mode.go

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

     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 readpref
     8  
     9  import (
    10  	"fmt"
    11  	"strings"
    12  )
    13  
    14  // Mode indicates the user's preference on reads.
    15  type Mode uint8
    16  
    17  // Mode constants
    18  const (
    19  	_ Mode = iota
    20  	// PrimaryMode indicates that only a primary is
    21  	// considered for reading. This is the default
    22  	// mode.
    23  	PrimaryMode
    24  	// PrimaryPreferredMode indicates that if a primary
    25  	// is available, use it; otherwise, eligible
    26  	// secondaries will be considered.
    27  	PrimaryPreferredMode
    28  	// SecondaryMode indicates that only secondaries
    29  	// should be considered.
    30  	SecondaryMode
    31  	// SecondaryPreferredMode indicates that only secondaries
    32  	// should be considered when one is available. If none
    33  	// are available, then a primary will be considered.
    34  	SecondaryPreferredMode
    35  	// NearestMode indicates that all primaries and secondaries
    36  	// will be considered.
    37  	NearestMode
    38  )
    39  
    40  // ModeFromString returns a mode corresponding to
    41  // mode.
    42  func ModeFromString(mode string) (Mode, error) {
    43  	switch strings.ToLower(mode) {
    44  	case "primary":
    45  		return PrimaryMode, nil
    46  	case "primarypreferred":
    47  		return PrimaryPreferredMode, nil
    48  	case "secondary":
    49  		return SecondaryMode, nil
    50  	case "secondarypreferred":
    51  		return SecondaryPreferredMode, nil
    52  	case "nearest":
    53  		return NearestMode, nil
    54  	}
    55  	return Mode(0), fmt.Errorf("unknown read preference %v", mode)
    56  }
    57  
    58  // String returns the string representation of mode.
    59  func (mode Mode) String() string {
    60  	switch mode {
    61  	case PrimaryMode:
    62  		return "primary"
    63  	case PrimaryPreferredMode:
    64  		return "primaryPreferred"
    65  	case SecondaryMode:
    66  		return "secondary"
    67  	case SecondaryPreferredMode:
    68  		return "secondaryPreferred"
    69  	case NearestMode:
    70  		return "nearest"
    71  	default:
    72  		return "unknown"
    73  	}
    74  }
    75  
    76  // IsValid checks whether the mode is valid.
    77  func (mode Mode) IsValid() bool {
    78  	switch mode {
    79  	case PrimaryMode,
    80  		PrimaryPreferredMode,
    81  		SecondaryMode,
    82  		SecondaryPreferredMode,
    83  		NearestMode:
    84  		return true
    85  	default:
    86  		return false
    87  	}
    88  }
    89
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