Stream Cache

The Stream Cache step converts a Body::Stream into Body::Bytes up to a threshold. A stream drains on the first read. Steps that must read the body more than once cannot do so against a stream. Stream Cache reads the stream once, stores the bytes, and replaces the body. Every later step sees the same bytes.

RouteBuilder::from("timer:tick?period=1000")
    .route_id("stream-cache-demo")
    .stream_cache_default()
    .to("log:cached?showBody=true")
    .build()?;

- id: stream-cache-demo
  from: timer:tick?period=1000
  steps:
    - stream_cache: true
    - to: log:cached?showBody=true

The .stream_cache(threshold) call sets the maximum byte count the step stores in memory. Bodies smaller than the threshold become Body::Bytes. Bodies larger than the threshold stay as Body::Stream. The default threshold is 128 KB (DEFAULT_STREAM_CACHE_THRESHOLD). Call .stream_cache_default() to use this default.

In YAML, stream_cache: true enables caching with the default threshold. The form stream_cache: { threshold: N } sets a custom threshold in bytes.

Stream Cache is not an EIP. It is a pipeline utility that makes stream bodies safe for multi-read steps. Place a Stream Cache step before a Splitter that reads the body line by line. Place it before a Content Enricher that sends the original body and then inspects the response.

Per ADR-0001, the step compiles into a Service<Exchange> in the Tower pipeline. The stream body type is documented in camel-api/CONTEXT.md.