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Version: 2.4.0

ChronoGrapher

ChronoGrapher is the component that continues the job of sequencing and merging of the partial StoryChunks created by the ChronoKeepers on the first tier, assembling the complete time-range bound StoryChunks out of them, and archiving the complete StoryChunks into the persistent storage tier.

The ChronoGrapher design follows the StoryPipeline Data Model and mirrors the design of the ChronoKeeper. The ChronoLog deployment allows for only one ChronoGrapher process within the RecordingGroup, and it's usually deployed on the storage node.

ChronoGrapher

  • Recording Process Registry Client is the client side of RPC communication between the ChronoGrapher process and ChronoVisor's RecordingProcessRegistryService. RecordingProcessRegistryClient is used to send Register/Unregister and periodic Heartbeat/Statistics messages to the ChronoVisor.
  • DataStore Admin Service is the service listening to the Start/Stop Story recording notifications from the ChronoVisor, these notifications trigger instantiation or dismantling of the appropriate StoryPipelines based on the clients data access requests.
  • Grapher Recording Service in the RPC service that receives partial StoryChunks from ChronoKeeper processes, using Thallium RDMA communication.
  • StoryChunk Ingestion Queue ensures thread-safe communication between the ingestion threads of the Recording Service and the sequencing threads of the Grapher Data Store. Each active StoryPipeline has a pair of active and passive StoryChunkIngestionHandles to manage StoryChunk processing efficiently.
  • Grapher Data Store maintains a StoryPipeline for each active story, merging the ingested partial StoryChunks into complete time-range bound StoryChunks and retiring the complete StoryChunks to the Story Chunk Extraction Queue.
  • StoryChunk Extraction Queue facilitates thread safe communication boundary between the Grapher Data Store and the Extractor modules as the retired StoryChunks leave their StoryPipelines and wait in the Queue for being picked up by the extractor.
  • StoryChunk Archiving Extractor handles the serialization and archiving of StoryChunks from the Story Chunk Extraction Queue to persistent storage.