docs: arch: 2nd and 3rd party plugins

Co-authored-by: Yash Lamba <yashlamba2000@gmail.com>
Signed-off-by: John Andersen <johnandersenpdx@gmail.com>

docs/arch/0001-2nd-and-3rd-party-plugins.rst

@@ -0,0 +1,184 @@
+1. 2nd and 3rd party plugins
+============================
+
+Date: 2021-04-01
+
+Status
+------
+
+Draft
+
+Context
+-------
+
+DFFML currency has the main package and all plugins maintained within a single
+repo. We always intended to support 3rd party plugins, meaning displaying them
+on the main docs site as options for users. We are just now getting around to
+it.
+
+We decided that we will have the main package, 2nd party plugins, and 3rd party
+plugins.
+
+- The main package is ``dffml``.
+
+- 2nd party plugins are plugins that are maintained by the core maintainers and
+  who's repos reside in the ``dffml`` organization.
+
+- 3rd party plugins are hosted in user or other org repos and core maintainers
+  are not owners of those repos.
+
+We need to take the plugins that are currency maintained within the main repo
+and put them in their own repos. We need the docs site to reflect the working /
+not-working status of plugins on tutorial pages. We need to have a set of
+plugins that we don't release unless those all work together. This is because a
+core part of our functionality is letting users swap out underlying libraries,
+which they can't do if they can't be installed together.
+
+What do we know
+~~~~~~~~~~~~~~~
+
+- Main package has no dependencies
+
+- The plugins page lists all plugins that are in ``dffml/plugins.py``
+
+- There are tutorials that are associated with specific plugins
+
+  - If a plugin's latest release doesn't pass CI against DFFML's latest
+    release, any tutorials should show that it's not working.
+
+- A main point of DFFML is to have a set of ML libraries that work together in
+  a single install environment so that a user can try multiple libraries and
+  choose the best one.
+
+  - This means we have to know which plugins can be installed together.
+
+Decision
+--------
+
+- We want to do the compatibility matrix check in the main plugin and in each
+  plugin.
+
+  - This lets the main plugin know at time of docs build, what status is for
+    each plugin.
+
+  - This lets plugin authors know in PR CI, etc. if they are about to cause a
+    compatibility issue.
+
+- We need the ability to move things from level 1 to level 2 if we want to
+  deicide that that it's not longer a showstopper for release.
+
+- Working / not-working status of tutorials we want to show two things
+  This only applies to support levels 2 and 3. Because support levels 0 and 1
+  must always work for release.
+
+  - Does this tutorial work when other packages are installed latest / master?
+
+  - Does this tutorial does work against all dependent packages for latest /
+    master?
+
+    - Some plugins rely only on the main package
+
+      - Main package never has any dependencies. So from a dependency checking
+        perspective, there should never be any issue.
+
+    - Some plugin rely on other plugins as well
+
+      - Main package never has any dependencies. So from a dependency checking
+        perspective, there should never be any issue.
+
+- To know which plugins can be installed together
+
+  - Which plugins failure to validate against master branch warrant blocking
+    release
+
+    - We need some sort of support level tracking.
+
+    - Support level tracking means test against latest release and master
+      branch.
+
+    - Possible support levels
+
+      - 0 main package
+
+      - 1 2nd party required pass for release
+
+      - 2 2nd party not required pass for release
+
+        - Note on tutorials that involve level 2 plugins to say they aren't
+          working at the moment
+
+      - 3 3rd party not required pass for release
+
+        - Note on tutorials that involve level 3 plugins to say they aren't
+          working at the moment
+
+Consequences
+------------
+
+- Based on support levels
+
+  - The ``dffml/plugins.json`` should list the plugin, and it's support level
+
+- Tutorials that pip install packages of support level 2 or 3 must have some
+  element that the top of the page that can show the working / not-working
+  status.
+
+- Matrix check, two perspectives
+
+  - Main package
+
+    - Support level 1
+
+      - For master, does installing all the plugins from their master zip
+        archive URL work when all given to ``pip install`` at the same time.
+
+      - For latest release, does installing all the plugins by PyPi name work
+        when all given to ``pip install`` at the same time.
+
+      - "work" here meaning does pip raise any issues about conflicting
+        dependency versions.
+
+    - Support level 2
+
+      - For master
+
+          - Does installing all the plugins in support levels 1 and 2 work from
+            their master zip archive URL work when all given to ``pip install``
+            at the same time.
+
+            - PASS: No warning on tutorials.
+
+            - FAIL: Warning on tutorials, this may not work when other plugins
+              are install. This tutorial should still work when no other plugins
+              are installed.
+
+      - For latest release, does installing all the plugins by PyPi name work
+        when all given to ``pip install`` at the same time.
+
+          - Does installing all the plugins in support levels 1 and 2 work from
+            their PyPi name when all given to ``pip install`` at the same time.
+
+            - PASS: No warning on tutorials.
+
+            - FAIL: Warning on tutorials, this may not work when other plugins
+              are install. This tutorial should still work when no other plugins
+              are installed.
+
+      - "work" here meaning does pip raise any issues about conflicting
+        dependency versions.
+
+        - If they don't. Do we care about finding more info about which one's
+          are braking it. No, we do not care, because figuring out matrix is
+          exponential.
+
+    - Support level 3
+
+      - Always have a warning on tutorials, this may not work when other plugins
+        are installed, because this a tutorial based on a third party plugin.
+        This tutorial should still work when no other plugins are installed.
+        In the event that it doesn't please report issues to third party here:
+        <Link to third party project URL for plugin>
+
+  - Plugin package
+
+    - TODO: Fill out this area

docs/arch/index.rst

@@ -7,4 +7,5 @@ https://cognitect.com/blog/2011/11/15/documenting-architecture-decisions
 .. toctree::
     :titlesonly:
 
+    0001-2nd-and-3rd-party-plugins
     0002-Object-Loading-and-Instantiation-in-Examples