On second thought, your scenario would not be possible even if you initiate a server with the current config plus only itself. I agree that you should not do union of old and new configs. Alex
Sent from mobile On Jul 28, 2012, at 3:26 PM, Jared Cantwell <[email protected]> wrote: > Having to "make up" a configuration for new servers that are non voting > followers is something I keep getting stuck on, because if a couple of these > servers start with just the wrong configuration they can all have an > unspecified version and actually form a standalone quorum and not know a > newer one exists. I would feel much better if new servers that are to become > non voting followers could simply copy the configuration file from an > existing voting participant (including the version) and still start up. This > is particularly an issue for us because servers with arbitrarily old > configurations can start up at any time, and if the wrong things happen then > they could form a quorum if they have the right "bootstrap" configurations > with unspecified versions. > > Does this make sense as a concern? We may patch the server to allow starting > up without its myid in the configuration. > > Jared > > On Jul 28, 2012, at 12:15 PM, Alexander Shraer <[email protected]> wrote: > >> yes, if the server reboots (this is when it would read the config file). >> Otherwise, it has the last config in memory (this is held in a >> QuorumVerifier object in QuorumPeer) and it doesn't look in the config file. >> >> BTW the config file (when overwritten by the system) has an auto-generated >> version using which we know which config is later than which. Users are not >> supposed to specify this version at all - its supposed to be managed by the >> system. If you replace the file and set the version to something low or not >> specify it at all, chances are that the config file will be overwritten >> during synchronization with the leader or during communication with other >> servers in FastLeaderElection. >> If you set it to something high, its possible that your server will be able >> to convince others that this is the latest config :) >> >> Alex >> >> >> On Sat, Jul 28, 2012 at 10:57 AM, Jared Cantwell <[email protected]> >> wrote: >> No that you would want to do this, but simply overwriting a config file >> would "uncommit" a configuration and make that server think the last >> committed configuration was whatever is in the file? >>
