website/content/docs/operators/configuration/config-intro.md

---
title: Intro to Heron Cluster Configuration
---

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](../../../concepts/topologies#topology-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](http://www.yaml.org/) 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](../../../developers/compiling) 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](../system).

## 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](../instance)
* [Heron Metrics Manager](../metrics-manager)
* [Heron Stream Manager](../stmgr)
* [Heron Topology Master](../tmaster)

### 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](../../heron-cli).