vdk-meta-jobs: add VEP Summary and Motivation sections (#1698)

What: 
Add Meta Jobs VEP template file and introduce first version of the
Summary and Motivation sections.

Why:
This VEP is needed in order to provide details about the necessity and
the power of the Meta Jobs.

This is a first version of the aforementioned sections and the idea is
to incrementally fill the document with useful information.

---------

Signed-off-by: Yoan Salambashev <[email protected]>

specs/vep-1243-vdk-meta-jobs/README.md

@@ -0,0 +1,169 @@
+
+# VEP-1243: VDK Meta jobs
+
+* **Author(s):** Yoan Salambashev ([email protected])
+* **Status:** draft
+
+- [Summary](#summary)
+- [Glossary](#glossary)
+- [Motivation](#motivation)
+- [Requirements and goals](#requirements-and-goals)
+- [High-level design](#high-level-design)
+- [API Design](#api-design)
+- [Detailed design](#detailed-design)
+- [Implementation stories](#implementation-stories)
+- [Alternatives](#alternatives)
+
+## Summary
+
+<!--
+Short summary of the proposal. It will be used as user-focused
+documentation such as release notes or a (customer facing) development roadmap.
+The tone and content of the `Summary` section should be
+useful for a wide audience.
+-->
+
+The Meta Job is a new feature in VDK that enables users to manage job dependencies in their data processing workflows.
+It allows a Data Job to manage other Data Jobs by triggering them on certain job completion conditions (i.e. job1
+and job2 complete before job3 starts) resulting in more accurate and consistent data output. An integration with
+Apache Airflow is available, but it requires users to manage their own instance or pay for an externally managed
+service. Meta Jobs provide a more lightweight alternative that simplifies the process and reduces cost.
+
+## Glossary
+<!--
+Optional section which defines terms and abbreviations used in the rest of the document.
+-->
+
+## Motivation
+<!--
+It tells **why** do we need X?
+Describe why the change is important and the benefits to users.
+Explain the user problem that need to be solved.
+-->
+
+Data teams are constantly looking for ways to optimize and streamline their data processing workflows.
+One critical aspect of these workflows is managing job dependencies, which ensures that Data Jobs are executed
+in the appropriate order. Until now, we addressed this problem
+by integrating with the external tool Apache Airflow. However, this approach comes with its downsides: teams would
+have to manage their instance of Airflow or pay for an externally managed service.
+
+To address this problem, VDK is introducing the Meta Jobs plugin. Meta Jobs are providing users with the ability
+to manage job dependencies natively within the framework. They ensure that one or more Data Jobs will be triggered
+upon successful completion (or other specified criteria) of one or more other Data Jobs. Similarly to other
+orchestrating services, Meta Jobs express the dependencies as a DAG. As Data Jobs themselves, they go with
+all the powerful features as every other Data Job, such as scheduling and monitoring.
+This new feature gives users the ability to easily orchestrate the workflow the way they want it.
+
+Meta Jobs allow for greater job segmentation, which can prove beneficial when working with complex
+pipelines. Breaking down the pipelines into more manageable Data Jobs can help users with maintaining and debugging.
+Thus, this feature will save time, resources, and worries about external dependencies.
+Our data engineering framework empowers data teams to manage job dependencies with control, leading to more
+reliable and efficient data processing workflows.
+
+## Requirements and goals
+<!--
+It tells **what** is it trying to achieve?
+List the specific goals (functional and nonfunctional requirements)? How will we
+know that this has succeeded?
+
+Specify non-goals. Clearly, the list of non-goals can't be exhaustive.
+Non-goals are only features, which a contributor can reasonably assume were a goal.
+One example is features that were cut during scoping.
+-->
+
+## High-level design
+
+<!--
+All the rest sections tell **how** are we solving it?
+
+This is where we get down to the specifics of what the proposal actually is.
+This should have enough detail that reviewers can understand exactly what
+you're proposing, but should not include things like API designs or
+implementation. What is the desired outcome and how do we measure success?
+
+Provide a valid UML Component diagram that focuses on the architecture changes
+implementing the feature. For more details on how to write UML Component Spec -
+see https://en.wikipedia.org/wiki/Component_diagram#External_links.
+
+For every new component on the diagram, explain which goals does it solve.
+In this context, a component is any separate software process.
+
+-->
+
+
+## API design
+
+<!--
+
+Describe the changes and additions to the public API (if there are any).
+
+For all API changes:
+
+Include Swagger URL for HTTP APIs, no matter if the API is RESTful or RPC-like.
+PyDoc/Javadoc (or similar) for Python/Java changes.
+Explain how does the system handle API violations.
+-->
+
+
+## Detailed design
+<!--
+Dig deeper into each component. The section can be as long or as short as necessary.
+Consider at least the below topics but you do not need to cover those that are not applicable.
+
+### Capacity Estimation and Constraints
+    * Cost of data path: CPU cost per-IO, memory footprint, network footprint.
+    * Cost of control plane including cost of APIs, expected timeliness from layers above.
+### Availability.
+    * For example - is it tolerant to failures, What happens when the service stops working
+### Performance.
+    * Consider performance of data operations for different types of workloads.
+       Consider performance of control operations
+    * Consider performance under steady state as well under various pathological scenarios,
+       e.g., different failure cases, partitioning, recovery.
+    * Performance scalability along different dimensions,
+       e.g. #objects, network properties (latency, bandwidth), number of data jobs, processed/ingested data, etc.
+### Database data model changes
+### Telemetry and monitoring changes (new metrics).
+### Configuration changes.
+### Upgrade / Downgrade Strategy (especially if it might be breaking change).
+  * Data migration plan (it needs to be automated or avoided - we should not require user manual actions.)
+### Troubleshooting
+  * What are possible failure modes.
+    * Detection: How can it be detected via metrics?
+    * Mitigations: What can be done to stop the bleeding, especially for already
+      running user workloads?
+    * Diagnostics: What are the useful log messages and their required logging
+      levels that could help debug the issue?
+    * Testing: Are there any tests for failure mode? If not, describe why._
+### Operability
+  * What are the SLIs (Service Level Indicators) an operator can use to determine the health of the system.
+  * What are the expected SLOs (Service Level Objectives).
+### Test Plan
+  * Unit tests are expected. But are end to end test necessary. Do we need to extend vdk-heartbeat ?
+  * Are there changes in CICD necessary
+### Dependencies
+  * On what services the feature depends on ? Are there new (external) dependencies added?
+### Security and Permissions
+  How is access control handled?
+  * Is encryption in transport supported and how is it implemented?
+  * What data is sensitive within these components? How is this data secured?
+      * In-transit?
+      * At rest?
+      * Is it logged?
+  * What secrets are needed by the components? How are these secrets secured and attained?
+-->
+
+Although having all these pros, the user should have in mind the cons of the Meta Jobs as well. The limitation that
+have to be considered is that there is a limit on the number of concurrent running jobs in a single DAG. If this
+limit is exceeded, the upcoming jobs would be delayed for a while until there is an empty spot for them.
+
+## Implementation stories
+<!--
+Optionally, describe what are the implementation stories (eventually we'd create github issues out of them).
+-->
+
+## Alternatives
+<!--
+Optionally, describe what alternatives has been considered.
+Keep it short - if needed link to more detailed research document.
+-->