topology.go

Documentation: go.mongodb.org/mongo-driver/mongo/description

     1  // Copyright (C) MongoDB, Inc. 2017-present.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License"); you may
     4  // not use this file except in compliance with the License. You may obtain
     5  // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
     6  
     7  package description
     8  
     9  import (
    10  	"fmt"
    11  
    12  	"go.mongodb.org/mongo-driver/mongo/readpref"
    13  )
    14  
    15  // Topology contains information about a MongoDB cluster.
    16  type Topology struct {
    17  	Servers []Server
    18  	SetName string
    19  	Kind    TopologyKind
    20  	// Deprecated: Use SessionTimeoutMinutesPtr instead.
    21  	SessionTimeoutMinutes    uint32
    22  	SessionTimeoutMinutesPtr *int64
    23  	CompatibilityErr         error
    24  }
    25  
    26  // String implements the Stringer interface.
    27  func (t Topology) String() string {
    28  	var serversStr string
    29  	for _, s := range t.Servers {
    30  		serversStr += "{ " + s.String() + " }, "
    31  	}
    32  	return fmt.Sprintf("Type: %s, Servers: [%s]", t.Kind, serversStr)
    33  }
    34  
    35  // Equal compares two topology descriptions and returns true if they are equal.
    36  func (t Topology) Equal(other Topology) bool {
    37  	if t.Kind != other.Kind {
    38  		return false
    39  	}
    40  
    41  	topoServers := make(map[string]Server)
    42  	for _, s := range t.Servers {
    43  		topoServers[s.Addr.String()] = s
    44  	}
    45  
    46  	otherServers := make(map[string]Server)
    47  	for _, s := range other.Servers {
    48  		otherServers[s.Addr.String()] = s
    49  	}
    50  
    51  	if len(topoServers) != len(otherServers) {
    52  		return false
    53  	}
    54  
    55  	for _, server := range topoServers {
    56  		otherServer := otherServers[server.Addr.String()]
    57  
    58  		if !server.Equal(otherServer) {
    59  			return false
    60  		}
    61  	}
    62  
    63  	return true
    64  }
    65  
    66  // HasReadableServer returns true if the topology contains a server suitable for reading.
    67  //
    68  // If the Topology's kind is Single or Sharded, the mode parameter is ignored and the function contains true if any of
    69  // the servers in the Topology are of a known type.
    70  //
    71  // For replica sets, the function returns true if the cluster contains a server that matches the provided read
    72  // preference mode.
    73  func (t Topology) HasReadableServer(mode readpref.Mode) bool {
    74  	switch t.Kind {
    75  	case Single, Sharded:
    76  		return hasAvailableServer(t.Servers, 0)
    77  	case ReplicaSetWithPrimary:
    78  		return hasAvailableServer(t.Servers, mode)
    79  	case ReplicaSetNoPrimary, ReplicaSet:
    80  		if mode == readpref.PrimaryMode {
    81  			return false
    82  		}
    83  		// invalid read preference
    84  		if !mode.IsValid() {
    85  			return false
    86  		}
    87  
    88  		return hasAvailableServer(t.Servers, mode)
    89  	}
    90  	return false
    91  }
    92  
    93  // HasWritableServer returns true if a topology has a server available for writing.
    94  //
    95  // If the Topology's kind is Single or Sharded, this function returns true if any of the servers in the Topology are of
    96  // a known type.
    97  //
    98  // For replica sets, the function returns true if the replica set contains a primary.
    99  func (t Topology) HasWritableServer() bool {
   100  	return t.HasReadableServer(readpref.PrimaryMode)
   101  }
   102  
   103  // hasAvailableServer returns true if any servers are available based on the read preference.
   104  func hasAvailableServer(servers []Server, mode readpref.Mode) bool {
   105  	switch mode {
   106  	case readpref.PrimaryMode:
   107  		for _, s := range servers {
   108  			if s.Kind == RSPrimary {
   109  				return true
   110  			}
   111  		}
   112  		return false
   113  	case readpref.PrimaryPreferredMode, readpref.SecondaryPreferredMode, readpref.NearestMode:
   114  		for _, s := range servers {
   115  			if s.Kind == RSPrimary || s.Kind == RSSecondary {
   116  				return true
   117  			}
   118  		}
   119  		return false
   120  	case readpref.SecondaryMode:
   121  		for _, s := range servers {
   122  			if s.Kind == RSSecondary {
   123  				return true
   124  			}
   125  		}
   126  		return false
   127  	}
   128  
   129  	// read preference is not specified
   130  	for _, s := range servers {
   131  		switch s.Kind {
   132  		case Standalone,
   133  			RSMember,
   134  			RSPrimary,
   135  			RSSecondary,
   136  			RSArbiter,
   137  			RSGhost,
   138  			Mongos:
   139  			return true
   140  		}
   141  	}
   142  
   143  	return false
   144  }
   145
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