RedisCodec Implementation Question

[dalegaspi]

Hello! I have a question regarding implementing a custom codec.

I am using lettuce to read a gzip-compressed string in Redis and deserializing the said string in a Scala application using json4s::parse (with Jackson).

Currently we are reading the gzip data into a String then call json4s::parse. I thought the conversion to String is not necessary (and waste of memory) since json4s::parse already takes in an InputStream parameter.

Now I have implemented a custom codec (for reads only) that returns an InputStream

public class StringInputStreamCodec implements RedisCodec<String, InputStream> {
    private final Charset charset = StandardCharsets.UTF_8;

    @Override
    public String decodeKey(final ByteBuffer bytes) {
        return charset.decode(bytes).toString();
    }

    @Override
    public InputStream decodeValue(final ByteBuffer bytes) {
        return new ByteBufferBackedInputStream(bytes);
    }

    @Override
    public ByteBuffer encodeKey(final String key) {
        return charset.encode(key);
    }

    @Override
    public ByteBuffer encodeValue(final InputStream value) {
        throw new NotImplementedException("This is a read-only codec!");
    }
}

And the ByteBufferBackedInputStream was an implementation from Jackson's com.fasterxml.jackson.databind.util.ByteBufferBackedInputStream

Usage:

val conn = client.connect(CompressionCodec.valueCompressor(
    new StringInputStreamCodec(), CompressionCodec.CompressionType.GZIP)).async();

The question: my tests shows that it is working but...is this a sound approach? I'm reading here about the Codecs being thread-safe but it didn't warn anything about NOT referencing the underlying implementation of the data returned as ByteBuffer so I figured it should be safe to use directly by "wrapping" it with an InputStream reader?

Thanks!

[mp911de]

I converted the issue into a discussion.

The ByteBuffer interface in codecs is used by Lettuce accepting and providing buffers. When decoding, you should either copy or consume buffers as the input buffer is attached to a Netty buffer. Keeping a reference may result in a changed underlying buffer and undesired consequences.

[dalegaspi]

ok. that makes sense. thanks, @mp911de.