# Ice Core
[](https://crates.io/crates/ice_core)
[](https://travis-ci.org/losfair/IceCore)
Build efficient and reliable backend applications in WebAssembly.
# What is it?
Ice is a container for backend applications in WebAssembly.
[WebAssembly](http://webassembly.org/), which is mainly used to build client-side Web applications, can also be used to build server-side applications. With a managed execution environment and the underlying JIT ([wasm-core](https://github.com/losfair/wasm-core)) based on LLVM, Ice is able to achieve a higher level of security (and additional safety for C/C++ applications), provide platform-independent high-level abstractions, and bring a few special features like dynamic inter-machine application migration and more accurate service monitoring.
# Build
Latest nightly Rust and LLVM 6 are required.
```
cargo build --release
```
# Get started
First, create a root directory to place configurations & applications:
```
mkdir my_ice_root
cd my_ice_root
```
Then, create a config file `config.yaml` in the root directory, whose format is defined in `config.rs`/`Config`:
```yaml
applications:
- name: hello_world
path: ./apps/hello_world
```
Here we've specified an application named `hello_world` located at `./apps/hello_world`, and the application will be automatically initialized when `ice_core` is launched.
Now let's initialize the `hello_world` application:
```
mkdir apps
cd apps
cargo new hello_world
cd hello_world
```
Add a `[lib]` section and the runtime library `ia` to the newly-created `Cargo.toml`:
```toml
[lib]
name = "hello_world"
crate-type = ["cdylib"]
[dependencies]
ia = "0.1"
```
And create another `config.yaml` in the `hello_world` directory, which is the application-level metadata definition (defined in `config.rs`/`AppMetadata`:
```yaml
package_name: com.example.hello_world
bin: target/wasm32-unknown-unknown/release/hello_world.wasm
```
Write some code to print "Hello, world!" in `src/lib.rs`:
```rust
#[macro_use]
extern crate ia;
app_init!({
println!("Hello, world!");
0
});
```
Build it:
```
cargo build --release --target wasm32-unknown-unknown
```
cd back to my_ice_root and launch `ice_core`:
```
ice_core config.yaml
```
and you should see your first `hello_world` application running!
# Comparison with native binaries
The WebAssembly VM has to do some necessary checks and translations to ensure things work correctly. Therefore, it is always a little slower than precompiled native binaries. However, the difference is quite small and normally doesn't become the performance bottleneck for real-world applications.
In addition, Ice Core is able to provide a few features that a native environment doesn't provide:
- Accurate permission control
- Run-time inter-machine application migration (in progress)
- Service monitoring and management (in progress)