Snapshot algorithm

Under snapshot algorithm or distributed snapshot of a process is understood to be used to determine a global state of an active distributed system. It was developed by Leslie Lamport and K. Mani Chandy and is therefore also known as the Chandy - Lamport algorithm.

Assumptions

For the algorithm, the following assumptions are made:

  • Errors are excluded, sent messages only once
  • The communication channel has a direction and is arranged according to the FIFO principle,
  • There is a communication path between any pair of processes in the system
  • Any process can initiate the algorithm
  • The algorithm has no impact on the normal execution of the process
  • Each process in the system records its local state and the state herführender channels on

Expiration

The process that starts the Schnappschussalgortihmus, creates a snapshot of its local state and sends a marker at each continued leading channel. Upon receipt of a marker message there are two possibilities:

By this method, both the actual states of the processes and messages between processes are recorded.

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