Has anyone else had CPU spikes after switching over to NHibernate?
We switched to using NHibernate about 2 years ago. Since then we've had issues with the server running using the CPU near 60 - 80. We also had issues with the server running out of memory.
Weve consistently been told to optimize our query. Which we did with only limited success. It wasnt until I recently upgraded from NHibernate 2.1 to 3.2 that we finally saw an improvement in the CPU. It dropped from a 60 percent average to about 30 percent. I was amazed, I was told by many who consider themselves experts that upgrading NHibernate would only produce limited improvements if any at all.
My question is ... Has anyone else noticed CPU spikes with NHibernate nd have they seen any improvement after doing a major version upgrade. And last, why exactly is the new version performing so much better? I know NHibernate 3 has a lot better support for linq and about 70 percent of my queries use Linq, so my guess is that may be part of the reason I'm seeing better performace.
Also, does anyone have any ideas how I can optimism NHibernate to produce even better CPU performance other than upgrading the dlls which I have already done.
I'm currently running NHibernate 3.2 and fluent NHibernate 1.2 upgraded from 2.1 and 1.0 respectively.
I suspect you have been told the same as I am about to recommend, but I urge you to look at all possibilities and discount them.
Weve consistently been told to optimize our query - Suspicions always lie with either the SQL generated by the ORM or the amount of time the DB takes to execute the query. This is sound advice and you must disprove this by using the following methods.
First I would set up a trace on the live database server that runs for a week. Once this is done you may find that you get suggestions on indexes or SQL related issues.
Secondly I would fire up NHProf on my development box and run some stress tests against heavily used pages or pages that have a lot of database trips to see what is going on behind the scenes with NHibernate. NHProf will give you advice about various problems including; select n+1, unbounded results, large number of rows returned, queries with too many joins etc. Again this tool is invaluable to bridge the gap between SQL server and your code.
Hopefully after this exercise you will have ideas on how to fix certain issues, introduce caching OR if you find you don't have any items to address give you valuable feedback that you can then post to the NHUser group.
After all if you think about it tens of thousands of users use NHibernate. I have used NHibernate myself for several years and subscribe to the NHusers group and I have not seen the CPU spike issue before. Always it turns out to be either; the SQL generated, the database is under pressure or large recordsets being hydrated
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We use Flyway 4 via Java API against MySQL 5.6 (which does not support transactional DDL). We run into infrequent cases where migrations fail, sometimes logical errors and sometimes because someone mucked with the database and things aren't in the right state.
So I'm wondering, should we delete rows from schema_version in this case and let the migration re-run, with either fixes to the migration or fixes to the database? We generally run a repair before migrate to fix any failed migrations, but then add a new one.
See also: Should I be worried about creating idempotent migrations while using Flyway?
I've been using Flyway 3 for the past couple of years and have just upgraded to 4 recently. So far it's successfully managed about 30 or so different projects and fits nicely into the delivery pipeline.
In that two year's we have definitely experienced a couple of migrations that made it out of a developers machine that we have wanted to eliminate from history. In those cases, deleting a row from schema_version is usually the answer - it's quicker, less process intensive than repair and has less risk in our situation. That being said, it's only ever made it as far as development / testing environments - so there has always been an not-prod environment that has received only the working migrations and no failed / undesired ones.
We definitely aim to make failed migrations a build time problem. So migration versions are validated, migrations themselves are executed and a component run against that migrated database as part of the build for a component. I'd say this largely contributes to our infrequent issues when dealing with such a large number of migration managed projects.
Can't recall where I read it and if it was in the context of Flyway, but it was something along the lines of The price we pay for this kind of automation is discipline - so hearing something like "someone mucked around with the database manually" would definitely be a red flag for me.
In conclusion...
Minimizing the opportunities for failures I think is the key. But when failures do happen, having your strategy defined to meet an acceptable level of risk is the best you can do - repair and deleting of schema_version both have their drawbacks.
We have the following setup:
Virtual server, Intel Xeon X5650 # 2.67Ghz (4 processors)
8GB RAM
Windows server 2008 Standard 64bit
Sql Server Express
IIS 7.5
Our database is only 200mb. We are running an ASP.net app. We recently ran into some performance issues, ~200 concurrent connections was causing 100% CPU usage (mostly consumed by IIS) and bringing the response time to around 20sec! After some tweaks to our code we have been able to run a load test from loader.io with 1500 concurrent users over 1 minute and our response time at the end was around 5 seconds and CPU was around 95%, again consumed mainly by IIS, our memory was sitting at around 4GB usage. However we are expecting bigger spikes than 1500, anywhere up to around 4000 users in a short amount of time.
My questions are the following:
1) Is this normal performance for our current setup? Our site is quite intensive on the database and we are using Entity Framework.
2) Would upgrading to Sql Web edition have any benefit seeing as though our Database is so small?
3) Do you think that this type of setup could handle 4000 users?
4) Any suggestions on what we could do to handle this load?
I know this is somewhat subjective, but any answers are much appreciated.
Is this normal performance for our current setup?
Depends on your code. Did you profile the code to make sure you dont have anything stupid in there?
Our site is quite intensive on the database and we are using Entity Framework.
Again, did you pofile to figure out you spend a lot of time in entity framework? It is slow, ut the question is what "intensive" means. This is what profilers are for.
Would upgrading to Sql Web edition have any benefit seeing as though our Database is so
small?
Help, my pizza comes too late. Wiould upgrade to a larger car help? You say yourself that you spend the time in IIS, not sql server.
Do you think that this type of setup could handle 4000 users?
You think my car is big enough? Note I don't tell you what I need it for. Without looking at usage patterns and your code - no idea. THAT SAID: the server is pathetic compared to what you buy today. As such, this is a irrelevant question - just upgrade if you have to.
Any suggestions on what we could do to handle this load?
Load test + profiler, optimize code. Get bigger server. Realize that we dont have crystal balls to figure out how good / bad / stupid your code is.
Number one question arising here, is: did you deploy RELEASE or DEBUG compiled binaries of your project?
Upgrade to WebEdition will not solve any problem here, since the difference in the versions is very simple: WebEdition is just throttled in the internal scheduler/etc. - so you will be just fine with the standard edition.
My experience is that the most crucial aspect of concurrent request is the amount of server memory and the consumption of this memory by your code.
As the physical memory is consumed, the server starts to swap from physical to virtual memory which slows down processing dramatically and leads to symptoms you describe.
I would start with putting another 8gb of ram into the server. In the meantime try to optimize your code so that less data is processed during requests or less memory is used. Also, move sql server to a separate machine so that there is no competition between iis and sql server when it comes to memory availability.
With your current machine, I doubt the problem is the IIS itself, but rather related to the way your app is designed and/or utilize frameworks. I personally learned just recently that IIS requests including multiple rounds trips to the database can be measured in hundreds of micro-seconds, not hundreds of milliseconds... A single locking bug, or unbalanced queuing can limit your application scalability and regardless of your hardware specs [https://twitter.com/michaelzino/status/454512110165184512].
Entity Framework is known for validating your models against the database schema for the first initial calls. I would suggest profiling your app layers, starting from the data access layer, or the intrinsic database calls, and going up.
I got problems with memory in my asp.net application. The problem is that I can't see any problems when running it locally (between 100-200mb) but on the production system I get 503-errors because of the memory limit (512mb) being reached (running it on shared hosting).
How can I pin down the problem? I don't think that I have access to the current memory usage, at least I have not found any way and the company who hosts my site says that there is no way.
I have absolutely no experience tracking down memory leaks. :)
Thanks
Use a trial version of RedGate's Memory Profiler
http://www.red-gate.com/products/ants_memory_profiler/index.htm?utm_source=google&utm_medium=cpc&utm_content=unmet_need&utm_campaign=antsmemoryprofiler&gclid=CJLijJblm6UCFQqAgwodHjokHg
or JetBrains dotTrace
http://www.jetbrains.com/profiler/
Both tools are very simple and easy to use and do a great job of identifying protential memory leaks etc.
Most common sources of leaks are missed dispose calls, or poor management of event handlers... depending on the size of your code base, you may be able to just "spot" the trouble spots, but I find using a tool speeds up the process greatly as both will present before/after snapshots of the object graphs so you can see what is and is not being cleaned up by th GC.
Good overview of memory management:
http://msdn.microsoft.com/en-us/library/ee817660.aspx
I don't know that this is completely answerable here, but here's a start for you... The other answers are addressing specific memory issues, but tirst, you need to understand how memory is allocated and deallocated (reserved, used, and released) by the computer, the .NET runtime and in turn, your program.
Then you need to understand your code well enough to understand which functions happen on a per-user bases, and look at how much memory is being used. From there, you can get into your code and track down issues, but you need a firm understanding of the basics.
If I were you, I'd start with this article, and plan on spending some more time researching and learning. Hoefully, this article will not only answer questions, but give you enough knowledge to ask more specific/better questions. It's a good article, and I believe it will really help you, but it's not the whole kit-n-kaboodle. There's a quite a bit to learn.
http://msdn.microsoft.com/en-us/magazine/cc188781.aspx
The article is a bit old, and I'm assuming you're using more recent tools, so when you're done digesting that article, jump to http://msdn.microsoft.com/en-us/library/ms182372.aspx to learn about the Visual Studio Profiler.
This isn't necessarily an answer to your problem, per se, but more of a suggestion as to how to track things like this down.
One thing that I've found helps in tracking down these sorts of issues is to build into your application some sort of instrumentation. It could start as simple as providing a cache of sorts to keep track of pages request durations. This could be accomplished by creating a static cache class to hold either all (not recommended) or just long-running requests that you define (a safer approach) and have it all triggered in the OnBegin and OnEnd events (an HTTP module would be ideal). You could then create a basic dashboard page to list the contents of the cache to see potential places for trouble.
First things first... 503 is not only because of memory. If your application crashes 5 times in 5 minutes, due to rapid fail the application pool gets shut down and you get 503 - Service unavailable error.
500 MB odd memory seems pretty less to me and hence, memory could be adding to your problem. If it is 503 error, it means you have troubleshoot the issue from a crash perspective. Link
If you are having memory issues, you will typically get Out of memory exceptions, in which case, you should take multiple memory dumps of your process (w3wp.exe) and analyze it. Link has many posts on how you should analyze the memory dumps for memory leak. Right now, it would be too early for you to call it a memory leak.
I am interested to create portal on cassandra services, since I faced some performance and scale issues starting from 1 million of records.
Definitely, it could be solved, but I am interested on other options.
My main issues is cost of updating all necessary indexes, to make reading fast.
First, is cassandra is good way for asp.net programmers? I mean, maybe there is some other projects, which worth to take a look
And second, can you provide any documentation samples on how to start with cassandra programming from C#?
since I faced performance and scale issues starting from 1 million of records.
Maybe your design was not that good, NoSQL is not a magic bullet for bad design. I have multi billion row tables and 95% of the response is sub second. Also what do you mean by updating indexes, do you mean updating statistics or rebuilding indexes?
since I faced performance and scale
issues starting from 1 million of
records.
You know, the one million mark for modern databases is where it is not something "totally ridiculously small" where you can ignore actually knowing what you do. Below one million is "tiny". I have a 800 million row table and get a LOT of sql running through with it - no problem at all.
First, is cassandra is good way for
asp.net programmers?
I would more suggest a basic book about SQL, reading the documentation and POSSIBLY throwing some hardware on the problem. As in: having totally bad hardware will kill all data management systems.
If you are using Cassandra for your .NET Application take a look at Aquiles. I developed it based on my company needs. If you find it useful or need any help let me know.
You can't really speak of Cassandra documentation. There's a myriad of partial tutorials on the web.
You may want to setup Linux in a virtual machine, because the windows build process is quite challenging, to say the least. (http://www.virtualbox.org, http://www.ubuntu.com)
Here's the howto:
http://www.ridgway.co.za/archive/2009/11/06/net-developers-guide-to-getting-started-with-cassandra.aspx
Note that the cassandra SVN url and the code sample have changed since the writing of this tutorial.
Here's another C# client:
http://github.com/mattvv/hectorsharp
And here some sample code:
http://www.copypastecode.com/26752/
Note that you need to download the latest Java Development Kit (JDK) from Sun for Linux.
It's not in the repositories of Ubuntu 10.04.
Then you need to type
export JAVA_HOME="/path/to/jdk"
in order for Cassandra to find your Java installation.
You might also want to take a look at:
http://en.wikipedia.org/wiki/NoSQL
Especially the taxonomy section is interesting.
Make sure Cassandra is the right type of NoSQL solution for your problem, e.g. use Neo4J if your problem actually is a graph problem.
Also, you need to make sure your NoSQL solution is ACID-compliant.
For example, Neo4J is the only ACID-compliant NoSQL graph engine.
Edit: Here's a jumpstart guide for Windows, without compiling:
http://coderjournal.com/2010/03/cassandra-jump-start-for-the-windows-developer/
http://www.ronaldwidha.net/2010/06/23/running-cassandra-on-windows-first-attempt/
http://www.yafla.com/dforbes/Getting_Started_with_Apache_Cassandra_a_NoSQL_frontrunner_on_Windows/
Instead of cassandra you might take a look at: ravendb. Supposedly it is a document store made with and created for .Net. It has Linq integration, and is (again supposedly) very fast.
As with any new technology, read if it helps you with your specific case, and check if it is proven technology (Do they have mainstream clients using it).
Before you go into this route see if you can't optimize your current solution first. Check if your queries are fast, if the indexes are done correctly, and if you can't remove load by adding caching.
Last nut not least, if adding some processors to your SQL machine might fix issues, it is typically a much cheaper solution.
If you want to do something new, then instead of going for noSQL, you might want to consider trying a database cluster.
The idea is when two machines each search half of the original database at the same time, you have half the search time without totally redesigning your existing database.
I am curious as to what others are using in this situation. I know a couple of the options that are out there like a memcached port or ScaleOutSoftware. The memcached ports don't seem to be actively worked on (correct me if I'm wrong). ScaleOutSoftware is too expensive for me (I don't doubt it is worth it). This is not to say that I don't want to hear about people using memcached or ScaleOutSoftware. I'm just stating what I "know" at this point.
So my question is basically this: for those of you ACTIVELY using distributed caching, what are you using, are you happy with it, and what should I look out for?
I am moving to two servers very soon...both will be at the same location. I use caching fairly heavily (but carefully) to reduce the load on my database server.
Edit: I downloaded Scaleout Software's solution. I've coded for it and it seems to work real well. I just have to decide if my wallet will part with the cash for it. :) Anyone have experiences good or bad with ScaleoutSoftware?
Edit Again: It's been a little while since I asked this? Any more thoughts on it? We ended up buying the solution from ScaleOutSoftware and have been happy with it, but I'm curious what others are doing.
Microsoft has a product pending code-named Velocity. It's still in CTP, and is moving slowly, but looks like it will be pretty good. We'll be beating it up in the near future to see how it handles what we want it to do (> 2 million read/writes per hour). Will post back with results.
There is a 100% native .NET, well documented open source (LGPL) project called Shared Cache. Looks like it is not yet mentioned on SO, but it's promising and should be able to do what most people expect from a distributed cache. It even supports different strategies like distributed or replicated caching etc.
I will update this post with more details as soon as I had a chance to try it on a real project.
We're currently using an incredibly simple cache that I wrote in a couple of hours, based on re-hosting the ASP.NET cache in a Windows Service (more info and source code here). I won't pretend it's anywhere near as optimised as something like Memcached but we were just looking for something simple and free until Velocity came along, and it's held up extremely well even under fairly heavy load.
It comes down to our personal preference for core components - i.e. ones that affect whether the site is available or not - that they are either (a) supported by a vendor with a history of rapid and high quality support, or (b) written by us so that if something goes wrong we can fix it quickly. Open source is all well and good, and indeed we do use some OSS, but if your site is offline then unfortunately newsgroups et al don't have a 1 hour SLA, and just because it's OSS doesn't mean you have the necessary understanding or ability to fix it yourself.
We are using the memcached port for Windows and we are very pleased with it. The enyim.com memcached client API is great and easy to work with. It's also open source, which is a big advantage, if you ask me.
We are now using this setup in a production web-app and it has helped a lot in improving its performance.
There's a great .NET wrapper/port found here on Codeplex. Awesomesauce!
We use memcached with the enyim library in a production environment (www.funda.nl). Works fine, very pleased with it, but we did notice a substantial raise in CPU use on the clients. Presumably due to the serializing/deserializing going on. We do around 1000 reads per second.
One tried and tested product by 100's of customers worldwide is NCache. Its
a feature rich product that lets you store session state in a redundant and highly available manner, lets you share data
within the enterprise as well as bridging for WAN communication essentially acting as a data fabric and lastly it lets you build an elastic caching tier so that when
your application scales, you can add servers to the cache and actually boost performance further.