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Allow multiple endpoints in Envoy clusters configured with hostnames #21655

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merged 2 commits into from
Oct 28, 2024
Merged

Allow multiple endpoints in Envoy clusters configured with hostnames #21655

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a80ee72
xds: allow multiple endpoints for strict_dns
t-davies Aug 24, 2024
f270ab5
xds: fixes typo in multi hostname warning
t-davies Aug 24, 2024
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3 changes: 3 additions & 0 deletions .changelog/21655.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
```release-note:improvement
xds: configures Envoy to load balance over all instances of an external service configured with hostnames when "envoy_dns_discovery_type" is set to "STRICT_DNS"
```
15 changes: 10 additions & 5 deletions agent/xds/clusters.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1824,13 +1824,15 @@ func configureClusterWithHostnames(
cluster.DnsRefreshRate = durationpb.New(rate)
cluster.DnsLookupFamily = envoy_cluster_v3.Cluster_V4_ONLY

envoyMaxEndpoints := 1
discoveryType := envoy_cluster_v3.Cluster_Type{Type: envoy_cluster_v3.Cluster_LOGICAL_DNS}
if dnsDiscoveryType == "strict_dns" {
discoveryType.Type = envoy_cluster_v3.Cluster_STRICT_DNS
envoyMaxEndpoints = len(hostnameEndpoints)
}
cluster.ClusterDiscoveryType = &discoveryType

endpoints := make([]*envoy_endpoint_v3.LbEndpoint, 0, 1)
endpoints := make([]*envoy_endpoint_v3.LbEndpoint, 0, envoyMaxEndpoints)
uniqueHostnames := make(map[string]bool)

var (
Expand All @@ -1848,12 +1850,15 @@ func configureClusterWithHostnames(
continue
}

if len(endpoints) == 0 {
if len(endpoints) < envoyMaxEndpoints {
endpoints = append(endpoints, makeLbEndpoint(addr, port, health, weight))

hostname = addr
idx = i
break

if len(endpoints) == envoyMaxEndpoints {
break
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@t-davies t-davies Aug 25, 2024 •
edited
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Pretty sure we do still need to break early here to maintain the same behaviour that we had before with regards to how fallbacks are determined, but happy to be corrected so we can remove this slightly clunky check.

}
}
}

Expand All @@ -1867,8 +1872,8 @@ func configureClusterWithHostnames(

endpoints = append(endpoints, fallback)
}
if len(uniqueHostnames) > 1 {
logger.Warn(fmt.Sprintf("service contains instances with more than one unique hostname; only %q be resolved by Envoy", hostname),
if len(uniqueHostnames) > 1 && envoyMaxEndpoints == 1 {
logger.Warn(fmt.Sprintf("service contains instances with more than one unique hostname; only %q will be resolved by Envoy", hostname),
"dc", dc, "service", service.String())
}

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