MeasurementFetchStrategy (OpenNMS 2022.1.1 API)

All Known Implementing Classes:

AbstractRrdBasedFetchStrategy, JrobinFetchStrategy, JRrd2FetchStrategy, NewtsFetchStrategy, NullFetchStrategy, RrdtoolXportFetchStrategy, TimeseriesFetchStrategy
```
public interface MeasurementFetchStrategy
```
Used to retrieve measurements from the current persistence mechanism.

Author:

Jesse White

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`FetchResults`	`fetch(long start, long end, long step, int maxrows, Long interval, Long heartbeat, List<Source> sources, boolean relaxed)`	Fetches the measurements for the given sources.

- Method Detail
  - fetch
```
FetchResults fetch(long start,
                   long end,
                   long step,
                   int maxrows,
                   Long interval,
                   Long heartbeat,
                   List<Source> sources,
                   boolean relaxed)
            throws Exception
```
    Fetches the measurements for the given sources.
    
    Parameters:
    
    start - timestamp in milliseconds
    
    end - timestamp in milliseconds
    
    step - desired resolution in milliseconds - actual resolution might differ
    
    maxrows - maximum number of rows - no limit when <= 0
    
    interval - duration in milliseconds, used by strategies that implement late aggregation
    
    heartbeat - duration in milliseconds, used by strategies that implement late aggregation
    
    sources - array of sources - these should have unique labels
    
    relaxed - if false a missing source results in a return of null. true on the other hand ignores that source.
    
    Returns:
    
    null when a resource id or attribute cannot be found
    
    Throws:
    
    Exception