@@ -18,15 +18,24 @@ import (
1818 "fmt"
1919
2020 networking "istio.io/api/networking/v1alpha3"
21+
22+ "istio.io/istio/pkg/config/visibility"
2123)
2224
2325// This function merges one or more destination rules for a given host string
2426// into a single destination rule. Note that it does not perform inheritance style merging.
2527// IOW, given three dest rules (*.foo.com, *.foo.com, *.com), calling this function for
2628// each config will result in a final dest rule set (*.foo.com, and *.com).
27- func (ps * PushContext ) mergeDestinationRule (p * processedDestRules , destRuleConfig Config ) {
29+ //
30+ // The following is the merge logic:
31+ // 1. Unique subsets (based on subset name) are concatenated to the original rule's list of subsets
32+ // 2. If the original rule did not have any top level traffic policy, traffic policies from the new rule will be
33+ // used.
34+ // 3. If the original rule did not have any exportTo, exportTo settings from the new rule will be used.
35+ func (ps * PushContext ) mergeDestinationRule (p * processedDestRules , destRuleConfig Config , exportToMap map [visibility.Instance ]bool ) {
2836 rule := destRuleConfig .Spec .(* networking.DestinationRule )
2937 resolvedHost := ResolveShortnameToFQDN (rule .Host , destRuleConfig .ConfigMeta )
38+
3039 if mdr , exists := p .destRule [resolvedHost ]; exists {
3140 // Deep copy destination rule, to prevent mutate it later when merge with a new one.
3241 // This can happen when there are more than one destination rule of same host in one namespace.
@@ -39,6 +48,8 @@ func (ps *PushContext) mergeDestinationRule(p *processedDestRules, destRuleConfi
3948 }
4049 // we have an another destination rule for same host.
4150 // concatenate both of them -- essentially add subsets from one to other.
51+ // Note: we only add the subsets and do not overwrite anything else like exportTo or top level
52+ // traffic policies if they already exist
4253 for _ , subset := range rule .Subsets {
4354 if _ , ok := existingSubset [subset .Name ]; ! ok {
4455 // if not duplicated, append
@@ -56,10 +67,18 @@ func (ps *PushContext) mergeDestinationRule(p *processedDestRules, destRuleConfi
5667 if mergedRule .TrafficPolicy == nil && rule .TrafficPolicy != nil {
5768 mergedRule .TrafficPolicy = rule .TrafficPolicy
5869 }
70+
71+ // If there is no exportTo in the existing rule and
72+ // the incoming rule has an explicit exportTo, use the
73+ // one from the incoming rule.
74+ if len (p .exportTo [resolvedHost ]) == 0 && len (exportToMap ) > 0 {
75+ p .exportTo [resolvedHost ] = exportToMap
76+ }
5977 return
6078 }
6179
6280 // DestinationRule does not exist for the resolved host so add it
6381 p .hosts = append (p .hosts , resolvedHost )
6482 p .destRule [resolvedHost ] = & destRuleConfig
83+ p .exportTo [resolvedHost ] = exportToMap
6584}
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