Heron clusters can be configured at two levels:
Neither system- nor component-level configurations can be overridden by topology developers.
All system-level configs and component-level defaults are declared in a YAML config file in heron/config/src/yaml/conf/{cluster}/heron_internals.yaml
in the Heron codebase. You can leave that file as is when compiling Heron or modify the values to suit your use case.
There are a small handful of system-level configs for Heron. These are detailed in System-level Configuration.
There is a wide variety of component-level configurations that you can establish as defaults in your Heron cluster. These configurations tend to apply to specific components in a topology and are detailed in the docs below:
The Heron configuration applies globally to a cluster. It is discouraged to modify the configuration to suit one topology. It is not possible to override the Heron configuration for a topology via Heron client or other Heron tools.
More on Heron's CLI tool can be found in Managing Heron Topologies.