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  1. Documentation
  2. DOCS-4192

Document replica set behavior changes in version 2.7

    • Type: Icon: Task Task
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • v1.3.16, mongodb-3.0
    • Affects Version/s: None
    • Component/s: manual
    • Labels:

      This issue is to collect behavior changes worth noting in the release notes or which need special attention.

      Release Notes:

      • Can no longer load a config with an _id name different from what was specified by the "replSet" command line (or config file) option.
      • Replica Set Config Restriction
        • Can no longer have nodes with votes > 1
          • This was deprecated and printed a warning in mongod version 2.6
        • Arbiters can no longer have 0 votes
        • Unrecognized fields in a config now produce an invalid config and an error, rather than the fields being ignored.
        • Can no longer have "getLastErrorDefaults: .. w:0" in a config
      • Definition of w:'majority' write concern changed to mean majority of voting nodes.
      • Removed the local.slaves collection. Information is in the 'repl' section of serverStatus – you must explicitly request via arg.
        • Note: The local.slaves collection was a mirror of the internal map of all the slaves' replication progress
      • You cannot add a 2.6 (pre 2.6.6) member to a 2.8 replica set because initial sync may fail – specifically listDatabases may fail when the cloner runs on the 2.6 member talking to a 2.8 member since slaveOk is not set.
      • We can no longer parse oplog entries without v:2 – such entries were created by MongoDB 2.2 and prior. A 2.8 secondary will abort if it encounters such oplog entries.
      • Secondaries may abort if they replay an oplog from 2.4 or prior with an index build op that would normally fail on a 2.6 or later primary.
      • Built-in webserver no longer has replication information.
      • Adding a voting member to a two node set in which only one member votes will need force: true.
        • We need to receive positive responses from a majority of voting members in a new config to accept that config.

      Special Attention:

      • Initial sync
        • Builds indexes more efficiently for each collection
        • Now applies oplog entries in batches using threads, like normal application
      • Invalid Replica Set Config (votes>1, arbiter-no-vote)
        • Will not load – fix on primary, then restart node
        • Will be rejected leaving nodes with old config, until fixed on primary

            sam.kleinman Sam Kleinman (Inactive)
            scotthernandez Scott Hernandez (Inactive)
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              8 years, 39 weeks, 1 day ago