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a237444f0d
Originally, the dataobj package was a higher-level API around sections. This design caused it to become a bottleneck: * Implementing any new public behaviour for a section required bubbling it up to the dataobj API for it to be exposed, making it tedious to add new sections or update existing ones. * The `dataobj.Builder` pattern was focused on constructing dataobjs for storing log data, which will cause friction as we build objects around other use cases. This PR builds on top of the foundation laid out by #17704 and #17708, fully inverting the dependency between dataobj and sections: * The `dataobj` package has no knowledge of what sections exist, and can now be used for writing and reading generic sections. Section packages now create higher-level APIs around the abstractions provided by `dataobj`. * Section packages are now public, and callers interact directly with these packages for writing and reading section-specific data. * All logic for a section (encoding, decoding, buffering, reading) is now fully self-contained inside the section package. Previously, the implementation of each section was spread across three packages (`pkg/dataobj/internal/encoding`, `pkg/dataobj/internal/sections/SECTION`, `pkg/dataobj`). * Cutting a section is now a decision made by the caller rather than the section implementation. Previously, the logs section builder would create multiple sections. For the most part, this change is a no-op, with two exceptions: 1. Section cutting is now performed by the caller; however, this shouldn't result in any issues. 2. Removing the high-level `dataobj.Stream` and `dataobj.Record` types will temporarily reduce the allocation gains from #16988. I will address this after this PR is merged.
47 lines
1.4 KiB
Go
47 lines
1.4 KiB
Go
package dataobj
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import (
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"encoding/binary"
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"fmt"
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"io"
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"github.com/grafana/loki/v3/pkg/dataobj/internal/metadata/filemd"
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"github.com/grafana/loki/v3/pkg/dataobj/internal/streamio"
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"github.com/grafana/loki/v3/pkg/dataobj/internal/util/protocodec"
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)
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// decode* methods for metadata shared by Decoder implementations.
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// decodeTailer decodes the tailer of the file to retrieve the metadata size
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// and the magic value.
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func decodeTailer(r streamio.Reader) (metadataSize uint32, err error) {
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if err := binary.Read(r, binary.LittleEndian, &metadataSize); err != nil {
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return 0, fmt.Errorf("read metadata size: %w", err)
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}
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var gotMagic [4]byte
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if _, err := io.ReadFull(r, gotMagic[:]); err != nil {
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return 0, fmt.Errorf("read magic: %w", err)
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} else if string(gotMagic[:]) != string(magic) {
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return 0, fmt.Errorf("unexpected magic: got=%q want=%q", gotMagic, magic)
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}
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return
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}
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// decodeFileMetadata decodes file metadata from r.
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func decodeFileMetadata(r streamio.Reader) (*filemd.Metadata, error) {
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gotVersion, err := streamio.ReadUvarint(r)
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if err != nil {
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return nil, fmt.Errorf("read file format version: %w", err)
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} else if gotVersion != fileFormatVersion {
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return nil, fmt.Errorf("unexpected file format version: got=%d want=%d", gotVersion, fileFormatVersion)
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}
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var md filemd.Metadata
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if err := protocodec.Decode(r, &md); err != nil {
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return nil, fmt.Errorf("file metadata: %w", err)
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}
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return &md, nil
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}
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