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From Roman Shaposhnik <>
Subject [VOTE] Accept HTrace into the Apache Incubator
Date Wed, 05 Nov 2014 19:36:25 GMT
On Wed, Nov 5, 2014 at 11:16 AM, Roman Shaposhnik <> wrote:
> Following the discussion earlier in the thread:
> I would like to call a VOTE for accepting HTrace
> as a new incubator project.
> The proposal is available at:
>    (a full version of the proposal is attached)
> Vote is open until at least Sunday, 9th November 2014, 23:59:00 UTC
>  [ ] +1 accept Lens in the Incubator
>  [ ] ±0
>  [ ] -1 because...


== Abstract ==
HTrace is a tracing framework intended for use with distributed
systems written in java.

== Proposal ==
HTrace is an aid for understanding system behavior and for reasoning
about performance
issues in distributed systems. HTrace is primarily a low impedance
library that a java
distributed system can incorporate to generate ‘breadcrumbs’ or
‘traces’ along the path
of execution, even as it crosses processes and machines. HTrace also
includes various
tools and glue for collecting, processing and ‘visualizing’ captured
execution traces
for analysis ex post facto of where time was spent and what resources
were consumed.

== Background ==
Distributed systems are made up of multiple software components
running on multiple
computers connected by networks. Debugging or profiling operations run
over non-trivial
distributed systems -- figuring execution paths and what services, machines, and
libraries participated in the processing of a request -- can be involved.

== Rationale ==
Rather than have each distributed system build its own custom
‘tracing’ libraries,
ideally all would use a single project that provides necessary
primitives and saves
each project building its own visualizations and processing tools anew.

Google described “...[a] large-scale distributed systems tracing infrastructure”
in Dapper, a Large-Scale Distributed Systems Tracing Infrastructure. The paper
tells a compelling story of what is possible when disparate systems standardize
on a single tracing library and cooperate, ‘passing the baton’, filling out
trace context as executions cross systems.

HTrace aims to provide a rough equivalent in open source of the described core
Dapper tools and library.  As it is adopted by more projects, there will be a
‘network effect’ as HTrace will provide a more comprehensive view of activity
on the cluster.  For example, as HDFS gets HTrace support, we can connect this
with the HTrace support in HBase to follow HBase requests as they enter HDFS.

Given the success of HTrace depends on its being integrated by many  projects,
HTrace should be perceived as unhampered, free of any commercial, political,
or legal ‘taint’. Being an Apache project would help in this regard.

== Initial Goals ==
HTrace is a small project of narrow scope but with a grand vision:
  * Move the HTrace source and repository to Apache, a vendor-neutral
location. Currently HTrace resides at a Cloudera-hosted repository.
  * Add past contributors as committers and institute Apache governance.
  * Evangelize and encourage HTrace diffusion. Initially we will
continue a focus on the Hadoop space since that is where most of the
initial contributors work and it is where HTrace has been initially
  * Building out the standalone visualization tool that ships with HTrace.
  * Build more community and add more committers

== Current Status ==
Currently HTrace has a viable Java trace library that can be interpolated
to create ‘traces’.  The work that needs to be done on this library is mostly
bug fixes, ease-of-use improvements, and performance tweaks.  In the future,
we may add libraries for other languages besides Java.

HTrace has means of dumping traces to the filesystem, Twitters’ Zipkin
(a tracing
sink and visualization system developed by Twitter,
or Apache HBase.  Executions can be viewed either in Zipkin or in pygraph

Since the initial sprint in the summer of 2012 which saw HTrace patches proposed
for Apache HDFS and committed to Apache HBase, development has been sporadic;
mostly a single developer or two adding a feature or bug fixing. HTrace is
currently undergoing a new “spurt” of development with the effort to get HTrace
added to Apache HDFS revived and a new standalone viewing facility being added
in to HTrace itself.

HTrace has been integrated by Apache Phoenix.

=== Meritocracy ===
HTrace, up to this, has been run by Apache committers and PMC members.
We want to
build out a diverse developer and user community and run the HTrace project in
the Apache way.  Users and new contributors will be treated with respect and
welcomed; they will earn merit in the project by tendering quality patches
and support that move the project forward.  Those with a proven support and
quality patch track record will be encouraged to become committers.

=== Community ===
There are just a few developers involved at the moment. If our project
is accepted
by incubator, building community would be a primary initial goal.

=== Core Developers ===

Core developers include Apache members and members of the Hadoop and
HBase PMCs.
Of those listed, all have contributed to HTrace. Half are from Cloudera.
The remainder are Hortonworks, NTTData, Google, and Facebook employees.

=== Alignment ===
HTrace has been integrated into Apache HBase and Apache Phoenix.  Integration
into Apache HDFS is currently being worked on. Approaching the Apache YARN
project would be a likely next integration.

== Known Risks ==
As noted above, development has been sporadic up to this.  It may continue so.

For HTrace to tell a compelling story, it needs to be taken up by significant
projects that make up a traced distributed system.  For example, say YARN and
HBase take on HTrace but HDFS does not, then the HDFS portions of an end-to-end
operation will render opaque compromising our being able to tell a good story
around an execution. Because the picture painted has gaps, HTrace may be left
aside as ineffective.

=== Orphaned products ===
The proposers have a vested interest in making HTrace succeed, driving its
development and its insertion into projects we all work on. Its dispersion
will shine light on difficult to understand interactions amongst the various
systems we all work on. A working, integrated HTrace will add a useful
debugging mechanism to the Apache projects we all work on.

=== Inexperience with Open Source ===
The majority of the proposers here have day jobs that has them working near
full-time on (Apache) open source projects. A few of us have helped carry
other projects through incubator.  HTrace to date has been developed as
an open source project.

=== Homogenous Developers ===
The initial group of committers is small but already we have a healthy
diversity of participating companies.  We are bay-area challenged but
a Japanese contributor makes for a good counter balance.

=== Reliance on Salaried Developers ===
Most of the contributors are paid to work in the Hadoop ecosystem.
While we might wander from our current employers, we probably won’t
go far from the Hadoop tree.  Whoever the Hadoop employer, it is
plain a successful HTrace project is in everyone’s interest.
At least one of the developers has already changed employers but
his interest in seeing HTrace succeed prevails.

=== Relationships with Other Apache Products ===
For HTrace to succeed, it is critical we build good relations with
other distributed systems projects.  We intend to initially build
on relations we already have in place, mostly in the Hadoop space.

The HTrace project has been incorporated by Apache HBase and
Apache Phoenix. It is currently being actively integrated into
Apache HDFS.

We do not know of any equivalent or near-equivalent project
in the Apache space.

The Dapper paper notes precedent, in particular, the Berkeley
Rad Lab X-Trace project.

==== How HTrace relates to Zipkin ====
Zipkin is an Apache Licensed project from Twitter. It is a complete
tracing tool with trace collectors, trace viewers and tools to help
you generate traces. It is written in Scala.  If your project is
not Scala or if it is Java and you cannot afford a Scala dependency,
at a minimum, you need an alternate means of generating traces.
HTrace provides this facility for Java as well as bridging tools
to feed traces to Zipkin for query and display.

The projects complement each other.

=== A Excessive Fascination with the Apache Brand ===
While we intend to leverage the Apache ‘branding’ when talking to other
projects as testament of our project’s ‘neutrality’, we have no plans
for making use of Apache brand in press releases nor posting billboards
advertising acceptance of HTrace into Apache Incubator.

== Documentation ==
See [[|]] for the current state of the HTrace
project and documentation.

How to enable tracing in
[[|HBase using HTrace]]
Elliott Clark on
in HBase]]

== Initial Source ==
Jonathan Leavitt and Todd Lipcon built the first versions of HTrace in the
summer of 2012.  Jonathan was Todd’s summer intern at Cloudera.

== Source and Intellectual Property Submission Plan ==
We know of no legal encumberments in the way of transfer of source to Apache.

== External Dependencies ==
HTrace includes third party libs. These include guava, jetty, junit, protobuf,
hbase, and thrift.  All dependencies are Apache licensed or licenses that are
palatable: e.g. junit is EPL (Eclipse Public License v1.0) and
ProtoBufs are BSD licensed.


== Required Resources ==

=== Mailing lists ===
  * (moderated subscriptions)

=== Git Repository ===

=== Issue Tracking ===

=== Other Resources ===
Means of setting up regular builds for htrace on

== Initial Committers ==
  * Colin McCabe (
  * Elliott Clark (
  * Jonathan Leavitt ( -- CLA being submitted
  * Masatake Iwasaki ( -- CLA being submitted
  * Michael Stack (
  * Nick Dimiduk (
  * Todd Lipcon (

== Affiliations ==
  * Colin McCabe - Cloudera
  * Elliott Clark - Facebook
  * Jonathan Leavitt - Google
  * Masatake Iwasaki - NTTData
  * Michael Stack - Cloudera
  * Nick Dimiduk - Hortonworks
  * Todd Lipcon - Cloudera

== Sponsors ==

=== Champion ===
Roman Shaposhnik

=== Nominated Mentors ===
  * Michael Stack - Apache Member
  * Todd Lipcon - Apache Member
  * Jake Farrell - Apache Member
  * Billie Rinaldi - Apache Member
  * Andrew Purtell - Apache Member
  * Lewis John McGibbney - Apache Member

We will be soliciting more mentors as part of the proposal process.

=== Sponsoring Entity ===
We would like to propose Apache incubator to sponsor this project.

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