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e28cc79c92
This addresses https://github.com/go-gitea/gitea/issues/18352 It aims to improve performance (and resource use) of the `SyncReleasesWithTags` operation for pull-mirrors. For large repositories with many tags, `SyncReleasesWithTags` can be a costly operation (taking several minutes to complete). The reason is two-fold: 1. on sync, every upstream repo tag is compared (for changes) against existing local entries in the release table to ensure that they are up-to-date. 2. the procedure for getting _each tag_ involves a series of git operations ```bash git show-ref --tags -- v8.2.4477 git cat-file -t 29ab6ce9f36660cffaad3c8789e71162e5db5d2f git cat-file -p 29ab6ce9f36660cffaad3c8789e71162e5db5d2f git rev-list --count 29ab6ce9f36660cffaad3c8789e71162e5db5d2f ``` of which the `git rev-list --count` can be particularly heavy. This PR optimizes performance for pull-mirrors. We utilize the fact that a pull-mirror is always identical to its upstream and rebuild the entire release table on every sync and use a batch `git for-each-ref .. refs/tags` call to retrieve all tags in one go. For large mirror repos, with hundreds of annotated tags, this brings down the duration of the sync operation from several minutes to a few seconds. A few unscientific examples run on my local machine: - https://github.com/spring-projects/spring-boot (223 tags) - before: `0m28,673s` - after: `0m2,244s` - https://github.com/kubernetes/kubernetes (890 tags) - before: `8m00s` - after: `0m8,520s` - https://github.com/vim/vim (13954 tags) - before: `14m20,383s` - after: `0m35,467s` I added a `foreachref` package which contains a flexible way of specifying which reference fields are of interest (`git-for-each-ref(1)`) and to produce a parser for the expected output. These could be reused in other places where `for-each-ref` is used. I'll add unit tests for those if the overall PR looks promising.
85 lines
2.6 KiB
Go
85 lines
2.6 KiB
Go
// Copyright 2022 The Gitea Authors. All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package foreachref
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import (
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"encoding/hex"
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"fmt"
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"io"
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"strings"
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)
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var (
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nullChar = []byte("\x00")
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dualNullChar = []byte("\x00\x00")
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)
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// Format supports specifying and parsing an output format for 'git
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// for-each-ref'. See See git-for-each-ref(1) for available fields.
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type Format struct {
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// fieldNames hold %(fieldname)s to be passed to the '--format' flag of
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// for-each-ref. See git-for-each-ref(1) for available fields.
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fieldNames []string
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// fieldDelim is the character sequence that is used to separate fields
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// for each reference. fieldDelim and refDelim should be selected to not
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// interfere with each other and to not be present in field values.
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fieldDelim []byte
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// fieldDelimStr is a string representation of fieldDelim. Used to save
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// us from repetitive reallocation whenever we need the delimiter as a
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// string.
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fieldDelimStr string
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// refDelim is the character sequence used to separate reference from
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// each other in the output. fieldDelim and refDelim should be selected
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// to not interfere with each other and to not be present in field
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// values.
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refDelim []byte
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}
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// NewFormat creates a forEachRefFormat using the specified fieldNames. See
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// git-for-each-ref(1) for available fields.
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func NewFormat(fieldNames ...string) Format {
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return Format{
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fieldNames: fieldNames,
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fieldDelim: nullChar,
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fieldDelimStr: string(nullChar),
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refDelim: dualNullChar,
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}
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}
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// Flag returns a for-each-ref --format flag value that captures the fieldNames.
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func (f Format) Flag() string {
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var formatFlag strings.Builder
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for i, field := range f.fieldNames {
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// field key and field value
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formatFlag.WriteString(fmt.Sprintf("%s %%(%s)", field, field))
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if i < len(f.fieldNames)-1 {
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// note: escape delimiters to allow control characters as
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// delimiters. For example, '%00' for null character or '%0a'
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// for newline.
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formatFlag.WriteString(f.hexEscaped(f.fieldDelim))
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}
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}
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formatFlag.WriteString(f.hexEscaped(f.refDelim))
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return formatFlag.String()
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}
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// Parser returns a Parser capable of parsing 'git for-each-ref' output produced
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// with this Format.
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func (f Format) Parser(r io.Reader) *Parser {
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return NewParser(r, f)
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}
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// hexEscaped produces hex-escpaed characters from a string. For example, "\n\0"
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// would turn into "%0a%00".
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func (f Format) hexEscaped(delim []byte) string {
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escaped := ""
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for i := 0; i < len(delim); i++ {
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escaped += "%" + hex.EncodeToString([]byte{delim[i]})
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}
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return escaped
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}
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