Before going through this guide, you need to have the Docker engine installed on your machine (see installations instructions here). In addition, this guide assumes familiarity with Linux containers and the container-native paradigm to software development. You can read a high-level introduction to these concepts in this page, where you can also find references to external resources that explain them in depth.
To install or upgrade Popper, run the following in your terminal:
curl -sSfL https://raw.githubusercontent.com/getpopper/popper/master/install.sh | sh
Create Your First Workflow¶
Assume that as part of our work we want to carryout two tasks:
- Download a dataset (CSV) that we know is available at https://github.com/datasets/co2-fossil-global/raw/master/global.csv
- Modify the dataset, specifically we want to get the transpose of the this CSV table.
When we work under the container-native paradigm, instead of going ahead and installing these on our computer, we first look for available images on a container registry, for example https://hub.docker.com, to see if the software we need is available.
In this case we find two images that do what we need and proceed to
write this workflow in a
wf.yml file using your favorite editor:
steps: # download CSV file with data on global CO2 emissions - id: download uses: docker://byrnedo/alpine-curl:0.1.8 args: [-LO, https://github.com/datasets/co2-fossil-global/raw/master/global.csv] # obtain the transpose of the global CO2 emissions table - id: get-transpose uses: docker://getpopper/csvtool:2.4 args: [transpose, global.csv, -o, global_transposed.csv]
Run your workflow¶
To execute the workflow you just created:
popper run -f wf.yml
Since this workflow consists of two steps, there were two corresponding containers that were executed by the underlying container engine, which is Docker in this case. We can verify this by asking Docker to show the list of existing containers:
docker ps -a
You should see the two containers from the example workflow being
listed along with other containers. The name of the containers created
by popper are prefixed with
popper_. To obtain more detailed
information of what the
popper run command does, you can pass the
--help flag to it:
popper run --help
TIP: All popper subcommands allow you to pass
--helpflag to it to get more information about what the command does.
Debug your workflow¶
From time to time, we find ourselves with a step that does not quite
do what we want it to. In these cases, we can open an interactive
shell instead of having to update the YAML file and invoke
popper run again. In those cases, the
popper sh comes handy. For example,
if we would like to explore what other things can be done inside the
container for the second step:
popper sh -f wf.yml get-transpose
And the above opens a shell inside a container instantiated from the
docker.io/getpopper/csvtool:2.4 image. In this shell we can, for
example, obtain information about what else can the
Based on this exploration, we can see that we can pass a
-u TAB flag
csvtool in order to generate a tab-separated output file
instead of a comma-separated one. Assuming this is what we wanted to
achieve in our case, we then quit the container by running
Back on our host machine context, that is, not running inside the container anymore, we can update the second step by editing the YAML file to look like the following:
- id: get-transpose uses: docker://getpopper/csvtool:2.4 args: [transpose, global.csv, -u, TAB, -o, global_transposed.csv]
And test that what we changed worked by running in non-interactive mode again:
popper run -f wf.yml get-transpose
- Learn more about all the CLI features that Popper provides.
- Take a look at the “Workflow Language” for the details on what else can you specify as part of a Step’s attributes.
- Read the “Popper Execution Runtime” section to learn more about what other execution environments Popper supports, as well as how to customize the behavior of the underlying execution.
- Browse existing workflow examples.
- Take a self-paced tutorial to learn how to use other features of Popper.