Failover mechanism in a distributed computing system

A computer-readable storage medium storing computer-executable instructions, comprising:

• instructions for selecting one of multiple computing servers in a distributed computing system as a leader server, wherein the leader server is a computing server assigned to serve a read-write request from a client computing system, wherein a remaining of the computing servers are follower servers, and wherein the leader server replicates a log file associated with the leader server to the follower servers, the log file including a data set received from the client computing system;
• instructions for selecting one of the computing servers as an active server, wherein the active server is a computing server assigned to update a distributed data storage system with a log file associated with the active server;
• and
• instructions for selecting some of the computing servers as witness servers, the witness servers including (a) one or more active witness servers that include a replicated copy of the log file and an in-memory store of the leader server and (b) one or more shadow witness servers that include a replicated copy of the log file of the leader server.

A system, comprising:

• a processor;
• a first module configured to select:
• one of multiple computing servers of a distributed computing system as a leader server and a remaining of the computing servers as follower servers, the leader server assigned to serve a data access request from a client computing system,
• one of the computing servers as an active server,
• some of the follower servers as active witness servers, the active witness servers including a replicated copy of a log file and an in-memory store of the leader server, and
• some of the follower servers as shadow witness servers, the shadow witness servers including a replicated copy of the log file of the leader server;
• a second module configured to cause the leader server to process a data access request received at the distributed computing from a client computing system, the data access request including a dataset;
• a third module configured to cause the leader server to write the dataset to the log file stored at a data storage system associated with the leader server;
• a fourth module configured to cause the leader server to replicate the log file and the in-memory store to the active witness servers, and replicate the log file to the shadow witness servers;
• and
• a fifth module configured to cause the active server to update a distributed data storage system associated with the active server with the dataset from the log file.