Advanced Echo Server

Delay Features

Simulate network conditions with delay patterns controlled via HTTP headers or environment variables. Delays are capped at 300s to prevent hangs. Prometheus histograms track latency.

Control Flow

graph TD
  A[Request] --> B{Check Headers/Env}
  B -->|X-Echo-Delay| C[Simple Delay]
  B -->|X-Echo-Jitter| D[Jitter Delay]
  B -->|X-Echo-Random-Delay| E[Random Delay]
  B -->|X-Echo-Exponential| F[Exponential Backoff]
  B -->|X-Echo-Latency| G[Latency Injection]
  C --> H[Apply Delay]
  D --> H
  E --> H
  F --> H
  G --> H
  H --> I[Continue Processing]

Simple Delay

Applies a fixed delay in milliseconds.

• Header: X-Echo-Delay: 500ms
• Env: ECHO_DELAY=100ms
• Max: 300000ms (300s)
• Example:

curl -H "X-Echo-Delay: 200ms" http://localhost:8080/ -d "test"
# Logs: "Simple delay: 200ms"

Jitter Delay

Base delay ± random variance (ms).

• Header: X-Echo-Jitter: 100,50 (100ms ± 50ms)
• Env: ECHO_JITTER=200,100
• Bounds: Delay clamped to 0–300000ms
• Example: Delays ~150-250ms randomly

curl -H "X-Echo-Jitter: 100,50" http://localhost:8080/
# Logs: "Jitter delay: 120ms (base: 100ms, jitter: 20ms)"

Random Delay

Uniform random delay in a range (ms).

• Header: X-Echo-Random-Delay: 100,500
• Env: ECHO_RANDOM_DELAY=50,200
• Bounds: Max capped at 300000ms
• Example:

curl -H "X-Echo-Random-Delay: 100,300" http://localhost:8080/
# Logs: "Random delay: 150ms (range: 100-300)"

Exponential Backoff

Delay = base * 2^(attempt-1) + 25% jitter, for retry testing.

• Header: X-Echo-Exponential: 100,3 (~400ms + jitter)
• Env: ECHO_EXPONENTIAL=50,2
• Bounds: Result clamped to 0–300000ms
• Example:

curl -H "X-Echo-Exponential: 100,3" http://localhost:8080/
# Logs: "Exponential delay: 410ms (base: 100ms, attempt: 3)"

Latency Injection

Fixed or random latency (ms).

• Header: X-Echo-Latency: 100ms or 100-200ms
• Env: ECHO_LATENCY=50-150
• Bounds: Clamped to 0–300000ms
• Example:

curl -H "X-Echo-Latency: 100-200ms" http://localhost:8080/
# Logs: "Latency injection: 130ms (range: 100-200)"

Notes

• Only one delay type applies per request (first matched: Simple, Jitter, Random, Exponential, Latency).
• Maximum delay: 300s to prevent abuse.
• Check /metrics for echo_request_duration_seconds histogram.