mongodb - 为什么 mongodb arbiter 需要 dbpath？

Question

一个 mongodb 仲裁者角色如下：

An arbiter does not have a copy of data set and cannot become a primary. However, an arbiter participates in elections for primary. An arbiter has exactly 1 election vote.

仲裁器是 mongod 实例，它们是副本集的一部分，但不保存数据。那么，为什么 arbiter 需要 dbpath？

标签： mongodbnosql

Answer 1

仲裁器存储各种管家数据，您可以通过查看local数据库来检查这些数据：

MongoDB Enterprise ruby-driver-rs:ARBITER> db.getMongo().setSlaveOk()
MongoDB Enterprise ruby-driver-rs:ARBITER> use local
switched to db local
MongoDB Enterprise ruby-driver-rs:ARBITER> db.runCommand({listCollections:1})
{
        "cursor" : {
                "id" : NumberLong(0),
                "ns" : "local.$cmd.listCollections",
                "firstBatch" : [
                        {
                                "name" : "system.replset",
                                "type" : "collection",
                                "options" : {

                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("108fbabe-4139-4d3d-8326-fc8e169b811d")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        },
                        {
                                "name" : "startup_log",
                                "type" : "collection",
                                "options" : {
                                        "capped" : true,
                                        "size" : 10485760
                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("1c3ed741-a7f8-4fad-89f9-36f979cbfa22")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        },
                        {
                                "name" : "replset.oplogTruncateAfterPoint",
                                "type" : "collection",
                                "options" : {

                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("37c4d64b-8fcc-4aa5-b1e0-2ac6b71e893a")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        },
                        {
                                "name" : "replset.election",
                                "type" : "collection",
                                "options" : {

                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("53fc68a9-19c9-4262-b152-fafa99ea55f5")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        },
                        {
                                "name" : "replset.minvalid",
                                "type" : "collection",
                                "options" : {

                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("5564332b-3c3f-4103-acbd-c53c7a71581c")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        },
                        {
                                "name" : "system.rollback.id",
                                "type" : "collection",
                                "options" : {

                                },
                                "info" : {
                                        "readOnly" : false,
                                        "uuid" : UUID("fa26f83a-8843-4b6d-8d4d-4cde192976bd")
                                },
                                "idIndex" : {
                                        "v" : 2,
                                        "key" : {
                                                "_id" : 1
                                        },
                                        "name" : "_id_"
                                }
                        }
                ]
        },
        "ok" : 1
}