# Pipeline components

> Short overview of ZAPP pipeline components and target wiring.

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LLMS index: [llms.txt](/datacenter/zapp/llms.txt)

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A ZAPP pipeline is a YAML map of named components. Each component declares a `type`, component-specific fields, and optional `targets`. Targets connect one component output to another component input.

Components usually fit one of three roles:

- Source components receive or collect telemetry
- Processing components convert or route telemetry
- Terminal components forward telemetry to a service, network endpoint, or consumer API

## Channels

Pipeline components pass data through typed channels. Source and processing components expose outputs with `targets`, and downstream components receive those outputs as inputs. During startup, ZAPP creates the channels, connects each `target` to the named component, and validates that the receiving component accepts that input type.

Each target can tune how the channel behaves during back pressure:

| Setting or Pattern | Behavior |
| --- | --- |
| Blocking channel | The default behavior when `leaky` is omitted or set to `false`. The `cap` field sets the channel buffer capacity. If the buffer is full, the upstream component waits until the downstream component reads data. |
| Leaky channel | Enabled with `leaky: true`. The `cap` field sets the channel buffer capacity. If the buffer is full, the item being sent is dropped instead of blocking upstream collection. Set `dropCounter` to record those drops as a Prometheus counter. |
| Fan-out | Sends one component output to multiple target channels. Each target keeps its own `cap`, `leaky`, and `dropCounter` settings. |
| Fan-in | Combines multiple input channels of the same data type for a component that accepts more than one upstream source. |

Use blocking channels when every telemetry item must be preserved and back pressure is acceptable. Use leaky channels for high-rate telemetry paths where keeping collection moving is more important than retaining every sample during a downstream slowdown.

For the telemetry data model shared by these components, see [Time-series telemetry](/docs/concepts/time-series/).

- [gRPC pipeline component](/docs/components/pipeline/grpc/)
- [Redfish listener pipeline](/docs/components/pipeline/redfish-listener/)
- [UDP listener and writer](/docs/components/pipeline/udp/)

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Section pages:

- [gRPC pipeline component](/datacenter/zapp/docs/components/pipeline/grpc/): Configuration reference for the ZAPP grpcServer pipeline component.
- [Redfish listener pipeline](/datacenter/zapp/docs/components/pipeline/redfish-listener/): Configuration overview for Redfish listener pipelines and the redfishCollector component.
- [UDP listener and writer](/datacenter/zapp/docs/components/pipeline/udp/): Configuration reference for the ZAPP UDP listener and writer pipeline components.