[SYSTEMDS-3930] OOCEvictionManager implementation

[j143]

Implemented a base OOC Eviction Manager & used it in ResettableStream instead of _cache.

[j143]

Hi @mboehm7 - could you please check if this is the implementation that's on your mind?

<the tests run fine on local, checking why it's failing on github actions>

[mboehm7]

Thanks for the patch @j143. Overall, this eviction manager looks already very good. Once the minor comments are addressed we can already merge it in, and after some preliminary experiments than do the major performance improvements incrementally (e.g., not writing individual blocks but configurable partitions of blocks).

[mboehm7]

you can simply make the methods static synchronized, and remove this getInstance method (right now every stream would work with the common object but use non-synchronized methods, and thus, are not thread-safe)

[mboehm7]

maybe use stream ID instead of the string key

[mboehm7]

Since you are deadline with many blocks, I would recommend to keep only shallow copies of the individual blocks without any serialization (which might increase the size but reduce the overhead)

[mboehm7]

put a TODO in here, that we should improve the evictBuffer to avoid storing a file a second time if it already exists (I would have to double check if we correctly do that in our normal lazywritebuffer).

[mboehm7]

let's avoid this string concatenation and parsing by simply using the stream ID and blockID as is.

[j143]

Hi @mboehm7 , I have addressed most of the comments. The tests are failing in GitHub actions - I tried to test with similar memory configuration in my local and couldn't reproduce.

[mboehm7]

Maybe test your eviction logic with very small buffer pool size (e.g., 4KB) in order to force eviction. The differences in results indicate that as soon as we're evicting we produce incorrect results.

[j143]

Now, I am able to reproduce this issue in a linux machine - it's retrieving incorrect blocks due to index mismatch. checking the root cause further.

---

_size + requiredSize: 4000009 + 4000009; _limit: 4718 bytes

I have decreased the buffer limit still the same. I checked that the eviction logic is triggered.

_size + requiredSize: 4000009 + 4000009; _limit: 4718
Evicting directory: target\testTemp\functions\ooc\lmDSTest\lmDS/localtmp/_p24484_10.120.110.127//ooc_stream/tmp0/0_0
_size + requiredSize: 4000009 + 4000009; _limit: 4718
Evicting directory: target\testTemp\functions\ooc\lmDSTest\lmDS/localtmp/_p24484_10.120.110.127//ooc_stream/tmp0/0_1
_size + requiredSize: 4000009 + 4000009; _limit: 4718
``

[mboehm7]

alright, I'll have a look either today or tomorrow.