Concepts

The words used across the documentation and the dashboard, and how they fit together. For the language itself, see the Mélodium Language Book ; for every treatment, model and function available, the Mélodium Reference .

From a Program to Its Runs

You launch a program from an entrypoint. The engine that starts is the direct run. Each time the program sends a step elsewhere, a distribution run starts on a runner, a machine Cadence.CI starts in your cloud account for that step. Together, they form one execution group, shown as a hierarchy on the group page.

Writing Pipelines

• Program: A Mélodium project : a Compo.toml file and .mel source files. In CI/CD, it usually lives in .melodium-ci/ at the root of the repository. Cadence.CI requires Mélodium 0.11 or later.
• Treatment: A unit of processing , with inputs, outputs and parameters. Treatments are connected to each other, and a treatment can be made of other treatments: build and test in the CI/CD template are treatments, made of many smaller ones.
• Model: A configured component  that treatments share, such as the dispatch engine that requests machines (CicdDispatchEngine), an HTTP server, or a remote language model (RemoteLlm).
• Connection: A typed link  from an output to an input. A Stream<T> carries a flow of values, such as the bytes of a file; a Block<T> carries one value, such as the trigger signal (Block<void>). Connecting mismatched types is an error found by the check, before anything runs.
• Entrypoint: The treatment a run starts from , declared under [entrypoints] in Compo.toml. A program can have several, for example main and advanced in the CI/CD template.
• Check: melodium check validates the whole program, types, connections and parameters, without running anything. melodium run performs the same check before starting.
• Secret: A value typed Secret, such as a token or a password. It is given as a locator, env:MELODIUM_SECRET_<NAME> for an environment variable or file:<path> for a file, and resolved by the engine that uses it. Secret values are masked in logs and never sent to Cadence.CI, which only sees a secret’s name and type.

Running Pipelines

• Engine: The Mélodium process that executes a program. It appears as the Mélodium Engine service on a run page.
• Run: One engine’s execution, as reported to Cadence.CI: its status (scheduling, unschedulable, running, finished), its result, the entrypoint and parameters it started with, its logs, debug events and program.
• Direct run: A run you launch yourself, for example with melodium run --api-report from your machine or from a CI job.
• Distribution run: A run started to receive work from another run, its parent. A CI/CD step dispatched with CicdDispatchEngine is a distribution run.
• Execution group: The direct run and every distribution run it started. The group page draws them as a hierarchy.
• Work location: Where dispatched steps go. api, the default, asks Cadence.CI for machines in your cloud account; compose starts containers with Podman or Docker Compose on the machine running the program. See Where It Runs.
• Runner: Where a distribution run executes: an instance Cadence.CI starts in your cloud account for the step and stops after it, or a container when steps run locally with compose.
• Instance: A virtual machine Cadence.CI started in one of your connected cloud accounts. Each connected account lists its instances, with the run each one served.
• Debug events: The record of what the engine did: models and treatments built, started and finished, data sent and received on each connection. At the detailed level, they also carry the value of every transmission, except secrets, which never appear. The run page plays them back on a timeline.

Access

• Organization: The unit that owns runs, cloud accounts, tokens and the plan. Members hold a role: Administrator, Operator or Member.
• Run token: Lets a program report runs and request machines on behalf of an organization. Set it in the MELODIUM_API_TOKEN environment variable: --api-report uses it, and so does the CI/CD template to request machines.
• Cloud account: An account with one of the supported providers, connected in Clouds, where Cadence.CI starts instances for your runs. See Connect a Cloud.