As far as I know there is Terracotta and Maglev. Are there any others?
Pretty much every big vendor got one, plus a handful of independent vendors:
memcached [1] — ubiquitous, community-driven;
Infinispan [2] — backed by JBoss, open-source;
Velocity [3] — commercial (Microsoft), in beta, .NET only;
Gemfire [4] — commercial (VMWare)
Coherence [5] — commercial (Oracle)
GigaSpaces XAP [6] — commercial
ScaleOut [7] — commercial
Terracotta [8] — commercial
Note that there is a pretty thin line between state sharing solutions and distributed caching solutions. I only listed the ones that keep the state in main memory, which are often dubbed "data grids" on the street.
Hope this helps.
[1] memcached.org
[2] jboss.org/infinispan
[3] blogs.msdn.com/b/velocity/
[4] www.gemstone.com/products/gemfire
[5] www.oracle.com/technetwork/middleware/coherence/overview/index.html
[6] gigaspaces.com
[7] www.scaleoutsoftware.com/products/scaleout-stateserver/
[8] www.terracotta.org
memcache : many major sites use it, Google AppEngine included. There are bindings to it for everything under the sun (pretty much ;-)
Memcached is probably the most heavily used one (as their biggest user Facebook shares 28TB of RAM with it at the moment).
Apart from MemCached, there is Velocity from Microsoft.
Since you mentioned MagLev, there's obviously also GemStone/S on top of which MagLev is built, and GemFire, their JVM/.NET/C++ product.
Related
I am writing a web application using VisualWorks Smalltalk, Seaside and Gemstone/S.
At the moment the session state for the client can be maintained only if the client always returns to the same image (though if the session expires the client can restart with any image).
I would like to understand whether it's feasible to share session state using the Gemstone/S database. This means straightforward http load balancing could be used and I wouldn't need to worry about image affinity for a large population of users.
I can see that all this is done "for free" with the Gemstone implementation of Seaside, but I would like to use Visualworks because it has a much more powerful IDE and I am already familiar with it. All references I can find on Google to this assume use of Gemstone smalltalk and the Gemstone implementation of Seaside.
Has anybody done this? If so are there any write ups of findings or tutorials I can follow? Many apologies if I have missed an obvious link on a search but I really couldn't see it.
As far as I know there is no easy way to do it. Very simplified, and ignoring many optimizations taken by Seaside, Seaside session is snapshot of execution stack waiting to be resumed. Migrating that frozen execution stack to another image and restarting it there is non trivial.
Our application uses the same stack (Seaside, VW, GS), but we're not using the full GBS interface between VW & GS which allows for one VW image to service several Seaside sessions. Even in this mix, however, session affinity to each VW image is required.
Your reasons for developing your Seaside app in VW makes sense. It is indeed a better development environment, but you may consider splitting development and deployment: write your code in VW and deploy in GLASS. That's the conventional way to use GLASS, although with Pharo for development.
I come across Terracotta as a distributed JVM that is stable and robust, however as my understanding of Terracotta is shallow, i am not sure if Terracotta is an alternative to JVMs?
It looks promising.
Terracotta is not a JVM, it's a shared memory backplane. It does not replace the JVM in any way. Terracotta now owns and makes several projects which can leverage this backplane.
They include
Ehcache
Sessions
Quartz
Amongst others. Their product BigMemory also helps to overcome some of the JVM Heap issues with very large allocations.
As Oracle sues Google over the Dalvik VM it becomes clear, that you cannot implement a Java VM without license from Oracle (EDIT: Matthew Flaschen points out, that the claims of Oracle may not be valid. Anyways we have currently a situation, where Oracle threats VM-implementations.). That may become the death for Open-Source-implementations of Java (like Apache Harmony).
I don't want to discuss the impact or the legitimation of this lawsuit. but as a Java-programmer I want to take a deeper look into the alternatives, to be prepared for every case. As I see the creation of a compiler as a minor problem, my main interest are alternative VM-implementations, that serve a similar purpose as the JVM.
The VM I'm looking for, should meet some conditions:
free of patent-issues
an Open-Source-implementation exists
potential for optimizations/good performance
platform independent (the VM can be ported to different platforms without bigger hurdles)
Please add some recommendations for me.
LLVM is a really good optimizing, low level virtual machine. It can support languages like C and C++, and does not have built in support for high level features like garbage collection.
VMKit is an implementation of the Java and CLI virtual machines on top of LLVM. Since it uses Java bytecode, this probably wouldn't help with the patent issues.
HLVM is another interesting high level virtual machine built on top of LLVM. It is probably different enough to avoid most well known patents, but it is mainly targeted at numerical computing and functional programming.
On the dynamically typed side, there is Parrot.
I am actually working on a compiler and VM for a language of my own design, but don't count on it ever being finished. ;-)
Keep in mind that any large piece of software will infringe on numerous patents, the important thing is how well known they are (and how much the patents' owners actively seek out infringers). Of course, the whole patent system is absurd, and we would be much better off getting rid of it.
I don't think there is any significant piece of software that is free from patent issues.
If you are an independent developer or working for a smaller company you probably won't get hit directly by the problems though. It's unlikely that big companies holding patents will go after lots of small claims - it's an expensive process and causes a lot of resentment. SCO tried something like that and it didn't work out too well for them.
I would concentrate on finding the best tool for the job without worrying too much about the patent issues, otherwise you will never get anything done.
GraalVM is a research project developed by Oracle Labs and already in production at Twitter. I can't believe my eyes that no one mentions anything about it, it’s so weird. Anyways, GraalVM is a well promising extension of the java virtual machine to support more language and execution modes for running applications like JavaScript, Python, Ruby, R, JVM-based languages, and LLVM-based languages such as C and C++.The GraalVM project includes a new high-performance Java compiler, itself called Graal, which can be used in a just-in-time configuration on the HotSpot VM, or in an ahead-of-time configuration on the SubstrateVM. The main goal of this project is to improve the performance of the java virtual machine base language to match the performance of native languages. Let’s sum up the novel features that this project offers and make a brief explanation according to the docs why you should adopt it.
Polyglot: All languages (even LLVM-based) share the same VM and its capabilities. Zero overhead interoperability between programming languages allows you to write polyglot applications and select the best language for your task
Native: Native images compiled with GraalVM ahead-of-time improve the startup time and reduce the memory footprint of JVM-based applications.
Embeddable: GraalVM can be embedded in both managed and native applications. There are existing integrations into OpenJDK, Node.js, Oracle Database, and MySQL GraalVM removes the isolation between programming languages and enables interoperability in a shared runtime. It can run either standalone or in the context of OpenJDK, Node.js, Oracle Database, or MySQL.
Performance: Graal benchmark reports show great performance improvements in almost all of its implementations thanks to the way that GraalVM performs object allocations
If someone don’t get convinced by now that is a good choice and it is a really awesome project you can see this talk by Christian Thalinger on “on why Graal is a good fit for Twitter”
As it is included in the license (according to SAP) we would prefer using Solution Manager over other tools, for the entire life-cycle of software development. Or is it highly recommended to use specific tools for the particular processes like Test Management? Any opinions?
in general before answering this question, please be aware that SAP will bring out a new support model and the features and functions available in your SolMan installation will differ according to the support you requested from SAP. If you stick to the Enterprise Support you will (nearly) get every functionality, for Standard Support you well get less and a lot of features will not be included. At the moment, SolMan 7.10 is in Ramp Up Phase and 7.20 will be released in 2011. Due to the fact, that SAP changes the kernel of the Solution Manager Stack, which is apparently CRM from 5.0 to 7.0 you should keep in mind, that any functionality you implement in your current SolMan will lead to high migration efforts.
Apart from this, if you look at the Enterprise version, my experience is that not all features are rather good and suitable. It also depends on the organization you are working in. The SAP tools focus only on SAP, so if you are working in an environment where non-SAP Java has an important part I would look for different tools. If you look into the change management (ChaRM), it is suitable for small landscapes and for big ones only with some effort. Here you should also consider at least to have a look at different technologies and tools. From my point, there are some things like monitoring, job scheduling etc. which are quite good, but for the more general application lifecycle management tools you should at least take other options into account.
Imagine that a large player is undertaking the construction of a new operating system, where backward compatibility requirements are limited to:
Run existing applications written in (or compiled to) JavaScript which are presented in HTML5 and styled with CSS3
Plug and play support for printers, external storage, and optical drives
Degrade gracefully when disconnected from the internet
Sufficient process quotas to support safely permitting tasks to run in the background, including timers
What specific features from existing research operating systems (such as Plan 9) would you like to see enter the mainstream through this channel? Please limit your suggestions to things that have been implemented, and provide a link to the implementation (or at least search terms).
From the Plan 9 docs:
Plan 9 began in the late 1980’s as an
attempt to have it both ways: to build
a system that was centrally
administered and cost-effective using
cheap modern microcomputers as its
computing elements.
Netbooks qualify as cheap modern microcomputers, and The Cloud qualifies as centrally administered. There is an opportunity to implement the features (in DDaviesBrackett's words) that we want netbooks to have other than by extending a 1970's time-sharing OS; the research operating systems may have proved the value of alternatives by example.
From the Plan 9 FAQ:
Subject: What are its key ideas?
Plan 9 exploits, as far as possible,
three basic technical ideas: first,
all the system objects present
themselves as named files that are
manipulated by read/write operations;
second, all these files may exist
either locally or remotely, and
respond to a standard protocol; third,
the file system name space - the set
of objects visible to a program - is
dynamically and individually
adjustable for each of the programs
running on a particular machine. The
first two of these ideas were
foreshadowed in Unix and to a lesser
extent in other systems, while the
third is new: it allows a new
engineering solution to the problems
of distributed computing and graphics.
Plan 9's approach means that
application programs don't need to
know where they are running; where,
and on what kind of machine, to run a
Plan 9 program is an economic decision
that doesn't affect the construction
of the application itself.
Does that not appear to be an excellent fit for the netbook/Cloud domain?
What operating system features I would advocate for Chrome OS?
Here my wish list as a Plan 9/Inferno fan:
Resources (ip stack, graphics, etc) as file systems.
Network transparent file system (ie., 9P).
Private per-process namespaces.
Factotum-like auth system (ie., no root user).
Pure UTF-8 everywhere.
Extremely lightweight processes.
Automatic snapshot and de-duplicating storage (ala venti+fossil).
And I guess many others, but this would be enough to make me quite happy.
This is not a 'OS feature' per see, but I would love to have a GUI with mouse-chording.
None.
I'd prefer for a new consumer OS, especially one targeted at Netbooks, to be very very good at doing the things that we already want OSes to be able to do rather than having time spent on features that are, by their nature, experimental.
(Of course, I'd be totally un-bothered by features I wasn't forced to use to develop on the platform; other people's toys are welcome as long as they don't make my job harder.)
I really think that Google might look into Plan9 for inspiration actually. Hearsay (the Internet) claims that several of those that initially developed UNIX and then later scrapped it for a better design (Plan9) are employed by Google. Google is also hosting its own version of Inferno, but I am not sure whether this is any central part of their plan. Further "evidence" could be that the plan9 authorization system (p9auth) for Linux was published by a Google researcher. The third "evidence" would be that Google claim that Chrome OS will have a novel security architecture.
The authorization seems to me to be one of the GREATEST parts of the Plan9 that can be included right now (/net would also be nice but there is no working code for that yet). The idea that a program that needs root access only gets limited access to the parts that are determined by the authorization server is definitely a great step forward compared to the now prevalent user/superuser/root division in Linux, where "a man in the middle" attacks can (theoretically) be done by gaining (full, as opposed to limited by the authorization server) root access via a bug in a program granted root.