Migrating from Library to Service Mode

This guide walks through converting an existing embedded Rust workflow into a packaged workflow for deployment. Library mode (embedded) means your application owns the Tokio runtime and calls Cloacina directly. Service mode (packaged) means the workflow is compiled as a shared library and loaded by the daemon or server.

Prerequisites

An existing workflow using the library/embedded tutorials (1-4)
Familiarity with Packaged Workflows

What Changes

Aspect	Library Mode	Service Mode
Macro	`#[workflow]`	`#[workflow]` (same) plus a one-line `cloacina_workflow_plugin::package!()` shell in `lib.rs`
Crate type	`bin` or `lib`	`cdylib` — but you don’t declare it; the compiler injects the `cdylib` crate-type + `packaged` feature at build time
Dependencies	`cloacina` (full crate)	`cloacina-workflow` (with `packaged`, `macros` features) + `cloacina-workflow-plugin`
Registration	`inventory::submit!` entries seeded into `Runtime` at startup via `seed_from_inventory()`	FFI vtable exports (9 methods, indices 0–8) loaded dynamically; the unified `cloacina_workflow_plugin::package!()` shell macro emits the entry points
Runtime	Your `#[tokio::main]`	Daemon or server loads and runs it
Build	`cargo build`	`cloacinactl package pack` archives the source; the compiler compiles it

Step 1: Restructure as a Library Crate

Convert your binary crate to a library crate. Move your workflow module from main.rs to lib.rs:

Before (library mode):

my-workflow/
├── Cargo.toml
└── src/
    └── main.rs     # contains #[workflow] + #[tokio::main]

After (service mode):

my-workflow/
├── Cargo.toml
├── package.toml    # package manifest (name/version + [metadata])
└── src/
    └── lib.rs      # contains package!() + #[workflow]

There is no build.rs and no [lib] crate-type / [features] wiring to add — the compiler injects the cdylib crate-type and the packaged feature when it builds the package.

Step 2: Update Cargo.toml

Swap the full cloacina crate for the packaged dependencies. This is the whole shell — no [lib] crate-type, no [features] table, no build.rs, no cloacina-build build-dependency. The compiler adds the cdylib crate-type and packaged feature at build time, and the shell macro routes its runtime companions (async-trait, chrono, computation-graph) — you hand-add none of them.

Before:

[package]
name = "my-workflow"
version = "0.1.0"
edition = "2021"

[dependencies]
cloacina = { version = "0.7.0", features = ["macros", "sqlite"] }
async-trait = "0.1"
serde_json = "1.0"
tokio = { version = "1", features = ["full"] }

After:

[package]
name = "my-workflow"
version = "0.1.0"
edition = "2021"

[dependencies]
cloacina-workflow = { version = "0.7", features = ["packaged", "macros"] }
cloacina-workflow-plugin = "0.7"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"

Key changes:

cloacina-workflow with "packaged" and "macros" features — the packaged authoring surface plus the workflow/task macros
cloacina-workflow-plugin — provides the package!() shell macro
Removed cloacina, tokio, async-trait, and any [lib]/[features]/[build-dependencies] ceremony — the host provides the runtime and the compiler injects the build wiring

Step 3: Add a package.toml

Packages carry a package.toml manifest alongside Cargo.toml. The minimal form is just a name/version and a [metadata] block — the resolver defaults the interface header and infers the language from the crate layout:

[package]
name = "my-workflow"
version = "0.1.0"

[metadata]
workflow_name = "data_processing"
description = "Data processing pipeline"

Step 4: Update the Workflow Code

Add the cloacina_workflow_plugin::package!() shell macro at the crate root, remove the main() function, and keep the #[workflow] module:

Before (main.rs):

use cloacina::*;

#[workflow(
    name = "data_processing",
    description = "Data processing pipeline"
)]
mod data_processing {
    use super::*;

    #[task]
    async fn extract(context: &mut Context<serde_json::Value>) -> Result<(), TaskError> {
        context.insert("data", serde_json::json!(42))?;
        Ok(())
    }

    #[task(dependencies = ["extract"])]
    async fn transform(context: &mut Context<serde_json::Value>) -> Result<(), TaskError> {
        let data = context.get("data").unwrap().as_i64().unwrap();
        context.insert("result", serde_json::json!(data * 2))?;
        Ok(())
    }
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let runner = DefaultRunner::new(":memory:").await?;
    let result = runner.execute("data_processing", Context::new()).await?;
    println!("Result: {:?}", result.status);
    Ok(())
}

After (lib.rs):

use cloacina_workflow::{task, workflow, Context, TaskError};

// Turns this crate into a fully-formed Cloacina plugin. Un-gated —
// the compiler injects the `packaged` feature it expands under.
cloacina_workflow_plugin::package!();

#[workflow(
    name = "data_processing",
    description = "Data processing pipeline"
)]
pub mod data_processing {
    use super::*;

    #[task]
    pub async fn extract(context: &mut Context<serde_json::Value>) -> Result<(), TaskError> {
        context.insert("data", serde_json::json!(42))?;
        Ok(())
    }

    #[task(dependencies = ["extract"])]
    pub async fn transform(context: &mut Context<serde_json::Value>) -> Result<(), TaskError> {
        let data = context.get("data").unwrap().as_i64().unwrap();
        context.insert("result", serde_json::json!(data * 2))?;
        Ok(())
    }
}

Key differences:

Add cloacina_workflow_plugin::package!() at the crate root
Import from cloacina_workflow instead of cloacina
Module and functions are pub (required for FFI visibility)
No main() — the daemon/server provides the runtime
No DefaultRunner — execution is managed by the host

Step 5: Package the Source

Archive the source directory into a .cloacina package:

cloacinactl package pack ./my-workflow

This produces my-workflow.cloacina — a source archive carrying the resolved package.toml. The compiler compiles it (injecting the cdylib crate-type and packaged feature) when it is uploaded. See the Packaged Workflows Tutorial for the full flow.

Step 6: Deploy

Copy the .cloacina package to the daemon’s watch directory:

cp my-workflow.cloacina ~/.cloacina/packages/

Or upload to the server:

curl -X POST \
  -H "Authorization: Bearer $API_KEY" \
  -F "package=@my-workflow.cloacina" \
  https://cloacina.example.com/v1/tenants/my_tenant/workflows

Step 7: Keep Local Tests Working

Add integration tests that use the full cloacina crate (via dev-dependencies):

#[cfg(test)]
mod tests {
    use cloacina::DefaultRunner;
    use cloacina_workflow::Context;

    #[tokio::test]
    async fn test_workflow_executes() {
        let runner = DefaultRunner::new(":memory:").await.unwrap();
        let result = runner
            .execute("data_processing", Context::new())
            .await
            .unwrap();
        assert_eq!(result.status.to_string(), "completed");
        runner.shutdown().await;
    }
}

Checklist

cloacina swapped for cloacina-workflow (packaged, macros) + cloacina-workflow-plugin
No build.rs, no [lib] crate-type, no [features] table (the compiler injects them)
cloacina_workflow_plugin::package!() added at the crate root
package.toml present with [metadata].workflow_name
Module and functions are pub
No main() in lib.rs
cloacinactl package pack ./my-workflow produces a .cloacina archive
Integration tests pass with cargo test

Migrating from Library to Service Mode

Migrating from Library to Service Mode

Prerequisites

What Changes

Step 1: Restructure as a Library Crate

Step 2: Update Cargo.toml

Step 3: Add a package.toml

Step 4: Update the Workflow Code

Step 5: Package the Source

Step 6: Deploy

Step 7: Keep Local Tests Working

Checklist

See Also