Default Brotli compression level is too slow

I’ve recently upgraded from 3.1.0 to 5.0.1 and without any other change, I noticed a huge slow down in my application.

Requests that previously took about 50ms suddenly took over 1s to complete. Downgrading to 3.1.0 again solved this issue.

I wonder if this has something to do with the new Brotli support? But since Node 10 is not actually supporting that natively, maybe it should then be disabled there?

[damianaiamad]

I stand corrected—I’ve discovered that it is in fact possible to set brotli compression level (1-11). A little obscure, but there you are:

        const options: zlib.BrotliOptions = {
            params: {
                [zlib.constants.BROTLI_PARAM_QUALITY]: 7
            }
        }

For koa:

    koa.use(koaCompress({
        br: {
            params: {
                [zlib.constants.BROTLI_PARAM_QUALITY]: 7
            }
        }
    }))

With a 12MB json payload typical for my app:

BROTLI Level 1 Compression 88.7% Time 36ms Level 2 Compression 89.3% Time 72ms Level 3 Compression 89.6% Time 74ms Level 4 Compression 91.1% Time 112ms Level 5 Compression 92.0% Time 180ms Level 6 Compression 92.1% Time 222ms Level 7 Compression 92.2% Time 302ms Level 8 Compression 92.3% Time 397ms Level 9 Compression 92.4% Time 545ms Level 10 Compression 93.1% Time 6441ms Level 11 Compression 93.6% Time 33956ms

GZIP Level 1 Compression 87.4% Time 75ms Level 2 Compression 87.8% Time 79ms Level 3 Compression 88.2% Time 91ms Level 4 Compression 89.1% Time 115ms Level 5 Compression 89.4% Time 135ms Level 6 Compression 89.9% Time 169ms Level 7 Compression 90.0% Time 215ms Level 8 Compression 90.2% Time 505ms Level 9 Compression 90.3% Time 557ms

So this makes things a lot more interesting. For the kind of json data I work with, there seems to be a large sweet spot where brotli has the edge: both faster and smaller file size!

You may need to run some experiments with your own data to tune the compression level (1-11 for brotli, 1-9 for gzip).

[damianaiamad]

I think koa-compress can use brotli by default so long as it sets the compression level to something suitable for doing realtime compression.

NodeJS default is Brotli L11, which is great for offline compression, but woeful for realtime compression. Since koa-compress is all about realtime compression, it must not use the NodeJS default.

I suggest Brotli L5. From my experiments (above), this works out 3x faster then default GZIP L9 compression. Of course your mileage will vary.