WebAssembly for Proxies (C++ SDK)
The SDK has dependencies on specific versions of the C++ WebAssembly toolchain Emscripten (https://emscripten.org) and the protobuf library, therefor use of a Docker image is recommended.
Docker
A Dockerfile for the C++ SDK is provided in Dockerfile-sdk.
It can built in this directory by:
docker build -t wasmsdk:v2 -f Dockerfile-sdk .
The docker image can be used for compiling wasm files.
Creating a project for use with the Docker build image
Create a directory with your source files and a Makefile:
PROXY_WASM_CPP_SDK=/sdk
all: myproject.wasm
include ${PROXY_WASM_CPP_SDK}/Makefile.base_lite
Source file (myproject.cc):
#include <string>
#include <unordered_map>
#include "proxy_wasm_intrinsics.h"
class ExampleContext : public Context {
public:
explicit ExampleContext(uint32_t id, RootContext* root) : Context(id, root) {}
FilterHeadersStatus onRequestHeaders(uint32_t headers, bool end_of_stream) override;
void onDone() override;
};
static RegisterContextFactory register_ExampleContext(CONTEXT_FACTORY(ExampleContext));
FilterHeadersStatus ExampleContext::onRequestHeaders(uint32_t headers, bool end_of_stream) {
logInfo(std::string("onRequestHeaders ") + std::to_string(id()));
auto path = getRequestHeader(":path");
logInfo(std::string("header path ") + std::string(path->view()));
return FilterHeadersStatus::Continue;
}
void ExampleContext::onDone() { logInfo("onDone " + std::to_string(id())); }
Compiling with the Docker build image
Run docker:
docker run -v $PWD:/work -w /work wasmsdk:v2 /build_wasm.shCaching the standard libraries
The first time that emscripten runs it will generate the standard libraries. To cache these in the docker image, after the first successful compilation (e.g myproject.cc above), commit the image with the standard libraries:
docker commit `docker ps -l | grep wasmsdk:v2 | awk '{print $1}'` wasmsdk:v2This will save time on subsequent compiles.
Using the SDK from a newer/specific version of Envoy
To use a newer/specific version of the SDK (e.g. from the version of Enovy you are going to deploy the WebAssembly module to) bind that volume and use it in the Makefile.
Here is an example Makefile referencing the SDK at ../envoy/api/wasm/cpp and mounted as 'sdk' in the /work directory:
PROXY_WASM_CPP_SDK=/work/sdk
all: myproject.wasm
include ${PROXY_WASM_CPP_SDK}/Makefile.base_lite
Run docker pointing to Envoy sources in a directory parallel (at the same level) as your project directory:
docker run -v $PWD:/work -v $PWD/../envoy/api/wasm/cpp:/work/sdk -w /work wasmsdk:v2 bash /build_wasm.shUsing abseil form the image
Abseil (optionally) is built in /root/abseil and can be used. Note that the abseil containers (e.g. absl::flat_hash_set) exercise many syscalls which are not supported. Consequantally individual files should be pulled in which are relatively self contained (e.g. strings). Example customized Makefile:
PROXY_WASM_CPP_SDK=/sdk
CPP_API:=${PROXY_WASM_CPP_SDK}
CPP_CONTEXT_LIB = ${CPP_API}/proxy_wasm_intrinsics.cc
ABSL = /root/abseil-cpp
ABSL_CPP = ${ABSL}/absl/strings/str_cat.cc ${ABSL}/absl/strings/str_split.cc ${ABSL}/absl/strings/numbers.cc ${ABSL}/absl/strings/ascii.cc
all: plugin.wasm
%.wasm %.wat: %.cc ${CPP_API}/proxy_wasm_intrinsics.h ${CPP_API}/proxy_wasm_enums.h ${CPP_API}/proxy_wasm_externs.h ${CPP_API}/proxy_wasm_api.h ${CPP_API}/proxy_wasm_intrinsics.js ${CPP_CONTEXT_LIB}
ls /root
em++ -s STANDALONE_WASM=1 -s EMIT_EMSCRIPTEN_METADATA=1 -s EXPORTED_FUNCTIONS=['_malloc'] --std=c++17 -O3 -flto -s WASM_OBJECT_FILES=0 --llvm-lto 1 -I${CPP_API} -I${CPP_API}/google/protobuf -I/usr/local/include -I${ABSL} --js-library ${CPP_API}/proxy_wasm_intrinsics.js ${ABSL_CPP} $*.cc ${CPP_API}/proxy_wasm_intrinsics.pb.cc ${CPP_CONTEXT_LIB} ${CPP_API}/libprotobuf.a -o $*.wasm
Precompiled abseil libraries are also available, so the above can also be done as:
PROXY_WASM_CPP_SDK=/sdk
CPP_API:=${PROXY_WASM_CPP_SDK}
CPP_CONTEXT_LIB = ${CPP_API}/proxy_wasm_intrinsics.cc
ABSL = /root/abseil-cpp
ABSL_LIBS = ${ABSL}/absl/strings/libabsl_strings.a ${ABSL}/absl/strings/libabsl_strings_internal.a ${ABSL}/absl/strings/libabsl_str_format_internal.a
all: plugin.wasm
%.wasm %.wat: %.cc ${CPP_API}/proxy_wasm_intrinsics.h ${CPP_API}/proxy_wasm_enums.h ${CPP_API}/proxy_wasm_externs.h ${CPP_API}/proxy_wasm_api.h ${CPP_API}/proxy_wasm_intrinsics.js ${CPP_CONTEXT_LIB}
ls /root
em++ -s STANDALONE_WASM=1 -s EMIT_EMSCRIPTEN_METADATA=1 -s EXPORTED_FUNCTIONS=['_malloc'] --std=c++17 -O3 -flto -s WASM_OBJECT_FILES=0 --llvm-lto 1 -I${CPP_API} -I${CPP_API}/google/protobuf -I/usr/local/include -I${ABSL} --js-library ${CPP_API}/proxy_wasm_intrinsics.js $*.cc ${CPP_API}/proxy_wasm_intrinsics.pb.cc ${CPP_CONTEXT_LIB} ${CPP_API}/libprotobuf.a ${ABSL_LIBS} -o $*.wasm
Ownership of the resulting .wasm files
The compiled files may be owned by root. To chown them add the follow lines to the Makefile and docker invocation:
PROXY_WASM_CPP_SDK=/sdk
all: myproject.wasm
chown ${uid}.${gid} $^
include ${PROXY_WASM_CPP_SDK}/Makefile.base_lite
Invocation file (e.g. build.sh):
#!/bin/bash
docker run -e uid="$(id -u)" -e gid="$(id -g)" -v $PWD:/work -w /work wasmsdk:v2 /build_wasm.shDependencies for building WASM modules:
If you do not wish to use the Docker file, the dependencies can be installed by script (sdk_container.sh), or by hand.
protobuf v3.9.1
You must install the version of protobuf on your build system that matches the libprotobuf.a files (without any patches) so that the generated code matches the .a library. Currently this is based on tag v3.9.1 of https://github.com/protocolbuffers/protobuf.
git clone https://github.com/protocolbuffers/protobuf
cd protobuf
git checkout v3.9.1
git submodule update --init --recursive
./autogen.sh
./configure
make
make check
sudo make installemscripten
git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
./emsdk update-tags
./emsdk install 1.39.2
./emsdk activate 1.39.2
source ./emsdk\_env.shIt is possible later versions will work, e.g.
./emsdk update-tags
./emsdk install latest
./emsdk activate latestHowever 1.39.2 is known to work.
Rebuilding the libprotobuf.a files
If want to rebuild the libprotobuf.a files or use a different version see the instructions at https://github.com/kwonoj/protobuf-wasm. Commit 4bba8b2f38b5004f87489642b6ca4525ae72fe7f works for protobuf v3.9.x.
git clone https://github.com/protocolbuffers/protobuf protobuf-wasm
cd protobuf-wasm
git checkout v3.9.1
git clone https://github.com/kwonoj/protobuf-wasm wasm-patches
cd wasm-patches && git checkout 4bba8b2f38b5004f87489642b6ca4525ae72fe7f && cd ..
git apply wasm-patches/*.patch
./autogen.sh
emconfigure ./configure --disable-shared CXXFLAGS="-O3 -flto -s WASM_OBJECT_FILES=0 --llvm-lto 1"
emmake make
cp src/.libs/libprotobuf-lite.a ${CPP_API}/libprotobuf-lite.a
cp src/.libs/libprotobuf.a ${CPP_API}/libprotobuf.aWAVM binaries
git clone [email protected]:WAVM/WAVM.git
cd WAVM
cmake "."
make
sudo make installNote: ensure /usr/local/bin is in your path
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