Crate taskcluster_download
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Support for downloading data from the object service.
This crate provides a set of functions to download data from the object service. These functions negotiate a download method with the object service, then perform the download, following all of the Taskcluster recommended practices.
Each function takes the necessary metadata for the download, a handle to the a destination for the data, and a taskcluster::Object client. The destination can take a variety of forms, as described below. The client must be configured with the necessary credentials to access the object service.
Convenience Functions
Most uses of this crate can utilize one of the following convenience functions:
- download_to_buf – download data to a fixed-size buffer;
- download_to_vec – download data to a dynamically allocated buffer; or
- download_to_file – download data to a tokio::fs::File.
Artifacts
This crate also supports downloads of artifacts, including all defined storage types.
This combines a query to the queue service to request the artifact metadata with the appropriate process to download that data.
In the case of error artifacts, a Result::Err is returned.
- download_artifact_to_buf – download artifact data to a fixed-size buffer;
- download_artifact_to_vec – download artifact data to a dynamically allocated buffer; or
- download_artifact_to_file – download artifact data to a tokio::fs::File.
Factories
A download may be retried, in which case the download function must have a means to truncate the data destination and begin writing from the beginning.
This is accomplished with the AsyncWriterFactory trait, which defines a get_writer method to generate a fresh tokio::io::AsyncWrite for each attempt.
Users for whom the supplied convenience functions are inadequate can add their own implementation of this trait.
Structs
A CusorWriterFactory creates AsyncWrite objects from a std::io::Cursor, allowing
downloads to in-memory buffers. It is specialized for Vec&mut [u8] (which has a fixed maximum size)
A FileWriterFactory creates AsyncWrite objects by rewinding and cloning a tokio::fs::File. The file must be open in write mode and must be clone-able (that is, File::try_clone() must succeed) in order to support retried uploads.
Traits
An AsyncWriterFactory can produce, on demand, an AsyncWrite object. In the event of a download failure, the restarted download will use a fresh writer to restart writing at the beginning.
Functions
Download an artifact into the given buffer and return the slice of that buffer containing the
artifact. If the artifact is larger than the buffer, then resulting error can be downcast to
std::io::Error with kind WriteZero and the somewhat cryptic message “write zero byte into
writer”. Returns (slice, content_type). If run_id is None then the latest run will be used.
Download an artifact into the given File. The file must be open in write mode and must be
clone-able (that is, File::try_clone() must succeed) in order to support retried downloads.
The File is returned with all write operations complete but with unspecified position. If
run_id is None then the latest run will be used. Returns (file, content_type).
Download an artifact to a Vecrun_id is None then the latest run will be
used. Returns (data, content_type).
Download an artifact using an AsyncWriterFactory. This is useful for advanced cases where one
of the convenience functions is not adequate. Returns the artifact’s content type. If
run_id is None then the latest run will be used. Returns the content type.
Download an object into the given buffer and return the slice of that buffer containing the
object. If the object is larger than the buffer, then resulting error can be downcast to
std::io::Error with kind WriteZero and the somewhat cryptic message “write zero byte into
writer”. Returns (slice, content_type)
Download an object into the given File. The file must be open in write mode and must be clone-able (that is, File::try_clone() must succeed) in order to support retried downloads. The File is returned with all write operations complete but with unspecified position. Returns (file, content_type).
Download an object to a Vec
Download an object using an AsyncWriterFactory. This is useful for advanced cases where one of the convenience functions is not adequate. Returns the object’s content type.