Cassandra gossip protocol
The basic idea is that a node’s state is not only up or down. It is not true or false. Rather, it is an educated guess which takes multiple factors into account.
Cassandra approximates Phi using exponential distribution. Thus, the higher the Phi, the bigger the confidence that Node B has failed.
But if other nodes in the system also see that other node is dead then you can with some confidence conclude that that node is dead.
Stats like load average, free memory, etc. would allow a local node to decide where to send work, for example.
Local nodes make local decisions based on local data. This can scale as far as the gossip protocol can scale.
http://ift.tt/sll1jX
The gossip process runs every second and exchanges state messages with up to three other nodes in the cluster.
The seed node designation has no purpose other than bootstrapping the gossip process for new nodes joining the cluster.
a node remembers other nodes it has gossiped with between subsequent restarts.
http://ift.tt/1cthAHH
http://ift.tt/1H2D9sC
Phi Accrual Failure Detection is a famous algorithm for distributed computing.
Cassandra uses an accrual detection mechanism to calculate a per-node threshold that takes into account network performance, workload, and historical conditions.
http://ift.tt/1cthyiT
http://ift.tt/1H2DafX
The basic idea is that a node’s state is not only up or down. It is not true or false. Rather, it is an educated guess which takes multiple factors into account.
Cassandra approximates Phi using exponential distribution. Thus, the higher the Phi, the bigger the confidence that Node B has failed.
But if other nodes in the system also see that other node is dead then you can with some confidence conclude that that node is dead.
Stats like load average, free memory, etc. would allow a local node to decide where to send work, for example.
Local nodes make local decisions based on local data. This can scale as far as the gossip protocol can scale.
http://ift.tt/sll1jX
The gossip process runs every second and exchanges state messages with up to three other nodes in the cluster.
The seed node designation has no purpose other than bootstrapping the gossip process for new nodes joining the cluster.
a node remembers other nodes it has gossiped with between subsequent restarts.
http://ift.tt/1cthAHH
http://ift.tt/1H2D9sC
Phi Accrual Failure Detection is a famous algorithm for distributed computing.
Cassandra uses an accrual detection mechanism to calculate a per-node threshold that takes into account network performance, workload, and historical conditions.
http://ift.tt/1cthyiT
http://ift.tt/1H2DafX
from Public RSS-Feed of Jeffery yuan. Created with the PIXELMECHANICS 'GPlusRSS-Webtool' at http://gplusrss.com http://ift.tt/1cthAHJ
via LifeLong Community
No comments:
Post a Comment