ci: cache Nix store with cache-nix-action (#2992)

* ci: try nix-community/cache-nix-action

* ci: add cache-id param to setup-nix action

* ci: tidy up cache keys for non-nix jobs

* ci: merge-nix-caches-linux job

* ci: merge caches other way around

* ci: reduce number of caches

Should prevent disk overflow

* ci: change cache id prefix for merge

* ci: comment out cache merging job

* ci: revert cache id prefix

* ci: setup-nix: use latest cache-nix-action

Among others, makes action logs look more tidy (see https://github.com/nix-community/cache-nix-action/commit/17d19d3d8be918757589635bc1a6830be0b129d2)

* ci: use test-pg cache key for loadtest

.github/actions/setup-nix/action.yaml

@@ -7,13 +7,23 @@ inputs:
     description: Token to pass to cachix
   tools:
     description: Tools to install with nix-env -iA <tools>
+  cache-id:
+    description: Cache id to use for cache-nix-action
+    default: "default"
 
 runs:
   using: composite
   steps:
-    - uses: cachix/install-nix-action@v23
+    - uses: nixbuild/nix-quick-install-action@v26
       with:
-        install_url: https://releases.nixos.org/nix/nix-2.13.3/install
+        nix_version: '2.13.6'
+    - name: Restore and cache Nix store
+      uses: nix-community/cache-nix-action@v4.0.3
+      with:
+        key: cache-nix-${{ runner.os }}-id-${{ inputs.cache-id }}-${{ hashFiles('nix/**/*.nix') }}
+        restore-keys: |
+          cache-nix-${{ runner.os }}-common-
+        restore-key-hit: true
     - uses: cachix/cachix-action@v12
       with:
         name: postgrest

.github/workflows/ci.yaml

@@ -22,6 +22,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: style
+          cache-id: style
       - name: Run linter (check locally with `nix-shell --run postgrest-lint`)
         run: postgrest-lint
       - name: Run style check (auto-format with `nix-shell --run postgrest-style`)
@@ -42,6 +43,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: tests
+          cache-id: test-pg
 
       - name: Run coverage (IO tests and Spec tests against PostgreSQL 15)
         run: postgrest-coverage
@@ -77,6 +79,9 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: tests withTools
+          # It seems like they are installing the same set of derivations, so we can assign them the same cache id. 
+          # This would decrease the amount of caches dowloaded on merge cache step and will prevent disk space issues.
+          cache-id: test-pg 
 
       - name: Run spec tests
         if: always()
@@ -96,6 +101,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: memory
+          cache-id: test-memory
       - name: Run memory tests
         run: postgrest-test-memory
 
@@ -109,6 +115,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: tests
+          cache-id: static-nix
 
       - name: Build static executable
         run: nix-build -A postgrestStatic
@@ -130,6 +137,32 @@ jobs:
           path: postgrest-docker.tar.gz
           if-no-files-found: error
 
+  # TODO: Enable this again in a PR by PostgREST admins, because regular users don't have permission to delete cache entries, which this job does.
+  #
+  # merge-nix-caches-linux:
+  #   name: "Merge Nix caches (Linux)"
+  #   needs: [Test-Nix, Test-Pg-Nix, Test-Memory-Nix, Build-Static-Nix, Lint-Style]
+  #   runs-on: ubuntu-latest
+  #   strategy:
+  #     max-parallel: 1
+  #     matrix:
+  #       cache-id: ['static-nix', 'test-pg', 'style', 'test-memory']
+  #   steps:
+  #     - uses: actions/checkout@v4
+  #     - uses: nixbuild/nix-quick-install-action@v26
+  #       with:
+  #         nix_version: '2.13.6'
+  #     - name: Restore and cache Nix store
+  #       uses: nix-community/cache-nix-action@v4
+  #       with:
+  #         key: cache-nix-${{ runner.os }}-common-${{ hashFiles('nix/**/*.nix') }}
+  #         extra-restore-keys: |
+  #           cache-nix-${{ runner.os }}-cid-
+  #         purge: true
+  #         purge-keys: |
+  #           cache-nix-${{ runner.os }}-cid-
+  #           cache-nix-${{ runner.os }}-common-
+  #         purge-created-max-age: 0
 
   Build-Macos-Nix:
     name: Build MacOS (Nix)
@@ -180,7 +213,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ${{ matrix.cache }}
-          key: ${{ runner.os }}-${{ hashFiles('stack.yaml.lock') }}
+          key: cache-stack-${{ runner.os }}-${{ hashFiles('stack.yaml.lock') }}
       - name: Install dependencies
         if: ${{ matrix.deps }}
         run: ${{ matrix.deps }}
@@ -236,9 +269,9 @@ jobs:
         uses: actions/cache@v3
         with:
           path: ~/.cabal
-          key: ${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('**/*.cabal') }}-${{ hashFiles('**/cabal.project') }}
+          key: cache-cabal-${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('**/*.cabal') }}-${{ hashFiles('**/cabal.project') }}
           restore-keys: |
-            ${{ runner.os }}-${{ matrix.ghc }}-
+            cache-cabal-${{ runner.os }}-${{ matrix.ghc }}-
       - name: Install dependencies
         run: |
           cabal update

.github/workflows/loadtest.yaml

@@ -23,6 +23,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: loadtest
+          cache-id: test-pg
       - uses: actions-ecosystem/action-get-latest-tag@v1
         id: get-latest-tag
         with:
@@ -54,6 +55,7 @@ jobs:
         uses: ./.github/actions/setup-nix
         with:
           tools: loadtest
+          cache-id: test-pg
       - name: Run loadtest
         run: |
           postgrest-loadtest-against ${{ steps.get-latest-tag.outputs.tag }}