When we introduced Flux and Mono, we showed an example of a "marble diagram". These are found throughout the javadoc in order to explain the behavior of an operator in a more visual way.

In this section we’ll dig a little deeper into the conventions used by the Reactor documentation for these marble diagrams. First, let’s see how the most common patterns of operators are represented.

Some operators are instance methods: their output is produced by calling a method on a source Flux instance (like Flux<T> output = source.fluxOperator()):

Other operators are static methods. They can still take a source as an input parameter, like in Flux<T> output = Flux.merge(sourceFlux1, sourcePublisher2). These are represented like below:

Note that sometimes we represent multiple variants or behaviors depending on the operator’s input, in which case there’s a single operator "box", but the source and output variants are separated like below:

These are the basic cases, yet some operators display slightly more advanced patterns.

For instance, ParallelFlux creates multiple rails so they have multiple output Flux. These are represented one below the other, like in the following diagram:

Windowing operators produce a Flux<Flux<T>>: the main Flux notifies of each window opening, while inner Flux represent the windows content and termination. Windows are represented as branching out of the main Flux, like in the following diagram:

Sometimes, operators take a "companion publisher" as input (a Flux, Mono or arbitrary Reactive Stream Publisher). Such companion publishers help to customize the operator’s behavior, which will use some of the companion’s signals as trigger for its own internal behavior. They are represented like in the following diagram:

Now that we’ve seen the most common operator patterns, let’s show the graphical representation of all the different signals, events and elements that can occur in a Flux or Mono:

Finally, in the same vein we have the graphical representation of side effects, which occur alongside the Reactive Stream signals: