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From Alexey Goncharuk <alexey.goncha...@gmail.com>
Subject Re: Class field ThreadLocal. Why not static?
Date Mon, 10 Sep 2018 09:46:15 GMT
Maxim,

Ignite supports starting multiple instances of Ignite in the same VM, so
having static thread locals for the fields you mentioned does not work.

Generally, I think thread-local should be bound to the lifespan of the
component it describes. Static thread-locals are hard to clean-up and they
often lead to leaks, so I would rather changed existing static
thread-locals to be non-static.

--AG

пн, 10 сент. 2018 г. в 11:54, Maxim Muzafarov <maxmuzaf@gmail.com>:

> Igniters,
>
> According to javadoc [1] class ThreadLocal:
> `ThreadLocal instances are typically private *static* fields in classes
> that wish to associate state with a thread (e.g., a user ID or Transaction
> ID).`
>
> So, AFAIK non-static ThreadLocal usage means as `per thread - per class
> instance`. What the real cases of using non-static ThreadLocal class fields
> in Ignite code project? When we need it?
>
> In Ignite code project I've found ThreadLocal usage as:
>  - non-static - 67
>  - static  - 68
>
> Back to my example, I've checked FileWriteAheadLogManager. It has:
> 1) private final ThreadLocal<Boolean> interrupted [2]
> 2) private final ThreadLocal<WALPointer> lastWALPtr [3]
> I think both of these fields should be set and used as `static`. Can anyone
> confirm it?
>
>
> [1] https://docs.oracle.com/javase/8/docs/api/java/lang/ThreadLocal.html
> [2]
>
> https://github.com/apache/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/processors/cache/persistence/wal/FileWriteAheadLogManager.java#L253
> [3]
>
> https://github.com/apache/ignite/blob/master/modules/core/src/main/java/org/apache/ignite/internal/processors/cache/persistence/wal/FileWriteAheadLogManager.java#L340
> --
> --
> Maxim Muzafarov
>

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