The document discusses benchmarking distributed tracers in the context of web request tracing and latency challenges faced in microservice architectures. It details the methodology for measuring instrumentation overhead and compares different tracers (Spring Cloud Sleuth, Jaeger, Minke) with varying numbers of tracepoints in performance metrics. The results indicate that the choice of tracer and configuration significantly impacts latency and throughput, with specific conditions noted for load balanced and fan-out services.

1. Benchmarking
distributed tracers
Han Qiao
Imperial College London

2. What is tracing?
- Follows a web request along its
critical path
- Records runtime parameters
that contribute to high latency
Source: Zipkin.io

3. Motivation
- Current web architecture makes
tail latency issues pervasive and
difficult to diagnose
- Microservice
architecture
- Asynchronous RPCs
Source: The Tail at Scale by Jeff Dean

4. Benchmark
Application
- EchoService
- Acts as a database
- HelloService
- Concatenates results
from 3 requests to
EchoService
- All requests are
asynchronous
- Written as Spring Boot
applications and deployed on
docker swarm

5. Methodology
- Single host
- Baseline measurement
- Minimize network fluctuation
- Measure instrumentation overhead only
- Multi-node cluster
- More realistic to real world deployment
- Load balanced service (replicas)
- Fan-out service (search engine)

6. Baseline
measurement
- Host machine
- Quad-core 3.7 GHz
- 8GB RAM
- Ubuntu 16.04
- docker 17.04
- wrk2 load generator
- 2 threads
- 40 connections
- 80 requests / second
- 40% peak load
- No queuing
- No coordinated omission

7. Baseline
measurement
- Host machine
- Quad-core 3.7 GHz
- 8GB RAM
- Ubuntu 16.04
- docker 17.04
- wrk2 load generator
- 2 threads
- 40 connections
- 80 requests / second
- 40% peak load
- No queuing
- No coordinated omission
TCP delayed acknowledgement

8. Instrumented
with tracers
- Spring Cloud Sleuth
- mean: 7.29 ms
- stdev: 8.70 ms
- Jaeger
- mean: 3.75 ms
- stdev: 1.38 ms
- Minke
- mean: 3.75 ms
- stdev: 1.21 ms
- Baseline
- mean: 3.26 ms
- stdev: 0.99 ms

9. Increasing no. of
tracepoints
(Minke tracer)
- 1000
- mean: 46.79 ms
- stdev: 21.53 ms
- 100
- mean: 4.47 ms
- stdev: 2.38 ms
- 10
- mean: 3.75 ms
- stdev: 1.21 ms
- 0 (Baseline)
- mean: 3.26 ms
- stdev: 0.99 ms

10. Increasing no. of
tracepoints
(mean latency)
- Enclose instrumented method in
a for loop and vary loop count
- Biased towards logging
and instrumentation
overhead
- 12.5 ms wait time between
every request
- 4.47 ms mean response time @
100 tracepoints (server handles
only one request at a time)
- 46.79 ms mean response time @
1000 tracepoints (combined
effect of higher overhead and
queueing of requests)

11. Load balanced service

12. Load balanced
service
- 90% requests complete within
20 ms @ 1000 tracepoints
- 90% requests took more than
50 ms on a single host
- The reduced mean response
time is likely a result of
distributing logging activities
across more nodes

13. Fan-out service

14. Fan-out service
- 1 second latency outlier due to
TCP retransmission delay
- Reduced throughput to 10
requests per second to
eliminate effects from queueing
- Vary fan-out value by changing
query parameter

15. Fan-out service
- 1 second latency outlier due to
TCP retransmission delay
- Reduced throughput to 10
requests per second to
eliminate effects from queueing
- Vary fan-out value by changing
query parameter
TCP retransmission delay

16. Fan-out service
- 1 second latency outlier due to
TCP retransmission delay
- Reduced throughput to 10
requests per second to
eliminate effects from queueing
- Vary fan-out value by changing
query parameter

17. Fan-out service
- 1 second latency outlier due to
TCP retransmission delay
- Reduced throughput to 10
requests per second to
eliminate effects from queueing
- Vary fan-out value by changing
query parameter

18. Fan-out service
- 1 second latency outlier due to
TCP retransmission delay
- Reduced throughput to 10
requests per second to
eliminate effects from queueing
- Vary fan-out value by changing
query parameter

19. Usability comparison between different tracers
11
includes dependencies in docker base image
12
instruments concurrency libraries by default
13
logs to local disk and waits for collection event

20. Open source benchmarks
- https://github.com/sweatybridge/spring-jaeger
- https://github.com/sweatybridge/spring-zipkin
- https://github.com/sweatybridge/minke (coming soon)