Operation (Query) Metrics #1633
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| public void start() { | ||
| startNanoTime = System.nanoTime(); |
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from what i remember nano time is more expensive https://www.tutorialspoint.com/java-system-nanotime-vs-system-currenttimemillis
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I've found some good doc from JDK developer https://web.archive.org/web/20160308031939/https://blogs.oracle.com/dholmes/entry/inside_the_hotspot_vm_clocks
It explains why nanoTime() may be slow and what should be used for precise measurement.
Conclusion:
- nanoTime() may be slow in scale of microseconds
- nanoTime() may require hardware IO and that is why it may be slow
- nanoTime() is what recommended for elapsed time measurements.
- currentTimeMillis() is not so precise and may have a lag of 10ms
- we will use nanoTime() until we see a noticeable drop in performance.
| private static final String INTERNAL_OPERATION_ID = "operationID"; | ||
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| private String startOperation() { | ||
| String operationId = UUID.randomUUID().toString(); |
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Are we sending operationId also as query_id this can be a good connection between our code and the actual operation in ClickHouse
Summary
Adds class to represent metrics of an operation.
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