Greg Pavlik

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Welcome to the blog of Greg Pavlik, software technologist and frustrated adventurer. Currently, I am working on technologies related to Cloud Computing and Cloud Platform as a Service capabilities.Greg Pavlik
Updated: 1 hour 25 min ago

Spark: A Discussion

Wed, 2014-07-23 09:36
A great presentation, worth watching in its entirety.

With apologies to my Hadoop friends but this is good for you too.

Exactly Wrong

Mon, 2014-07-21 09:58
I normally avoid anything that smacks of a competitive discussion on what I consider to be a space for personal reflection. So while I want to disclose the fact that I am not disinterested in the points I am making from a professional standpoint, my main interest is to frame some architecture points that I think are extremely important for the maturation and success of the Hadoop ecosystem.

A few weeks back, Mike Olson of Cloudera spoke at Spark Summit on how Spark relates to the future of Hadoop. The presentation can be found here:

In particular I want to draw attention to the statement made at 1:45 in the presentation that describes Spark as the "natural successor to MapReduce" - it becomes clear very quickly that what Olson is talking about is batch processing. This is fascinating as everyone I've talked to immediately points out one obvious thing: Spark isn't a general purpose batch processing framework - that is not its design center. The whole point of Spark is to enable fast data access and interactivity.
The guys that clearly "get" Spark - unsurprisingly - are DataBricks. In talking with Ion and company, it's clear they understand the use cases where Spark shines - data scientist driven data exploration and algorithmic development, machine learning, etc. - things that take advantage of the memory mapping capabilities and speed of the framework. And they have offered an online service that allows users to rapidly extract value from cloud friendly datasets, which is smart.

Cloudera's idea of pushing SQL, Pig and other frameworks on to Spark is actually a step backwards - it is a proposal to recreate all the problems of MapReduce 1: it fails to understand the power of refactoring resource management away from the compute model. Spark would have to reinvent and mature models for multi-tenancy, resource managemnet, scheduling, security, scaleout, etc that are frankly already there today for Hadoop 2 with YARN.

The announcement of an intent to lead an implementation of Hive on Spark got some attention. This was something that I looked at carefully with my colleagues almost 2 years ago, so I'd like to make a few observations on why we didn't take this path then.

The first was maturity, in terms of the Spark implementation, of Hive itself, and Shark. Candidly, we knew Hive itself worked at scale but needed significant enhancement and refactoring for both new features on the SQL front and to work at interactive speeds. And we wanted to do all this in a way that did not compromise Hive's ability to work at scale - for real big data problems. So we focused on the mainstream of Hive and the development of a Dryad like runtime for optimal execution of operators in physical plans for SQL in a way that meshed deeply with YARN. That model took the learnings of the database community and scale out big data solutions and built on them "from the inside out", so to speak.

Anyone who has been tracking Hadoop for, oh, the last 2-3 years will understand intuitively the right architectural approach needs to be based on YARN. What I mean is that the query execution must - at the query task level - be composed of tasks that are administered directly by YARN. This is absolutely critical for multi-workload systems (this is one reason why a bolt on MPP solution is a mistake for Hadoop - it is at best a tactical model while the system evolves).  This is why we are working with the community on Tez, a low level framework for enabling YARN native domain specific execution engines. For Hive-on-Tez, Hive is the engine and Tez provides the YARN level integration for resource negotiation and coorindation for DAG execution: a DAG of native operators analogous the the execution model found in the MPP world (when people compare Tez and Spark, they are fundamentally confused - Spark could be run on Tez for example for a much deeper integration with Hadoop 2 for example). This model allows the full range of use cases from interactive to massive batch to be administered in a deeply integrated, YARN native way.

Spark will undoubtedly mature into a great tool for what it is designed for: in memory, interactive scenarios - generally script driven - and likely grow to subsume new use cases we aren't anticipating today. It is, however, exactly the wrong choice for scale out big data batch processing in anything like the near term; worse still, returning to a monolithic general purpose compute framework for all Hadoop models would be a huge regression and is a disastrously bad idea.

Dependent Rational Animals

Sun, 2014-07-20 17:32
I wanted to briefly comment on Alisdair MacIntyre's lectures collected as "Dependent Rational Animals", but let me precede that with a couple of comments for context: first, as I alluded in my last post referencing Levinas, it is my view that the the ethics demands a certain primacy in any healthy conception of life and society; second, in the area of ethics, Macintyre's After Virtue is the book that has had perhaps the biggest impact on my own thinking.

One of the criticisms of MacIntyre is that his critique of rational ethics is, on the one hand, devastating; on the other hand, his positive case for working out a defense of his own position - a revivification of social ethics in the Aristotelian-Thomist tradition(s) was somewhat pro forma. I think this is legitimate in so far as it relates to After Virtue itself (I believe I have read the latest edition - 3 - most recently), though I am not enough of a MacIntyre expert to offer a defensible critique of his work overall.

I do, however, want to draw attention to Dependent Rational Animals specifically in this light. Here MacIntyre begins with is the position of human as animal - as a kind of naturalist starting point for developing another pass at the importance of the tradition of the virtues. What is most remarkable is that in the process of exploring the implications of our "animality" MacIntyre manages to subvert yet another trajectory of twentieth century philosophy, this time as it relates to the primacy of linguistics. The net effect is to restore philosophical discourse back toward the reality of the human condition in the context of the broader evolutionary context of life on earth without - and this I must say is the most amazing part of this book - resorting to fables-masked-as-science (evolutionary psychology).

George EP Box

Mon, 2014-07-07 16:22
"Essentially, all models are wrong. Some models are useful."

The Other

Thu, 2014-07-03 12:33
It is the nature of short essays or speeches that they can at best explore the surface of an idea. This is a surprisingly difficult task, since ideas worth exploring usually need to be approached with some rigor. The easy use of the speech form is to promote an idea to listeners or readers who already share a common view - that is one reason speeches are effective forms for political persuasion for rallying true believers. It's much more difficult to create new vantage points or vistas into a new world - a sense of something grander that calls for further exploration.

Yet this is exactly what Ryszard Kapuscinski accomplishes in his series of talks published as The Other. Here, the Polish journalist builds on his experience and most importantly on the reflections on the Lithuanian-Jewish philosopher Emmanual Levinas to reflect on how the encounter with the Other in a broad, cross cultural sense is the defining event - and opportunity - in late (or post) modernity. For Kapuscinski, the Other is the specifically the non-European cultures in which he spent most of his career as a journalist. For another reader it might be someone very much like Kapuscinski himself.

There are three simple points that Kapuscinski raises that bear attention:

1) The era we live in provides a unique, interpersonal opportunity for encounter with the Other - which is to say that we are neither in the area of relative isolation from the Other that dominated much of human history nor are we any longer in the phase of violent domination that marked the period of European colonial expansion. We have a chance to make space for encounter to be consistently about engagement and exchange, rather than conflict.

2) This encounter cannot primarily technical, its must be interpersonal. Technical means are not only anonymous but more conducive to inculcating mass culture rather than creating space for authentic personal engagement. The current period of human history - post industrial, urbanized, technological - is given to mass culture, mass movements, as a rule - this is accelerated by globalization and communications advances. And while it is clear that the early "psychological" literature of the crowd - and I am thinking not only of the trajectory set by Gustave LeBon, but the later and more mature reflections of Ortega y Gasset - were primarily reactionary, nonetheless they point consistently to the fact that the crowd involves not just a loss of identity, but a loss of the individual: it leaves little room for real encounter and exchange.

While the increasing ability to encounter different cultures offers the possibility of real engagement,  at the same time modern mass culture is the number one threat to the Other - in that it subordinates the value of whatever is unique to whatever is both common and most importantly sellable. In visiting Ukraine over the last few years, what fascinated me the most were the things that made the country uniquely Ukrainian. Following a recent trip, I noted the following in a piece by New York Times columnist Nicholas Kristof on a visit to Karapchiv: "The kids here learn English and flirt in low-cut bluejeans. They listen to Rihanna, AC/DC and Taylor Swift. They have crushes on George Clooney and Angelina Jolie, watch “The Simpsons” and “Family Guy,” and play Grand Theft Auto. The school here has computers and an Internet connection, which kids use to watch YouTube and join Facebook. Many expect to get jobs in Italy or Spain — perhaps even America."

What here makes the Other both unique and beautiful is being obliterated by mass culture. Kristof is, of course, a cheerleader for this tragedy, but the true opportunity Kapuscinski asks us to look for ways to build up and offer support in encounter.

3) Lastly and most importantly, for encounter with the Other to be one of mutual recognition and sharing, the personal encounter must have an ethical basis. Kapuscinski observes that the first half of the last century was dominated by Husserl and Heidegger - in other words by epistemic and ontological models. It is no accident, I think, that the same century was marred by enormities wrought by totalizing ideologies - where ethics is subordinated entirely, ideology can rage out of control. Kapuscinski follows Levinas in response - ultimately seeing the Other as a source of ethical responsibility is an imperative of the first order.

The diversity of human cultures is, as Solzhenitzyn rightly noted, the "wealth of mankind, its collective personalities; the very least of them wears its own special colors and bears within itself a special facet of God's design." And yet is only if we can encounter the Other in terms of mutual respect and self-confidence, in terms of exchange and recognition of value in the Other, that we can actually see the Other as a treasure - one that helps ground who I am as much as reveals the treasure for what it is. And this is our main challenge - the other paths, conflict and exclusion, are paths we cannot afford to tread.

Telling Tales

Sun, 2014-06-08 18:50
After struggling to find time for many months, I finally was able to sit down and watch without interruption Benjamin Bagby's Beowulf performance - an adaptation that relies on Bagby's voice and a reconstruction of a 6th century 6 tone Anglo-Saxon harp. The performance is engrossing and provokes a strong imaginative response, one that would have been communally experienced. Of course the only way to revive a sense of communal experience in the case of Bagby is to see him perform live - however, given the performance is entirely in Old English and as such most unintelligible without subtitles, I think a digital adaptation may be a necessary tradeoff. In many ways, Bagby's Beowulf is a reminder of how impoverished our notion of entertainment is - ephemeral, base, isolating and essentially throw away as a rule.

By the way, it's not entirely the case that the English are unable to create something of the same texture today - several times during the performance I thought of Judith Weir's one person, unaccompanied opera King Harald's Saga. Weir's work is much shorter, principally a musical composition and less poetically rich, so it is difficult to compare the two directly: Beowulf remains the provenance of a balladeer first and foremost, and this is a genre that more and more feels lost to our world - poetry today rarely seems to be meant to be read allowed and even more rarely follows epic formats. This is a lost social phenomena, for which we are impoverished: in fact, the last long work of a balladeer I read was Ethiopian Enzira Sebhat, itself a medieval work dedicated to the Virgin Mary. The closest - though only indirectly comparable - works to the Enzira Sebhat that I am aware of currently being composed are akathistos hymns of the Russian Orthodox tradition. And while many of those recent compositions are less-than-accomplished literary works, they unquestionably represent a rich and living and at times very beautiful means of transmission of communal memory and values. I am not aware of any recent akathistos compositions that have the expressive beauty and originality of the Byzantine hymnographer Romanos the Melodist, the modern akathist has sometimes proven a source of inspiration for exceptionally great art: the late Sir John Tavener's setting of the "thanksgiving akathist" being perhaps the most significant case in point.

Memories of the way we were...

Sat, 2014-05-31 16:13
The fascinating thing about Hadoop is the obviousness of its evolutionary needs. For example, MapReduce coupled with reliable scale out storage was a powerful - even revolutionary - effect for organizations with both lots of and multi-structured data. Out of the gate, Hadoop unlocked data "applications" that were for all intents and purposes unimplementable. At the same time, it didn't take much imagination to see that separating the compute model from resource management would be essential for future applications that did not fit well with MapReduce itself. It took a lot of work and care to get YARN defined, implemented and hardened, but the need for YARN itself was fairly obvious. Now it is here and Hadoop is no longer about "batch" data processing.

Note, however, it takes a lot of work to make the evolutionary changes available. In some cases, bolt on solutions have emerged to fill the gap. For key value data management, HBase is a perfect example. Several years ago, Eric Baldeschwieler was pointing out that HDFS could have filled that role. I think he was right, but the time it would take to get "HBase-type" functionality implemented via HDFS would have been a very long path indeed. In that case, the community filled the gap with HBase and it is being "back integrated" into Hadoop via YARN in a way that will make for a happier co-existence.

Right now we are seeing multiple new bolt on attempts to add functionality to Hadoop. For example, there are projects to add MPP databases on top of Hadoop itself. It's pretty obvious that this is at best a stop gap again - and one that comes at a pretty high price - I don't know of anyone that seriously thinks that a bolt on MPP is ultimately the right model for the Hadoop ecosystem. Since the open source alternatives look to be several years away from being "production ready", that raises an interesting question: is Hadoop evolution moving ahead at a similar or even more rapid rate to provide a native solution - a solution that will be more scalable, more adaptive and more open to a wider range of use cases and applications - including alternative declarative languages and compute models?

I think the answer is yes: while SQL on Hadoop via Hive is really the only open source game in town for production use cases - and its gotten some amazing performance gains in the first major iteration on Tez that we'll talk more about in the coming days - its clear that the Apache communities are beginning to deliver a new series of building blocks for data management at scale and speed: Optiq's Cost Based Optimizer; Tez for structuring multi-node operator execution; ORC and vectorization for optimal storage and compute; HCat for DDL. But what's missing? Memory management. And man has it ever been missing - that should have been obvious as well (and it was - one reason that so many people are interested in Spark for efficient algorithm development).

What we've seen so far has been two extremes available when it comes to supporting memory management (especially for SQL) - all disk and all memory. An obvious point here is that neither is ultimately right for Hadoop. This is a long winded intro to point to two, interrelated pieces by Julian Hyde and Sanjay Radia unveiling a model that is being introduced across multiple components called Discardable In-memory Materialized Query (DIMMQ). Once you see this model, it becomes obvious that the future of Hadoop for SQL - and not just SQL - is being implemented in real time. Check out both blog posts: