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General information

Purpose

The goal of the collector is to support high volume data. It uses plain TCP connections tunneled in SSL/TLS. Connections are stream-based (as opposed to request-based) and long running. Payload is binary-encoded (currently we are using Google Protocol Buffers). HV-VES uses direct connection to DMaaP's Kafka. All these decisions were made in order to support high-volume data with minimal latency.

Implementation details

Technology stack

  • Project Reactor is used as a backbone of the internal architecture.
  • Netty is used by means of reactor-netty library.
  • We are using Kotlin so we can write very concise code with great interoperability with existing Java libraries.
  • Types defined in Λrrow library are also used when it improves readability or general cleanness of the code.

Rules

  • Do not block. Use non-blocking libraries. Do not use block* Reactor calls inside the core of the application.
  • Pay attention to memory usage.
  • Do not decode the payload - it can be of a considerable size. The goal is to direct the event into a proper Kafka topic. The routing logic should be based only on VES Common Header.
  • All application logic should be defined in hv-collector-core module and tested on a component level by tests defined in hv-collector-ct. The core module should have a clean interface (defined in boundary package: api and adapters).
  • Use Either functional data type when designing fail-cases inside the main Flux. Using exceptions is a bit like using goto + it adds some performance penalty: collecting stack trace might be costly but we do not usually need it in such cases. RuntimeExceptions should be treated as application bugs and fixed.
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