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From Łukasz Dywicki <l...@code-house.org>
Subject Re: [discuss] Modernization of Cassandra build system
Date Mon, 13 Apr 2015 20:31:45 GMT
Hey Benedict,
My replies in line


>> According to some recordings from DataStax there is a plan to support in
>> Cassandra multiple kinds of store - document, graph so it won’t get easier
>> with the time but rather harder - ask yourself do you really want to mess
>> all these things together?
> Well, these certainly won't live in the same repository, so I wouldn't
> worry about that
That’s good. That’s very good cause it will force separation. If you will do that please
consider using other build system to don’t repeat mistakes which are present now in main
Cassandra build.

>> As I briefly counted in my ealier mail there was 116 issues related to
>> artifacts published by build process.
> That does sound like a lot of bugs. How many actual maintenance releases
> were necessary, did you happen to also count? This is something that could
> be raised at the new retrospective that Ariel has begun, to see if there's
> anything that can be done to reduce their incidence and risk.
There have been 159 minor releases of cassandra (git tag —list | egrep rc | egrep beta |
wc -l). I did not track exactly what is correnation of the bug ration. These 116 vs 159 are
just numbers. From my understanding there is 116 unecessary issues which could be avoided.
You can read these numbers in two different ways - every second minor release was fixing maven
artifacts OR every second release was broken due the maven artifacts. Seems you preffer first
one while users usualy observes second.


>> however it gives real boost when it comes to community donations, tool
>> development, or even debugging
> You're conflating the task of upgrading the build system with
> modularisation, which is a bad idea if you want to make progress on either
> one, since they're each a different and difficult discussion, even if they
> relate.
I do that cause this is typical chicken vs egg problem. One thing can not be done without
another it’s just question which one is fist to follow. Code modularization/package separation
without strict bounds is hard to follow. However nothing prevents doing this in reverse mode
- by solving code issues first and then introducing new build tool. It’s up to cassandra
developers to decide.

> On the topic of the build system: if you can justify why you think Maven
> has a significant chance of reducing our bug burden here, a case can
> perhaps be made, and I will defer to the members of this list with more
> experience of our build system for that in depth discussion. At the moment,
> it seems to be taken as a given this would occur, but I don't yet see a
> clear reason that we should expect this to occur.
You see - I don’t have to justify Maven. I have proposed you a help with it. I also gave
you couple of reasons why Ant is not first sort of tools these days. I don’t feel myself
responsible for doing any advocating for Maven itself. It’s up to you what you choose. The
major thing, major problem which modern tools are doing for you is build time classpath management
(both compile & test) and separate javac executions for both of these. Take what you preffer
- gradle, sbt, leiningen. Anything which does things from previous sentence. Do your own evaluation.
Take what work for you, not only for me.

> On the topic of modularisation: Like I said previously, everyone on this
> list is sympathetic to that goal, I think. However the practical reality is
> likely to be too confounding. But that doesn't mean it is absolutely a
> losing battle, if you can demonstrate a sufficiently painless and
> worthwhile transition.
I don't quite get you at this point. From one side you suppose everyone is for taking such
step, from another one you ask for proofs. In case of code relocation there are always multiple
ways. Cause of what you have currently forces solution of multiple problems. You can start
on any of it (ie. circular dependencies I did mention in earlier conversation doesn’t require
changing a tool). In place where you stay at this moment there will be no such thing as painless
transition. As said ealier - it will be only harder over time.
Given example from my life. We do use Cassandra. We do have plenty of mid level integration
tests which are verifying end to end functionality. Starting from frontend or messaging layer
up to data persistence. Now each of our tests even if it consist a low amount of data hits
IO on multiple levels - starting from socket ending on disk. We do not test in such cases
consistency levels as it’s assumed to be tested by cassandra itself - we are ensuring that
incoming data passes storage interface and can be retrieved back via same interface. With
what cassandra is now we can not make our tests running fast. People are prisoners of cassandra-unit
cause embedding cassandra is impossible, even if it’s written using portable language. It
has too many inner and outer dependencies. On other hand we have for example ActiveMQ which
has lots of options. Even with all of these it might be embedded with no stress, making people
use it for tests even if in production they use different messaging provider. Cause it’s
dead easy.
By taking a look on things such netty or jackson json processor which consisted just two or
three modules in 1.x version you can find fasterxml-jackson 2.x continuing library evolution
in much wider way. It does provide more customizable approach, supports pluggable data formats,
data types and so on. Library users did suffer a bit from changes, package renaming and all
crazy stuff which was going on, but now only legacy projects are dependant on old 1.x version.
Please don’t get me wrong - I don't want to confront library with database - I am just showing
an approach which is affecting popular software. Also as mentioned above - even entire systems
which are older and has similar complexity level such Cassandra are making better these days
than you. All because they have serval jars more. From assembly point of view, for users which
just download ZIP and unpack it - it doesn’t change anything if you have cassandra-all only
or devided it into 10 pieces, but from developers point of view it makes huge change because
these people can decide what parts of cassandra they actually need and in which configuration.

Kind regards,
Lukasz

> On Sat, Apr 11, 2015 at 11:12 AM, Łukasz Dywicki <luke@code-house.org>
> wrote:
> 
>> Sorry for not coming back to topic for long time.
>> 
>> You are right that what Cassandra project have currently - does work and
>> keeping package scoping discipline in such big development community as
>> Cassandra is clearly impossible without tool support (if you insist to keep
>> ant please try to separate javac tasks for logical parts in current build
>> to verify that). I clearly pointed out that it doesn’t work in reliable way
>> causing troubles with artifacts uploaded to maven central. As I briefly
>> counted in my ealier mail there was 116 issues related to artifacts
>> published by build process. It is a lot and these changes requires another
>> mainanance releases to fix for example one or another bytecode level
>> dependency causing NoClassDefErrors with invalid artifacts. According to
>> some recordings from DataStax there is a plan to support in Cassandra
>> multiple kinds of store - document, graph so it won’t get easier with the
>> time but rather harder - ask yourself do you really want to mess all these
>> things together?
>> 
>> Starting from 2.x Cassandra supports triggers but writing even a simplest
>> trigger which will drop a log message or publish UDP packet requires entire
>> cassandra and all it’s dependencies to be present during development.
>> Fact that everything sits in one big ant build.xml is caused by troubles
>> generated by ant itself to support multiple build modules, placeholders and
>> so on, not because it’s handsome to do such.
>> 
>> Modernization of build and internal dependencies is not something which
>> brings huge benefit in first run cause now your frontend is CQL, however it
>> gives real boost when it comes to community donations, tool development, or
>> even debugging. Sadly keeping current Ant build is silent agreement to keep
>> mess internally and rickety architecture of project. Ant was already legacy
>> tool when Cassandra has been launched. The longer you will stay with it the
>> more troubles you will get with it over time.
>> 
>> Kind regards,
>> Lukasz
>> 
>> 
>>> Wiadomość napisana przez Robert Stupp <snazy@snazy.de> w dniu 2 kwi
>> 2015, o godz. 14:51:
>>> 
>>> TL;DR - Benedict is right.
>>> 
>>> IMO Maven is a nice, straight-forward tool if you know what you’re doing
>> and start on a _new_ project.
>>> But Maven easily becomes a pita if you want to do something that’s not
>> supported out-of-the-box.
>>> I bet that Maven would just not work for C* source tree with all the
>> little nice features that C*’s build.xml offers (just look at the scripted
>> stuff in build.xml).
>>> 
>>> Eventually gradle would be an option; I proposed to switch to gradle
>> several months ago. Same story (although gradle is better than Maven ;) ).
>>> But… you need to know that build.xml is not just used to build the code
>> and artifacts. It is also used in CI, ccm, cstar-perf and a some other
>> custom systems that exist and just work. So - if we would exchange ant with
>> something else, it would force a lot of effort to change several tools and
>> systems. And there must be a guarantee that everything works like it did
>> before.
>>> 
>>> Regarding IDEs: i’m using IDEA every day and it works like a charm with
>> C*. Eclipse is ”supported natively” by ”ant generate-eclipse-files”. TBH
I
>> don’t know NetBeans.
>>> 
>>> As Benedict pointed out, the code has improved and still improves a lot
>> - in structure, in inline-doc, in nomenclature and whatever else. As soon
>> as we can get rid of Thrift in the tree, there’s another big opportunity to
>> cleanup more stuff.
>>> 
>>> TBH I don’t think that (beside the tools) there would be a need to
>> generate multiple artifacts for C* daemon - you can do ”separation of
>> concerns” (via packages) even with discipline and then measure it.
>>> IMO The only artifact worth to extract out of C* tree, and useful for a
>> (limited) set of 3rd party code, is something like
>> ”cassandra-jmx-interfaces.jar”
>>> 
>>> Robert
>>> 
>>>> Am 02.04.2015 um 11:30 schrieb Benedict Elliott Smith <
>> belliottsmith@datastax.com>:
>>>> 
>>>> There are three distinct problems you raise: code structure,
>> documentation,
>>>> and build system.
>>>> 
>>>> The build system, as far as I can tell, is a matter of personal
>> preference.
>>>> I personally dislike the few interactions I've had with maven, but
>>>> gratefully my interactions with build system innards have been fairly
>>>> limited. I mostly just use them. Unless a concrete and significant
>> benefit
>>>> is delivered by maven, though, it just doesn't seem worth the upheaval
>> to
>>>> me. If you can make the argument that it actually improves the project
>> in a
>>>> way that justifies the upheaval, it will certainly be considered, but so
>>>> far no justification has been made.
>>>> 
>>>> The documentation problem is common to many projects, though: out of
>>>> codebase documentation gets stale very rapidly. When we say to "read the
>>>> code" we mean "read the code and its inline documentation" - the
>> quality of
>>>> this documentation has itself generally been substandard, but has been
>>>> improving significantly over the past year or so, and we are
>> endeavouring
>>>> to improve with every change. In the meantime, there are videos from a
>>>> recent bootcamp we've run for both internal and external contributors
>>>> http://www.datastax.com/dev/blog/deep-into-cassandra-internals.
>>>> 
>>>> The code structure would be great to modularise, but the reality is
>> that it
>>>> is not currently modular. There are no good clear dividing lines for
>> much
>>>> of the project. The problem with refactoring the entire codebase to
>> create
>>>> separate projects is that it is a significant undertaking that makes
>>>> maintenance of the project across versions significantly more costly.
>> This
>>>> create a net drag on all productivity in the project. Such a major
>> change
>>>> requires strong consensus, and strong evidence justifying it. So the
>>>> question is: would this create more new work than it loses? The evidence
>>>> isn't there that it would. It might, but I personally guess that it
>> would
>>>> not, judging by the results of our other attempts to drive up
>> contributions
>>>> to the project. Perhaps we can have a wider dialogue about the
>> endeavour,
>>>> though, and see if a consensus can in fact be built.
>>>> 
>>>> 
>>>> 
>>>> On Thu, Apr 2, 2015 at 9:31 AM, Pierre Devops <pierredevops@gmail.com>
>>>> wrote:
>>>> 
>>>>> Hi all,
>>>>> 
>>>>> Not a cassandra contributor here, but I'm working on the cassandra
>> sources
>>>>> too.
>>>>> 
>>>>> This big cassandra source root caused me trouble too, firstly it was
>> not
>>>>> easy to import in an IDE, try to import cassandra sources in netbeans,
>> it's
>>>>> a headcache.
>>>>> 
>>>>> It would be great if we had more small modules/projects in separate
>> POM. It
>>>>> will be more easier to work on small part of the project, and as a
>>>>> consequences, I'm sure you will have more external contribution to this
>>>>> project.
>>>>> 
>>>>> I know cassandra devs are used to ant build model, but it's like a
>> thread I
>>>>> opened about updated and more complete documentation about sstable
>>>>> structures. I got answer that it was not needed to understand how to
>> use
>>>>> Cassandra, and the only way to learn about that is to rtfcode. Because
>>>>> people working on cassandra already know how sstable structure are,
>> it's
>>>>> not needed to provide up to date documentation.
>>>>> So it will take me a very long time to read and understand all the
>>>>> serialization code in cassandra to understand the sttable structure
>> before
>>>>> I can work on the code. Up to date documentation about internals would
>> have
>>>>> gave me the knowledge I need to contribute much quicker.
>>>>> 
>>>>> Here we have the same problem, we have a complex non modular build
>> system,
>>>>> and core cassandra dev are used to it, so it's not needed to make
>> something
>>>>> more flexible, even if it could facilite external contribution.
>>>>> 
>>>>> 
>>>>> 
>>>>> 2015-03-31 23:42 GMT+02:00 Benedict Elliott Smith <
>>>>> belliottsmith@datastax.com>:
>>>>> 
>>>>>> I think the problem is everyone currently contributing is comfortable
>>>>> with
>>>>>> ant, and as much as it is imperfect, it isn't clear maven is going
to
>> be
>>>>>> better. Having the requisite maven functionality linked under the
hood
>>>>>> doesn't seem particularly preferable to the inverse. The status quo
>> has
>>>>> the
>>>>>> bonus of zero upheaval for the project and its contributors, though,
>> so
>>>>> it
>>>>>> would have to be a very clear win to justify the change in my opinion.
>>>>>> 
>>>>>> 
>>>>>> On Tue, Mar 31, 2015 at 10:24 PM, Łukasz Dywicki <luke@code-house.org
>>> 
>>>>>> wrote:
>>>>>> 
>>>>>>> Hey Tyler,
>>>>>>> Thank you very much for coming back. I already lost faith that
I will
>>>>> get
>>>>>>> reply. :-) I am fine with code relocations. Moving constants
into one
>>>>>> place
>>>>>>> where they cause no circular dependencies is cool, I’m all
for doing
>>>>> such
>>>>>>> thing.
>>>>>>> 
>>>>>>> Currently Cassandra uses ant for doing some of maven functionalities
>>>>>> (such
>>>>>>> deploying POM.xml into repositories with dependency information),
it
>>>>> uses
>>>>>>> also maven type of artifact repositories. This can be easily
flipped.
>>>>>> Maven
>>>>>>> can call ant tasks for these parts which can not be made with
>> existing
>>>>>>> maven plugins. Here is simplest example:
>>>>>>> http://docs.codehaus.org/display/MAVENUSER/Antrun+Plugin <
>>>>>>> http://docs.codehaus.org/display/MAVENUSER/Antrun+Plugin>
- you can
>>>>> see
>>>>>>> ant task definition embedded in maven pom.xml.
>>>>>>> 
>>>>>>> Most of things can be made at this moment via maven plugins:
>>>>>>> apache-rat-plugin:
>>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.rat/apache-rat-plugin/0.11
>>>>>> <
>>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.rat/apache-rat-plugin/0.11>
>>>>>>> maven-thrift-plugin:
>>>>>>> 
>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.thrift.tools/maven-thrift-plugin/0.1.11
>>>>>>> <
>>>>>>> 
>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.thrift.tools/maven-thrift-plugin/0.1.11
>>>>>>>> 
>>>>>>> antlr4-maven-plugin:
>>>>>>> http://mvnrepository.com/artifact/org.antlr/antlr4-maven-plugin/4.5
>> <
>>>>>>> http://mvnrepository.com/artifact/org.antlr/antlr4-maven-plugin/4.5>
>>>>> or
>>>>>>> antlr3-maven-plugin:
>>>>>>> 
>> http://mvnrepository.com/artifact/org.antlr/antlr3-maven-plugin/3.5.2
>>>>> <
>>>>>>> 
>> http://mvnrepository.com/artifact/org.antlr/antlr3-maven-plugin/3.5.2>
>>>>>>> maven-gpg-plugin:
>>>>>>> 
>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.maven.plugins/maven-gpg-plugin/1.6
>>>>>>> <
>>>>>>> 
>>>>>> 
>>>>> 
>> http://mvnrepository.com/artifact/org.apache.maven.plugins/maven-gpg-plugin/1.6
>>>>>>>> 
>>>>>>> maven-cobertura-plugin:
>>>>> http://mojo.codehaus.org/cobertura-maven-plugin/
>>>>>> <
>>>>>>> http://mojo.codehaus.org/cobertura-maven-plugin/> (but these
days
>>>>> jacoco
>>>>>>> with java agent instrumentation perfoms better)
>>>>>>> .. and so on
>>>>>>> 
>>>>>>> I already made some evaluation of impact and it is big. Code
has to
>> be
>>>>>>> separated into different source roots. It’s not easy even for
keeping
>>>>>>> current artifact structure: cassandra-all, cassandra-thrift and
>>>>>> clientutil
>>>>>>> (cause of cyclic dependencies). What I can do is prepare of these
src
>>>>>> roots
>>>>>>> with dependencies which are declared for them and push that to
my
>>>>>> cassandra
>>>>>>> fork so you will be able to verify that and continue with relocations
>>>>> if
>>>>>>> you will like new build. Creating new modules (source roots)
with
>> maven
>>>>>> is
>>>>>>> simple so you could possibly extract more than these 3 predefined
>>>>>>> artifacts/package roots.
>>>>>>> Just let me know if you are interested.
>>>>>>> 
>>>>>>> Kind regards,
>>>>>>> Lukasz
>>>>>>> 
>>>>>>> 
>>>>>>>> Wiadomość napisana przez Tyler Hobbs <tyler@datastax.com>
w dniu 31
>>>>>> mar
>>>>>>> 2015, o godz. 21:57:
>>>>>>>> 
>>>>>>>> Hi Łukasz,
>>>>>>>> 
>>>>>>>> I'm not very familiar with the build system, but I'll try
to
>> respond.
>>>>>>>> 
>>>>>>>> The Serializer dependencies on org.apache.cassandra.transport
are
>>>>>> almost
>>>>>>>> certainly uses of Server.CURRENT_VERSION and Server.VERSION_3.
>> These
>>>>>> are
>>>>>>>> constants that represent the native protocol version in use,
which
>>>>>>> affects
>>>>>>>> how certain types are serialized.  These constants could
easily be
>>>>>> moved.
>>>>>>>> 
>>>>>>>> The o.a.c.marshal dependency in MapSerializer is on AbstractType,
>> but
>>>>>>> could
>>>>>>>> easily be replaced with java.util.Comparator.
>>>>>>>> 
>>>>>>>> In any case, I'm not necessarily opposed to improving the
build
>>>>> system
>>>>>> to
>>>>>>>> make these errors more apparent.  Would your proposal still
allow us
>>>>> to
>>>>>>>> build with ant (and just change the way those artifacts are
built)?
>>>>>>>> 
>>>>>>>> On Tue, Mar 24, 2015 at 7:58 PM, Łukasz Dywicki <
>> luke@code-house.org
>>>>>>> <mailto:luke@code-house.org>> wrote:
>>>>>>>> 
>>>>>>>>> Dear cassandra commiters and development process followers,
>>>>>>>>> I would like to bring an important topic off build process
of
>>>>>>> cassandra. I
>>>>>>>>> am an external user from community point of view, however
I been
>>>>>> walking
>>>>>>>>> around various  projects close to cassandra over past
year or even
>>>>>> more.
>>>>>>>>> What is worrying me a lot is how cassandra is publishing
artifacts
>>>>> and
>>>>>>> how
>>>>>>>>> many problems are reported due that.
>>>>>>>>> 
>>>>>>>>> First of all - I want to note that I am not born enemy
of Ant
>>>>> itself.
>>>>>> I
>>>>>>>>> never used it. I am also aware of problems with custom
builds made
>>>>>> with
>>>>>>>>> Maven, however I don’t really want to discuss any particular
>>>>>>> replacement,
>>>>>>>>> yet I want to note that Cassandra JIRA project contains
about 116
>>>>>> issues
>>>>>>>>> related somehow to maven (http://bit.ly/1GRoXl5 <
>>>>>> http://bit.ly/1GRoXl5>
>>>>>>> <http://bit.ly/1GRoXl5 <http://bit.ly/1GRoXl5>>,
>>>>>>>>> project=CASSANDRA, text ~ maven). Depends on the point
of view it
>>>>>> might
>>>>>>> be
>>>>>>>>> a lot or a little. By simple statistics it is around
21 issues a
>>>>> year
>>>>>> or
>>>>>>>>> almost 2 issues a month, many of them breaking maintanance/major
>>>>>>> releases
>>>>>>>>> from user point of view. From other hand it’s not bad
considering
>>>>> how
>>>>>>>>> project is being built.
>>>>>>>>> 
>>>>>>>>> Current structure has a very big disadvantage - ONE source
root for
>>>>>>>>> multiple artifacts published in maven repositories and
copying
>>>>> classes
>>>>>>> to
>>>>>>>>> jar AFTER they are compiled. Obviously ant copy task
doesn’t follow
>>>>>>> import
>>>>>>>>> statements and does not include dependant classes. For
example just
>>>>> by
>>>>>>>>> making test relocations and extraction of clientutil
jar on master
>>>>>>> branch
>>>>>>>>> into separate source root I have found a bug where ListSerializer
>>>>>>> depends
>>>>>>>>> on org.apache.cassandra.transpor package. More over clientutil
>>>>>>>>> (MapSerializer) does depends on org.apache.cassandra.db.marshal
>>>>>> package
>>>>>>>>> leading to the fact that it can not be used without cassandra-all
>>>>>>> present
>>>>>>>>> at classpath.
>>>>>>>>> Luckily for cassandra CQL as a new interface reduces
thrift and
>>>>>>> clientutil
>>>>>>>>> usage reducing amount of issues reported around these,
however this
>>>>>> just
>>>>>>>>> hides a real problem in previous paragraph. I have found
a handy
>>>>> tool
>>>>>>> and
>>>>>>>>> made a graph of circular dependencies in cassandra-all.jar.
Graph
>> of
>>>>>>>>> results can found here: http://grab.by/FRnO <http://grab.by/FRnO>
>> <
>>>>>>> http://grab.by/FRnO <http://grab.by/FRnO>>. As you
>>>>>>>>> can see this graph has multiple levels and solving it
is not a
>>>>> simple
>>>>>>> task.
>>>>>>>>> I am afraid a current way of building and packaging cassandra
can
>>>>>> create
>>>>>>>>> huge hiccups when it will come to code rafactorings cause
entire
>>>>>>> cassandra
>>>>>>>>> will become a house of cards.
>>>>>>>>> Restructuring project into smaller pieces is also beneficiary
for
>>>>>>>>> community since solving bugs in smaller units is definitelly
>> easier.
>>>>>>>>> 
>>>>>>>>> At the end of this mail I would like to propose moving
Cassandra
>>>>> build
>>>>>>>>> system forward, regardless of tool which will be choosen
for it.
>>>>>>> Personally
>>>>>>>>> I can volunteer in maven related changes to extract
>>>>> cassandra-thrift,
>>>>>>>>> cassandra-clientutil and cassandra-all to make regular
maven build.
>>>>> It
>>>>>>>>> might be seen as a switch from one big XML into couple
smaller. :-)
>>>>>> All
>>>>>>>>> this depends on Cassandra developers decission to devide
source
>>>>> roots
>>>>>> or
>>>>>>>>> not.
>>>>>>>>> 
>>>>>>>>> Kind regards,
>>>>>>>>> Łukasz Dywicki
>>>>>>>>> —
>>>>>>>>> luke@code-house.org
>>>>>>>>> Twitter: ldywicki
>>>>>>>>> Blog: http://dywicki.pl
>>>>>>>>> Code-House - http://code-house.org
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> --
>>>>>>>> Tyler Hobbs
>>>>>>>> DataStax <http://datastax.com/ <http://datastax.com/>>
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>> 
>>> 
>>> —
>>> Robert Stupp
>>> @snazy
>>> 
>> 
>> 


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