43 lines
1.5 KiB
Markdown
43 lines
1.5 KiB
Markdown
# Stream Processors
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## Processor API
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Processors are a binary API that works off of content streams.
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The incoming content stream will be provided to the binary via `STDIN`
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and the stream processor is expected to output the processed stream on
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`STDOUT`. If errors are encountered, errors MUST be returned via `STDERR`
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with a non-zero exit status.
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Additional information can be provided to stream processors via a payload.
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Payloads are marshaled as `protobuf.Any` types and can wrap any type of
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serialized data structure.
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On Unix systems, the payload, if available, is provided on `fd 3` for the process.
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On Windows systems, the payload, if available, is provided via a named pipe with the
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pipe's path set as the value of the environment variable `STREAM_PROCESSOR_PIPE`.
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## Configuration
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To configure stream processors for containerd, entries in the config file need to be made.
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The `stream_processors` field is a map so that users can chain together multiple processors
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to mutate content streams.
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Processor Fields:
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* Key - ID of the processor, used for passing a specific payload to the processor.
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* `accepts` - Accepted media-types for the processor that it can handle.
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* `returns` - The media-type that the processor returns.
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* `path` - Path to the processor binary.
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* `args` - Arguments passed to the processor binary.
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```toml
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[stream_processors]
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[stream_processors."io.containerd.processor.v1.pigz"]
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accepts = ["application/vnd.docker.image.rootfs.diff.tar.gzip"]
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returns = "application/vnd.oci.image.layer.v1.tar"
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path = "unpigz"
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args = ["-d", "-c"]
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```
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