I have a requirement to bulk upload an excel sheet to a DynamoDB table and the maximum number of rows are 200,000. The website for bulk upload will be used less frequently, so we can assume there are only 1 - 2 bulk uploads being processed at a given time. In the backend, I am using Apache POI API to parse the excel sheet into DynamoDB Items.
Because we can only send up to 25 items in a batchWriteItem call, the currently latency is around 15 minutes (900 seconds) to completely upload all the 200,000 items. Hence I am planning to implement multi threading to execute multiple batchWriteItem API calls in parallel. Can you help me understand which EC2 host types are best suited for multi-threading for this purpose.
Any references will be really helpful.
Normally, multi-threading would be helped by using an Instance Type that has multiple CPUs.
However, you are describing behaviour that is waiting on network rather than CPU. Therefore, it is likely that the operation you describe is not being heavily impacted by CPU Utilization.
The best way to answer your question is to recommend that you experiment with different instance types to find the one that is best for your application's combination of needs:
Pick an instance family (eg m5) and try a few different sizes
Compare this against another family (eg c5) to see whether the improved performance is worth the extra cost
Monitor the application to find the bottleneck, which would either be RAM, CPU, Network or Disk access
Please note that smaller instances have less Network bandwidth, so you might need to choose a larger instance type to avoid being throttled on network bandwidth. This might result in excess CPU that isn't being fully utilized.
I have the requirement to insert 10,000 docs into marklogic in less than 10 seconds.
I tested in one single-node marklogic server in the following way:
use xdmp:spawn to pass the doc insertion task to task server;
use xdmp:document-insert without specify forest explicitly;
the task server has 8 theads to process tasks;
We have enabled CPF.
The performance is very bad: it took 2 minutes to finish the 10,000 doc creation.
I'm sure the performance will be better if I tested it in a cluster environment, but I'm not sure whether it can finish in less than 10 seconds.
Please advise the way of improving the performance.
I would start by gathering more information. What version of MarkLogic is this? What OS is it running on? What's the CPU? RAM? What's the storage subsystem? How many forests are attached to the database?
Then gather OS-level metrics, to see if one of the subsystems is an obvious bottleneck. For now I won't speculate beyond that.
If you need a fast load, I wouldn't use xdmp:spawn for each individual document, nor use CPF. But 2 minutes for 10k docs doesn't necessarily sound slow. On the other hand, I have reached up to 3k/sec, but without range indexes, transforms, whatsoever. And a very fast disk (e.g. ssd)..
HTH!
Assuming 2 socket server, 128GB-256GB of ram, fast IO (400-800MB/sec sustained)
Appropriate number of forests (12 primary or 6 primary/6 secondary)
More than 8 threads assuming enough cores
CPF off
Turn on perf history, look in metrics, and you will see where the bottleneck is.
SSD is not required - just IO throughput...which multiple spinning disks provide without issue.
Do you think using an EC2 instance (Micro, 64bit) would be good for MongoDB replica sets?
Seems like if that is all they did, and with 600+ megs of RAM, one could use them for a nice set.
Also, would they make good primary (write) servers too?
My database is only 1-2 gigs now but I see it growing to 20-40 gigs this year (hopefully).
Thanks
They COULD be good - depending on your data set, but likely they will not be very good.
For starters, you dont get much RAM with those instances. Consider that you will be running an entire operating system and all related services - 613mb of RAM could get filled up very quickly.
MongoDB tries to keep as much data in RAM as possible and that wont be possible if your data set is 1-2 gigs and becomes even more of a problem if your data set grows to 20-40 gigs.
Secondly they are labeled as "Low IO performance" so when your data swaps to disk (and it will based on the size of that data set), you are going to suffer from disk reads due to low IO throughput.
Be aware that micro instances are designed for spiky CPU usage, and you will be throttled to the "low background level" if you exceed the allotment.
The AWS Micro Documentation has good information of what they are intended for.
Between the CPU and not very good IO performance my experience with using micros for development/testing has not been very good. (larger instance types have been fine though), but a micro may work for your use case.
However, there are exceptions for a config or arbiter nodes, I believe a micro should be good enough for these types of machines.
There is also some mongodb documentation specific to EC2 which might help.
I am looking to use Berkeley DB to create a simple key-value storage system. The keys will be SHA-1 hashes, so they are in 160-bit address space. I have a simple server working, that was easy enough thanks to the fairly well written documentation from Berkeley DB website. However, I have some questions about how best to set up such a system, to get good performance and flexibility. Hopefully, someone has had more experience with Berkeley DB and can help me.
The simplest setup is a single process, with a single thread, handling a single DB; inserts and gets are performed on this one DB, using transactions.
Alternative 1: single process, multiple threads, single DB; inserts and gets are performed on this DB, by all the threads in the process.
Does using multiple threads provide much performance improvements? There is one single DB, and therefore it's on one disk, and therefore I am guessing I won't get too much boost. But if Berkeley DB caches a lot of stuff in memory, then perhaps one thread will be able to run and answer from cache while another has blocked waiting for disk? I am using GNU Pth, user level cooperative threading. I am not familiar with the details of Pth, so I am also not sure if with Pth you can have a userlevel thread run while another userlevel thread has blocked.
Alternative 2: single process, one or multiple threads, multiple DBs where each DB covers a fraction of the 160-bit address space for keys.
I see a few advantages in having multiple DBs: we can put them on different disks, less contention, easier to move/partition DBs onto different physical hosts if we want to do that. Does anyone have experience with this setup and see significant benefits?
Alternative 3: multiple processes, each with one thread, each handles a DB that covers a fraction of the 160-bit address space for keys.
This has the advantages of using multiple DBs, but we are using multiple processes. Is this better than the second alternative? I suspect using processes rather than user-level threads to get parallelism will get you better SMP caching behaviors (less invalidates, etc), but will I get killed with all the process overheads and context switches?
I would love to hear if someone has tried the options, and have seen positive or negative results.
Thanks.
Alternative 2 gives you high scalability. You basically partition your database across
multiple servers. If you need a high performance distributed key/value database, I would
suggest looking at membase. I am doing that right now but we need to run on an appliance
and would like to limit dependencies (of membase).
You can use BerkeleyDB replication and have read only copies with servers to serve read/get
requests.
I want to create a system that delivers user interface response within 100ms, but which requires minutes of computation. Fortunately, I can divide it up into very small pieces, so that I could distribute this to a lot of servers, let's say 1500 servers. The query would be delivered to one of them, which then redistributes to 10-100 other servers, which then redistribute etc., and after doing the math, results propagate back again and are returned by a single server. In other words, something similar to Google Search.
The problem is, what technology should I use? Cloud computing sounds obvious, but the 1500 servers need to be prepared for their task by having task-specific data available. Can this be done using any of the existing cloud computing platforms? Or should I create 1500 different cloud computing applications and upload them all?
Edit: Dedicated physical servers does not make sense, because the average load will be very, very small. Therefore, it also does not make sense, that we run the servers ourselves - it needs to be some kind of shared servers at an external provider.
Edit2: I basically want to buy 30 CPU minutes in total, and I'm willing to spend up to $3000 on it, equivalent to $144,000 per CPU-day. The only criteria is, that those 30 CPU minutes are spread across 1500 responsive servers.
Edit3: I expect the solution to be something like "Use Google Apps, create 1500 apps and deploy them" or "Contact XYZ and write an asp.net script which their service can deploy, and you pay them based on the amount of CPU time you use" or something like that.
Edit4: A low-end webservice provider, offering asp.net at $1/month would actually solve the problem (!) - I could create 1500 accounts, and the latency is ok (I checked), and everything would be ok - except that I need the 1500 accounts to be on different servers, and I don't know any provider that has enough servers that is able to distribute my accounts on different servers. I am fully aware that the latency will differ from server to server, and that some may be unreliable - but that can be solved in software by retrying on different servers.
Edit5: I just tried it and benchmarked a low-end webservice provider at $1/month. They can do the node calculations and deliver results to my laptop in 15ms, if preloaded. Preloading can be done by making a request shortly before the actual performance is needed. If a node does not respond within 15ms, that node's part of the task can be distributed to a number of other servers, of which one will most likely respond within 15ms. Unfortunately, they don't have 1500 servers, and that's why I'm asking here.
[in advance, apologies to the group for using part of the response space for meta-like matters]
From the OP, Lars D:
I do not consider [this] answer to be an answer to the question, because it does not bring me closer to a solution. I know what cloud computing is, and I know that the algorithm can be perfectly split into more than 300,000 servers if needed, although the extra costs wouldn't give much extra performance because of network latency.
Lars,
I sincerely apologize for reading and responding to your question at a naive and generic level. I hope you can see how both the lack of specifity in the question itself, particularly in its original form, and also the somewhat unusual nature of the problem (1) would prompt me respond to the question in like fashion. This, and the fact that such questions on SO typically emanate from hypotheticals by folks who have put but little thought and research into the process, are my excuses for believing that I, a non-practionner [of massively distributed systems], could help your quest. The many similar responses (some of which had the benefits of the extra insight you provided) and also the many remarks and additional questions addressed to you show that I was not alone with this mindset.
(1) Unsual problem: An [apparently] mostly computational process (no mention of distributed/replicated storage structures), very highly paralellizable (1,500 servers), into fifty-millisecondish-sized tasks which collectively provide a sub-second response (? for human consumption?). And yet, a process that would only be required a few times [daily..?].
Enough looking back!
In practical terms, you may consider some of the following to help improve this SO question (or move it to other/alternate questions), and hence foster the help from experts in the domain.
re-posting as a distinct (more specific) question. In fact, probably several questions: eg. on the [likely] poor latency and/or overhead of mapreduce processes, on the current prices (for specific TOS and volume details), on the rack-awareness of distributed processes at various vendors etc.
Change the title
Add details about the process you have at hand (see many questions in the notes of both the question and of many of the responses)
in some of the questions, add tags specific to a give vendor or technique (EC2, Azure...) as this my bring in the possibly not quite unbuyist but helpful all the same, commentary from agents at these companies
Show that you understand that your quest is somewhat of a tall order
Explicitly state that you wish responses from effective practionners of the underlying technologies (maybe also include folks that are "getting their feet wet" with these technologies as well, since with the exception of the physics/high-energy folks and such, who BTW traditionnaly worked with clusters rather than clouds, many of the technologies and practices are relatively new)
Also, I'll be pleased to take the hint from you (with the implicit non-veto from other folks on this page), to delete my response, if you find that doing so will help foster better responses.
-- original response--
Warning: Not all processes or mathematical calculations can readily be split in individual pieces that can then be run in parallel...
Maybe you can check Wikipedia's entry from Cloud Computing, understanding that cloud computing is however not the only architecture which allows parallel computing.
If your process/calculation can efficitively be chunked in parallelizable pieces, maybe you can look into Hadoop, or other implementations of MapReduce, for an general understanding about these parallel processes. Also, (and I believe utilizing the same or similar algorithms), there also exist commercially available frameworks such as EC2 from amazon.
Beware however that the above systems are not particularly well suited for very quick response time. They fare better with hour long (and then some) data/number crunching and similar jobs, rather than minute long calculations such as the one you wish to parallelize so it provides results in 1/10 second.
The above frameworks are generic, in a sense that they could run processes of most any nature (again, the ones that can at least in part be chunked), but there also exist various offerings for specific applications such as searching or DNA matching etc. The search applications in particular can have very short response times (cf Google for example) and BTW this is in part tied to fact that such jobs can very easily and quickly be chunked for parallel processing.
Sorry, but you are expecting too much.
The problem is that you are expecting to pay for processing power only. Yet your primary constraint is latency, and you expect that to come for free. That doesn't work out. You need to figure out what your latency budgets are.
The mere aggregating of data from multiple compute servers will take several milliseconds per level. There will be a gaussian distribution here, so with 1500 servers the slowest server will respond after 3σ. Since there's going to be a need for a hierarchy, the second level with 40 servers , where again you'll be waiting for the slowest server.
Internet roundtrips also add up quickly; that too should take 20 to 30 ms of your latency budget.
Another consideration is that these hypothethical servers will spend much of their time idle. That means they're powered on, drawing electricity yet not generating revenue. Any party with that many idle servers would turn them off, or at the very least in sleep mode just to conserve electricity.
MapReduce is not the solution! Map Reduce is used in Google, Yahoo and Microsoft for creating the indexes out of the huge data (the whole Web!) they have on their disk. This task is enormous and Map Reduce was built to make it happens in hours instead of years, but starting a Master controller of Map Reduce is already 2 seconds, so for your 100ms this is not an option.
Now, from Hadoop you may get advantages out of the distributed file system. It may allow you to distribute the tasks close to where the data is physically, but that's it. BTW: Setting up and managing an Hadoop Distributed File System means controlling your 1500 servers!
Frankly in your budget I don't see any "cloud" service that will allow you to rent 1500 servers. The only viable solution, is renting time on a Grid Computing solution like Sun and IBM are offering, but they want you to commit to hours of CPU from what I know.
BTW: On Amazon EC2 you have a new server up in a couple of minutes that you need to keep for an hour minimum!
Hope you'll find a solution!
I don't get why you would want to do that, only because "Our user interfaces generally aim to do all actions in less than 100ms, and that criteria should also apply to this".
First, 'aim to' != 'have to', its a guideline, why would u introduce these massive process just because of that. Consider 1500 ms x 100 = 150 secs = 2.5 mins. Reducing the 2.5 mins to a few seconds its a much more healthy goal. There is a place for 'we are processing your request' along with an animation.
So my answer to this is - post a modified version of the question with reasonable goals: a few secs, 30-50 servers. I don't have the answer for that one, but the question as posted here feels wrong. Could even be 6-8 multi-processor servers.
Google does it by having a gigantic farm of small Linux servers, networked together. They use a flavor of Linux that they have custom modified for their search algorithms. Costs are software development and cheap PC's.
It would seem that you are indeed expecting at least 1000-fold speedup from distributing your job to a number of computers. That may be ok. Your latency requirement seems tricky, though.
Have you considered the latencies inherent in distributing the job? Essentially the computers would have to be fairly close together in order to not run into speed of light issues. Also, the data center in which the machines would be would again have to be fairly close to your client so that you can get your request to them and back in less than 100 ms. On the same continent, at least.
Also note that any extra latency requires you to have many more nodes in the system. Losing 50% of available computing time to latency or anything else that doesn't parallelize requires you to double the computing capacity of the parallel portions just to keep up.
I doubt a cloud computing system would be the best fit for a problem like this. My impression at least is that the proponents of cloud computing would prefer to not even tell you where your machines are. Certainly I haven't seen any latency terms in the SLAs that are available.
You have conflicting requirements. You're requirement for 100ms latency is directly at odds with your desire to only run your program sporadically.
One of the characteristics of the Google-search type approach you mentioned in your question is that the latency of the cluster is dependent on the slowest node. So you could have 1499 machines respond in under 100ms, but if one machine took longer, say 1s - whether due to a retry, or because it needed to page you application in, or bad connectivity - your whole cluster would take 1s to produce an answer. It's inescapable with this approach.
The only way to achieve the kinds of latencies you're seeking would be to have all of the machines in your cluster keep your program loaded in RAM - along with all the data it needs - all of the time. Having to load your program from disk, or even having to page it in from disk, is going to take well over 100ms. As soon as one of your servers has to hit the disk, it is game over for your 100ms latency requirement.
In a shared server environment, which is what we're talking about here given your cost constraints, it is a near certainty that at least one of your 1500 servers is going to need to hit the disk in order to activate your app.
So you are either going to have to pay enough to convince someone to keep you program active and in memory at all times, or you're going to have to loosen your latency requirements.
Two trains of thought:
a) if those restraints are really, absolutely, truly founded in common sense, and doable in the way you propose in the nth edit, it seems the presupplied data is not huge. So how about trading storage for precomputation to time. How big would the table(s) be? Terabytes are cheap!
b) This sounds a lot like a employer / customer request that is not well founded in common sense. (from my experience)
Let´s assume the 15 minutes of computation time on one core. I guess thats what you say.
For a reasonable amount of money, you can buy a system with 16 proper, 32 hyperthreading cores and 48 GB RAM.
This should bring us in the 30 second range.
Add a dozen Terabytes of storage, and some precomputation.
Maybe a 10x increase is reachable there.
3 secs.
Are 3 secs too slow? If yes, why?
Sounds like you need to utilise an algorithm like MapReduce: Simplified Data Processing on Large Clusters
Wiki.
Check out Parallel computing and related articles in this WikiPedia-article - "Concurrent programming languages, libraries, APIs, and parallel programming models have been created for programming parallel computers." ... http://en.wikipedia.org/wiki/Parallel_computing
Although Cloud Computing is the cool new kid in town, your scenario sounds more like you need a cluster, i.e. how can I use parallelism to solve a problem in a shorter time.
My solution would be:
Understand that if you got a problem that can be solved in n time steps on one cpu, does not guarantee that it can be solved in n/m on m cpus. Actually n/m is the theoretical lower limit. Parallelism is usually forcing you to communicate more and therefore you'll hardly ever achieve this limit.
Parallelize your sequential algorithm, make sure it is still correct and you don't get any race conditions
Find a provider, see what he can offer you in terms of programming languages / APIs (no experience with that)
What you're asking for doesn't exist, for the simple reason that doing this would require having 1500 instances of your application (likely with substantial in-memory data) idle on 1500 machines - consuming resources on all of them. None of the existing cloud computing offerings bill on such a basis. Platforms like App Engine and Azure don't give you direct control over how your application is distributed, while platforms like Amazon's EC2 charge by the instance-hour, at a rate that would cost you over $2000 a day.