minio/cmd/lock-instrument.go

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/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* 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 cmd
import (
"fmt"
"time"
)
const (
debugRLockStr = "RLock"
debugWLockStr = "WLock"
)
// struct containing information of status (ready/running/blocked) of an operation with given operation ID.
type debugLockInfo struct {
lockType string // "Rlock" or "WLock".
lockOrigin string // contains the trace of the function which invoked the lock, obtained from runtime.
status string // status can be running/ready/blocked.
since time.Time // time info of the since how long the status holds true.
}
// debugLockInfo - container for storing locking information for unique copy (volume,path) pair.
// ref variable holds the reference count for locks held for.
// `ref` values helps us understand the n locks held for given <volume, path> pair.
// `running` value helps us understand the total successful locks held (not blocked) for given <volume, path> pair and the operation is under execution.
// `blocked` value helps us understand the total number of operations blocked waiting on locks for given <volume,path> pair.
type debugLockInfoPerVolumePath struct {
ref int64 // running + blocked operations.
running int64 // count of successful lock acquire and running operations.
blocked int64 // count of number of operations blocked waiting on lock.
lockInfo (map[string]debugLockInfo) // map of [operationID] debugLockInfo{operation, status, since} .
}
// returns an instance of debugLockInfo.
// need to create this for every unique pair of {volume,path}.
// total locks, number of calls blocked on locks, and number of successful locks held but not unlocked yet.
func newDebugLockInfoPerVolumePath() *debugLockInfoPerVolumePath {
return &debugLockInfoPerVolumePath{
lockInfo: make(map[string]debugLockInfo),
ref: 0,
blocked: 0,
running: 0,
}
}
// LockInfoNil - Returned if the lock info map is not initialized.
type LockInfoNil struct {
}
func (l LockInfoNil) Error() string {
return fmt.Sprintf("Debug Lock Map not initialized:\n1. Enable Lock Debugging using right ENV settings \n2. Make sure initNSLock() is called.")
}
// LockInfoOriginNotFound - While changing the state of the lock info its important that the entry for
// lock at a given origin exists, if not `LockInfoOriginNotFound` is returned.
type LockInfoOriginNotFound struct {
volume string
path string
operationID string
lockOrigin string
}
func (l LockInfoOriginNotFound) Error() string {
return fmt.Sprintf("No lock state stored for the lock origined at \"%s\", for <volume> %s, <path> %s, <operationID> %s.",
l.lockOrigin, l.volume, l.path, l.operationID)
}
// LockInfoVolPathMssing - Error interface. Returned when the info the
type LockInfoVolPathMssing struct {
volume string
path string
}
func (l LockInfoVolPathMssing) Error() string {
return fmt.Sprintf("No entry in debug Lock Map for Volume: %s, path: %s.", l.volume, l.path)
}
// LockInfoOpsIDNotFound - Returned when the lock state info exists, but the entry for
// given operation ID doesn't exist.
type LockInfoOpsIDNotFound struct {
volume string
path string
operationID string
}
func (l LockInfoOpsIDNotFound) Error() string {
return fmt.Sprintf("No entry in lock info for <Operation ID> %s, <volume> %s, <path> %s.", l.operationID, l.volume, l.path)
}
// LockInfoStateNotBlocked - When an attempt to change the state of the lock form `blocked` to `running` is done,
// its necessary that the state before the transsition is "blocked", otherwise LockInfoStateNotBlocked returned.
type LockInfoStateNotBlocked struct {
volume string
path string
operationID string
}
func (l LockInfoStateNotBlocked) Error() string {
return fmt.Sprintf("Lock state should be \"Blocked\" for <volume> %s, <path> %s, <operationID> %s.", l.volume, l.path, l.operationID)
}
// change the state of the lock from Blocked to Running.
func (n *nsLockMap) statusBlockedToRunning(param nsParam, lockOrigin, operationID string, readLock bool) error {
// This operation is not executed under the scope nsLockMap.mutex.Lock(), lock has to be explicitly held here.
n.lockMapMutex.Lock()
defer n.lockMapMutex.Unlock()
if n.debugLockMap == nil {
return LockInfoNil{}
}
// new state info to be set for the lock.
newLockInfo := debugLockInfo{
lockOrigin: lockOrigin,
status: "Running",
since: time.Now().UTC(),
}
// set lock type.
if readLock {
newLockInfo.lockType = debugRLockStr
} else {
newLockInfo.lockType = debugWLockStr
}
// check whether the lock info entry for <volume, path> pair already exists and its not `nil`.
if debugLockMap, ok := n.debugLockMap[param]; ok {
// ``*debugLockInfoPerVolumePath` entry containing lock info for `param <volume, path>` is `nil`.
if debugLockMap == nil {
return LockInfoNil{}
}
} else {
// The lock state info foe given <volume, path> pair should already exist.
// If not return `LockInfoVolPathMssing`.
return LockInfoVolPathMssing{param.volume, param.path}
}
// Lock info the for the given operation ID shouldn't be `nil`.
if n.debugLockMap[param].lockInfo == nil {
return LockInfoOpsIDNotFound{param.volume, param.path, operationID}
}
if lockInfo, ok := n.debugLockMap[param].lockInfo[operationID]; ok {
// The entry for the lock origined at `lockOrigin` should already exist.
// If not return `LockInfoOriginNotFound`.
if lockInfo.lockOrigin != lockOrigin {
return LockInfoOriginNotFound{param.volume, param.path, operationID, lockOrigin}
}
// Status of the lock should already be set to "Blocked".
// If not return `LockInfoStateNotBlocked`.
if lockInfo.status != "Blocked" {
return LockInfoStateNotBlocked{param.volume, param.path, operationID}
}
} else {
// The lock info entry for given `opsID` should already exist for given <volume, path> pair.
// If not return `LockInfoOpsIDNotFound`.
return LockInfoOpsIDNotFound{param.volume, param.path, operationID}
}
// All checks finished.
// changing the status of the operation from blocked to running and updating the time.
n.debugLockMap[param].lockInfo[operationID] = newLockInfo
// After locking unblocks decrease the blocked counter.
n.blockedCounter--
// Increase the running counter.
n.runningLockCounter++
n.debugLockMap[param].blocked--
n.debugLockMap[param].running++
return nil
}
// change the state of the lock from Ready to Blocked.
func (n *nsLockMap) statusNoneToBlocked(param nsParam, lockOrigin, operationID string, readLock bool) error {
if n.debugLockMap == nil {
return LockInfoNil{}
}
newLockInfo := debugLockInfo{
lockOrigin: lockOrigin,
status: "Blocked",
since: time.Now().UTC(),
}
if readLock {
newLockInfo.lockType = debugRLockStr
} else {
newLockInfo.lockType = debugWLockStr
}
if lockInfo, ok := n.debugLockMap[param]; ok {
if lockInfo == nil {
// *debugLockInfoPerVolumePath entry is nil, initialize here to avoid any case of `nil` pointer access.
n.initLockInfoForVolumePath(param)
}
} else {
// State info entry for the given <volume, pair> doesn't exist, initializing it.
n.initLockInfoForVolumePath(param)
}
// lockInfo is a map[string]debugLockInfo, which holds map[OperationID]{status,time, origin} of the lock.
if n.debugLockMap[param].lockInfo == nil {
n.debugLockMap[param].lockInfo = make(map[string]debugLockInfo)
}
// The status of the operation with the given operation ID is marked blocked till its gets unblocked from the lock.
n.debugLockMap[param].lockInfo[operationID] = newLockInfo
// Increment the Global lock counter.
n.globalLockCounter++
// Increment the counter for number of blocked opertions, decrement it after the locking unblocks.
n.blockedCounter++
// increment the reference of the lock for the given <volume,path> pair.
n.debugLockMap[param].ref++
// increment the blocked counter for the given <volume, path> pair.
n.debugLockMap[param].blocked++
return nil
}
// deleteLockInfoEntry - Deletes the lock state information for given <volume, path> pair. Called when nsLk.ref count is 0.
func (n *nsLockMap) deleteLockInfoEntryForVolumePath(param nsParam) error {
if n.debugLockMap == nil {
return LockInfoNil{}
}
// delete the lock info for the given operation.
if _, found := n.debugLockMap[param]; found {
// Remove from the map if there are no more references for the given (volume,path) pair.
delete(n.debugLockMap, param)
} else {
return LockInfoVolPathMssing{param.volume, param.path}
}
return nil
}
// deleteLockInfoEntry - Deletes the entry for given opsID in the lock state information of given <volume, path> pair.
// called when the nsLk ref count for the given <volume, path> pair is not 0.
func (n *nsLockMap) deleteLockInfoEntryForOps(param nsParam, operationID string) error {
if n.debugLockMap == nil {
return LockInfoNil{}
}
// delete the lock info for the given operation.
if infoMap, found := n.debugLockMap[param]; found {
// the opertion finished holding the lock on the resource, remove the entry for the given operation with the operation ID.
if _, foundInfo := infoMap.lockInfo[operationID]; foundInfo {
// decrease the global running and lock reference counter.
n.runningLockCounter--
n.globalLockCounter--
// decrease the lock referee counter for the lock info for given <volume,path> pair.
// decrease the running operation number. Its assumed that the operation is over once an attempt to release the lock is made.
infoMap.running--
// decrease the total reference count of locks jeld on <volume,path> pair.
infoMap.ref--
delete(infoMap.lockInfo, operationID)
} else {
// Unlock request with invalid opertion ID not accepted.
return LockInfoOpsIDNotFound{param.volume, param.path, operationID}
}
} else {
return LockInfoVolPathMssing{param.volume, param.path}
}
return nil
}
// return randomly generated string ID if lock debug is enabled,
// else returns empty string
func getOpsID() (opsID string) {
// check if lock debug is enabled.
if globalDebugLock {
// generated random ID.
opsID = string(generateRequestID())
}
return opsID
}