Update CI script

.github/workflows/deploy.yml

@@ -29,18 +29,53 @@ jobs:
         ssh-agent -a $SSH_AUTH_SOCK > /dev/null   
         ssh-add /home/runner/.ssh/*
         ssh-keyscan ${{ secrets.INSTANCE_IP }} >> /home/runner/.ssh/known_hosts
-    - uses: cachix/install-nix-action@v14.1
+    - uses: cachix/install-nix-action@v17
       with:
         extra_nix_config: |
+          # save space on disk and in cache
+          auto-optimise-store = true
+          # keep all store paths necessary to build the outputs
+          keep-outputs = true
+          keep-derivations = true
+          # Enable flakes
           experimental-features = nix-command flakes
+          # Deploy tokens
           access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
     - uses: actions/cache@v2
       with:
         path: |
           /nix/store
-        key: ${{ runner.os }}-${{ hashFiles('flake.lock') }}
+        key: nki-nix-${{ github.sha }}
+        restore-keys: |
+          nki-nix-
+        path: |
+          nix_store_dir
+          nix_store_db.sqlite
+    - name: restore cached nix store
+      run: |
+        if [ -e nix_store_db.sqlite ]; then
+          sudo systemctl stop nix-daemon
+          # put cached store paths back in their proper locations
+          sudo rm -rf /nix/store /nix/var/nix/db/db.sqlite
+          sudo mv nix_store_dir /nix/store
+          sudo cp nix_store_db.sqlite /nix/var/nix/db/db.sqlite
+          # fix store permissions
+          sudo chmod 1775 /nix/store
+          sudo chown root:nixbld /nix/store
+          sudo chmod 0644 /nix/var/nix/db/db.sqlite
+          sudo chown -R root:root /nix/store /nix/var/nix/db/db.sqlite
+          sudo systemctl start nix-daemon
+        fi
     - name: Deploy with deploy-rs
       env:
         SSH_AUTH_SOCK: /tmp/ssh_agent.sock
       run: |
         nix run -L github:Serokell/deploy-rs . -- --hostname ${{ secrets.INSTANCE_IP }} -- -L
+    - name: prepare nix store for caching
+      run: |
+        # delete old stuff not relevant to this build
+        nix store gc
+        sudo systemctl stop nix-daemon
+        # move store to a place where the cache action can read it
+        sudo mv /nix/store nix_store_dir
+        sudo mv /nix/var/nix/db/db.sqlite nix_store_db.sqlite