MongoDB nosql notes

Login

• $ mongo 10.32.2.4 --authenticationDatabase admin --username test --password mypass

• > db

  • test

• > show dbs

• > use 9spokes

• > db.getCollection("")

• > show collections

• db.getCollection("config_data").find()

Backup/Export

• Use mongodump mongorestore for full bson that handles all mongo types.

• To get json formatted data

  mongo --quiet mydatabase --eval "db.getCollectionNames().join('\n')" | \
  grep -v system.indexes | \
  xargs -L 1 -I {} mongoexport -d mydatabase -c {} --out {}.json

Basic mongo find and update examples

• > db.getCollection('widget_data').find({"obj_type":"summary", "obj_category":"Widget", "obj_origin":"sample"}).pretty()

• patch/update

  db.widget_data.update( {"obj_type":"summary", "obj_category":"Widget", "obj_origin":"sample"}, {$set: {
      "data_sets" : [ 
          {
              "rows" : [ 
                  {
                      "col_1" : "Total",
                      "col_2" : "10"
                  }, 
                  {
                      "col_1" : "Limit",
                      "col_2" : "20"
                  }, 
                  {
                      "col_1" : "Max",
                      "col_2" : "50"
                  }
              ]
          }
      ]
  
  }}
  
  )

Replicaset

• View members

  •  mongo admin --host $ip -u root -p $pass  -eval "rs.status()" 

• Check if current server is the write

  •  mongo admin --host $ip -u root -p $pass --quiet --eval "db.isMaster()['ismaster']"  

Recover password

• stop the mongod service
• edit /etc/mongod.conf

  •    :PRIMARY>  use admin
       :PRIMARY> db.createUser({user:"root",pwd:"mongopwd",roles:[{role:"root",db:"admin"}]});
       :PRIMARY> db.changeUserPassword("root","mongopwd")

  • mongo admin --host 192.168.70.13 -u root -p mongopassword --eval 'rs.initiate({_id: "local_sandbox-MongoDB", members: [{_id: 0, host: "192.168.70.11:27017"},{_id: 1, host: "192.168.70.12:27017"},{_id: 2, host: "192.168.70.13:27017"}]})'

Slow / Long running queries

• * $ mongo 10.32.2.4 --authenticationDatabase admin --username test --password mypass

• > db.currentOp()

• > db.currentOp({"secs_running": {$gte: 3}})

• Count documents in <db> <collection>

  • use <db>;

  • db.<collection>.count()

• DB locks

  • > db.serverStatus().globalLock

  • > db.serverStatus().locks

• DB version , want > 3.2 wiretiger document level locking

  • > db.version()

• DB memory usage should be less than ram

  • > db.serverStatus().mem

  • > db.serverStatus().wiredTiger.cache

• Check number of connections
  • db.serverStatus().connections
• Check indexs on a collection

  • db.<collection>.getIndexes()

...

CategoryLinux