Centralized Logging: Spring Boot Meets Grafana, Alloy, and Loki

Tech Stack

Spring-boot, maven, java21, Docker, H2, Grafana, Loki, Alloy

Run Locally

Clone the project

  git clone https://github.com/anicetkeric/spring-boot-logging-grafana-alloy-loki/

Documentation

Blog Post

Example Log Output

Inbound request (INFO, log-body: false)

{
  "@timestamp": "2026-03-21T21:27:19.571043105+01:00",
  "@version": "1",
  "message": "HTTP POST /api/books -> 201 (42ms)",
  "logger": "com.bootlabs.logging.filter.HttpLoggingFilter",
  "thread": "http-nio-8080-exec-3",
  "level": "INFO",
  "application.name": "spring-boot-logging-grafana-alloy-loki",
  "application.version": "0.0.1-SNAPSHOT",
  "environment": "dev",
  "traceId": "a3f7b2c1-9e4d-4f8a-b123-56789abcdef0",
  "correlationId": "9d1e4f82-1234-5678-abcd-ef0123456789",
  "event.kind": "inbound",
  "http.method": "POST",
  "http.url": "/api/books",
  "http.query": "",
  "http.status_code": 201,
  "event.duration": 42,
  "client.ip": "127.0.0.1",
  "http.request.headers.content-type": "application/json",
  "http.request.headers.authorization": "***",
  "http.request.headers.accept": "*/*",
  "http.response.headers.content-type": "application/json",
  "http.response.headers.x-trace-id": "a3f7b2c1-9e4d-4f8a-b123-56789abcdef0",
  "http.response.headers.x-correlation-id": "9d1e4f82-1234-5678-abcd-ef0123456789"
}

Inbound request (INFO, log-body: true)

Same as above, plus:

{
  "http.request.body":  "{\"title\":\"Clean Code\",\"isbn\":\"978-0-13-235088-4\",\"authorId\":1}",
  "http.response.body": "{\"id\":11,\"title\":\"Clean Code\",\"isbn\":\"978-0-13-235088-4\"}"
}

Outbound RestClient call

{
  "@timestamp": "2026-03-21T21:27:19.612084721+01:00",
  "@version": "1",
  "message": "HTTP OUT GET https://api.example.com/covers/978-0-13-235088-4 -> 200 (15ms)",
  "logger": "com.bootlabs.logging.interceptor.OutgoingHttpLoggingInterceptor",
  "level": "INFO",
  "application.name": "spring-boot-logging-grafana-alloy-loki",
  "environment": "dev",
  "traceId": "a3f7b2c1-9e4d-4f8a-b123-56789abcdef0",
  "correlationId": "9d1e4f82-1234-5678-abcd-ef0123456789",
  "event.kind": "outbound",
  "http.method": "GET",
  "http.url": "/covers/978-0-13-235088-4",
  "http.target": "https://api.example.com/covers/978-0-13-235088-4",
  "http.status_code": 200,
  "event.duration": 15,
  "http.request.headers.x-trace-id": "a3f7b2c1-9e4d-4f8a-b123-56789abcdef0",
  "http.response.headers.content-type": "application/json"
}

Notice both the inbound and outbound log lines carry the same traceId — you can reconstruct the full request lifecycle from a single ID.

Error with stack trace

{
  "@timestamp": "2026-03-21T21:27:55.003142890+01:00",
  "message": "HTTP GET /api/books/999 -> 500 (8ms)",
  "level": "ERROR",
  "traceId": "f9a2b3c4-...",
  "event.kind": "inbound",
  "http.status_code": 500,
  "error.stack_trace": "java.util.NoSuchElementException: No value present\n\tat java.base/java.util.Optional.get(Optional.java:143)\n\t..."
}

Authors

👤 anicetkeric

• Website: https://medium.com/@boottechnologies-ci
• Twitter: @AnicetKEric
• Github: @anicetkeric
• LinkedIn: @eric-anicet-kouame

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