sequenceDiagram
    box Purple Healthprocessor platform
    participant ProcessorService
    participant SolrUndersizedTransactionsHealthProcessorPlugin
    end
    box Darkblue SolrUndersizedTransactionsHealthProcessorPlugin internal workings
    participant Shared thread pool
    participant Worker thread
    end
    box Darkgreen Alfresco components (or Healthprocessor platform proxies)
    participant AbstractNodeDAOImpl
    participant TransactionHelper
    end

    par Receive new tasks
        ProcessorService->>SolrUndersizedTransactionsHealthProcessorPlugin: .doProcess(set of nodeRefs)
        SolrUndersizedTransactionsHealthProcessorPlugin->>SolrUndersizedTransactionsHealthProcessorPlugin: Update state.
        opt Too many queued tasks
            SolrUndersizedTransactionsHealthProcessorPlugin->>SolrUndersizedTransactionsHealthProcessorPlugin: Wait until a previous task has been handled.
        end
        SolrUndersizedTransactionsHealthProcessorPlugin->>Shared thread pool: Queue new task.
        SolrUndersizedTransactionsHealthProcessorPlugin-->>ProcessorService: return healthy reports for all nodeRefs
    
    and Process old tasks in the background
        Shared thread pool-->>Worker thread: execute in separate thread
        Worker thread->>AbstractNodeDAOImpl: Fetch node IDs for nodeRefs.
        AbstractNodeDAOImpl-->>Worker thread: node IDs
        Worker thread->>TransactionHelper: Start new transaction.
        Worker thread->>TransactionHelper: .getCurrentTransactionId(...)
        TransactionHelper-->>Worker thread: transaction ID
        Worker thread->>AbstractNodeDAOImpl: .touchNodes(transaction ID, node IDs)
        Worker thread->>TransactionHelper: finalize transaction.
        Worker thread->>SolrUndersizedTransactionsHealthProcessorPlugin: Update state.
        Worker thread->>SolrUndersizedTransactionsHealthProcessorPlugin: Notify about processed task.
    end

sequenceDiagram
    box Purple Healthprocessor platform
    participant ProcessorService
    participant ThresholdIndexingStrategy
    end
    box Darkblue ThresholdIndexingStrategy internal workings
    participant Shared queue A
    participant ThresholdIndexingStrategyTransactionIdFetcher
    participant Shared queue B
    participant ThresholdIndexingStrategyTransactionIdMerger
    end
    box Darkgreen Alfresco components
    participant SearchTrackingComponent
    participant dataSource (through JdbcTemplate)
    end

    
    ProcessorService->>ThresholdIndexingStrategy: .onStart()
    ThresholdIndexingStrategy->>ThresholdIndexingStrategy: Initialize state & progress.
    ThresholdIndexingStrategy->>ThresholdIndexingStrategyTransactionIdFetcher: .run() (in separate thread)
    ThresholdIndexingStrategy->>ThresholdIndexingStrategyTransactionIdMerger: .run() (in seperate thread(s))
    
    par Fetch TxnIDs
        loop while not stopped
            ThresholdIndexingStrategyTransactionIdFetcher->>dataSource (through JdbcTemplate): Fetch a preconfigured amount of transaction IDs for each worker.
            dataSource (through JdbcTemplate)-->>ThresholdIndexingStrategyTransactionIdFetcher: transaction IDs
            ThresholdIndexingStrategyTransactionIdFetcher->>ThresholdIndexingStrategyTransactionIdFetcher: Stop if no transaction IDs are received. Otherwise, divide the transaction IDs for the workers.
            loop foreach worker
                ThresholdIndexingStrategyTransactionIdFetcher->>Shared queue B: Queue batch of transaction IDs.
            end
            ThresholdIndexingStrategyTransactionIdFetcher->>ThresholdIndexingStrategyTransactionIdFetcher: Update state. Also, stop if amount of transactions != amount of workers * worker batch size.
        end
        loop foreach background worker
            ThresholdIndexingStrategyTransactionIdFetcher->>Shared queue B: Queue a stop signal.
        end

    and Process TxnIDs
        loop while not stopped
            ThresholdIndexingStrategyTransactionIdMerger->>Shared queue B: Fetch next batch of transaction IDs. 
            Shared queue B-->>ThresholdIndexingStrategyTransactionIdMerger: next batch
            ThresholdIndexingStrategyTransactionIdMerger->>ThresholdIndexingStrategyTransactionIdMerger: Stop if an end signal is received.
            ThresholdIndexingStrategyTransactionIdMerger->>SearchTrackingComponent: Fetch nodes associated with transaction IDs.
            SearchTrackingComponent-->>ThresholdIndexingStrategyTransactionIdMerger: nodes
            loop foreach transaction
                opt if the transaction size is not sufficiently large (e.g. has not been merged previously)
                    loop foreach node in transaction
                        ThresholdIndexingStrategyTransactionIdMerger->>ThresholdIndexingStrategyTransactionIdMerger: Add the ref. of the to a temporary cache / bucket.
                        opt bucket is full
                            ThresholdIndexingStrategyTransactionIdMerger->>ThresholdIndexingStrategyTransactionIdMerger: Create a copy of the bucket and clear the original one.
                            ThresholdIndexingStrategyTransactionIdMerger->>Shared queue A: Queue copy of bucket.
                        end
                    end
                end
            end
        end
        ThresholdIndexingStrategyTransactionIdMerger->>Shared queue A: Queue a stop signal.
    
    and Fetch nodeRefs
        ProcessorService->>ThresholdIndexingStrategy: .getNextNodeIds(ignored value)
        loop while not all background workers have stopped working
            ThresholdIndexingStrategy->>Shared queue A: Fetch next batch of NodeRefs.
            Shared queue A-->>ThresholdIndexingStrategy: next batch
            opt next batch is not a stop signal
                ThresholdIndexingStrategy-->>ProcessorService: next batch
            end
            ThresholdIndexingStrategy->>ThresholdIndexingStrategy: Keep track of amount of stopped background workers.
            opt all background workers have stopped working
                ThresholdIndexingStrategy-->>ThresholdIndexingStrategy: break
            end
        end
        ThresholdIndexingStrategy-->>ProcessorService: empty batch
    end

    ProcessorService->>ThresholdIndexingStrategy: .onStop()
    ThresholdIndexingStrategy->>ThresholdIndexingStrategy: Reset state and progress.
    ThresholdIndexingStrategy->>ThresholdIndexingStrategyTransactionIdFetcher: .interrupt() (single thread)
    ThresholdIndexingStrategy->>ThresholdIndexingStrategyTransactionIdMerger: .interrupt() (all threads)