Dann brown

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Apache Kafka Lab — Try It Yourself (cURL)

Hands-on curls for my str-producer / str-consumer lab. Source: curso-apache-kafka-master/POSTMAN-CURL.md (local study repo).

Before you start:

  1. docker-compose up -d (Kafka + Kafdrop)
  2. Start str-consumer (port 8197)
  3. Start str-producer (port 8097)
  4. Open Kafdrop: http://localhost:19000

HTTP requests go to the producer (8097). The consumer (8197) reads from Kafka — it does not expose /casos for publishing.

See Lab architecture · Concepts · Windows setup

Quick reference

Service URL
Producer API http://localhost:8097
Consumer API http://localhost:8197
Kafdrop http://localhost:19000
Kafka broker localhost:9092

Case 01 — Basic message

Field Value
Method POST
URL http://localhost:8097/casos/01-basico
Content-Type text/plain
Topic str-topic
Response 201 Created 
curl -X POST http://localhost:8097/casos/01-basico \
  -H "Content-Type: text/plain" \
  -d "Hola Kafka"

Verify: Producer log [CASO-01] Particion X, Offset Y; consumer logs [CASO-01] LISTENER1/2/3.

Case 02 — Message key (partition affinity)

Field Value
URL http://localhost:8097/casos/02-con-key
Content-Type application/json
Topic order-topic (3 partitions)
Key orderId 
curl -X POST http://localhost:8097/casos/02-con-key \
  -H "Content-Type: application/json" \
  -d "{\"orderId\":\"ORD-001\",\"product\":\"Laptop\",\"quantity\":1}"

curl -X POST http://localhost:8097/casos/02-con-key \
  -H "Content-Type: application/json" \
  -d "{\"orderId\":\"ORD-001\",\"product\":\"Mouse\",\"quantity\":2}"

Verify: Same orderId → same partition; consumer log [CASO-02] Orden ORD-001 (key=ORD-001) -> particion X.

Case 03 — Typed JSON event

Field Value
URL http://localhost:8097/casos/03-evento-json
Topic user-event-topic
Key userId 
curl -X POST http://localhost:8097/casos/03-evento-json \
  -H "Content-Type: application/json" \
  -d "{\"userId\":\"user-42\",\"action\":\"LOGIN\"}"

Verify: Consumer log [CASO-03] Usuario user-42 ejecuto 'LOGIN' en ...

Case 04 — Payment + retry + DLT

Field Value
URL http://localhost:8097/casos/04-pago
Topic payment-topic

Valid payment:

curl -X POST http://localhost:8097/casos/04-pago \
  -H "Content-Type: application/json" \
  -d "{\"paymentId\":\"PAY-001\",\"userId\":\"user-1\",\"amount\":99.99}"

Invalid payment (→ DLT after retries):

curl -X POST http://localhost:8097/casos/04-pago \
  -H "Content-Type: application/json" \
  -d "{\"paymentId\":\"PAY-002\",\"userId\":\"user-2\",\"amount\":-50.0}"
Scenario Expected consumer log
amount > 0 [CASO-04] Pago PAY-001 procesado exitosamente
amount ≤ 0 3 retries → [CASO-04] DLT >>> Pago PAY-002 rechazado

Verify in Kafdrop: topics payment-topic-retry-* and payment-topic-dlt.

Case 05 — Request-reply

Field Value
URL http://localhost:8097/casos/05-request-reply
Topics request-topic → reply-topic
Response 200 OK with body 
curl -X POST http://localhost:8097/casos/05-request-reply \
  -H "Content-Type: text/plain" \
  -d "Hola desde cURL"

Expected response:

Echo: Hola desde cURL

Case 06 — Text filter (RecordInterceptor)

Field Value
URL http://localhost:8097/casos/06-texto-filtro
Topic text-filter-topic 
curl -X POST http://localhost:8097/casos/06-texto-filtro \
  -H "Content-Type: text/plain" \
  -d "Hola Mundo!  Niño café"

Verify: Consumer tabulated analysis [CASO-06] ========== ANALISIS TABULADO ==========; double spaces → tabs via interceptor.

Case 07 — Inventory + database

POST movements (producer):

curl -X POST http://localhost:8097/casos/07-inventario \
  -H "Content-Type: application/json" \
  -d '{"productId":"PROD-001","productName":"Laptop Dell","quantity":10,"operation":"STOCK_IN"}'

curl -X POST http://localhost:8097/casos/07-inventario \
  -H "Content-Type: application/json" \
  -d '{"productId":"PROD-001","productName":"Laptop Dell","quantity":3,"operation":"STOCK_OUT"}'

GET queries (consumer — exception: read API on 8197):

curl http://localhost:8197/casos/07-inventario
curl http://localhost:8197/casos/07-inventario/resumen
curl http://localhost:8197/casos/07-inventario/PROD-001

Database: SQLite at str-consumer/data/kafka-lab.db, table inventory_records.

Case 08 — Kafka Streams (08a / 08b / 08c)

Start one Streams app first: run-streams-pipe.bat, run-streams-linesplit.bat, or run-streams-wordcount.bat. Consumer (8197) not required.

08a — Pipe

curl -X POST http://localhost:8097/casos/08a-pipe \
  -H "Content-Type: text/plain" \
  -d "Hola Kafka Streams"

Verify: streams-pipe-output in Kafdrop; topology log in Pipe console.

08b — LineSplit

curl -X POST http://localhost:8097/casos/08b-linesplit \
  -H "Content-Type: text/plain" \
  -d "Hola Kafka Streams"

Verify: individual words in streams-linesplit-output.

08c — WordCount

curl -X POST http://localhost:8097/casos/08c-wordcount \
  -H "Content-Type: text/plain" \
  -d "hello kafka streams hello"

Verify: word counts in streams-wordcount-output; state store counts-store in topology log.

See full Streams walkthrough.

curl -X POST http://localhost:8097/casos/01-basico -H "Content-Type: text/plain" -d "Hola Kafka"
curl -X POST http://localhost:8097/casos/02-con-key -H "Content-Type: application/json" -d "{\"orderId\":\"ORD-001\",\"product\":\"Laptop\",\"quantity\":1}"
curl -X POST http://localhost:8097/casos/03-evento-json -H "Content-Type: application/json" -d "{\"userId\":\"user-42\",\"action\":\"LOGIN\"}"
curl -X POST http://localhost:8097/casos/04-pago -H "Content-Type: application/json" -d "{\"paymentId\":\"PAY-001\",\"userId\":\"user-1\",\"amount\":99.99}"
curl -X POST http://localhost:8097/casos/05-request-reply -H "Content-Type: text/plain" -d "Hola Kafka"
curl -X POST http://localhost:8097/casos/06-texto-filtro -H "Content-Type: text/plain" -d "Hola Mundo!  Niño café"
curl -X POST http://localhost:8097/casos/07-inventario -H "Content-Type: application/json" -d "{\"productId\":\"PROD-001\",\"productName\":\"Laptop Dell\",\"quantity\":10,\"operation\":\"STOCK_IN\"}"
curl http://localhost:8197/casos/07-inventario/resumen

Windows (PowerShell)

From the lab repo: .\demo.ps1

Postman

Import from lab repo:

  • postman/Kafka-Curso.postman_collection.json
  • postman/Kafka-Curso.postman_environment.json (baseUrl = http://localhost:8097)

Checklist

  • Case 01 → 201
  • Case 02 → same key, same partition
  • Case 03 → consumer action log
  • Case 04 valid → success log
  • Case 04 invalid → DLT after ~6s
  • Case 05 → Echo: ... in HTTP response
  • Case 06 → tabulated analysis in consumer
  • Case 07 → POST + GET resumen + .db file exists
  • Case 08c → WordCount in streams-wordcount-output
  • Kafdrop shows all topics