soam's home

home mail us syndication

Archive for delve

Escape From Amazon: Tips/Techniques for Reducing AWS Dependencies

Slides from my talk at CloudTech III in early October 2012:

Escape From Amazon: Tips/Techniques for Reducing AWS Dependencies from Soam Acharya


Talk abstract:

As more startups use Amazon Web Services, the following scenario becomes increasingly frequent – the startup is acquired but required by the parent company to move away from AWS and into their own data centers. Given the all encompassing nature of AWS, this is not a trivial task and requires careful planning at both the application and systems level. In this presentation, I recount my experiences at Delve, a video publishing SaaS platform, with our post acquisition migration to Limelight Networks, a global CDN, during a period of tremendous growth in traffic. In particular, I share some of the tips/techniques we employed during this process to reduce AWS dependence and evolve to a hybrid private/AWS global architecture that allowed us to compete effectively with other digital video leaders.

Flattering Streaming Media Coverage for Our Video Platform

Streaming Media writes that OVP (Online Video Platform) is a pretty crowded space with more than a hundred vendors. They then list the top ten platforms and yes, we’re in there. Here’s what they say:

The OVP formerly known as Delve (until Limelight bought it) stands out for its user experience and workflow. The user interface was designed to be friendly and to make it easy to accomplish tasks. When a user uploads a video, he or she can update its metadata and set the channel even before the video is fully uploaded. That’s a timesaver few can match. It also offers strong analytics and APIs.

The platform’s Video Clipper tool makes it easy to shorten videos and works well in combination with Limelight’s real-time analytics. If users see that viewers are routinely quitting a video at a certain point, they have the option of ending the video there.

The OVP was acquired by Limelight in August 2010. Rather than focusing on just the mobile experience or just analytics, the Limelight Video Platform focuses on offering the best end-to-end user experience. Since it’s now under the same roof as a top CDN, it’s able to offer tie-ins that others can’t. Users gain from functionality such as player edge scaling, which the video platform is able to offer through low-level access to the CDN. Users also get to use developer APIs that aren’t open to the public.

Given that we started relatively late in this space (the company had started to pivot away from semantic video search to the platform SaaS approach just prior to my coming on board), this recognition is particularly heartening. It has been a monumental amount of work and accumulation of many battle scars for all of us. Full credit to Alex, Edgardo and the rest of the team!

Being committed to a startup means you have to be prepared to do anything and everything. That and my own role(s) at Delve/Limelight mean involvement with pretty much all system aspects, especially the backend. I am particularly chuffed at the repeated mentions of analytics since a lot of my own blood, sweat and tears go into it.

Okay, better stop now before this starts reading like an acceptance speech 🙂

Reverse Migration – Moving Out of AWS Part I

It’s been a while since I updated and with good reason. We were acquired by Limelight Networks last year and are now happily ensconced within the extended family of other acquisitions like Kiptronics and Clickability. While it was great to have little perks like my pick of multiple offices (Limelight has a couple scattered around the Bay Area) after toiling at home for most of two plus years, we had other mandates to fulfill. A big one was moving our infrastructure from AWS to Limelight. The reason for this was simple enough. Limelight operates a humongous number of data centers around the world, all connected by private fiber. Business cost efficiencies aside, it really didn’t make sense for us to not leverage this.

Amazon Web Services

AWS makes it really easy to migrate to the cloud. Firing up machines and leveraging new services is a snap. All you really need is a credit card and a set of digital keys. It’s not until you try going the other way you realize how intertwined your applications are with AWS. I am reminded of the alien wrapped around the face of John Hurt!

Obviously, we’d not be where we were if we hadn’t been able to leverage AWS infrastructure – and for that I am eternally thankful. However, as we found, if you do need to move off of it for whatever reason, you’ll find the difficulty of your task to be directly proportional to the number of cloud services you use. In our case, we employed a tremendous amount – EC2, S3, SimpleDB, Elastic Map Reduce, Elastic Load Balancing, CloudFront, Cloud monitoring and, to a lesser extent, Elastic Block Storage and SQS. This list doesn’t even include the management tools that we used to handle our applications in the AWS cloud. Consequently, part of our task was to find suitable replacements for all of these and perform migration while ensuring our core platform continued to run (and scale) smoothly.

I’ll be writing more about our migration strategy, planning and execution further on down the line but for now, I thought it would be useful to summarize some of our experiences with Amazon services over the past couple of years. Here goes:

  • EC2 – one of the things I’d expected when I first moved our services to EC2 would be that instances would be a lot more unstable. You’re asked to plan for instances going down at any time and I’ve experienced instances of all types crashing but when taking out the failures due to application issues, the larger instances turned out to be definitely more stable. Very much so, actually.
  • S3 is both amazing and frustrating. It’s mind blowing how it’s engineered to store an indefinite number of files per bucket. It’s astonishing at how highly available it is. In my 3 years with AWS, I can recall S3 having serious issues only twice or thrice. It’s also annoying because it does not behave like a standard file system, in particular, in its eventual consistency policy, yet it’s very easy to write your applications to treat it like one. That’s dangerous. We kept changing our S3 related code to include many, many retries as the eventual consistency model doesn’t guarantee that just because you have successfully written a file to S3, it will actually be there.
  • Cloudfront is an expensive service and the main reason to use it is because of its easy integration with S3. Other CDNs are more competitive price-wise.
  • Elastic Map Reduce provides Hadoop as a service. Currently, there are two main branches of hadoop supported – 0.18.3 and 0.20.2 although EMR folks encourage you to use the latter, and I believe, is the default for job submission tools. The EMR team has incorporated many fixes of their own into the hadoop code base. I’ve heard of grumblings of this causing yet further splintering of the hadoop codebase (in addition to what comes out of Yahoo and Cloudera). I’ve also heard these will be merged back into the main branches but I am not sure of the status. Being one of the earliest and consistent users of this service (we run every couple of hours and at peak can have 100 plus instances running), I’ve found it to be very stable and the EMR team to be very responsive when jobs fail for whatever reason. Our map reduce applications use 0.18.3 and I am currently in the process of moving over to 0.20.2, something recommended by the EMR team. Once that occurs, I’d expect performance and stability to improve further. Two further thoughts regarding our EMR usage:
    • EMR is structured such that it’s extremely tempting to scale your job by simply increasing the number of nodes in your cluster. It’s just a number after all. In doing so, however, you run the risk of ignoring fundamental issues with your workflow until it assumes calamitous proportions, especially as the size of your unprocessed data increases. Changing node types is a temporary palliative but at some point you have to bite the bullet and get down to computational efficiency and job tuning.
    • Job run time matters! I’ve found similar jobs to run much faster in the middle of the night than during the day. I can only assume this is the dark side of multi tenancy in a shared cloud. In other words, the performance a framework like hadoop relying heavily on network interconnectivity is going to be dependent on the load imposed on the network by other customers. Perhaps this is why AWS has rolled out the new cluster instance types that can run in a more dedicated network setting.
  • SimpleDB: my experience with SimpleDB is not particularly positive. The best thing I can say about it is that it rarely goes down wholesale. However, retrieval performance is not that great and endemic with 503 type errors. Whatever I said for S3 and retries goes double for SimpleDB. In addition, there’s been no new features added to SimpleDB for quite a while and I am not sure what AWS long term goals are for it, if any.

That’s it for now. I hope to add more in a future edition.

Note: post updated thanks to Sid Anand.

Data Trends For 2011

From Ed Dumbill at O’Reilly Radar comes some nice thoughts on key data trends for 2011. First, the emergence of a data marketplace:

Marketplaces mean two things. Firstly, it’s easier than ever to find data to power applications, which will enable new projects and startups and raise the level of expectation—for instance, integration with social data sources will become the norm, not a novelty. Secondly, it will become simpler and more economic to monetize data, especially in specialist domains.

The knock-on effect of this commoditization of data will be that good quality unique databases will be of increasing value, and be an important competitive advantage. There will also be key roles to play for trusted middlemen: if competitors can safely share data with each other they can all gain an improved view of their customers and opportunities.

There’s a number of companies emerging that crawl the general web, Facebook and Twitter to extract raw data, process/cross-reference that data and sell access. The article mentions InfoChimp and Gnip. Other practitioners include BackType, Klout, RapLeaf etc. Their success indicates a growing hunger for this type of information. I definitely seeing this need where I am currently. Limelight, by virtue of its massive CDN infrastructure and customers such as Netflix, collects massive amounts of user data. Such data could greatly increase in value when cross referenced against other databases which provide additional dimensions such as demographic information. This is something that might best be obtained from some sort of third party exchange.

Another trend that seems familiar is the rise of real time analytics:

This year’s big data poster child, Hadoop, has limitations when it comes to responding in real-time to changing inputs. Despite efforts by companies such as Facebook to pare Hadoop’s MapReduce processing time down to 30 seconds after user input, this still remains too slow for many purposes.
It’s important to note that MapReduce hasn’t gone away, but systems are now becoming hybrid, with both an instant element in addition to the MapReduce layer.

The drive to real-time, especially in analytics and advertising, will continue to expand the demand for NoSQL databases. Expect growth to continue for Cassandra and MongoDB. In the Hadoop world, HBase will be ever more important as it can facilitate a hybrid approach to real-time and batch MapReduce processing.

Having built Delve’s (near) real time analytics last year, I am familiar with the pain points of leveraging hadoop to fit into this kind of role. In addition NoSQL based solutions, I’d note that other approaches are emerging:

It’s interesting to see how a new breed of companies have evolved from treating their actual code as a valuable asset to giving away their code and tools and treating their data (and the models they extract from that data) as major assets instead. With that in mind, I would add a third trend to this list: the rise of cloud based data processing. Many of the startups in the data space use Amazon’s cloud infrastructure for storage and processing. Amazon’s ElasticMapReduce, which I’ve written about before, is a very well put together and stable system that obviates the need to maintain a continuously running Hadoop cluster. Obviously, not all applications fit this criteria but if it does, it can be very cost effective.

Peak Load

The graph below shows the requests/sec on the Delve production load balancers for our playlist service system. The time frame roughly covers the past 7 days.

As you can see, we’ve had at least three major peaks over the past couple of days. Some of these have been due to some big traffic partners coming online (including Pokemon) and at least one of them (the most recent one) was because of singer/songwriter Jay Reatard’s untimely passing and the subsequent massive demand for his videos by way of pitchfork, a partner of ours. In other words, some we predicted. Others – well those just happen.

All of these hits are great for the business and for our growth but is definitely white knuckle time for those of us responsible for keeping the system running. Fortunately, through some luck and a whole lot of planning, things have gone very smoothly thus far, fingers crossed. Some of the things we did in advance to prepare:

  • load testing the entire system to isolate the weakest links: we found apachebench and httperf to be our good friends
  • instrument components to print out response times: in particular, we did this with nginx, our load balancer of choice, as it is very easy to print out upstream and client response times
  • utilize the cloud to prepare testbeds: instead of hitting our production system, we were able to set up smaller replicas in the cloud and test there
  • monitor each machine in the chain: running something as simple as top or a little more sophisticated as netstat during load testing can provide great insights. In fact, this is something not limited to load testing. Simply, monitoring production machines during heavy traffic can provide a lot of information.

Our testing showed that:

  • we needed to offload serving more static files to the CDN
  • we could use the load balancer to serve some files which were generated dynamically in the backend, yet never changed. This was an enormous saving.
  • our backend slave cloud dbs needed some semblance of tuning. I don’t consider myself to be a mysql expert by any stretch of the imagination. However, I found that our dbs were small enough and there was sufficient RAM in our AWS instances such that tweaks like increasing the query cache size and raising the innodb buffer pool ensured no disk I/O when serving requests.
  • altering our backend caching to evict after a longer period of time – this would reduce load on our dbs
  • smoothen our deployment process so we can fire up additional backend nodes and load balancers if necessary

There’s much more to be done but surviving the onslaught thus far (with plenty of remaining capacity) has definitely been very heartening. It almost (but not quite) makes up for working through most of the holiday season 🙂

Architecting For The Cloud: Some Thoughts


A key advantage associated with cloud computing is that of scalability. Theoretically, it should be easy to provision new machines or decommission older ones from an existing application and scale thus. In reality, things are not so simple. The application has to be suitably structured from ground up in order to best leverage this feature. Merely adding more CPUs or storage will not deliver linear performance improvements unless the application was explicitly designed with that goal. Most legacy systems are not and consequently, as traffic and usage grows, must be continually monitored and patched to keep performing at an acceptable level. This is not optimal. Consequently, extracting maximum utility from the cloud requires applications follow a set of architectural guidelines. Some thoughts on what those should be:

Stateless, immutable components

An important guideline for linear scalabilty is to have relatively lightweight, independent stateless processes which can execute anywhere and run on newly deployed resource (threads/nodes/cpus) as appropriate in order to serve an increasing number of requests. These services share nothing with others, merely processing asynchronous messages. At Delve, we make extensive use of this technique for multimedia operations such as thumbnail extraction, transcoding and transcription that fit well into this paradigm. Scaling for these services involves spinning up, automatically configuring and deploying additional dedicated instances which can be put to work immediately and subsequently taken down once they are no longer needed. Without planning for this type of scenario, however, it is difficult for legacy applications to leverage this type of functionality.

Reduced reliance on relational databases

Relational databases are primarily designed for managing updates and transactions on a single instance. They scale well, but usually on a single node. When the capacity of that single node is reached, it is necessary to scale out and distribute the load across multiple machines. While there are best practices such as clustering, replication and sharding to allow this type of functionality, they have to be incorporated into the system design from the beginning for the application to benefit. Moving into the cloud does not get rid of this problem.

Furthermore, even if these techniques are utilized by the application, their complexity makes it very difficult to scale to hundreds or thousands of nodes, drastically reducing their viability for large distributed systems. Legacy applications are more likely to be reliant on relational databases and moving the actual database system to the cloud does not eliminate any of these issues.

Alternatively, applications designed for the cloud have the opportunity to leverage a number of cloud based storage systems to reduce their dependence on RDBMS systems. For example, we use Amazon’s SimpleDB as core for a persistent key/value store instead of MySQL. Our use case does not require relational database features such as joining multiple tables. However, scalability is essential and SimpleDB provides a quick and uncomplicated way for us to implement this feature. Similarly, we use Amazon’s Simple Storage Service (S3) to store Write Once Read Many data such as very large video file backups and our analytics reports. Both of these requirements, were we to use MySQL like many legacy applications providing similar functionality, would require a heavy initial outlay of nodes and management infrastructure. By using SimpleDB and S3, we are able to provide functionality comparable to or better than legacy systems at lower cost.

There are caveats, however, with using nosql type systems. They have their own constraints and using them effectively requires understanding those limitations. For example, S3 works under a version of the eventual consistency model which does not provide the same guarantees as a standard file system. Treating it as such would lead to problems. Similarly, SimpleDB provides limited db functionality – treating it as a mysql equivalent would be a mistake.

Integration with other cloud based applications

A related advantage of designing for the cloud is the ability to leverage systems offered by the cloud computing provider. In our case, we extensively use Amazon’s Elastic Map Reduce (EMR) service for our analytics. EMR, like Amazon’s other cloud offerings, is a pay as you go system. It is also tightly coupled with the rest of Amazon’s cloud infrastructure such that transferring data within Amazon is free. At periodic intervals, our system spins up a number of nodes within EMR, transfers data from S3, performs computations, saves the results and tears down the instances. The functionality we thus achieve is similar to constantly maintaining a large dedicated map-reduce cluster such as that would be required by a legacy application but at a fraction of the cost.

Deployment Issues

Deploying an application to the cloud demands special preparation. Cloud machines are typically commodity hardware – preparing an environment able to run the different types of services required by an application is time consuming. In addition, deployment is not a one time operation. The service may need additional capacity to be added later, fast. Consequently, it is important to be able to quickly commission, customize and deploy a new set of boxes as necessary. Existing tools do not provide the functionality required. As cloud computing is relatively new, tools to deploy and administer in the cloud are similarly nascent and must be developed in addition to the actual application. Furthermore, developing, using and maintaining such tools requires skills typically not found in the average sysadmin. The combination of tools and personnel required to develop and run them poses yet another hurdle for moving existing applications to the cloud. For new applications, these considerations must be part of any resource planning.

Fault Tolerance

Typically, cloud infrastructure providers do not guarantee uptime for a node. This implies a box can go down at any time. Additionally, providers such as Amazon will provide a certain percentage uptime confidence level for data centers. While in reality nodes are usually stable, an application designed for the cloud has to have redundancy built in such that a) backups are running and b) they are running in separate data centers. These backup systems also must meet other application requirements such as scalability. Their data must also be in sync with that of the primary stores. Deploying and coordinating such a system, imposes additional overhead in terms of design, implementation, deployment and maintenance, particularly relational databases are involved. Consequently, applications designed from the grounds up with these constraints in mind are much more likely to have an easier transition to the cloud.


Video Clip Lengths

In a NYT article, Rise of Web Video, Beyond 2-Minute Clips, Brian Stelter writes:

Video creators, by and large, thought their audiences were impatient. A three-minute-long comedy skit? Shrink it to 90 seconds. Slow Internet connections made for tedious viewing, and there were few ads to cover high delivery costs. And so it became the first commandment of online video: Keep it short.

I recall coming across this phenomenon in 1997 and 1998 while doing research work into characteristics of web video stored on the web at that point in time. Here’s an interesting graph from the paper I wrote on the subject:

Web Video Lengths (1997)

Web Video Lengths (1997)

The number of videos on the web were relatively small and their sizes could be measured in seconds. 90% were 45 seconds or less. The graph is capped at around 2 minutes for maximum length although I did find outliers that were longer.

What I found interesting, however, in a followup study was that if you took away the bandwidth chokepoints, video lengths ballooned. I was studying the video access patterns of a Video On Demand experiment at the Lulea University in Sweden – the setup here was over a dedicated high speed network, effectively removing slow access as a determinant of behavior. Specifically:

Since 1995, the Centre for Distance-spanning Technology at Luleå University (CDT) has been researching distance education and collaboration on the Internet [17]. Specifically, it has developed a hardware/software infrastructure for giving WWW-based courses and creating a virtual student community. The hardware aspects include the deployment of a high speed network (2-34 Mbps backbone links) to attach the local communities to the actual University campus. The campus is also connected to the national academic backbone by a high speed 34 Mbps link [13] with student apartments being wired together with the rest of campus via 10 or 100 Mbps ethernet.

The following graph shows the distribution of video lengths for the files used in the system:

VoD Video Durations

The mean duration of these files were around 75 minutes or so. This finding hinted that as videos grew in popularity and infrastucture hurdles fell away, video durations would increase. From the original NYT article:

New Web habits, aided by the screen-filling video that faster Internet access allows, are now debunking the rule. As the Internet becomes a jukebox for every imaginable type of video — from baby videos to “Masterpiece Theater” — producers and advertisers are discovering that users will watch for more than two minutes at a time.
“People are getting more comfortable, for better or for worse, bringing a computer to bed with them,” said Dina Kaplan, the co-founder of

Ms. Kaplan’s firm distributes dozens of Web series. A year ago all but one of the top 25 shows on her Web servers clocked in at under five minutes. Now, the average video hosted by Blip is 14 minutes long — “surprising even to us,” she said. The longest video uploaded in May was 133 minutes long, equivalent to a feature-length film.

Interested by this, I took a look at the duration of the videos hosted by Delve. This is based on data a couple of weeks old, so this is not representative of the latest trends. However, I found the average video duration to be a little under 6 minutes. However, within this I found definite disparities between publishers. Our top 25 publishers (by video duration) had videos that were a little under 25 minutes on average. This indicates mixed video use by our publishers. While some are still sticking to shorter videos, a significant number are definitely taking full advantage of long form clips – one of the largest videos is around 12 hours in length!

It’ll be interesting to see how these trends hold over the next year or so.

NoSQL vs S3

MongoDB, Tokyo Cabinet, Project Voldemort … Systems that provide distributed, persistent key value store functionality are proliferating like kudzu. Sometimes it seems that not a day goes by without my hearing about a new one. Case in point: just right now, while browsing, I came across Riak, a “decentralized key-value store, a flexible map/reduce engine, and a friendly HTTP/JSON query interface to provide a database ideally suited for Web applications.”

I understand the motivation behind the NoSQL movement: one of them has to be backlash at the problems associated with MySQL. It’s one of those beasts that is very easy to get started on but, if you don’t start with the right design decisions and growth plan, can be hellacious to scale and maintain. Sadly, this is something I’ve seen happen at places repeatedly throughout my tenure at various companies. It happens all too often. Small wonder then that developers and companies have identified one of the most frequent use cases with modern web applications and MySQL – that of needing to quickly look up key value pairs reliably – and have built or are building numerous pieces of software optimized for doing precisely that at very high performance levels.

The trouble is if you need one yourself. Which one to pick? There are some nice surveys out there (here’s one from highscalability with many good links) but most are in various stages of development, usually with version numbers less than 1 and qualifiers like “alpha” or “beta” appended. Some try to assuage your fears:

Version 0.1? Is it ready for my production data?

That kind of decision depends on many factors, most of which cannot be answered in general but depend on your business. We gave it a low version number befitting a first public appearance, but Riak has robustly served the needs of multiple revenue-generating applications for nearly two years now.

In other words, “we’ve had good experiences with it but caveat emptor. You get what you pay for.”

This is why I really enjoyed the following entry in BJ Clark’s recent survey:

Amazon S3

type: key/value store
Conclusion: Scales amazingly well

You’re probably all like “What?!?”. But guess what, S3 is a killer key/value store. It is not as performant as any of the other options, but it scales *insanely* well. It scales so well, you don’t do anything. You just keep sticking shit in it, and it keeps pumping it out. Sometimes it’s faster than other times, but most of the time it’s fast enough. In fact, it’s faster than hitting mysql with 10 queries (for us). S3 is my favorite k/v data store of any out there.

I couldn’t agree more. Recently, I finished a major project at Delve (and I hope to write about more of this later) where one of our goals was to have all our reports we computed for our customers to be available indefinitely. Our current system stores all the reports in, you guessed it, MySQL. The trouble is this eats up MySQL resources and since we don’t do any queries on these reports, we, in essence, are simply using MySQL as a repository. By moving our reporting storage to S3 (and setting up a simple indexing scheme to list and store lookup keys), we have greatly increased the capacity for our current MySQL installation and are now able to keep and lookup reports for customers indefinitely. We are reliant on S3 lookup times and availability – but, for this use case, the former is not as big an issue and having Amazon take care of the latter frees us to worry about other pressing problems of which are fairly plentiful at a startup!


Delve Reviewed On InformationWeek

Fritz Nelson reviews our publishing system on InformationWeek and posts a video walkthrough with Edgardo, our VP of Products:

Having spent much time of late working on our analytics, I was particularly gratified by Fritz’s comments:

I also liked Delve’s reporting. Most of the video hosting solutions I’ve worked with tend to be a bit sparse on detail — in fact, I’ve found this to be a glaring weakness in most every platform. It’s fine to know how many views a video got, or the length of viewing time, but being able to hone in on viewership numbers based on syndicated player, for example, or time of day is becoming increasingly important. While I only got a cursory look at the reporting, it seems quite robust, and as with many systems, you can pull its data into something like Omniture.

More to come here, stay tuned!