As the bulk/recursive delete will require multiple connections to open at an instance,
The default open connections limit will be reached which results in the following error
```FATAL: sorry, too many clients already```
By setting the open connections to a reasonable value - `2`, We ensure that the max open connections
will not be exhausted and lie under bounds.
The queries are simple inserts/updates/deletes which is operational and sufficient with the
the maximum open connection limit is 2.
Fixes#10553
Allow user configuration for MaxOpenConnections
Currently, cache purges are triggered as soon as the low watermark is exceeded.
To reduce IO this should only be done when reaching the high watermark.
This simplifies checks and reduces all calls for a GC to go through
`dcache.diskSpaceAvailable(size)`. While a comment claims that
`dcache.triggerGC <- struct{}{}` was non-blocking I don't see how
that was possible. Instead, we add a 1 size to the queue channel
and use channel semantics to avoid blocking when a GC has
already been requested.
`bytesToClear` now takes the high watermark into account to it will
not request any bytes to be cleared until that is reached.
I have built a fuzz test and it crashes heavily in seconds and will OOM shortly after.
It seems like supporting Parquet is basically a completely open way to crash the
server if you can upload a file and run s3 select on it.
Until Parquet is more hardened it is DISABLED by default since hostile
crafted input can easily crash the server.
If you are in a controlled environment where it is safe to assume no hostile
content can be uploaded to your cluster you can safely enable Parquet.
To enable Parquet set the environment variable `MINIO_API_SELECT_PARQUET=on`
while starting the MinIO server.
Furthermore, we guard parquet by recover functions.
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