fyoo 0.0.1b2

Templated Arguments

The simplest flow (subparser) built in is hello, which has an optional argument for the message. All arguments on every flow are templated, assuming the argument type is a string.

fyoo hello --message 'The date is {{ date() }}'
# The date is 2020-02-25

But arguments on Fyoo precurse the Flow subcommand, so you can provide context in the same way on every different Flow. Arguments to fyoo will always be the same, but the Flow subcommand may have any arguments it wishes.

# `hello` has an optional argument --message,
# and `touch` has a required argument filename.
# But both receive context from the --jinja-context
# argument on `fyoo`.

fyoo --jinja-context='{"a": "any_var"}' \
  hello --message 'Hello {{ a }}!'
# Hello any_var!

fyoo --jinja-context='{"a": "any_var"}' \
  touch '{{ a }}.txt'
ls -Ut | head -1
# any_var.txt

Resource Configuration

Note: Run postgres in the background if you’d like to try the following examples:

docker run --name fyoo-pg \
    -e POSTGRES_PASSWORD=secretpass \
    -p 5432:5432 \
    -d postgres

Fyoo resources are configured in a single way for all Flows. Simply add to a fyoo.ini file, and run Fyoo from the same directory.

# fyoo.ini

[postgres]
username = postgres
password = %(FYOO_POSTGRES_PASSWORD)s
host = 127.0.0.1

FYOO_POSTGRES_PASSWORD=supersecret \
fyoo \
  postgres_query_to_csv_file \
  'select {{ date() }} as d' out.csv
cat out.csv
# d
# "2020-01-01"

Running it All Together

The real power of Fyoo comes together when you use templating and resources together. Template and resource specification are generally static, so they can and should be declaratively set (with particular resource credentials provided at runtime). This means that executable arguments never change.

Here is an example putting it all together. We use the contents of a sql template file to run a query, and output to a csv file of the current date.

-- table_counter.tpl.sql

{% for i in range(0, num) %}
  {% if not loop.first %}union all{% endif %}
  select {{ i }} as a
{% endfor %}

FYOO_POSTGRES_PASSWORD=supersecret \
fyoo \
  --jinja-context '{"num": 5}' \
  postgres_query_to_csv_file \
  "$(cat table_counter.tpl.sql)" \
  'results-{{ date() }}.csv'