Re: Does Cassandra support operations in a transaction?

Short story is that few if any of the NoSql systems supprot transactions natively. Thats oen of the big compromises they make. What they call "eventual consistancy" is actually eventual Durabiltiy in ACID terms. Consistancy, as meant by the C in ACID, is not gauranteed at all. On Wed, Aug 1, 20

Re: Does Cassandra support operations in a transaction?

t; col families. > > > You cannot have 2 different entities and ensure that changes to both will > be done and then only be visible to others. > > > Regards, > > > From: Jeffrey Kesselman mailto:jef...@gmail.com>> > Reply-To: "user@cassandra.apache.org&l

Re: Does Cassandra support operations in a transaction?

True consistancy, btw, pretty much is only possible in a transactional environment. On Thu, Aug 2, 2012 at 12:56 AM, Jeffrey Kesselman wrote: > Roshni, > > Thats not what consistancy in ACID means. Its not consistancy of reading > the ame data, its referntial integrity between re

Re: force gc?

Cassandra at least used to do disc cleanup as a side effect of garbage collection through finalizers. (This is a mistake for the reason outlined below.) It is important to understand that you can *never* "force* a gc in java. Even calling System.gc() is merely a hint to the VM. What you are doing

Re: Recommended OS

I haven't run Cassandra in production myself, but for other high load Java based servers I've had really good scaling success with OpenSolaris. In particular I've used Joyent's "SmartOS" which has the additional advantage of "bursting" to cover brief periods of exceptional load. On Tue, Feb 11,

Re: Recommended OS

rvers I've built. On Wed, Feb 12, 2014 at 1:52 PM, Robert Coli wrote: > On Wed, Feb 12, 2014 at 8:55 AM, Jeffrey Kesselman wrote: > >> I haven't run Cassandra in production myself, but for other high load >> Java based servers I've had really good scaling success wi

Re: Cequel is a full-featured Ruby ORM for Cassandra

why do you call it an ORM when Cassandra is not relational? On Wed, Feb 19, 2014 at 11:39 AM, Matthew A. Brown wrote: > Hi all, > > I recently released version 1.0 of Cequel, > a high-level Ruby library for Cassandra using CQL3. Version 1.0 provides an > object-

Re: Disable Nagle algoritm in thrift i.e. TCP_NODELAY

Most operating systems have a way to do this at the OS level. On Thu, Jan 26, 2012 at 8:17 AM, ruslan usifov wrote: > Hello > > Is it possible set TCP_NODELAY on thrift socket in cassandra? > -- It's always darkest just before you are eaten by a grue.

Re: Disable Nagle algoritm in thrift i.e. TCP_NODELAY

#x27;t need patch cassandra or thrift > code. > > I found this article > https://wiki.cs.columbia.edu:8443/pages/viewpage.action?pageId=12585536, > where упоминается mentioned coreTransport.TcpClient.NoDelay, but what is > this i misunderstand > > > > 2012/1/26 Jeffrey K

Re: Server Side Logic/Script - Triggers / StoreProc

It should be noted that, in a distributed storage environment, scripting *at the node of storage* is much more powerful then higher up at some broker. Its easy to do this wrong. 2012/4/27 Data Craftsman > Howdy, > > Some Polyglot Persistence(NoSQL) products started support server side > script

Re: Much more native memory used by Cassandra then the configured JVM heap size

What is your Native heap size? And how are you measuring memory usage? It woudl also hep to see the commandlien you are using to launch the JVM On Mon, Jun 11, 2012 at 9:14 PM, Jason Tang wrote: > Hi > > We have some problem with Cassandra memory usage, we configure the JVM > HEAP 6G, but after

Re: Much more native memory used by Cassandra then the configured JVM heap size

Btw. I suggest you spin up JConsole as it will give you much more detai kon what your VM is actually doing. On Mon, Jun 11, 2012 at 9:14 PM, Jason Tang wrote: > Hi > > We have some problem with Cassandra memory usage, we configure the JVM > HEAP 6G, but after runing Cassandra for several hour

Does anyone have Cassandra running on OpenSolaris?

I get this error: bin/cassandra: syntax error at line 29: `system_memory_in_mb=$' unexpected Thanks JK -- It's always darkest just before you are eaten by a grue.

Re: Does anyone have Cassandra running on OpenSolaris?

Ah. That solved it. ty. On Mon, May 9, 2011 at 11:29 AM, Roland Gude wrote: > > Use bash as a shell > > #bash bin/cassandra -f > > > -Ursprüngliche Nachricht- > Von: Jeffrey Kesselman [mailto:jef...@gmail.com] > Gesendet: Montag, 9. Mai 2011 17:12 >

Re: Crash when uploading large data sets

If this a 64bit VM? A 32bit Java VM with default c-heap settings can only actually use about 2GB of Java Heap. On Thu, May 12, 2011 at 8:08 PM, James Cipar wrote: > Oh, forgot this detail:  I have no swap configured, so swapping is not the > cause of the crash.  Could it be that I'm running out

Re: Cassandra Vs. Oracle Coherence

I believe coherence is their name for the TimesTen technology they bought. TT is an in memory SQL database that can run as a cache for Oracle. Its totally different from Cassandra. On the one hand it supports trad SQL whereas Cassandra does not. On the other hand Cassandra is truly distribute

Re: How to reduce the Read Latency.

What consistency are you asking for? On Fri, May 20, 2011 at 7:42 AM, Dikang Gu wrote: > Hi All, > I'm running three cassandra 0.7.4 nodes in a cluster, and I give 2G memory > to each node. > Now, I get the cfstats here: > Keyspace: UserMap > Read Count: 38411 > Read Latency: 123.54214613001484 m

Re: Inter node communication over UDP

TCP/IP byte over-head v. UDP really isnt that much if your packets are of any significant size (its 30 bytes). And as others have pointed out you can easily get more over-head with worse results trying to reinvent reliable transport on top of UDP. Remember that TCP/IP has had 30 years of developme

Re: Cassandra Vs. Oracle Coherence

s > massively scalable across LAN and WAN. > > In terms of comparing Cassandra and Coherence, I wouldn't. Coherence > is a data grid and most often used as a fault tolerant distributed > cache, though it does a lot more than that. Oracle bought Tangosol a > few years back. > >

Re: Forcing Cassandra to free up some space

Actually this is no gaurantee. Its a common misunderstanding that System.gc "forces" gc. It does not. It is a suggestion only. The vm always has the option as to when and how much it gcs On May 26, 2011 2:51 PM, "Jonathan Ellis" wrote:

Re: Forcing Cassandra to free up some space

ing that system.gc is only a suggestion; on > any VM you're likely to run Cassandra on, System.gc will actually > invoke a full collection. > > On Thu, May 26, 2011 at 2:18 PM, Jeffrey Kesselman wrote: >> Actually this is no gaurantee.   Its a common misunderstanding that >

Re: Forcing Cassandra to free up some space

s I have given on this subject over the years at Java One Conferences On Thu, May 26, 2011 at 3:53 PM, Jonathan Ellis wrote: > It's a common misunderstanding that system.gc is only a suggestion; on > any VM you're likely to run Cassandra on, System.gc will actually > invoke

Re: Forcing Cassandra to free up some space

ehavior is simply good engineering. On Thu, May 26, 2011 at 4:51 PM, Jonathan Ellis wrote: > I've read the relevant source. While you're pedantically correct re > the spec, you're wrong as to what the JVM actually does. > > On Thu, May 26, 2011 at 3:14 PM, Jeffrey

Re: Forcing Cassandra to free up some space

to get rid of all of the extra space it is using on disk? > > - Original Message ----- > From: "Jeffrey Kesselman" > To: user@cassandra.apache.org > Sent: Thursday, May 26, 2011 8:57:49 PM > Subject: Re: Forcing Cassandra to free up some space > > Which JVM

Re: Forcing Cassandra to free up some space

sing on disk? >> >> ----- Original Message - >> From: "Jeffrey Kesselman" >> To: user@cassandra.apache.org >> Sent: Thursday, May 26, 2011 8:57:49 PM >> Subject: Re: Forcing Cassandra to free up some space >> >> Which JVM?  Which coll

Re: Forcing Cassandra to free up some space

ing the -XX:-DisableExplicitGC flag. > > On Thu, May 26, 2011 at 5:58 PM, Konstantin  Naryshkin > wrote: >> So, in summary, there is no way to predictably and efficiently tell >> Cassandra to get rid of all of the extra space it is using on disk? >> >> ----- Original Message ---

Re: JRockit

Well, my information is old... But back in the heyday of VMs, JRockit really only had one specific area of performance advantage, which was in message passing, and all their benchmarks were tweaked to play to that. Id say its not coincidence that oracle has made this free shortly after they acqui

Re: CQL How to do

Is CQL really the path for the future for Cassandra? It seems to me by introducing a textual language that has to be parsed and understood, you are adding back in some of the inefficiency of SQl... 2011/6/4 aaron morton : > May be wrong but as far as I know thrift is still the official API, for n

Re: CQL How to do

helastpickle.com > > On 6 Jun 2011, at 03:27, Eric Evans wrote: > >> On Sun, 2011-06-05 at 00:51 -0400, Jeffrey Kesselman wrote: >>> Is CQL really the path for the future for Cassandra? >> >> CQL is no more or less "official" than the Thrift interface, an

Re: nosql yes but yescql, no?

While I agree the Thrift API sucks, Id love to see that sovled on a binary level, and CQl on top of that. JK On Wed, Jun 8, 2011 at 2:50 PM, Marcos Ortiz wrote: > On 06/08/2011 01:23 PM, SriSatish Ambati wrote: > > Gotta love, Eric! > http://www.slideshare.net/jericevans/nosql-yes-but-yescql-no

Re: nosql yes but yescql, no?

lse underneath that's > more efficient and CQL itself wouldn't have to change at all. > > On Jun 8, 2011, at 1:29 PM, Jeffrey Kesselman wrote: > >> While I agree the Thrift API sucks, Id love to see that sovled on a >> binary level, and CQl on top of that. >&

Re: New web client & future API

Correct me if I'm wrong, but AFAIK Hector is the only higher level APi I would consider "complete' right now, with support for things like fail-over. I notice in the latest Hector build he is starting to add CQL support, so thats what I'm sticking with. When he has CQL support done I'll decide i

Re: Forcing Cassandra to free up some space

eft. >> Some files stay more than 10 hours already. There is no guarantee that >> gc will cleanup all compacted sstable files. >> >> We have a great interest on the following ticket. >> https://issues.apache.org/jira/browse/CASSANDRA-2521 >> >> >> Regards

Re: Cassandra Clients for Java

I'm using Hector. AFAIK its the only one that supports failover today. On Fri, Jun 17, 2011 at 6:02 PM, Daniel Colchete wrote: > Good day everyone! > I'm getting started with a new project and I'm thinking about using > Cassandra because of its distributed quality and because of its performance.

Re: Cassandra Clients for Java

If by this you are obliquely referring to JDBC, I understand there is a CQL JDBC driver under development > new semantics on them that are neither Java's or Cassandra's, and I > Obviously thats going to support CQL, not SQL like existing JDBC drivers.

Re: faster ByteBuffer comparison

GetLong has to get it a byte at a time still to support endianess. Id have to think about it, but what you really want is to get it all into a byte array and then process it in 64bits. AIR there are some new array recasting things in Java 5+. Ill need to go look at them more closely... On Fri,

Re: faster ByteBuffer comparison

I'd fetch it all at once into a single byte array and try Arrays.equals() On Sat, Jul 2, 2011 at 12:45 PM, Jeffrey Kesselman wrote: > GetLong has to get it a byte at a time still to support endianess. > > Id have to think about it, but what you really want is to get it all >

Re: What does a write lock ?

Hi Jonnathan, This brings up an important question. I have been assuming that the validation check is part of the atomic update operation. Is this NOT the case? Which is to say, can the row be changed between the time the validation method is executed and the validated data is written? The reas

Re: What does a write lock ?

This has me more confused. Does this mean that ALL rows on a given node are only updated sequentially, never in parallel? On Thu, Jul 7, 2011 at 3:21 PM, Yang wrote: > just to add onto what jonathan said > > the columns are immutable . if u overwrite/ reconcile a new obj is > created and

Re: What does a write lock ?

The old row is accessible and my validation requires a comparison of the two. JK On Thu, Jul 7, 2011 at 3:23 PM, Yang wrote: > validation is on the new incoming column ,not the old row,right? > On Jul 7, 2011 8:25 AM, "Jeffrey Kesselman" wrote: > > Hi Jonnathan, >

Re: What does a write lock ?

rtion can happen in parallel > On Jul 7, 2011 9:24 AM, "Jeffrey Kesselman" wrote: > > This has me more confused. > > > > Does this mean that ALL rows on a given node are only updated > sequentially, > > never in parallel? > > > > On Thu, Jul 7,

Re: What does a write lock ?

to change underneath the validation call? On Thu, Jul 7, 2011 at 3:43 PM, Yang wrote: > no , the memtable is a concurrentskiplistmap > > insertion can happen in parallel > On Jul 7, 2011 9:24 AM, "Jeffrey Kesselman" wrote: > > This has me more confused. > > >

Re: What does a write lock ?

Not confusing, but assuming a few things. I made a more detailed post in the Datatstax forums. On Thu, Jul 7, 2011 at 10:27 PM, Jonathan Ellis wrote: > Sounds to me like you're confusing atomicity with isolation. > > On Thu, Jul 7, 2011 at 2:54 PM, Jeffrey Kesselman > wrote:

Re: What does a write lock ?

ith isolation. > > On Thu, Jul 7, 2011 at 2:54 PM, Jeffrey Kesselman > wrote: > > Yup, im even more confused.Lets talk about the model, not the > > implementation. > > AIUI updates to a row are atomic across all columns in that row at once, > > true? > > If

Re: What does a write lock ?

Really, as i lay in the bath thinking nabout it, I concluded what I am looking for is a very limited form of Consistency. Its consistency over a single row on a single node just for the period of update. On Thu, Jul 7, 2011 at 10:34 PM, Jeffrey Kesselman wrote: > Its not really isolation,

Re: What does a write lock ?

before, during, and after a process. And A -> A' and A -> B will each > be atomic for the key (based on my understanding). But, if A' and B are > changes to a different set of columns, I believe that would interleave, > which itself could be "inconsistent" from your

Re: What does a write lock ?

I am confused by what you mean by "Cassandra client code." Is this part of the Cassnadra server? My architecture is my "user" talks thrift to Cassandra.

Re: What does a write lock ?

validates Am. > > If validation succeeds, coordinator sends Am to the replica owners, > effectively creating A'. > > Neither A nor A' is ever explicitly assembled on the write path. > > On Fri, Jul 8, 2011 at 9:22 AM, Jeffrey Kesselman > wrote: > > Not quite, its more

Re: What does a write lock ?

will > > > On Fri, Jul 8, 2011 at 11:08 AM, Jeffrey Kesselman wrote: > >> I am confused by what you mean by "Cassandra client code." Is this part >> of the Cassnadra server? >> >> My architecture is my "user" talks thrift to Cassandra. >> >> >> > -- It's always darkest just before you are eaten by a grue.

Re: What does a write lock ?

alidate says "validate that the > byte > > array is a valid sequence for the type we are supposed to be comparing", > > which sounds like a local operation to me (e.g. it shouldn't fetch remote > > data, it's just saying "yep, this is a valid member of type

Re: What does a write lock ?

t; > array is a valid sequence for the type we are supposed to be comparing", > > which sounds like a local operation to me (e.g. it shouldn't fetch remote > > data, it's just saying "yep, this is a valid member of type T"). > > > > will > > >

Re: Out of memory error in cassandra

Are you on a 64 bit VM? A 32 bit vm will basically ignore any setting over 2GB On Mon, Jul 11, 2011 at 4:55 PM, Anurag Gujral wrote: > Hi All, >I am getting following error from cassandra: > ERROR [ReadStage:23] 2011-07-10 17:19:18,300 > DebuggableThreadPoolExecutor.java (line 103) E

Re: b-tree

Im not sure if I have an answer for you, anyway, but I'm curious A b-tree and a binary tree are not the same thing. A binary tree is a basic fundamental data structure, A b-tree is an approach to storing and indexing data on disc for a database. Which do you mean? On Wed, Jul 20, 2011 at 4

Re: Force a garbage collection with jmxterm from the shell

Technically, by the VM spec, you can never *force* a java VM to garbage collect. You can request, but thats it. Rather then open that whole debate again if anyone doubts this, i suggets they look back in the archives. JK On Thu, Aug 4, 2011 at 6:35 PM, Teijo Holzer wrote: > Hi, > > The foll