Element data is the container for data that is returned as a result of the processing performed by a flow element.
Data Structure
The precise details of the storage structure used internally by element data will vary by language and even by flow element implementation. However, element data must always expose its contents as a collection of key/value pairs.
Select a tab to view language specific information on the internal data structure.
By default, the Dictionary class is used with a case-insensitive key comparer. This can be overridden in the constructor to use any other IDictionary implementation or an alternative key comparer.
By default, the TreeMap class is used with a case-insensitive key comparator. This can be overridden in the constructor to use any other Map<String,Object> implementation or an alternative key comparator.
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An element data also contains references to the Pipeline it is associated with. This is useful for data which may just be a translation layer for other data, or if metadata needs to be retrieved by the element data.
Life Cycle
Element data instances are typically created by a specific factory method that is associated with a given flow element. This can be used by the flow element to create new element data instances before they are added to flow data.
Although element data instances are stored within flow data, they must not be disposed of at the same time. This is because the element data may be stored in other locations such as a cache. Equally, it must not be disposed when it leaves a cache as it may still be in use externally to the Pipeline.
As such, memory managed languages rely on the finalizer to dispose of any associated resources cleanly.
Thread Safety
The thread-safety of a given element data instance is directly tied to its internal data structure.
Select a tab to view language specific information on thread safety.
By default, the Dictionary class is used. As such, accessing element data's stored values will not be thread-safe. However, this can be overridden to use another IDictionary implementation such as the ConcurrentDictionary. In this case, the accessing of the stored values will be thread-safe.
By default, the TreeMap class is used. As such, accessing element data's stored values will not be thread-safe. However, this can be overridden to use another Map<String,Object> implementation such as the ConcurrentHashMap. In this case, the accessing of the stored values will be thread-safe.
PHP runs in a single thread. Consequently, concurrency issues are not a concern.
Node runs in a single thread with asynchronous execution, except where worker threads are used. It is strongly recommended to not share an element data object with a worker thread.
