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feat: add "nearest.<service>.internal" mode to internal DNS (#159)

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* feat: Adding a "nearest.service.local" mode to internal DNS

* Pass listenAddr to internal DNS server (rather than calling into network.MachineIP)

Also adds an exact round-robin via "rr.{service}" mode. Not sure we want that over random or not, though.

* Remove the resolved count and rotating round-robin. "rr.name" mode is now the same as default with random shuffle.

* Add test on nearest internal DNS lookup

* Add docs on internal DNS order modes
This commit is contained in:
Justin Bradford
2025-10-29 14:25:59 +10:00
committed by GitHub
parent 6af7a9861d
commit ba6290d616
4 changed files with 147 additions and 4 deletions
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test/e2e/dns_test.go
+35
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@@ -3,6 +3,7 @@ package e2e
import (
"context"
"fmt"
"regexp"
"strings"
"testing"
"time"
@@ -224,4 +225,38 @@ func TestInternalDNS(t *testing.T) {
assertNoDNSErrors(t, dnsOutput)
})
t.Run("nearest mode prioritizes local subnet IPs", func(t *testing.T) {
// Test the "nearest" mode which should sort local subnet IPs first
dnsOutput := runDNSQuery(t, "dns-test-nearest", "nearest."+serviceName+".internal", "/tmp/dns_result_nearest.txt")
t.Logf("Nearest mode DNS query output:\n%s", dnsOutput)
// Find which machine ran the query
querySvc, err := cli.InspectService(ctx, "dns-test-nearest")
require.NoError(t, err)
require.NotEmpty(t, querySvc.Containers, "Query service should have a container")
queryMachineID := querySvc.Containers[0].MachineID
// Find the local container IP (on the same machine as the query)
var localIP string
for _, ctr := range svc.Containers {
if ctr.MachineID == queryMachineID {
localIP = ctr.Container.UncloudNetworkIP().String()
break
}
}
require.NotEmpty(t, localIP, "Should find local container IP on query machine %s", queryMachineID)
// Extract the first IP address from the DNS output using regex
// Pattern matches: "Name: nearest.test-dns-service.internal" followed by "Address: X.X.X.X"
re := regexp.MustCompile(`(?m)Name:\s+[\w\.\-]+\s+Address:\s+([\d\.]+)`)
matches := re.FindStringSubmatch(dnsOutput)
require.Len(t, matches, 2, "Should find Name's Address in DNS output")
firstIP := matches[1]
assert.Equal(t, localIP, firstIP,
"Nearest mode should return local subnet IP first (query machine: %s, local IP: %s, first DNS result: %s)",
queryMachineID, localIP, firstIP)
assertNoDNSErrors(t, dnsOutput)
})
}