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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
package description
import (
"fmt"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
// Topology contains information about a MongoDB cluster.
type Topology struct {
Servers []Server
SetName string
Kind TopologyKind
SessionTimeoutMinutes uint32
CompatibilityErr error
}
// String implements the Stringer interface.
func (t Topology) String() string {
var serversStr string
for _, s := range t.Servers {
serversStr += "{ " + s.String() + " }, "
}
return fmt.Sprintf("Type: %s, Servers: [%s]", t.Kind, serversStr)
}
// Equal compares two topology descriptions and returns true if they are equal.
func (t Topology) Equal(other Topology) bool {
if t.Kind != other.Kind {
return false
}
topoServers := make(map[string]Server)
for _, s := range t.Servers {
topoServers[s.Addr.String()] = s
}
otherServers := make(map[string]Server)
for _, s := range other.Servers {
otherServers[s.Addr.String()] = s
}
if len(topoServers) != len(otherServers) {
return false
}
for _, server := range topoServers {
otherServer := otherServers[server.Addr.String()]
if !server.Equal(otherServer) {
return false
}
}
return true
}
// HasReadableServer returns true if the topology contains a server suitable for reading.
//
// If the Topology's kind is Single or Sharded, the mode parameter is ignored and the function contains true if any of
// the servers in the Topology are of a known type.
//
// For replica sets, the function returns true if the cluster contains a server that matches the provided read
// preference mode.
func (t Topology) HasReadableServer(mode readpref.Mode) bool {
switch t.Kind {
case Single, Sharded:
return hasAvailableServer(t.Servers, 0)
case ReplicaSetWithPrimary:
return hasAvailableServer(t.Servers, mode)
case ReplicaSetNoPrimary, ReplicaSet:
if mode == readpref.PrimaryMode {
return false
}
// invalid read preference
if !mode.IsValid() {
return false
}
return hasAvailableServer(t.Servers, mode)
}
return false
}
// HasWritableServer returns true if a topology has a server available for writing.
//
// If the Topology's kind is Single or Sharded, this function returns true if any of the servers in the Topology are of
// a known type.
//
// For replica sets, the function returns true if the replica set contains a primary.
func (t Topology) HasWritableServer() bool {
return t.HasReadableServer(readpref.PrimaryMode)
}
// hasAvailableServer returns true if any servers are available based on the read preference.
func hasAvailableServer(servers []Server, mode readpref.Mode) bool {
switch mode {
case readpref.PrimaryMode:
for _, s := range servers {
if s.Kind == RSPrimary {
return true
}
}
return false
case readpref.PrimaryPreferredMode, readpref.SecondaryPreferredMode, readpref.NearestMode:
for _, s := range servers {
if s.Kind == RSPrimary || s.Kind == RSSecondary {
return true
}
}
return false
case readpref.SecondaryMode:
for _, s := range servers {
if s.Kind == RSSecondary {
return true
}
}
return false
}
// read preference is not specified
for _, s := range servers {
switch s.Kind {
case Standalone,
RSMember,
RSPrimary,
RSSecondary,
RSArbiter,
RSGhost,
Mongos:
return true
}
}
return false
}
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