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https://issues.apache.org/jira/browse/HADOOP-15566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16561193#comment-16561193
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Ben Sigelman commented on HADOOP-15566:
---------------------------------------
Re the actual technical issue (there's a PS below about the more FUD-oriented
points): rather than expecting maintainers of every ASF storage system *and*
the maintainers of every distributed tracing system to (a) decide on the
nuances of a data model, then (b) write bindings from "Storage System X's"
tracing hooks to "Tracing System Y's" client library (for all combinations of
X's and Y's), we can instrument the ASF storage systems with a single API that
has been specifically designed to be portable.
To address [~stack]'s question about performance, the noop implementation of
OpenTracing tracers amount to an empty function call but avoid the costs and/or
lock contention of generating random numbers, context objects, and so forth.
Another point that [~stack] made:
{quote}For me, the hard part is not which tracing lib to use – if a tracing lib
discussion, lets do it out on dev?
{quote}
I 90% agree with this. Certainly as a response to [~michaelsembwever], in any
case, I would be glad to see a side-by-side using OpenTracing vs "something
custom" to understand the amount of *additional* work required to actually get
end-to-end tracing to work. That said, doing the tracing lib analysis "on dev"
should also take the application developer experience into account... whatever
we decide to do must require a minimum of configuration work (or educational
work) for application developers, and that means that we should think hard
about being agnostic about the tracing system "above" the storage systems under
consideration here – ideally we are able to plug into any of them without
forcing the application developer / operator to write new code or go on a
yak-shaving mission.
As a concrete next step, I would be curious to see the code / branch that
[~jojochuang] used to generate the OT+Jaeger screenshots above. I would also
like to create a dev branch of HDFS or Cassandra that adds "native" OpenTracing
instrumentation to a distributed code path that the HDFS devs think would be
instructive/representative... I just think we're going to be hard-pressed to
make an informed decision without pairings of trace visualizations (ideally in
many tracing systems to illustrate portability) *and* the respective
instrumentation code to illustrate non-bloat / maintainability. Would that be
useful? [~stack] you were suggesting we try this on dev – any pointers to a
non-HDFS / non-HBase expert for a place to focus on for such an exercise?
{color:#707070}PS: {color}[~michaelsembwever]{color:#707070}, that was a lot of
FUD to pack into one message ("bloat its API with vendor concerns", "hostile to
the ASF", "hostile ... to those tracing solutions those vendors see as
competition", etc). These concerns were also presented without any evidence –
unsurprisingly, as I doubt that evidence exists. OpenTracing's two most common
"pairings" are Zipkin and Jaeger, neither of which are commercial solutions. To
the contrary of what you suggest, the API is intentionally – if not primarily –
designed to focus on _describing system behavior_ rather than the concerns of
any downstream tracing system (OSS or commercial). All OpenTracing meetings are
recorded and the notes are public if people here would like to judge for
themselves about the openness and intent of the actual decision process (as
opposed to the one you described/imagined). For those who want a primer on what
we're up to, I would recommend reading either [this doc that I wrote when we
were just getting
started|https://medium.com/opentracing/towards-turnkey-distributed-tracing-5f4297d1736],
or [this more recent doc explaining how OT fits into the larger
ecosystem|https://medium.com/opentracing/the-difference-between-tracing-tracing-and-tracing-84b49b2d54ea]
that's developed in the interim.{color}
> Remove HTrace support
> ---------------------
>
> Key: HADOOP-15566
> URL: https://issues.apache.org/jira/browse/HADOOP-15566
> Project: Hadoop Common
> Issue Type: Improvement
> Components: metrics
> Affects Versions: 3.1.0
> Reporter: Todd Lipcon
> Priority: Major
> Labels: security
> Attachments: Screen Shot 2018-06-29 at 11.59.16 AM.png,
> ss-trace-s3a.png
>
>
> The HTrace incubator project has voted to retire itself and won't be making
> further releases. The Hadoop project currently has various hooks with HTrace.
> It seems in some cases (eg HDFS-13702) these hooks have had measurable
> performance overhead. Given these two factors, I think we should consider
> removing the HTrace integration. If there is someone willing to do the work,
> replacing it with OpenTracing might be a better choice since there is an
> active community.
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