Update vendorized version of dsync that relaxes read quorum to N/2 (#2874)

This commit is contained in:
Frank 2016-10-07 17:02:59 +02:00 committed by Harshavardhana
parent 97f4989945
commit e53a9f6cab
3 changed files with 19 additions and 10 deletions

View File

@ -211,7 +211,8 @@ func lock(clnts []RPC, locks *[]string, lockName string, isReadLock bool) bool {
(*locks)[grant.index] = grant.lockUid
} else {
locksFailed++
if locksFailed > dnodeCount-dquorum {
if !isReadLock && locksFailed > dnodeCount-dquorum ||
isReadLock && locksFailed > dnodeCount-dquorumReads {
// We know that we are not going to get the lock anymore, so exit out
// and release any locks that did get acquired
done = true
@ -223,7 +224,7 @@ func lock(clnts []RPC, locks *[]string, lockName string, isReadLock bool) bool {
done = true
// timeout happened, maybe one of the nodes is slow, count
// number of locks to check whether we have quorum or not
if !quorumMet(locks) {
if !quorumMet(locks, isReadLock) {
releaseAll(clnts, locks, lockName, isReadLock)
}
}
@ -234,7 +235,7 @@ func lock(clnts []RPC, locks *[]string, lockName string, isReadLock bool) bool {
}
// Count locks in order to determine whterh we have quorum or not
quorum = quorumMet(locks)
quorum = quorumMet(locks, isReadLock)
// Signal that we have the quorum
wg.Done()
@ -263,8 +264,8 @@ func lock(clnts []RPC, locks *[]string, lockName string, isReadLock bool) bool {
return quorum
}
// quorumMet determines whether we have acquired n/2+1 underlying locks or not
func quorumMet(locks *[]string) bool {
// quorumMet determines whether we have acquired the required quorum of underlying locks or not
func quorumMet(locks *[]string, isReadLock bool) bool {
count := 0
for _, uid := range *locks {
@ -273,7 +274,11 @@ func quorumMet(locks *[]string) bool {
}
}
return count >= dquorum
if isReadLock {
return count >= dquorumReads
} else {
return count >= dquorum
}
}
// releaseAll releases all locks that are marked as locked

View File

@ -34,6 +34,8 @@ var ownNode int
// Simple majority based quorum, set to dNodeCount/2+1
var dquorum int
// Simple quorum for read operations, set to dNodeCount/2
var dquorumReads int
// SetNodesWithPath - initializes package-level global state variables such as clnts.
// N B - This function should be called only once inside any program that uses
@ -47,15 +49,17 @@ func SetNodesWithClients(rpcClnts []RPC, rpcOwnNode int) (err error) {
return errors.New("Dsync not designed for less than 4 nodes")
} else if len(rpcClnts) > 16 {
return errors.New("Dsync not designed for more than 16 nodes")
} else if len(rpcClnts)&1 == 1 {
return errors.New("Dsync not designed for an uneven number of nodes")
}
if rpcOwnNode > len(rpcClnts) {
return errors.New("Index for own node is too large")
}
dnodeCount = len(rpcClnts)
dquorum = dnodeCount/2 + 1
dquorumReads = dnodeCount/2
// Initialize node name and rpc path for each RPCClient object.
clnts = make([]RPC, dnodeCount)
copy(clnts, rpcClnts)

6
vendor/vendor.json vendored
View File

@ -111,10 +111,10 @@
"revisionTime": "2015-11-18T20:00:48-08:00"
},
{
"checksumSHA1": "0wc4gxRamjyjVSiZF73KIaCRC6k=",
"checksumSHA1": "5DKBTLXf5GY5RkVC9DGP2XFMabc=",
"path": "github.com/minio/dsync",
"revision": "531818cd6458e24e30eec2c67136a8bcb24520af",
"revisionTime": "2016-09-15T18:37:01Z"
"revision": "66c2a42bf14fcaad0322e9f06d9ab85dd6dba9b7",
"revisionTime": "2016-10-07T07:30:36Z"
},
{
"path": "github.com/minio/go-homedir",