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Events Hierarchy. Author: Anna Bekkerman Events Are Everywhere. Node. Client. LMM. Control signals. Node. Server. Data. Target system. LMM. Events. Data. Events. Node. LMM. Client. Basic Types. Messaging events

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Events hierarchy l.jpg

Events Hierarchy

Author: Anna Bekkerman

Events are everywhere l.jpg
Events Are Everywhere









Target system








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Basic Types

  • Messaging events

    • Occur when data is being read from/written to communication channels used in the DCAS system

    • Can be matched to form messages

  • Application events

    • Generated by DCAS applications

  • Metrics

    • Measurements of resource utilization

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LDM Events

  • Each event has a number of properties

    • Type: pq_insert or pq_remove

    • Feed type: class of a data product coming from a common source

    • Sequence number associated with the data product

    • Product size: number of bytes in data section of the product

    • Product ID: usually a string describing a product

      • For example: “Reflectivity_20070603_0112.netcdf.gz”

  • Two LDM events are matched if their types are different and the rest of the properties are equal

    • Source: pq_insert

    • Destination: pq_remove

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WDSS Events

  • Each event has a number of properties

    • Type: lb_read or lb_write

    • Linear buffer ID: a number associated with the linear buffer

    • Message length

      • Linear buffers contain messages describing which products/meteorological features have been processed

    • Message: a string describing a product/feature

  • Two WDSS events are matched if their types are different and messages are equal

    • Source: lb_write

    • Destination: lb_read

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Socket Events

  • Each event has a number of properties

    • Type: socket_write or socket_read

    • Sender address and port

    • Receiver address and port

    • Sequence number associated with the message

    • Message length

    • Message

      • For example: “control”, “features”

  • Two socket events are matched if their types are different and the rest of the properties are equal

    • Source: socket_write

    • Destination: socket_read

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Application Events

  • Must be explicitly generated using RAPIDS API calls

  • Need not be matched

  • Types:

    • Error

    • Variable

    • Algorithm

    • Debug

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Error events

  • Generated when an error occurs

  • Have three significance levels

    • Warning, Severe and Fatal

  • On the message diagram are depicted with cross ( )

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Variable events

  • Generated to report the current value of a variable

  • On the message diagram are depicted with five pointed star ( )

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Algorithm events

  • Have a type associated with them: start and end

  • Generated to report beginning/ending of some action

    • Algorithm, procedure, cycle etc.

  • On the message diagram are depicted with:

    • Start: small arrow pointing up ( )

    • End: small arrow pointing down ( )

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Dedug events

  • Generated to report debug messages

  • On the message diagram are depicted with vertical bar ( )

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Common Properties

  • Each messaging and application event has the following properties:

    • Timestamp

    • PID and name of the process which generated the event

    • ID of the node where the event came from

  • Detailed information about events can be obtained:

    • From log files

    • From the message diagram if RAPIDS visualization client is employed to view the events

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Obtaining Process Name

Events know names of the processes which generated them


  • The name of a process might be very long!

  • Solution: generate a signature for the process name and send it along with the events

  • When RAPIDS server receives an event it compares its process signature with signatures of monitored processes provided in the configuration file

  • Drawback: if a process has not been mentioned in the configuration file, its events will be ignored

    • Even ownerless events are logged!

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  • Each metric has a key and value

  • Process metrics also have a PIDs

  • Often a group of metrics must be used to calculate utilization of a resource

    • For example: to calculate utilization of the memory the following metrics are needed

      • The amount of free and used physical memory

      • The amount of free and used swap memory

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Implementation of Events Hierarchy





byte[] toBytes()

int key;

Object value;

int nodeID;

Date occurredAt;


String processName;

int mark;



boolean correspondTo(Event e)