CURATOR-725: Allow for global compression

[HoustonPutman]

https://issues.apache.org/jira/browse/CURATOR-725

Allow users to use a CuratorFramework setting to enable compression on all create/setData/getData requests. When using this flag with a custom CompressionProvider, this can easily allow for a filtered compression implementation.

[dsmiley]

+1 LGTM!
Disclaimer: I'm not a Curator internals expert

[kezhuw]

+1 to global compression

When using this flag with a custom CompressionProvider, this can easily allow for a filtered compression implementation.

I saw no per-operation way to opt out compression if it is enabled global while we have method to turn it on if it is not enabled globally. People will have to override CompressionProvider which complicate things.

I checked CreateBuilder, SetDataBuilder, AsyncCreateBuilder, AsyncSetDataBuilder and GetDataBuilder.

I am thinking whether we can solve this by:

1. Per operation compression(bool compression) to override global setting. I guess we probably could unify Compressible and Decompressible.
2. Independent global filter to separate compression filter and the algorithm. This way both parts are concentrated. And we probably could make the filter composable.

public interface CompressionFilter {
    boolean compressed(String path);

    CompressionFilter ENABLED = path -> true;
    CompressionFilter DISABLED = path -> false;

    Function<Collection<CompressionFilter>, CompressionFilter> OR = filters -> path -> {
        for (CompressionFilter filter : filters) {
            if (filter.compressed(path)) {
                return true;
            }
        }
        return false;
    };

    Function<String, CompressionFilter> CHILD_NODES = parent_path -> path -> {
        ZKPaths.PathAndNode nodes = ZKPaths.getPathAndNode(path);
        return nodes.getPath().equals(parent_path);
    };

    Function<String, CompressionFilter> THIS_NODE = this_path -> path -> path.equals(this_path);

    default void example() {
        CompressionFilter this_or_child_nodes =
                OR.apply(Arrays.asList(CHILD_NODES.apply("/xx"), THIS_NODE.apply("/xx")));
    }
}

[tisonkun]

Generally looks good. Thanks for your contribution!

One suggestion is that I'd prefer just name the option "compressionEnabled" and thus enableCompression accordingly. It's configured to the factory/framework and thus bound to that scope, instead of fully global anyway.

[HoustonPutman]

+1 to global compression

When using this flag with a custom CompressionProvider, this can easily allow for a filtered compression implementation.

I saw no per-operation way to opt out compression if it is enabled global while we have method to turn it on if it is not enabled globally. People will have to override CompressionProvider which complicate things.

I checked CreateBuilder, SetDataBuilder, AsyncCreateBuilder, AsyncSetDataBuilder and GetDataBuilder.

So I've gone ahead and added negative methods for both Compressible and Decompressible. I need to add tests for everything, but the Async APIs should be fully covered now too. Lots of ways to do everything, so lots of things to test here to make sure nothing got missed....

[kezhuw]

So I've gone ahead and added negative methods for both Compressible and Decompressible. I need to add tests for everything, but the Async APIs should be fully covered now too. Lots of ways to do everything, so lots of things to test here to make sure nothing got missed....

Thank you for the hard work! The result looks good! I left some minor inline comments.

[kezhuw]

Suggested change

	.forPath(path2, data1)
	.uncompressed()
	.forPath(path2, data1)

Also, I suggest to introduce new variables newData1/newData2 or reassign data1/data2. The following code is not friendly to eyeballs.

[kezhuw]

A separate test method for this case is also good from my side just like testSimple and testCreateCompressedAndUncompressed.

[tisonkun]

LGTM. Thanks for your contribution!