Prometheus endpoint (#5256)

* Add prometheus collector and route

* dep ensure -add github.com/prometheus/client_golang/prometheus

* dep ensure -update github.com/golang/protobuf

* add metrics to reserved usernames

* add comment head in metrics package

* fix style imports

* add metrics settings

* add bearer token check

* mapping metrics configs

* fix lint

* update config cheat sheet

* update conf sample, typo fix

vendor/github.com/prometheus/procfs/xfs/xfs.go

@@ -0,0 +1,163 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package xfs provides access to statistics exposed by the XFS filesystem.
+package xfs
+
+// Stats contains XFS filesystem runtime statistics, parsed from
+// /proc/fs/xfs/stat.
+//
+// The names and meanings of each statistic were taken from
+// http://xfs.org/index.php/Runtime_Stats and xfs_stats.h in the Linux
+// kernel source. Most counters are uint32s (same data types used in
+// xfs_stats.h), but some of the "extended precision stats" are uint64s.
+type Stats struct {
+	// The name of the filesystem used to source these statistics.
+	// If empty, this indicates aggregated statistics for all XFS
+	// filesystems on the host.
+	Name string
+
+	ExtentAllocation   ExtentAllocationStats
+	AllocationBTree    BTreeStats
+	BlockMapping       BlockMappingStats
+	BlockMapBTree      BTreeStats
+	DirectoryOperation DirectoryOperationStats
+	Transaction        TransactionStats
+	InodeOperation     InodeOperationStats
+	LogOperation       LogOperationStats
+	ReadWrite          ReadWriteStats
+	AttributeOperation AttributeOperationStats
+	InodeClustering    InodeClusteringStats
+	Vnode              VnodeStats
+	Buffer             BufferStats
+	ExtendedPrecision  ExtendedPrecisionStats
+}
+
+// ExtentAllocationStats contains statistics regarding XFS extent allocations.
+type ExtentAllocationStats struct {
+	ExtentsAllocated uint32
+	BlocksAllocated  uint32
+	ExtentsFreed     uint32
+	BlocksFreed      uint32
+}
+
+// BTreeStats contains statistics regarding an XFS internal B-tree.
+type BTreeStats struct {
+	Lookups         uint32
+	Compares        uint32
+	RecordsInserted uint32
+	RecordsDeleted  uint32
+}
+
+// BlockMappingStats contains statistics regarding XFS block maps.
+type BlockMappingStats struct {
+	Reads                uint32
+	Writes               uint32
+	Unmaps               uint32
+	ExtentListInsertions uint32
+	ExtentListDeletions  uint32
+	ExtentListLookups    uint32
+	ExtentListCompares   uint32
+}
+
+// DirectoryOperationStats contains statistics regarding XFS directory entries.
+type DirectoryOperationStats struct {
+	Lookups  uint32
+	Creates  uint32
+	Removes  uint32
+	Getdents uint32
+}
+
+// TransactionStats contains statistics regarding XFS metadata transactions.
+type TransactionStats struct {
+	Sync  uint32
+	Async uint32
+	Empty uint32
+}
+
+// InodeOperationStats contains statistics regarding XFS inode operations.
+type InodeOperationStats struct {
+	Attempts        uint32
+	Found           uint32
+	Recycle         uint32
+	Missed          uint32
+	Duplicate       uint32
+	Reclaims        uint32
+	AttributeChange uint32
+}
+
+// LogOperationStats contains statistics regarding the XFS log buffer.
+type LogOperationStats struct {
+	Writes            uint32
+	Blocks            uint32
+	NoInternalBuffers uint32
+	Force             uint32
+	ForceSleep        uint32
+}
+
+// ReadWriteStats contains statistics regarding the number of read and write
+// system calls for XFS filesystems.
+type ReadWriteStats struct {
+	Read  uint32
+	Write uint32
+}
+
+// AttributeOperationStats contains statistics regarding manipulation of
+// XFS extended file attributes.
+type AttributeOperationStats struct {
+	Get    uint32
+	Set    uint32
+	Remove uint32
+	List   uint32
+}
+
+// InodeClusteringStats contains statistics regarding XFS inode clustering
+// operations.
+type InodeClusteringStats struct {
+	Iflush     uint32
+	Flush      uint32
+	FlushInode uint32
+}
+
+// VnodeStats contains statistics regarding XFS vnode operations.
+type VnodeStats struct {
+	Active   uint32
+	Allocate uint32
+	Get      uint32
+	Hold     uint32
+	Release  uint32
+	Reclaim  uint32
+	Remove   uint32
+	Free     uint32
+}
+
+// BufferStats contains statistics regarding XFS read/write I/O buffers.
+type BufferStats struct {
+	Get             uint32
+	Create          uint32
+	GetLocked       uint32
+	GetLockedWaited uint32
+	BusyLocked      uint32
+	MissLocked      uint32
+	PageRetries     uint32
+	PageFound       uint32
+	GetRead         uint32
+}
+
+// ExtendedPrecisionStats contains high precision counters used to track the
+// total number of bytes read, written, or flushed, during XFS operations.
+type ExtendedPrecisionStats struct {
+	FlushBytes uint64
+	WriteBytes uint64
+	ReadBytes  uint64
+}