A Hybrid Distributed Mutual Exclusion Algorithm for Cluster-Based Systems

Algorithm 1

Raysuz’s algorithm for leader node.

Step  1. Upon a leader 𝐿_𝑗≠𝐿_{ℎ𝑜𝑙𝑑} receives request from process 𝑃_𝑖 and 𝐿_𝑗=𝐿_{𝑖𝑑𝑙𝑒}

 1.1  if  𝑃_𝑖∩𝐶_𝑗=∅

  1.1.1 add 𝑃_𝑖 to RaymQ

  1.1.2 send 𝐿_𝑗's request to Dir (as an external request)

 1.2 else

  1.2.1 increase corresponding request array element by 1

  1.2.2 enqueue RaymQ with 𝐿_𝑗

  1.2.3 send ExReq to Dir

 1.3 end if

 1.4  𝐿_𝑗=𝐿_{𝑤𝑎𝑖𝑡𝐸𝑥𝑇𝑜𝑘𝑒𝑛}

Step  2. Upon a 𝐿_𝑗=𝐿_{ℎ𝑜𝑙𝑑} receive request from process 𝑃_𝑖

 2.1  if  𝑃_𝑖∩𝐶_𝑗=∅ then

  2.1.1 increase 𝑗th element of request array and broadcast request

  2.1.2 enqueue 𝑃_𝑖 to RaymQ

  2.1.3  𝐿_𝑗=𝐿_{𝑖𝑛𝑇𝑜𝑘𝑒𝑛𝑆𝑡𝑒𝑎𝑙}

 2.2 else

  2.2.1 increase 𝑖th element of request array by 1

 2.3 end if

Step  3. Upon a 𝐿_𝑗=𝐿_{𝑖𝑛𝑇𝑜𝑘𝑒𝑛𝑆𝑡𝑒𝑎𝑙} receive InToken for 𝐿_𝑗

 3.1  if RaymQ.length > 1 or SuzQ.length > 1 then

  3.1.1 update SuzQ

  3.1.2 dequeue RaymQ and set Dir with dequeued node

  3.1.3 send ExToken and ExReq to Dir

  3.1.4 enqueue RaymQ with 𝐿_𝑗

  3.1.5  𝐿_𝑗=𝐿_{𝑤𝑎𝑖𝑡𝐸𝑥𝑇𝑜𝑘𝑒𝑛}

 3.2 else

  3.2.1 update SuzQ

  3.2.2 dequeue RaymQ and set Dir with dequeued node

  3.2.3 send ExToken to Dir

  3.2.4  𝐿_𝑗=𝐿_{𝑖𝑑𝑙𝑒}

 3.3 end if

Step  4. Upon a 𝐿_𝑗=𝐿_{𝑖𝑛𝑇𝑜𝑘𝑒𝑛𝑆𝑡𝑒𝑎𝑙} receive request from 𝑃_𝑗

 4.1 if  𝑃_𝑖∩𝐶_𝑗=∅ then

  4.1.1 add 𝑃_𝑗 to RaymQ

 4.2 else

  4.2.1 increase jth element of request array

 4.3 end if

Step  5. Upon a 𝐿_𝑗=𝐿_{𝑤𝑎𝑖𝑡𝐸𝑥𝑇𝑜𝑘𝑒𝑛} and receives request from 𝑃_𝑖

 5.1 if  𝑃_𝑖∩𝐶_𝑗=∅

  5.1.1 enqueue 𝑃_𝑖 to RaymQ

 5.2 else

  5.2.1 increase corresponding request array element by 1

  5.2.2 Update SuzQ

 5.3 end if

Step  6. Upon a 𝐿_𝑗=𝐿_{𝑤𝑎𝑖𝑡𝐸𝑥𝑇𝑜𝑘𝑒𝑛} and receives ExToken for 𝐿_𝑗

 6.1 update SuzQ and last and add them in InToken