AWS X-Ray

Overview

• Distributed tracing system
• "Follow-the-thread" - request oriented model
  • Contrast: service/resource oriented
• Samples data
• Use cases
  • Create service map
  • Identify bugs/errors
  • Build visualizations (API exposed)

Model

• Trace
  • Unique TraceId
    • Passed along to invoked services
  • Collections of 1+ segments
• Segment
  • Encapsulates datapoints for single component
    • e.g. invoked service, database, cache
  • Contains 0+ annotations
• Annotation
  • Data associated with a segment
  • System-defined (added by AWS)
  • User-defined
    • Additional data associated with a segment
• Error
  • System annotation associated with a segment for failed call

Instrumenting Code

• X-Ray SDK
  • Interceptor (incoming HTTP requests)
  • Client handlers (AWS SDK instrumentation)
  • HTTP client
• Send data to X-Ray Daemon

X-Ray Daemon

• Installed on instance
• Listens on UDP/2000
• Sends data to X-Ray service
• Compare 
  • CloudWatch Logs agent

References

• http://www.pdl.cmu.edu/PDL-FTP/SelfStar/CMU-PDL-14-102.pdf