fix: Require C++ server SDK 3.15.0 so that track sends metric values correctly

.github/variables/cpp-sdk-versions.env

@@ -1,2 +1,2 @@
-sdk=3.14.0
-redis_source=2.4.2
+sdk=3.15.0
+redis_source=2.4.3

.github/workflows/ci.yml

@@ -111,3 +111,26 @@ jobs:
             --env LAUNCHDARKLY_SDK_KEY="$LAUNCHDARKLY_SDK_KEY"  \
             --env LAUNCHDARKLY_FLAG_KEY="$LAUNCHDARKLY_FLAG_KEY" \
             launchdarkly:${{ matrix.name }}
+
+  contract-tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Get C++ Versions
+        id: cpp-versions
+        uses: ./.github/actions/cpp-versions
+      - name: Build contract test service image
+        run: |
+          docker build \
+          --build-arg="CPP_SDK_VERSION=${{ steps.cpp-versions.outputs.sdk }}" \
+          -t lua-contract-tests -f ./contract-tests/Dockerfile .
+      - name: Launch contract test service
+        run: docker run -d --name lua-contract-tests --network host lua-contract-tests
+      - uses: launchdarkly/gh-actions/actions/contract-tests@contract-tests-v1
+        with:
+          test_service_port: 8000
+          token: ${{ secrets.GITHUB_TOKEN }}
+          extra_params: -skip-from=./contract-tests/test-suppressions.txt -status-timeout=30
+      - name: Show contract test service logs
+        if: always()
+        run: docker logs lua-contract-tests

README.md

@@ -26,8 +26,8 @@ If Redis support is desired, then it optionally depends on the C++ server-side S
 
 | Dependency                     | Minimum Version                                                                                              | Notes                                      |
 |--------------------------------|--------------------------------------------------------------------------------------------------------------|--------------------------------------------|
-| C++ Server-Side SDK            | [3.9.0](https://github.com/launchdarkly/cpp-sdks/releases/tag/launchdarkly-cpp-server-v3.9.0)                | Required dependency.                       |
-| C++ Server-Side SDK with Redis | [2.1.19](https://github.com/launchdarkly/cpp-sdks/releases/tag/launchdarkly-cpp-server-redis-source-v2.1.19) | Optional, if using Redis as a data source. |
+| C++ Server-Side SDK            | [3.15.0](https://github.com/launchdarkly/cpp-sdks/releases/tag/launchdarkly-cpp-server-v3.15.0)              | Required dependency.                       |
+| C++ Server-Side SDK with Redis | [2.4.3](https://github.com/launchdarkly/cpp-sdks/releases/tag/launchdarkly-cpp-server-redis-source-v2.4.3)   | Optional, if using Redis as a data source. |
 
 
 3rd Party Dependencies

contract-tests/Dockerfile

@@ -0,0 +1,38 @@
+# Builds the contract test service: the Lua SDK from this checkout, served by OpenResty.
+FROM openresty/openresty:1.31.8.1-0-jammy
+
+ARG CPP_SDK_VERSION=3.15.0
+
+RUN apt-get update && apt-get install -y \
+    git netbase curl libssl-dev apt-transport-https ca-certificates \
+    software-properties-common \
+    cmake ninja-build locales-all
+
+# OpenResty bundles its own OpenSSL, and the SDK uses that OpenSSL at runtime.
+# The bundled OpenSSL looks for CA certificates in a directory that the image does not have.
+# This variable points it at the system CA bundle. nginx.conf passes it to the worker process.
+ENV SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
+
+RUN add-apt-repository ppa:mhier/libboost-latest && \
+     apt-get update && \
+     apt-get install -y boost1.81
+
+RUN mkdir cpp-sdk-libs
+RUN git clone --branch launchdarkly-cpp-server-v${CPP_SDK_VERSION} https://github.com/launchdarkly/cpp-sdks.git && \
+    cd cpp-sdks && \
+    mkdir build-dynamic && \
+    cd build-dynamic && \
+    cmake -GNinja \
+        -DLD_BUILD_EXAMPLES=OFF \
+        -DBUILD_TESTING=OFF \
+        -DLD_BUILD_SHARED_LIBS=ON \
+        -DLD_DYNAMIC_LINK_OPENSSL=ON .. && \
+    cmake --build . --target launchdarkly-cpp-server && \
+    cmake --install . --prefix=../../cpp-sdk-libs
+
+COPY . .
+COPY ./contract-tests/nginx.conf /usr/local/openresty/nginx/conf/nginx.conf
+COPY ./contract-tests/service.lua /usr/local/openresty/nginx/contract-tests/
+
+RUN luarocks make launchdarkly-server-sdk-[0-9]*-0.rockspec LD_DIR=./cpp-sdk-libs && \
+    cp launchdarkly_server_sdk.so /usr/local/openresty/lualib/

contract-tests/README.md

@@ -0,0 +1,27 @@
+# Lua SDK contract test service
+
+This directory contains the test service for the LaunchDarkly [SDK test harness](https://github.com/launchdarkly/sdk-test-harness). The service is an OpenResty application that runs the Lua SDK built from this checkout. It implements the harness's [service specification](https://github.com/launchdarkly/sdk-test-harness/blob/main/docs/service_spec.md).
+
+## Running locally
+
+From the **root** of the repository, build and start the service. It listens on port 8000:
+
+```bash
+docker build -t lua-contract-tests -f ./contract-tests/Dockerfile .
+docker run --rm --name lua-contract-tests --network host lua-contract-tests
+```
+
+Then run the test harness against it. The harness calls back to the SDK on port 8111, so the service uses host networking:
+
+```bash
+./sdk-test-harness -url http://localhost:8000 -skip-from ./contract-tests/test-suppressions.txt
+```
+
+`test-suppressions.txt` lists the tests that are known to fail. Remove a line from it when the SDK starts to pass that test.
+
+## Known failures
+
+- Evaluation reasons do not include `ruleIndex`, `ruleId` or `prerequisiteKey`. The C API of the C++ SDK does not expose these fields.
+- `allFlags` returns only flag values. The harness expects the full flags state, with `$flagsState` and `$valid`.
+- Lua tables cannot tell an empty JSON object from an empty JSON array, so `{}` becomes `[]` in contexts, event data and default values.
+- JSON null values inside objects are lost, because the SDK converts them to `nil`.

contract-tests/nginx.conf

@@ -0,0 +1,29 @@
+# The test service keeps its SDK clients in Lua memory, so it must run in one worker.
+worker_processes 1;
+error_log /dev/stderr info;
+
+events {
+    worker_connections 1024;
+}
+
+env SSL_CERT_FILE;
+
+http {
+    access_log off;
+
+    lua_package_path "/usr/local/openresty/nginx/contract-tests/?.lua;;";
+
+    # Keep request bodies in memory so that the service can read them with ngx.req.get_body_data.
+    client_max_body_size 10m;
+    client_body_buffer_size 10m;
+
+    server {
+        listen 8000;
+
+        location / {
+            content_by_lua_block {
+                require("service").handle()
+            }
+        }
+    }
+}