聊聊promtail的positions

最新推荐文章于 2025-04-24 14:33:57 发布

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最新推荐文章于 2025-04-24 14:33:57 发布 · 913 阅读

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#golang

Promtail的Positions接口定义了一系列方法，如GetString、Get、PutString、Put、Remove、SyncPeriod和Stop，用于跟踪文件读取进度。positions结构体实现了该接口，维护了一个映射来存储文件位置信息，并通过异步操作定期保存和清理。readPositionsFile从文件读取位置，writePositionFile则将位置信息写回文件。Positions接口和其实现确保了日志采集过程中的状态持久化和同步。

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本文主要研究一下promtail的positions

Positions

loki/pkg/promtail/positions/positions.go

type Positions interface {
	// GetString returns how far we've through a file as a string.
	// JournalTarget writes a journal cursor to the positions file, while
	// FileTarget writes an integer offset. Use Get to read the integer
	// offset.
	GetString(path string) string
	// Get returns how far we've read through a file. Returns an error
	// if the value stored for the file is not an integer.
	Get(path string) (int64, error)
	// PutString records (asynchronously) how far we've read through a file.
	// Unlike Put, it records a string offset and is only useful for
	// JournalTargets which doesn't have integer offsets.
	PutString(path string, pos string)
	// Put records (asynchronously) how far we've read through a file.
	Put(path string, pos int64)
	// Remove removes the position tracking for a filepath
	Remove(path string)
	// SyncPeriod returns how often the positions file gets resynced
	SyncPeriod() time.Duration
	// Stop the Position tracker.
	Stop()
}