This implementation of a distributed DNS server cluster allows multiple nodes (nameservers) to respond to direct DNS queries, while maintaining consistent resource records among them and propogating the addition of new resource records to one node.
This is a course project for the autumn 2017 offering of Stanford CS244B.
Our DNS server achieves high availability by maintaining a local datastore of resource records, which periodically copies new resource records from the raft-backed datastore. When an entry in the raft-backed datastore has been copied into the local datastores of all nodes, it is removed from the raft-backed datastore. This "checkpointing" process ensures that resource records are saved locally so that every DNS server can answer DNS queries even if the raft datastore becomes unavailable (e.g. when a majority of the nodes in the DNS cluster fail).
Each node functions as both a nameserver and a simple resolver over that nameserver's records.
The nodes in this distributed DNS cluster rely on the Twisted and pySyncObj python libaries. Pip install both before attempting to run.
The DNS server relies on the dns-config file, which is parsed as json. This file specifies which nodes use which ip:port pairs for querying and participating in raft.
To run a node, run
./dns-node -n X -c dns-config.json -z zone-files/zfX.txt
where X is the number of the node (and its corresponding zonefile) you want to
start. Because raft will not work on a minority of nodes, a running node will
hang at Initializing raft... until over half the nodes in the cluster have
started.
To test the DNS server as it runs locally, you can run a query over dig using the node's query port.
dig -p 10053 @localhost example.com MX
To test the DNS server's efficiency, run the metrics-collection.py script in the metrics directory.
To add a resource record to a node, enter the following in a node proc's STDIN, where the whitespace between the fields are spaces or tabs. The first field is the action performed (ADD: or REMOVE:) and the following fields are resource name, resource type, and resource value/payload.
ADD: newdomain.com A 1.3.3.7
Conversely, to remove resource records, enter the following:
REMOVE: newdomain.com A 1.3.3.7