Document backoff setting

[urso]

Output Backoff parameters have become configurable. Add missing settings to docs:

• Logstash backoff settings

Note: check all outputs expose backoff settings

[dedemorton]

@urso It looks like these settings aren't shown in the reference.yml files. Do we still want to document these? Looks like Logstash, Elasticsearch, and Kafka all have backoff settings. I can help add the content to the docs, but I don't see the options in the reference.yml.

[ruflin]

We should also add them to the reference file if they are missing.

[urso]

Checking the code, we have different backoff behavior/config per output.

Elasticsearch/Logstash have backoff.init and backoff.max settings. Both employ exponential backoff, with init (default=1s) being the initial waiting time and max (default=60s) being the max waiting time.

The kafka backoff setting is available regarding the meta-data update only. Setting is output.kafka.metadata.retry.backoff. Unfortunately the client doesn't always handle backoff correctly. This needs to be resolved.

Checking the redis output, we don't have any backoff settings in here.

If backoff settings are missing from reference.yml, they should be added as well. Anyways, backoff behavior needs some overhaul, so we can guarantee same settings/semantics for all outputs.

[urso]

I created issue: #6791

For now let's add only Elasticsearch and Logstash to the reference configs only.

[dedemorton]

I've added the backoff settings for the ES and LS outputs here: #5419.