WIP Introduce xcp-metrics-plugin-xen plugin for xcp-rrdd

xcp-metrics-plugin-xen is meant as a replacement for
- the metrics collection built into xcp-rrdd, which requires the
  latter to depend on libxenctrl
- the rrdp-pm plugin, which also fetches data through libxenctrl

Metrics are collected using the  Rust crate, structured in a
suitable way for upcoming OpenMetrics support, and communicated to
xcp-rrdd using its v2 protocol.

NOTE: at the time of this writing, we still rely on extra features we
had to add to the  crate, PR pending.

Signed-off-by: Teddy Astie <teddy.astie@outlook.fr>
Reviewed-by: Yann Dirson <yann.dirson@vates.fr>

.github/workflows/rust.yml

@@ -0,0 +1,79 @@
+name: Rust
+
+on:
+  push:
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    #container:
+    #  image: centos8 
+
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: 1.70.0
+        override: true
+    - name: Installing dependency packages
+      run: sudo apt update && sudo apt install -y libxen-dev protobuf-compiler
+
+    - name: Build
+      run: cargo build --verbose
+
+  doc:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: 1.70.0
+        override: true
+    - name: Installing dependency packages
+      run: sudo apt update && sudo apt install -y libxen-dev protobuf-compiler
+
+    - name: Build docs
+      run: cargo doc --workspace --no-deps
+
+    - name: Upload docs
+      uses: actions/upload-artifact@v3
+      with:
+        name: rustdoc-html
+        path: ./target/doc
+
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        override: true
+    - name: Installing dependency packages
+      run: sudo apt update && sudo apt install -y libxen-dev protobuf-compiler
+
+    - name: Run tests
+      run: |
+        cargo clean
+        cargo test --verbose
+      env:
+        CARGO_INCREMENTAL: '0'
+        RUSTFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Cpanic=abort -Zpanic_abort_tests'
+        RUSTDOCFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Cpanic=abort -Zpanic_abort_tests'
+
+    - name: Install grcov
+      run: cargo install grcov
+    - name: Test coverage report
+      run: grcov . -s . --binary-path ./target/debug/ -t html --branch --ignore-not-existing -o ./target/debug/coverage/
+
+    - name: Upload test coverage report
+      uses: actions/upload-artifact@v3
+      with:
+        name: coverage-html
+        path: ./target/debug/coverage/

.gitignore

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+/target
+/third-party/