Momento Functions

Momento Functions are how you can extend Momento.

Functions run on Momento's service hosts, and offer a powerful scripting capability.

• Use the Momento host interfaces to interact with Momento features within your cache
• Use the AWS host interfaces to use a managed, hot channel to talk to AWS resources
• Use the HTTP host interfaces to reach out to anything you want

This repository holds crates for Momento Functions guest code.

To see some of what you can do with Functions, you can look at the examples.

Getting started

One-time setup

• Install Rust: https://rustup.rs
• Add the Momento Functions compile target: rustup target add wasm32-unknown-unknown

Make a project

cargo init --lib hello

Set up build configuration

Add a file .cargo/config.toml that sets the build target, for convenience.

[build]
target = "wasm32-unknown-unknown"

Set up Cargo.toml

Add this to build the right kind of artifact:

[lib]
crate-type = ["cdylib"]

Import the Functions support library.

[dependencies]
momento-functions       = { version = "0" }

Write a Function

The simplest function is a pong response web function. You can put this in lib.rs.

momento_functions::post!(ping);
fn ping(_payload: Vec<u8>) -> FunctionResult<Vec<u8>> {
    Ok(b"pong".to_vec())
}

Build and deploy

Build: cargo build --release

Deploy

curl \
  https://api.cache.$MOMENTO_CELL_HOSTNAME/functions/your_cache/ping \
  -H "authorization: $MOMENTO_API_KEY" \
  -XPUT \
  --data-binary @target/wasm32-unknown-unknown/release/hello.wasm

Invoke

curl \
  https://api.cache.$MOMENTO_CELL_HOSTNAME/functions/your_cache/ping \
  -H "authorization: $MOMENTO_API_KEY" \
  -d 'ping'

Going further

From here, you should look at the examples. Momento Functions are a limited environment, but the supported feature set is growing.