remote_app_root }}"
        state: directory

    - name: Copy local app's source files to new remote folder
      ansible.posix.synchronize:
        src: "{{ local_app_root }}/"
        dest: "{{ remote_app_root }}"
        rsync_opts:
          - "--exclude=.git"
          - "--filter=':- .gitignore'"

    - name: Copy local app's .next build files to new remote folder
      ansible.posix.synchronize:
        src: "{{ local_app_root }}/.next/"
        dest: "{{ remote_app_root }}/.next"

    - name: Copy local app's .env secrets file to new remote folder
      ansible.posix.synchronize:
        src: "{{ local_app_root }}/.env"
        dest: "{{ remote_app_root }}/.env"

    - name: Check whether we can reuse the currently deployed node_modules.
      # First, compare the files. Then, ensure that node_modules is in a good
      # state and will be linkable. Finally, ensure that it's one of the 5 most
      # recent versions, so it won't be cleaned up. If this succeeds, we can do
      # the link cheat! If this fails, proceed and run `yarn install` instead.
      command: |
        bash -c "
          cmp '{{ remote_app_root }}/yarn.lock' '/srv/impress-2020/current/yarn.lock' &&
            test -e /srv/impress-2020/current/node_modules &&
            (ls -dt /srv/impress-2020/versions/* | head -n 5 | grep $(realpath /srv/impress-2020/current/node_modules/..))"        
      failed_when: no
      register: can_reuse_node_modules_when_successful

    - name: Link node_modules to current deployed version, if they match
      # Linking is a pretty wild cheat to make this much faster than copying!
      # We're counting on the assumptions that 1) versions' dependencies don't
      # change after the fact, and 2) the app doesn't mutate node_modules while
      # running. So, these two copies of node_modules *should* just stay
      # permanently the way they are forever, so linking shoouulld be safe 🤞
      command: |
        bash -c "ln -s $(realpath /srv/impress-2020/current/node_modules) {{ remote_app_root }}/node_modules"        
      when: "can_reuse_node_modules_when_successful.rc == 0"

    - name: Run `yarn install` to install dependencies in new remote folder
      command:
        chdir: "{{ remote_app_root }}"
        cmd: yarn install
      when: "can_reuse_node_modules_when_successful.rc > 0"

    - name: Update the `current` folder to point to the new version
      file:
        src: "{{ remote_app_root }}"
        dest: /srv/impress-2020/current
        state: link

    - name: Reload the app in pm2
      command: pm2 reload impress-2020

    - name: Find older versions to clean up
      # Print out all but the 5 last-recently-updated versions.
      # NOTE: If we change this count, change the count we use when checking
      #       whether to reuse node_modules too!
      # TODO: This *will* still break *older* versions that pointed to an old
      #       `node_modules` that got cleaned up, which could make rollback a
      #       pain. We don't roll back often for DTI so that's probably fine,
      #       but it'd be better to do something a bit more robust - or just
      #       drop it and accept the install perf hit every time. (It's only
      #       like 40 seconds on this last test, which isn't as bad as I
      #       remember, especially when deploys aren't super common.)
      command:
        chdir: "{{ remote_versions_root }}"
        cmd: bash -c 'ls -t | tail -n +6'
      register: versions_to_clean_up

    - name: Clean up older versions
      file:
        path: "{{ remote_versions_root }}/{{ item }}"
        state: absent
      with_items: "{{ versions_to_clean_up.stdout_lines }}"