opentracing: add timeout tag to fragment spans

[vigneshshanmugam]

• Helps in tracing when there are timeout issues with the remote fragment endpoint.

[vigneshshanmugam]

👍

[codecov]

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@@            Coverage Diff            @@
##             master     #270   +/-   ##
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  Coverage          ?   99.55%           
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  Files             ?       17           
  Lines             ?      670           
  Branches          ?      127           
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  Hits              ?      667           
  Misses            ?        3           
  Partials          ?        0

Impacted Files	Coverage Δ
lib/fragment.js	100% <ø> (ø)

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[mo-gr]

👍

[lmineiro]

This looked more appropriate as a log field if it will contain just the info about the current fragment timeout. It's expected to change and not very deterministic anyway. As information, it would be a good log field, imho

[vigneshshanmugam]

I agree with you, But I had put it as tag for two reasons

1. Need to keep the consistency of existing attributes and do not treat this field in any different way.
2. Since logs fields aren't searchable and for debugging purposes once I can get the timeout information, I can still search for timeout even though it isn't deterministic.

We already log on z-tailor with the timeout error with specified read and connection timeouts which maps with the error.