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default_selector.go
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/
default_selector.go
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package selector
import (
"context"
"sync/atomic"
)
var (
_ Rebalancer = (*Default)(nil)
_ Builder = (*DefaultBuilder)(nil)
)
// Default is composite selector.
type Default struct {
NodeBuilder WeightedNodeBuilder
Balancer Balancer
nodes atomic.Value
}
// Select is select one node.
func (d *Default) Select(ctx context.Context, opts ...SelectOption) (selected Node, done DoneFunc, err error) {
var (
options SelectOptions
candidates []WeightedNode
)
nodes, ok := d.nodes.Load().([]WeightedNode)
if !ok {
return nil, nil, ErrNoAvailable
}
for _, o := range opts {
o(&options)
}
if len(options.NodeFilters) > 0 {
newNodes := make([]Node, len(nodes))
for i, wc := range nodes {
newNodes[i] = wc
}
for _, filter := range options.NodeFilters {
newNodes = filter(ctx, newNodes)
}
candidates = make([]WeightedNode, len(newNodes))
for i, n := range newNodes {
candidates[i] = n.(WeightedNode)
}
} else {
candidates = nodes
}
if len(candidates) == 0 {
return nil, nil, ErrNoAvailable
}
wn, done, err := d.Balancer.Pick(ctx, candidates)
if err != nil {
return nil, nil, err
}
p, ok := FromPeerContext(ctx)
if ok {
p.Node = wn.Raw()
}
return wn.Raw(), done, nil
}
// Apply update nodes info.
func (d *Default) Apply(nodes []Node) {
weightedNodes := make([]WeightedNode, 0, len(nodes))
for _, n := range nodes {
weightedNodes = append(weightedNodes, d.NodeBuilder.Build(n))
}
// TODO: Do not delete unchanged nodes
d.nodes.Store(weightedNodes)
}
// DefaultBuilder is de
type DefaultBuilder struct {
Node WeightedNodeBuilder
Balancer BalancerBuilder
}
// Build create builder
func (db *DefaultBuilder) Build() Selector {
return &Default{
NodeBuilder: db.Node,
Balancer: db.Balancer.Build(),
}
}