Interface MetricStore

storage/interface.go:27–68

MetricStore is the interface to the storage layer for metrics. All its methods must be safe to be called concurrently.

// MetricStore is the interface to the storage layer for metrics. All its
// methods must be safe to be called concurrently.
type MetricStore interface {
	// SubmitWriteRequest submits a WriteRequest for processing. There is no
	// guarantee when a request will be processed, but it is guaranteed that
	// the requests are processed in the order of submission.
	SubmitWriteRequest(req WriteRequest)
	// GetMetricFamilies returns all the currently saved MetricFamilies. The
	// returned MetricFamilies are guaranteed to not be modified by the
	// MetricStore anymore. However, they may still be read somewhere else,
	// so the caller is not allowed to modify the returned MetricFamilies.
	// If different groups have saved MetricFamilies of the same name, they
	// are all merged into one MetricFamily by concatenating the contained
	// Metrics. Inconsistent help strings are logged, and one of the
	// versions will "win". Inconsistent types and inconsistent or duplicate
	// label sets will go undetected.
	GetMetricFamilies() []*dto.MetricFamily
	// GetMetricFamiliesMap returns a map grouping-key -> MetricGroup. The
	// MetricFamily pointed to by the Metrics map in each MetricGroup is
	// guaranteed to not be modified by the MetricStore anymore. However,
	// they may still be read somewhere else, so the caller is not allowed
	// to modify it. Otherwise, the returned nested map can be seen as a
	// deep copy of the internal state of the MetricStore and completely
	// owned by the caller.
	GetMetricFamiliesMap() GroupingKeyToMetricGroup
	// Shutdown must only be called after the caller has made sure that
	// SubmitWriteRequests is not called anymore. (If it is called later,
	// the request might get submitted, but not processed anymore.) The
	// Shutdown method waits for the write request queue to empty, then it
	// persists the content of the MetricStore (if supported by the
	// implementation). Also, all internal goroutines are stopped. This
	// method blocks until all of that is complete. If an error is
	// encountered, it is returned (whereupon the MetricStorage is in an
	// undefinded state). If nil is returned, the MetricStore cannot be
	// "restarted" again, but it can still be used for read operations.
	Shutdown() error
	// Healthy returns nil if the MetricStore is currently working as
	// expected. Otherwise, a non-nil error is returned.
	Healthy() error
	// Ready returns nil if the MetricStore is ready to be used (all files
	// are opened and checkpoints have been restored). Otherwise, a non-nil
	// error is returned.
	Ready() error
}

// WriteRequest is a request to change the MetricStore, i.e. to process it, a
// write lock has to be acquired.