Speed up the Build workflow

- Pass the MariaDB client library to mysqlclient-sys through its environment variables, so a cached build no longer recompiles mysqlclient-sys, diesel and diesel_migrations in every MySQL build.
- Split each channel into two parallel jobs, keeping the required check names through a result job per channel.
- Drop the sqlite,mysql,postgresql,enable_mimalloc test: enable_mimalloc is still tested on and off.
- Only save caches on main, so pull requests and branches no longer push main's caches out of the 10 GB limit.

.github/workflows/build.yml

@@ -40,24 +40,53 @@ defaults:
 
 jobs:
   build:
-    name: Build and Test ${{ matrix.channel }}
+    name: Build and Test ${{ matrix.channel }} (part ${{ matrix.part }})
     runs-on: ubuntu-24.04
     timeout-minutes: 120
     # Make warnings errors, this is to prevent warnings slipping through.
     # This is done globally to prevent rebuilds when the RUSTFLAGS env variable changes.
     env:
       RUSTFLAGS: "-Dwarnings"
+    # Which parts passed, read by the `result` job below. Matrix jobs combine their outputs.
+    outputs:
+      rust-toolchain-1: ${{ steps.passed.outputs.rust-toolchain-1 }}
+      rust-toolchain-2: ${{ steps.passed.outputs.rust-toolchain-2 }}
+      msrv-1: ${{ steps.passed.outputs.msrv-1 }}
+      msrv-2: ${{ steps.passed.outputs.msrv-2 }}
     strategy:
       fail-fast: false
       matrix:
         channel:
           - "rust-toolchain" # The version defined in rust-toolchain
           - "msrv" # The supported MSRV
+        # Each step builds the whole vaultwarden crate again, so the steps are split over two jobs of
+        # about the same length that run in parallel.
+        part:
+          - 1 # Several backends together, and the lints
+          - 2 # One backend at a time
 
     steps:
       # Install dependencies
       - name: "Install dependencies Ubuntu"
-        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends openssl build-essential libmariadb-dev-compat libpq-dev libssl-dev pkg-config
+        run: |
+          # Separate commands, so a failing update fails the step. The image already has Oracle's MySQL client
+          # library, so a skipped install would otherwise go unnoticed and build against that one.
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends openssl build-essential libmariadb-dev-compat libpq-dev libssl-dev pkg-config
+
+          # Pass the MariaDB client library to mysqlclient-sys through its environment variables.
+          # When it finds the library with pkg-config, its build script makes cargo rerun it whenever
+          # anything in the library directory changes, and the install above changes that directory on
+          # every run. So every MySQL build recompiled mysqlclient-sys, diesel and diesel_migrations,
+          # even with a cached build. Cargo compares environment variables by their value instead.
+          lib_dir="$(pkg-config --variable=libdir mysqlclient)"
+          version="$(pkg-config --modversion mysqlclient)"
+          {
+            echo "MYSQLCLIENT_NO_PKG_CONFIG=1"
+            echo "LIBMARIADB_NO_PKG_CONFIG=1"
+            echo "MYSQLCLIENT_LIB_DIR=${lib_dir}"
+            echo "MYSQLCLIENT_VERSION=${version}"
+          } | tee -a "${GITHUB_ENV}"
       # End Install dependencies
 
       # Checkout the repo
@@ -119,50 +148,50 @@ jobs:
           # Like changing the build host from Ubuntu 20.04 to 22.04 for example.
           # Only update when really needed! Use a <year>.<month>[.<inc>] format.
           prefix-key: "v2025.09-rust"
+          # The two parts build the dependencies with different features, so each has its own cache.
+          key: part-${{ matrix.part }}
+          # Only main saves caches. The repository can keep 10 GB of caches, and the ones saved by pull
+          # requests and other branches were mostly copies of main's that pushed other caches out.
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       # End Enable Rust Caching
 
       # Run cargo tests
-      # First test all features together, afterwards test them separately.
+      # Part 1 tests several features together, part 2 tests each database backend on its own.
+      # enable_mimalloc only selects the allocator, so it is tested on and off, not with every combination.
       - name: "test features: sqlite,mysql,postgresql,enable_mimalloc,s3"
         id: test_sqlite_mysql_postgresql_mimalloc_s3
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 1 }}
         run: |
           cargo test --profile ci --features sqlite,mysql,postgresql,enable_mimalloc,s3
 
-      - name: "test features: sqlite,mysql,postgresql,enable_mimalloc"
-        id: test_sqlite_mysql_postgresql_mimalloc
-        if: ${{ !cancelled() }}
-        run: |
-          cargo test --profile ci --features sqlite,mysql,postgresql,enable_mimalloc
-
       - name: "test features: sqlite,mysql,postgresql"
         id: test_sqlite_mysql_postgresql
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 1 }}
         run: |
           cargo test --profile ci --features sqlite,mysql,postgresql
 
       - name: "test features: sqlite"
         id: test_sqlite
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 2 }}
         run: |
           cargo test --profile ci --features sqlite
 
       - name: "test features: mysql"
         id: test_mysql
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 2 }}
         run: |
           cargo test --profile ci --features mysql
 
       - name: "test features: postgresql"
         id: test_postgresql
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 2 }}
         run: |
           cargo test --profile ci --features postgresql
 
       # The test seeder only exists with this feature, which no release build has
       - name: "test features: sqlite,unsafe_test_mode"
         id: test_unsafe_test_mode
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.part == 2 }}
         run: |
           cargo test --profile ci --features sqlite,unsafe_test_mode
       # End Run cargo tests
@@ -171,13 +200,13 @@ jobs:
       # Run cargo clippy, and fail on warnings
       - name: "clippy features: sqlite,mysql,postgresql,enable_mimalloc,s3"
         id: clippy
-        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' }}
+        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' && matrix.part == 1 }}
         run: |
           cargo clippy --profile ci --features sqlite,mysql,postgresql,enable_mimalloc,s3
 
       - name: "clippy features: sqlite,unsafe_test_mode"
         id: clippy_unsafe_test_mode
-        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' }}
+        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' && matrix.part == 1 }}
         run: |
           cargo clippy --profile ci --features sqlite,unsafe_test_mode
       # End Run cargo clippy
@@ -186,7 +215,7 @@ jobs:
       # Run cargo fmt (Only run on rust-toolchain defined version)
       - name: "check formatting"
         id: formatting
-        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' }}
+        if: ${{ !cancelled() && matrix.channel == 'rust-toolchain' && matrix.part == 1 }}
         run: |
           cargo fmt --all -- --check
       # End Run cargo fmt
@@ -198,7 +227,6 @@ jobs:
         if: ${{ failure() }}
         env:
           TEST_DB_M_S3: ${{ steps.test_sqlite_mysql_postgresql_mimalloc_s3.outcome }}
-          TEST_DB_M: ${{ steps.test_sqlite_mysql_postgresql_mimalloc.outcome }}
           TEST_DB: ${{ steps.test_sqlite_mysql_postgresql.outcome }}
           TEST_SQLITE: ${{ steps.test_sqlite.outcome }}
           TEST_MYSQL: ${{ steps.test_mysql.outcome }}
@@ -208,20 +236,25 @@ jobs:
           CLIPPY_UNSAFE_TEST_MODE: ${{ steps.clippy_unsafe_test_mode.outcome }}
           FMT: ${{ steps.formatting.outcome }}
         run: |
+          # Only list the checks this part runs
+          row() {
+            if [[ "${2}" != "skipped" ]]; then
+              echo "|${1}|${2}|" >> "${GITHUB_STEP_SUMMARY}"
+            fi
+          }
           echo "### :x: Checks Failed!" >> "${GITHUB_STEP_SUMMARY}"
           echo "" >> "${GITHUB_STEP_SUMMARY}"
           echo "|Job|Status|" >> "${GITHUB_STEP_SUMMARY}"
           echo "|---|------|" >> "${GITHUB_STEP_SUMMARY}"
-          echo "|test (sqlite,mysql,postgresql,enable_mimalloc,s3)|${TEST_DB_M_S3}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (sqlite,mysql,postgresql,enable_mimalloc,s3)" "${TEST_DB_M_S3}"
-          echo "|test (sqlite,mysql,postgresql,enable_mimalloc)|${TEST_DB_M}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (sqlite,mysql,postgresql)" "${TEST_DB}"
-          echo "|test (sqlite,mysql,postgresql)|${TEST_DB}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (sqlite)" "${TEST_SQLITE}"
-          echo "|test (sqlite)|${TEST_SQLITE}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (mysql)" "${TEST_MYSQL}"
-          echo "|test (mysql)|${TEST_MYSQL}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (postgresql)" "${TEST_POSTGRESQL}"
-          echo "|test (postgresql)|${TEST_POSTGRESQL}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "test (sqlite,unsafe_test_mode)" "${TEST_UNSAFE_TEST_MODE}"
-          echo "|test (sqlite,unsafe_test_mode)|${TEST_UNSAFE_TEST_MODE}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "clippy (sqlite,mysql,postgresql,enable_mimalloc,s3)" "${CLIPPY}"
-          echo "|clippy (sqlite,mysql,postgresql,enable_mimalloc,s3)|${CLIPPY}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "clippy (sqlite,unsafe_test_mode)" "${CLIPPY_UNSAFE_TEST_MODE}"
-          echo "|clippy (sqlite,unsafe_test_mode)|${CLIPPY_UNSAFE_TEST_MODE}|" >> "${GITHUB_STEP_SUMMARY}"
+          row "fmt" "${FMT}"
-          echo "|fmt|${FMT}|" >> "${GITHUB_STEP_SUMMARY}"
           echo "" >> "${GITHUB_STEP_SUMMARY}"
           echo "Please check the failed jobs and fix where needed." >> "${GITHUB_STEP_SUMMARY}"
           echo "" >> "${GITHUB_STEP_SUMMARY}"
@@ -231,7 +264,40 @@ jobs:
       # Check for any previous failures, if there are stop, else continue.
       # This is useful so all test/clippy/fmt actions are done, and they can all be addressed
       - name: "All checks passed"
+        id: passed
         if: ${{ success() }}
+        env:
+          PART: ${{ matrix.channel }}-${{ matrix.part }}
         run: |
           echo "### :tada: Checks Passed!" >> "${GITHUB_STEP_SUMMARY}"
           echo "" >> "${GITHUB_STEP_SUMMARY}"
+          echo "${PART}=success" >> "${GITHUB_OUTPUT}"
+
+  # The required status checks are named after these jobs, one per channel, so they stay the same
+  # however the build job is split. It runs even when a part failed or the run was cancelled, because
+  # a skipped job counts as passed for a required check.
+  result:
+    name: Build and Test ${{ matrix.channel }}
+    needs: build
+    if: ${{ always() }}
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
+    strategy:
+      fail-fast: false
+      matrix:
+        channel:
+          - "rust-toolchain"
+          - "msrv"
+
+    steps:
+      - name: "Check that both parts passed"
+        env:
+          CHANNEL: ${{ matrix.channel }}
+          PASSED: ${{ toJSON(needs.build.outputs) }}
+        run: |
+          for part in 1 2; do
+            if [[ "$(jq -r --arg part "${CHANNEL}-${part}" '.[$part] // ""' <<< "${PASSED}")" != "success" ]]; then
+              echo "::error::Build and Test ${CHANNEL} (part ${part}) did not pass"
+              exit 1
+            fi
+          done