Re: Usage of myId
I think automating this assignment has been discussed in the past. IIRC, some combination of MAC address and pid or timestamp would be sufficient to uniquely identify a ZK instance. There may be some detail I'm forgetting about maintaining the ID between process restarts, making these ephemeral values unacceptable. Cheers, -Nick On Mon, Mar 1, 2010 at 6:56 PM, Henry Robinson he...@cloudera.com wrote: If you have two servers with the same myid, two servers will identify themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used to map onto a hostname / port pair where messages for a given server are sent. Assuming a consistent quorum specification across all machines, messages for server X will only go to one machine and the other will think itself partitioned from the network. Servers need ids to distinguish themselves from other servers in order to break symmetry and successfully elect a leader. Henry On 27 February 2010 23:06, Qian Ye yeqian@gmail.com wrote: myid is used to identify your service instance, with its help, it is possible to start more than one Zookeeper service on one computer. If the configuration of myid is wrong, the service can not be started properly. On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman avinash.laksh...@gmail.com wrote: Why is this important? What breaks down if I have 2 servers with the same myId? Cheers A -- With Regards! Ye, Qian -- Henry Robinson Software Engineer Cloudera 415-994-6679
Re: Usage of myId
re previous discussion see this thread: http://www.mail-archive.com/zookeeper-user@hadoop.apache.org/msg00916.html Patrick Nick Dimiduk wrote: I think automating this assignment has been discussed in the past. IIRC, some combination of MAC address and pid or timestamp would be sufficient to uniquely identify a ZK instance. There may be some detail I'm forgetting about maintaining the ID between process restarts, making these ephemeral values unacceptable. Cheers, -Nick On Mon, Mar 1, 2010 at 6:56 PM, Henry Robinson he...@cloudera.com wrote: If you have two servers with the same myid, two servers will identify themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used to map onto a hostname / port pair where messages for a given server are sent. Assuming a consistent quorum specification across all machines, messages for server X will only go to one machine and the other will think itself partitioned from the network. Servers need ids to distinguish themselves from other servers in order to break symmetry and successfully elect a leader. Henry On 27 February 2010 23:06, Qian Ye yeqian@gmail.com wrote: myid is used to identify your service instance, with its help, it is possible to start more than one Zookeeper service on one computer. If the configuration of myid is wrong, the service can not be started properly. On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman avinash.laksh...@gmail.com wrote: Why is this important? What breaks down if I have 2 servers with the same myId? Cheers A -- With Regards! Ye, Qian -- Henry Robinson Software Engineer Cloudera 415-994-6679
Re: Usage of myId
If you have two servers with the same myid, two servers will identify themselves as the 'same' machine X in a ZooKeeper ensemble. This id is used to map onto a hostname / port pair where messages for a given server are sent. Assuming a consistent quorum specification across all machines, messages for server X will only go to one machine and the other will think itself partitioned from the network. Servers need ids to distinguish themselves from other servers in order to break symmetry and successfully elect a leader. Henry On 27 February 2010 23:06, Qian Ye yeqian@gmail.com wrote: myid is used to identify your service instance, with its help, it is possible to start more than one Zookeeper service on one computer. If the configuration of myid is wrong, the service can not be started properly. On Sun, Feb 28, 2010 at 11:39 AM, Avinash Lakshman avinash.laksh...@gmail.com wrote: Why is this important? What breaks down if I have 2 servers with the same myId? Cheers A -- With Regards! Ye, Qian -- Henry Robinson Software Engineer Cloudera 415-994-6679
