Page Comparison

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1. Scheduled-style mechanism

   This group of approaches is based on periodic scanning of all saved pieces and determining the status of poline on this basis. A typical algorithm for such mechanism might look as shown on Figure 1.

   

   Checking and updating the PO line status upon retrieving

   PostgreSQL Trigger Functions

   Figure 1 - A general algorithm of mechanisms based on periodic scanning of the entire set of pieces.
   
   

   
   

   Particular implementations of this approach are presented below.

   
   

   Vert.X Periodic Timer

   Within the Vert.X features #_executing_periodic_and_delayed_actions

   Interceptor-style mechanisms

   one can implement a mechanism that periodically retries the pieces and checks the status of the poline, changing it if necessary. There is a need to develop a mechanism that monitors pieces status in cluster mode, when each mod-orders / mod-orders-storage instance will start the scheduler entity. Thus, it is necessary to provide a solution so that the instances of the scheduler from each mod-orders / mod-orders-storage do not compete and do extra pieces checking.

   Separate Scheduler Application

   PostgreSQL cron-job

   pg_cron

2. Interceptor-style mechanisms

   Checking and updating the PO line status upon retrieving

   PostgreSQL Trigger Functions

Solution Proposal