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node_manager.go
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node_manager.go
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package riak
import (
"sync"
)
// NodeManager enforces the structure needed to if going to implement your own NodeManager
type NodeManager interface {
ExecuteOnNode(nodes []*Node, command Command, previousNode *Node) (bool, error)
}
var ErrDefaultNodeManagerRequiresNode = newClientError("Must pass at least one node to default node manager", nil)
type defaultNodeManager struct {
nodeIndex int
sync.RWMutex
}
// ExecuteOnNode selects a Node from the pool and executes the provided Command on that Node. The
// defaultNodeManager uses a simple round robin approach to distributing load
func (nm *defaultNodeManager) ExecuteOnNode(nodes []*Node, command Command, previous *Node) (bool, error) {
if nodes == nil {
panic("[defaultNodeManager] nil nodes argument")
}
if len(nodes) == 0 || nodes[0] == nil {
return false, ErrDefaultNodeManagerRequiresNode
}
var err error
executed := false
nm.RLock()
startingIndex := nm.nodeIndex
nm.RUnlock()
for {
nm.Lock()
if nm.nodeIndex >= len(nodes) {
nm.nodeIndex = 0
}
node := nodes[nm.nodeIndex]
nm.nodeIndex++
nm.Unlock()
// don't try the same node twice in a row if we have multiple nodes
if len(nodes) > 1 && previous != nil && previous == node {
continue
}
executed, err = node.execute(command)
if executed == true {
logDebug("[DefaultNodeManager]", "executed '%s' on node '%s', err '%v'", command.Name(), node, err)
break
}
nm.RLock()
if startingIndex == nm.nodeIndex {
nm.RUnlock()
// logDebug("[DefaultNodeManager]", "startingIndex %d nm.nodeIndex %d", startingIndex, nm.nodeIndex)
break
}
nm.RUnlock()
}
return executed, err
}