Deployment

Maestro is only of practical use if it’s deployed. It doesn’t matter if this deployment is cloud or on a local server, but the goal is to have it run automatically on a regular cadence. In this way, maestro can be the backbone of a small-moderate enterprise’s data orchestration.

Maestro deployment is not all that different from deploying any R script. The main difference is that you need to deploy the entire project (pipelines + orchestrator) and then target specifically the orchestrator script to execute repeatedly.

There are numerous avenues for deploying a maestro project, so here we’ll just look a handful of options. Here we will only focus on the execution of maestro and not on side effects like storage and networking (in practice, you’d probably have your pipelines do something like read from an external source and load to a data warehouse).

Our example to deploy will be as simple as it gets - just the bare bones skeleton generated from `maestro::create_maestro()`. This builds an empty maestro project with a single pipeline and an orchestrator script. It is sufficient for testing but does nothing of interest.

## Local Deployment using Cron/Task Manager

The easiest way to deploy maestro is to have it run on your own local machine and triggered on a schedule using Cron (Mac/Linux)/Task Scheduler (Windows).

### Cron

If your OS is Linux or Mac you can use Cron scheduling. The cronR package allows you to create and manage cron scheduled tasks from within R. Create a new script at the root level of the project:

    library(cronR)
    library(here) # makes it easier to deal with path issues

    cmd <- cron_rscript(
      here("orchestrator.R"),
      workdir = here()
    )

    cron_add(
      cmd,
      frequency = "daily",
      id = "maestro",
      ask = FALSE
    )

### Task Scheduler

If your OS is Windows you can leverage Task Scheduler. The taskscheduleR package allows you to create and manage scheduled tasks from within R. Create a new R script at the root level of the project:

    library(taskscheduleR)
    library(here) # makes it easier to deal with path issues

    taskscheduler_create(
      taskname = "maestro",
      rscript = here("orchestrator.R"),
      schedule = "DAILY",
      exec_path = here(),
      startdate = format(Sys.Date() - 1, "%m/%d/%Y")
    )

### Limitations

While this is the easiest approach it has a number of limitations. First, these will only run if the machine is constantly running (i.e., not in hibernation or sleep mode); so if you’re doing this on a desktop or laptop you’ll probably need to go through some extra steps to allow it to run even when closed.

Second, even if you have continuous availability, it is hard to monitor the success of the deployment. There are GUI-based managers for Cron and Task Scheduler, but they’re a far cry from true observability.

Third, it is difficult to version this kind of deployment. If you need to make changes or reversions you can quickly get lost in a swamp of stale and aborted deployments.

All said, this kind of deployment is probably only advisable for testing and proof-of-concept. There are probably more sophisticated Cron wrappers or substitutes that make local deployment more feasible (i.e., include monitoring, CI/CD, etc.), but we won’t focus on those here.

## Posit Connect

Seasoned R users will likely be familiar with Posit and its hosting platform Posit Connect. While traditionally seen as a hosting environment for dashboards, APIs, and reports, it is actually perfectly capable of data orchestration with maestro.

> Note

> A Posit Connect license and instance is required for this type of deployment. User must also have Publisher privileges to deploy to Connect.

The key difference for a Posit Connect deployment is the use of Quarto for the orchestrator.1 There’s no need for any visual embellishments in this Quarto doc (but, hey, here’s a pretty good place for some observability metrics and graphics!), all you need is at least one R chunk containing the orchestrator code.

Here’s a basic .qmd script that could be deployed on Posit Connect.

    ---
    title: "Maestro"
    format: html
    resources:
      - pipelines/*
      - renv.lock
    ---

    ```{r}
    library(maestro)

    schedule <- build_schedule()

    run_schedule(
      schedule,
      orch_frequency = "1 hour"
    )
    ```

You can then use the push deployment via RStudio or Positron. In RStudio it looks like this:

Make sure you select Publish with source code so that you can trigger the orchestrator to run on a schedule in Connect.

Once it has been published you can set the schedule using the Schedule tab. Be sure to use the same schedule frequency as your orchestration frequency:

This is a relatively easy way to deploy a maestro project assuming you have a Posit Connect license.

> Note

> Posit Connect Cloud, a managed instance of Posit Connect, may be another option for deploying maestro projects, although currently this has not be tested.

### Limitations

While a more robust deployment compared to local Cron/TaskManager, observability is still initially limited to manually viewing the rendered Quarto doc. With a bit of extra tinkering, however, you can trigger some side effects in the orchestration script such as sending the pipeline statuses to a database for display in a dashboard, or triggering an email to be sent if any pipelines fail.

On the other hand, you may not appreciate the additional overhead that comes with needing to execute the orchestrator as a Quarto doc. Personally, I don’t think this creates a meaningful cost in terms of run time or compute (assuming you’re not triggering too many side effects after the orchestration), but it does require a Quarto installation on the Posit Connect instance, which could be a non-starter in some cases.

Finally, if your Posit Connect instance is deployed on a server managed by someone other than yourself you may run into issues if the server becomes unavailable or you cannot debug problems at the server level. In particular, viewing pipeline logs can be difficult since the logs get stored at the project level and are thus not accessible in Connect. These instead will need to be sent somewhere they can be inspected.

## Cloud

There are virtually limitless options for deploying in the cloud. In fact, the options described above can also be applied to a cloud-based server (e.g., spin up a Linux server and use Cron to run the schedule and just keep the server running indefinitely).

Here we’ll focus on a specific pattern of maestro deployment that works well in the cloud both in terms of cost and ease of deployment. We’ll avoid tutorials with specific cloud providers and instead generalize the types of services needed while providing examples of popular specific services. If you’re looking for a walk through for a cloud-based deployment, check out this blog post using Google Cloud Platform (GCP).

### Serverless Cloud

The advantage of maestro is its serverless design. This means that for virtually all use cases you don’t need to have a server running continuously. Instead, you can only run the server when the orchestrator needs to run. This usually results in cost savings.

For a basic maestro cloud deployment, you need two services:

1. Serverless execution environment (i.e., something to run the code)
2. Scheduler (i.e., something to tell the code when to run)

Some cloud providers may bundle these services together, others may offer them as separate services.

For example, in Amazon Web Services (AWS), the serverless execution environment would be a Lambda function and the scheduler could be EventBridge. In GCP it would be Cloud Run scheduled via Cloud Scheduler. In Azure it would be Azure Functions configured with a Timer Trigger, and so on.

As usual, be sure to use the same scheduling frequency as the orchestrator frequency.

### Limitations

The only limitation in the cloud is your skill/time and your budget. Often these two limitations are inversely correlated: managed cloud services like Digital Ocean ease the pain of deployment at the cost of taking more of your money. Availability is not likely to be an issue, but custom tinkering will be needed to set up observability. Finally, it is worth considering best practices such as CI/CD to make it easier to update the maestro project. This will also require additional cloud services and therefore cost.

## Final Considerations

It’s important to remember that deploying a maestro project is not all that different from deploying a single R script. It just has a few extra files that need to go with it. One recommendation for deployment is to take advantage of maestro’s serverless nature. If you only need to run your orchestrator daily, don’t deploy it where you are charged for something that runs continuously (that’s 23 hours a day you’re paying for nothing).

It’s also important to consider that deployment for you likely means more than just maestro running in isolation. Maestro really only makes sense if it’s doing something like extracting data from a source and inserting it into a database, or generating and storing predictions from a model. All of this lies outside maestro’s functionality but is nevertheless part of the entire deployment stack.

1. This feels a bit odd given that Quarto is conventionally used for publishing reports, presentations, and dashboards. That said, there’s nothing stopping you from executing whatever R code you want in a Quarto document, and Posit Connect won’t let you “deploy” a stand-alone R script anyway. RMarkdown is also a valid option although we’ll stick with Quarto here.↩︎