fix: same server to be part of multiple pools (#19216)

our PoolNumber calculation was costly,
while we already had this information per
endpoint, we needed to deduce it appropriately.

This PR addresses this by assigning PoolNumbers
field that carries all the pool numbers that
belong to a server.

properties.PoolNumber still carries a valid value
only when len(properties.PoolNumbers) == 1, otherwise
properties.PoolNumber is set to math.MaxInt (indicating
that this value is undefined) and then one must rely
on properties.PoolNumbers for server participation
in multiple pools.

addresses the issue originating from #11327

cmd/admin-server-info.go

@@ -19,10 +19,12 @@ package cmd
 
 import (
 	"context"
+	"math"
 	"net/http"
 	"os"
 	"runtime"
 	"runtime/debug"
+	"sort"
 	"strings"
 	"time"
 
@@ -42,9 +44,13 @@ func getLocalServerProperty(endpointServerPools EndpointServerPools, r *http.Req
 	if globalIsDistErasure {
 		addr = globalLocalNodeName
 	}
+	poolNumbers := make(map[int]struct{})
 	network := make(map[string]string)
 	for _, ep := range endpointServerPools {
 		for _, endpoint := range ep.Endpoints {
+			if endpoint.IsLocal {
+				poolNumbers[endpoint.PoolIdx+1] = struct{}{}
+			}
 			nodeName := endpoint.Host
 			if nodeName == "" {
 				nodeName = addr
@@ -112,6 +118,17 @@ func getLocalServerProperty(endpointServerPools EndpointServerPools, r *http.Req
 		MinioEnvVars: make(map[string]string, 10),
 	}
 
+	for poolNumber := range poolNumbers {
+		props.PoolNumbers = append(props.PoolNumbers, poolNumber)
+	}
+	sort.Ints(props.PoolNumbers)
+	props.PoolNumber = func() int {
+		if len(props.PoolNumbers) == 1 {
+			return props.PoolNumbers[0]
+		}
+		return math.MaxInt // this indicates that its unset.
+	}()
+
 	sensitive := map[string]struct{}{
 		config.EnvAccessKey:         {},
 		config.EnvSecretKey:         {},