Random Access to Chronicle Queue?

[Francis Lalonde]

Is it possible to randomly read or update excerpts within a Queue? I could not find methods to do this in the Javadoc or examples.

I have an application metric library that writes to an event log and publishes stats based on time or task triggers. It currently uses on-heap pages of primitive arrays for the log and navigable tree maps for indexes - I'd like to use off-heap file backed structure instead. Writes are mostly sequential - only timer stops events go back to update reserved timestamps. Reads are forward-only but may start anywhere in the log and skip any number of events - I could do without a treemap if I could bisect across the queue to start at the right place. Both cases (timer stops and bisecting reads) would require position-indexed access to the queue, something like a a List.get(long id). All accesses are single-threaded - concurrency is not an issue.

Do you have any hints on how I could implement this? I also looked at MapDB, but the mosty sequential nature and real-time nature of the data seems to make Chronicle a better fit.

Francis

[Luca Burgazzoli]

Yes you can pick up any excerpt by setting the index like:

Excerpt ex= chronicle.createExcerpt()

ex.index(...)

Which index refers to your data is something you have to implement in your application. Once you have the excerpt you can read/update using read/write methods. 

If you have the chance best would be to use a data-value class so you do not need to worry about positions.

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[Francis Lalonde]

Thanks! Is the index absolute in time or relative to the current head?

[Luca Burgazzoli]

Absolute for vanilla, relative to the data file for indexed

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