---
id: "apache-helix"
type: "component"
kind: "coordination-service"
provider: "default"
category: "ops"
docs: "https://helix.apache.org/"
url: "https://localhost:3000/catalogue/components/apache-helix"
---

# Apache Helix

Cluster partition placement and state-machine management.

| | |
|---|---|
| Provider | [default](https://localhost:3000/catalogue?provider=default) |
| Kind | [Coordination service](https://localhost:3000/catalogue/kinds/coordination-service) |
| Category | Operations |
| Official docs | [https://helix.apache.org/](https://helix.apache.org/) |

## Properties

| property | type | values | required | kind default | this component |
|---|---|---|---|---|---|
| `consensus` | enum | `none`, `raft`, `paxos`, `zab` | no | "none" | **"none"** |
| `managed` | boolean | — | no | false | **false** |
| `nodes` | integer | — | no | — | inherited |
| `replicated` | boolean | — | no | false | inherited |
| `role` | enum | `metadata`, `lock`, `discovery`, `placement`, `sharding`, `leader-election`, `config` | yes | — | **"placement"** |
| `stateModel` | enum | `master-slave`, `online-offline`, `leader-standby`, `custom` | no | "online-offline" | inherited |

Bold values are the ones this component pins.

## Rules that apply · 2

### Shared dependency without redundancy `shared-dependency-without-redundancy` (error)

- Page: https://localhost:3000/catalogue/rules/shared-dependency-without-redundancy.md
- Why: The design requires redundant discovery, but this DNS or coordination service, which everything depends on, runs on a single provider or a single replica. Its failure is the whole system's failure.
- Applies to: every node of kind dns or coordination-service
- Message: Shared dependency '{{node.id}}' is not redundant, but the design requires redundant discovery.

It fires when:

- all of these hold:
  - the design requirement `availability.discoveryRedundant` is true
  - any of these hold:
    - the node's `redundantProviders` is false
    - the node's `replicated` is false

### Stateful engine pinned to a single zone `stateful-engine-pinned-to-single-zone` (error)

- Page: https://localhost:3000/catalogue/rules/stateful-engine-pinned-to-single-zone.md
- Why: A matching engine, coordination service or event store living in exactly one availability zone, with no failover and no replication, is lost with that zone. Everything that depends on it stops with it.
- Applies to: every node of kind matching-engine, coordination-service or event-store
- Message: '{{node.id}}' is pinned to a single availability zone with no failover or replication.

It fires when:

- all of these hold:
  - the node sits inside exactly 1 availability-zone group
  - any of these hold:
    - the node's `failover` is "none"
    - the node's `replicated` is false
    - the node's `replication` is "none"

## Other products of the same kind · 17

- [Microservices Engine](https://localhost:3000/catalogue/components/alibaba-mse.md) `alibaba-mse` — alibabacloud
- [AWS Cloud Map](https://localhost:3000/catalogue/components/aws-cloud-map.md) `aws-cloud-map` — aws
- [Azure Arc](https://localhost:3000/catalogue/components/azure-arc.md) `azure-arc` — azure
- [Azure Device Registry](https://localhost:3000/catalogue/components/azure-device-registry.md) `azure-device-registry` — azure
- [Durable Objects](https://localhost:3000/catalogue/components/cloudflare-durable-objects.md) `cloudflare-durable-objects` — cloudflare
- [Consul](https://localhost:3000/catalogue/components/consul.md) `consul` — default
- [Generic coordination service](https://localhost:3000/catalogue/components/coordination-service.md) `coordination-service` — default
- [etcd](https://localhost:3000/catalogue/components/etcd.md) `etcd` — default
- [Eureka](https://localhost:3000/catalogue/components/eureka.md) `eureka` — default
- [Nacos](https://localhost:3000/catalogue/components/nacos.md) `nacos` — default
- [Oxia](https://localhost:3000/catalogue/components/oxia.md) `oxia` — default
- [Apache ZooKeeper](https://localhost:3000/catalogue/components/zookeeper.md) `zookeeper` — default
- [Service Directory](https://localhost:3000/catalogue/components/google-service-directory.md) `google-service-directory` — gcp
- [Endpoints](https://localhost:3000/catalogue/components/k8s-endpoints.md) `k8s-endpoints` — k8s
- [OpenStack Blazar](https://localhost:3000/catalogue/components/openstack-blazar.md) `openstack-blazar` — openstack
- [OpenStack Cyborg](https://localhost:3000/catalogue/components/openstack-cyborg.md) `openstack-cyborg` — openstack
- [OpenStack Placement](https://localhost:3000/catalogue/components/openstack-placement.md) `openstack-placement` — openstack

## Use it in a design

```yaml
nodes:
  - { id: "apache-helix", component: "apache-helix" }
```

## Source (`component` YAML, verbatim)

```yaml
# yaml-language-server: $schema=../../schema/component.schema.json
# Apache Helix: partition placement and state management on top of ZooKeeper.
schemaVersion: "1"
type: "component"
id: "apache-helix"
kind: "coordination-service"
provider: "default"
docs: "https://helix.apache.org/"
defaults:
  role: "placement"
  consensus: "none"
  managed: false
properties:
  stateModel:
    type: "enum"
    values: ["master-slave", "online-offline", "leader-standby", "custom"]
    default: "online-offline"
```

Human page: https://localhost:3000/catalogue/components/apache-helix