make decoder check size of string before parsing the json

[jsvd]

This codec is a privileged position to avoid the creation of huge events from arbitrarily large json documents. Although the string itself has been alocated, if this codec had a size limit, we could prevent further damage down the pipeline flow.

All we need is a setting that by default is limited to some size like 50k, and here we can loudly refuse to parse the json if the json.byte_size is beyond that limit.

Thoughts?

[jordansissel]

What action would be taken if an event is too large?

[gwsales]

As long as the default is no truncation or max size of 0 / -1.

I deal with json events where the payload is often 500,000 characters and well beyond. It's not ideal for high volume throughput, but the need is there. Adding a default to 50k would only break existing things in my opinion.