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TiFlash Development Guide

To start developing TiFlash

TODO: need docs like Get Started chapter of TiDB Dev Guide.

TiFlash Engineering Practices Documentation

Recommendation

Code Review Guidelines

Basic Guidelines

Rules for Reviewer

  • Modifications should not reduce code coverage of unit-tests in most cases.
  • Ensure Labels and Release note conform to the specification.
  • Value the design of test cases. Find corner cases as more as possible.
  • Scope down pull request to specific issue.
  • Ensure each issue contains enough context.
  • Design documents is necessary for feature development.
  • TODO: need more details for each module

Development Guide

TODO: need more details for each module

Coding Style

General rules

  • Follow standard conventions.
  • Simpler is always better. Reduce complexity as much as possible.
  • Always find root cause. Always look for the root cause of a problem.

Design rules

  • Test First Development. Design unit-tests and integration-tests before functions.
  • Keep configurable data at high levels.
  • Prefer polymorphism to if/else or switch/case.
  • Separate multi-threading code.
  • Prevent over-configurability.
  • Use dependency injection.
  • Follow Law of Demeter. A class should know only its direct dependencies.

Tests

  • One assert per test.
  • Readable.
  • Fast.
  • Independent.
  • Repeatable.
  • Value code coverage.

Understandability tips

  • Be consistent. If you do something a certain way, do all similar things in the same way.
  • Use explanatory variables.
  • Encapsulate boundary conditions. Boundary conditions are hard to keep track of. Put the processing for them in one place.
  • Prefer dedicated value objects to primitive type.
  • Avoid logical dependency. Don't write methods which works correctly depending on something else in the same class.
  • Avoid negative conditionals.

Names rules

  • Choose descriptive and unambiguous names.
  • Make meaningful distinction.
  • Use pronounceable names.
  • Use searchable names.
  • Replace magic numbers with named constants.
  • Avoid encodings. Don't append prefixes or type information.

Functions rules

  • Small.
  • Do one thing.
  • Use descriptive names.
  • Prefer fewer arguments.
  • Have no side effects.
  • Don't use flag arguments. Split method into several independent methods that can be called from the client without the flag.

Comments rules

  • Always try to explain yourself in code.
  • Don't be redundant.
  • Don't add obvious noise.
  • Don't use closing brace comments.
  • Don't comment out code. Just remove.
  • Use as explanation of intent.
  • Use as clarification of code.
  • Use as warning of consequences.

Source code structure

  • Separate concepts vertically.
  • Related code should appear vertically dense.
  • Declare variables close to their usage.
  • Dependent functions should be close.
  • Similar functions should be close.
  • Place functions in the downward direction.
  • Keep lines short.
  • Don't use horizontal alignment.
  • Use white space to associate related things and disassociate weakly related.
  • Don't break indentation.

Objects and data structures

  • Hide internal structure.
  • Prefer data structures.
  • Avoid hybrids structures (half object and half data).
  • Should be small.
  • Do one thing.
  • Small number of instance variables.
  • Base class should know nothing about their derivatives.
  • Better to have many functions than to pass some code into a function to select a behavior.
  • Prefer non-static methods to static methods.