interfere with processing • processing and messages do not stop • Each process cast locally record its own state • Any process can initiate the algorithm 19 The Chandy-Lamport Algorithm ??? Vasiliki Kalavri Kalavri | Boston University 2020 Initiating a snapshot The initiator process: 1. Records its own state. 2. Sends a marker out on each of its outgoing channels. a. The marker is a special message that 2020 On receiving a marker (I) A process receiving a marker for the first time: 1. Records its own state. 2. Marks the channel that the marker came in on as empty. a. Future messages arriving on

to vertex ID • Iterative step: For each vertex • choose the min of neighbors’ component IDs and own component ID as the new ID • if the component ID changed since the last iteration, notify neighbors

be the result of one or more base and/or derived streams • Each query (operator) maintains its own state • Queries process raw streams, not synopses => results are typically exact • Challenges:

projects by creating a separate environment for each project. It is a directory tree which contains its own Python executable files and the installed Python packages. It is useful for local development to create

projects by creating a separate environment for each project. It is a directory tree which contains its own Python executable files and the installed Python packages. It is useful for local development to create