.. include:: ../common.txt

.. _custom_execution_environments:

######################
Execution Environments
######################

The Execution Environment is the Python environment in which the
|SNIPPET_FRAMEWORK| runs every Dynamic Application snippet. When you build a
custom Execution Environment for a PowerPack, you decide which libraries are
installed in it. The default set of libraries includes one
``silo-low-code-steps-*`` library for each family of
:ref:`Steps <steps>` (for example, ``silo-low-code-steps-ssh``), along with
every transitive dependency those Steps need. If your PowerPack or Dynamic
Application does not use a family of Steps, you can leave that ``steps``
library, and the dependencies only it requires, out of your Execution
Environment.

.. _ee_trimming:

********
Trimming
********

Trimming is the method for creating a custom Execution Environment: you
start from the default set of libraries and remove the ``steps`` libraries
(and the dependencies only they require) that your PowerPack or Dynamic
Application does not use.

.. important::

   Always duplicate (copy) the Execution Environment before you make any
   changes, and make your adjustments to the copy only. Never trim the
   original Execution Environment, so that you can always return to the
   original set of libraries.

Benefits of Trimming
====================

* **Smaller PowerPack**: every library in the Execution Environment is
  packaged into the PowerPack. Removing unused libraries (for example the
  compiled ``ssh2-python`` and ``gevent`` wheels used only by the ``ssh``
  Steps) reduces the size of the PowerPack that you build, upload, and
  distribute.
* **Faster snippet execution**: every ``silo-low-code-steps-*`` library that is
  installed registers all of its Steps each time a snippet executes, whether
  or not the snippet uses them. Removing a ``steps`` library that you do not
  use removes that registration work (and the imports it triggers) from every
  snippet execution.
* **Smaller dependency surface**: fewer installed libraries means fewer
  libraries to track for vulnerabilities and version conflicts.

.. note::

   Trimming is optional. Only remove a ``steps`` library when you are certain
   that no Dynamic Application in the PowerPack, and no
   :ref:`custom step <custom_steps>` it ships, uses any Step provided by that
   library. A snippet that references a Step that is not installed fails when
   it runs.

What Can Be Removed
===================

Each row below lists a ``steps`` library, the Steps it provides, and the
libraries to remove if you do not use
any of those Steps. The libraries to remove are the ``steps`` library itself
plus the transitive dependencies that no other library remaining in the
Execution Environment requires. You can remove any combination of rows.

.. warning::

   Never remove ``silo-low-code-steps-standard``. Removing it prevents the
   ``low_code`` syntax from being registered, and snippet arguments that use it will not
   run.

.. list-table::
   :header-rows: 1
   :widths: 20 25 40 15

   * - Steps library
     - Steps it provides
     - Libraries to remove if unused
     - Total libraries
   * - ``silo-low-code-steps-cli==3.2.1``
     - * ``parse_line``
       * ``parse_sectional_rows``
       * ``parse_proc_net_snmp``
       * ``parse_ifconfig``
       * ``parse_split_response``
       * ``parse_table_row``
       * ``parse_table_column``
       * ``parse_netstat``
       * ``ntc``
       * ``textfsm``
       * ``regex_select_table``
       * ``select_table_item``
       * ``format_remove_unit``
       * ``format_build_string``
     - * ``silo-low-code-steps-cli==3.2.1``
       * ``ifconfig-parser==0.0.5``
       * ``ntc-templates==4.4.0``
       * ``textfsm==1.1.3``
     - 4
   * - ``silo-low-code-steps-jmx==0.4.1``
     - * ``jmx``
     - * ``silo-low-code-steps-jmx==0.4.1``
       * ``jmxquery==1.1.0``
     - 2
   * - ``silo-low-code-steps-prometheus==1.1.3``
     - * ``promql``
       * ``promql_vector``
       * ``promql_matrix``
       * ``aggregation_percentile``
       * ``aggregation_mean``
       * ``aggregation_mode``
       * ``aggregation_median``
       * ``aggregation_max``
       * ``aggregation_min``
     - * ``silo-low-code-steps-prometheus==1.1.3``
     - 1
   * - ``silo-low-code-steps-rest==4.3.0``
     - * ``http``
       * ``paginator_offset``
     - * ``silo-low-code-steps-rest==4.3.0``
     - 1
   * - ``silo-low-code-steps-snmp==0.3.4``
     - * ``snmp``
     - * ``silo-low-code-steps-snmp==0.3.4``
     - 1
   * - ``silo-low-code-steps-ssh==3.2.0``
     - * ``ssh``
     - * ``silo-low-code-steps-ssh==3.2.0``
       * ``silo-ssh-requests==0.8.1``
       * ``parallel-ssh==2.16.0.post1``
       * ``gevent==26.8.0``
       * ``greenlet==3.5.5``
       * ``zope-event==6.2``
       * ``zope-interface==8.6``
       * ``ssh-python==1.2.0.post1``
       * ``ssh2-python==1.2.0.post1``
     - 9
   * - ``silo-low-code-steps-winrm==0.2.1``
     - * ``winrm``
       * ``powershell``
     - * ``silo-low-code-steps-winrm==0.2.1``
       * ``pywinrm==0.5.0``
       * ``pykerberos==1.2.4``
       * ``requests-ntlm==1.3.0``
       * ``pyspnego==0.12.2``
     - 5

Removing Libraries
==================

Libraries are removed manually from a custom Execution Environment using the
|PRODUCT_NAME| Execution Environment Manager in the user interface.