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Update kafka spring example to align with main spec
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lmolkova committed Jun 13, 2024
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49 changes: 30 additions & 19 deletions docs/messaging/kafka.md
Original file line number Diff line number Diff line change
Expand Up @@ -129,28 +129,39 @@ If an intermediary broker is present, `service.name` and `peer.service` will not

### Apache Kafka with Quarkus or Spring Boot Example

Given is a process P, that publishes a message to a topic T1 on Apache Kafka.
One process, CA, receives the message and publishes a new message to a topic T2 that is then received and processed by CB.

Frameworks such as Quarkus and Spring Boot separate processing of a received message from producing subsequent messages out.
For this reason, receiving (Span Rcv1) is the parent of both processing (Span Proc1) and producing a new message (Span Prod2).
The span representing message receiving (Span Rcv1) should not set `messaging.operation.type` to `receive`,
as it does not only receive the message but also converts the input message to something suitable for the processing operation to consume and creates the output message from the result of processing.

```
Process P: | Span Prod1 |
--
Process CA: | Span Rcv1 |
| Span Proc1 |
| Span Prod2 |
--
Process CB: | Span Rcv2 |
In this example, the producer publishes a message to a topic T on Apache Kafka.
Consumer receives the message, processes it and commits to offset.

Frameworks such as Quarkus and Spring Boot provide integrations with Kafka which allow to
configure processing callbacks, so corresponding instrumentations can create "Process"
spans in addition to "Receive" spans created by Kafka instrumentations for polling calls.

```mermaid
flowchart LR;
subgraph PRODUCER
P[Span Send T]
end
subgraph CONSUMER
direction TB
R1[Span Poll T]
R2[Span Process T]
R3[Span Commit T]
end
P-. link .-R1;
P-. link .-R2;
R2-- parent ---R3;
classDef normal fill:green
class P,R1,R2,R3 normal
linkStyle 0 color:green,stroke:green
linkStyle 1 color:green,stroke:green
```

| Field or Attribute | Span Prod1 | Span Rcv1 | Span Proc1 | Span Prod2 | Span Rcv2 |
| Field or Attribute | Span Publish | Span Receive | Span Process | Span Commit |
|-|-|-|-|-|-|
| Span name | `"T1 publish"` | `"T1 receive"` | `"T1 process"` | `"T2 publish"` | `"T2 receive`" |
| Parent | | Span Prod1 | Span Rcv1 | Span Rcv1 | Span Prod2 |
| Span name | `"send T"` | `"poll T"` | `"process T"` | `"commit T"` |
| Parent | | | (optional) Span Publish | Span Process |
| Links | | | | | |
| SpanKind | `PRODUCER` | `CONSUMER` | `CONSUMER` | `PRODUCER` | `CONSUMER` |
| Status | `Ok` | `Ok` | `Ok` | `Ok` | `Ok` |
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