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id: cluster-config-overview title: Cluster Config Overview sidebar_label: Cluster Config Overview

Heron clusters can be configured at two levels:

1. The system level --- System-level configurations apply to the whole Heron cluster rather than to any specific component (e.g. logging configurations).
2. The component level --- Component-level configurations enable you to establish default configurations for different components. These configurations are fixed at any stage of the topology's lifecycle, once the topology is deployed.

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.

The System Level

There are a small handful of system-level configs for Heron. These are detailed in System-level Configuration.

The Component Level

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:

• Heron Instance
• Heron Metrics Manager
• Heron Stream Manager
• Heron Topology Master

Overriding Heron Cluster Configuration

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.