Fix overflowing batch size

[pavolloffay]

Signed-off-by: Pavol Loffay ploffay@redhat.com

Description: <Describe what has changed.

This PR adds configuration property enfoce_batch_size to batch processor that ensures that batch size does not overflow the configured max_batch_size. The default value is false hence it does not change the default behavior.

If the incoming batch size is bigger than available space in cached traces then the incoming batch is split into reaming size and size of the maximum batch size. The spans that would overflow the buffer are sent again in trace data over the channel.

Link to tracking Issue:

Resolves #1140
Related to #1020

Testing: < Describe what testing was performed and which tests were added.>

Documentation: < Describe the documentation added.>

enfoce_batch_size has been added to the readme.

[codecov]

Codecov Report

Merging #1310 into master will increase coverage by 0.03%.
The diff coverage is 97.95%.

@@            Coverage Diff             @@
##           master    #1310      +/-   ##
==========================================
+ Coverage   90.01%   90.05%   +0.03%     
==========================================
  Files         216      217       +1     
  Lines       15200    15244      +44     
==========================================
+ Hits        13683    13728      +45     
  Misses       1101     1101              
+ Partials      416      415       -1     

Impacted Files	Coverage Δ
processor/batchprocessor/splittraces.go	97.05% <97.05%> (ø)
processor/batchprocessor/batch_processor.go	98.01% <100.00%> (+0.21%)	⬆️
translator/internaldata/resource_to_oc.go	86.04% <0.00%> (+2.32%)	⬆️

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[dmitryax]

The original idea of the batcher is to batch traces together and do it as performant as possible. That why it doesn't enforce any hard limit on the batch size. It might be not clearly described in docs, but we have this:

- `send_batch_size` (default = 8192): Number of spans or metrics after which a batch will be sent.

I don't think we should add the complexity to enforce the hard limit by default. This behavior might not be what the users want, but can degrade performance.

What do you think if we keep existing behavior for send_batch_size parameter (may be to make it more clear in docs that it's not a hard limit) and add another config parameter that would enforce the hard limit and cause splitting traces?

[pavolloffay]

What do you think if we keep existing behavior for send_batch_size parameter (may be to make it more clear in docs that it's not a hard limit) and add another config parameter that would enforce the hard limit and cause splitting traces?

It looks good to me

[pavolloffay]

@dmitryax thanks for the feedback. I have made the changes and made the splitting configurable.

[bogdandrutu]

What about some simpler approach. Add items as normal to the batch, then do a simple split not by max size. It is a bit more overhead maybe but simpler logic I feel.

[pavolloffay]

That might be even better from the perf standpoint. The buckets of max size would have to be probably split also bc there can be other items arriving in the meantime (unless we push them directly).

[pavolloffay]

@bogdandrutu I have rebased the PR and simplified it to do only a single split per consume.