Re: Repair has now effect

[Patricio Echagüe]

embarrassing.

Chef somehow ran in that box and updated the schema with a version of it
that had RF=1.

Sorry about that.

On Mon, Sep 3, 2012 at 1:45 AM, Radim Kolar  wrote:

>
>   INFO [AntiEntropySessions:6] 2012-09-02 15:46:23,022
>> AntiEntropyService.java (line 663) [repair #%s] No neighbors to repair with
>> on range %s: session completed
>>
> you have RF=1, or too many nodes are down.
>

Repair has now effect

[Patricio Echagüe]

Hey folks, perhaps a dumb question but I ran into this situation and it's a
bit unclear what's going on.

We are running a 3 nodes cluster with RF 3 (cass 1.0.11). We had one issue
with one node and it was down for like 1 hour.

I brought the node up again as soon as I realized it was down (and ganglia
+ nagios triggered some alerts). But when running repair to make sure it
had all the data, I get this message:

 INFO [AntiEntropySessions:6] 2012-09-02 15:46:23,022
AntiEntropyService.java (line 663) [repair #%s] No neighbors to repair with
on range %s: session completed

Am I missing something ?

thanks

Re: Efficiency of hector's setRowCount (and setStartKey!)

[Patricio Echagüe]

On Thu, Oct 13, 2011 at 9:39 AM, Don Smith  wrote:

> **
> It's actually setStartKey that's the important method call (in combination
> with setRowCount). So I should have been clearer.
>
> The following code performs as expected, as far as returning the expected
> data in the expected order.  I believe that the use of IndexedSliceQuery's
> setStartKey will support efficient queries -- avoiding repulling the entire
> data set from cassandra. Correct?
>

correct

>
>
> void demoPaging() {
> String lastKey = processPage("don","");  // get first
> batch, starting with "" (smallest key)
> lastKey = processPage("don",lastKey);// get second
> batch starting with previous last key
> lastKey = processPage("don",lastKey);// get third batch
> starting with previous last key
>//
> }
>
> // return last key processed, null when no records left
> String processPage(String username, String startKey) {
> String lastKey=null;
> IndexedSlicesQuery
> indexedSlicesQuery =
> HFactory.createIndexedSlicesQuery(keyspace,
> stringSerializer, stringSerializer, stringSerializer);
>
> indexedSlicesQuery.addEqualsExpression("user", username);
>
> indexedSlicesQuery.setColumnNames("source","ip");
>
> indexedSlicesQuery.setColumnFamily(ourColumnFamilyName);
> indexedSlicesQuery.setStartKey(startKey);
> //
> <
> indexedSlicesQuery.setRowCount(batchSize);
> QueryResult String>> result =indexedSlicesQuery.execute();
> OrderedRows rows =
> result.get();
> for(Row row:rows ){
> if (row==null) { continue; }
> totalCount++;
> String key = row.getKey();
>
>     if (!startKey.equals(key))
> {lastKey=key;}
> }
> totalCount--;
> return lastKey;
> }
>
>
>
>
>
>
> On 10/13/2011 09:15 AM, Patricio Echagüe wrote:
>
> Hi Don. No it will not. IndexedSlicesQuery will read just the amount of
> rows specified by RowCount and will go to the DB to get the new page when
> needed.
>
>  SetRowCount is doing indexClause.setCount(rowCount);
>
> On Mon, Oct 10, 2011 at 3:52 PM, Don Smith  wrote:
>
>> Hector's IndexedSlicesQuery has a setRowCount method that you can use to
>> page through the results, as described in
>> https://github.com/rantav/hector/wiki/User-Guide .
>>
>> rangeSlicesQuery.setRowCount(1001);
>>  .
>> rangeSlicesQuery.setKeys(lastRow.getKey(),  "");
>>
>> Is it efficient?  Specifically, suppose my query returns 100,000 results
>> and I page through batches of 1000 at a time (making 100 executes of the
>> query). Will it internally retrieve all the results each time (but pass only
>> the desired set of 1000 or so to me)? Or will it optimize queries to avoid
>> the duplication?  I presume the latter. :)
>>
>> Can IndexedSlicesQuery's setStartKey method be used for the same effect?
>>
>>   Thanks,  Don
>>
>
>
>

Re: Hector has a website

[Patricio Echagüe]

Hi Aaron. does it still happen ? We didn't set up any password on the page.

On Tue, Oct 11, 2011 at 9:15 AM, Aaron Turner  wrote:

> Just a FYI:
>
> http://hector-client.org is requesting a username/pass
> http://www.hector-client.org is working fine
>
> On Fri, Oct 7, 2011 at 12:51 AM, aaron morton 
> wrote:
> > Thanks, will be handy for new peeps.
> > A
> > -
> > Aaron Morton
> > Freelance Cassandra Developer
> > @aaronmorton
> > http://www.thelastpickle.com
> > On 7/10/2011, at 12:00 PM, Patricio Echagüe wrote:
> >
> > Hi, I wanted to let you all know that Hector client has a website.
> > http://hector-client.org
> > There are links to documentation, Javadoc and resources from the
> community.
> > If you have a personal blog and want us to include the link, let us know.
> > Feedback is always welcome.
> > Thanks!
> > Hector Team.
> >
>
>
>
> --
> Aaron Turner
> http://synfin.net/ Twitter: @synfinatic
> http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix &
> Windows
> Those who would give up essential Liberty, to purchase a little temporary
> Safety, deserve neither Liberty nor Safety.
> -- Benjamin Franklin
> "carpe diem quam minimum credula postero"
>

Re: Efficiency of hector's setRowCount

[Patricio Echagüe]

Hi Don. No it will not. IndexedSlicesQuery will read just the amount of rows
specified by RowCount and will go to the DB to get the new page when needed.

SetRowCount is doing indexClause.setCount(rowCount);

On Mon, Oct 10, 2011 at 3:52 PM, Don Smith  wrote:

> Hector's IndexedSlicesQuery has a setRowCount method that you can use to
> page through the results, as described in https://github.com/rantav/**
> hector/wiki/User-Guide .
>
> rangeSlicesQuery.setRowCount(**1001);
>  .
> rangeSlicesQuery.setKeys(**lastRow.getKey(),  "");
>
> Is it efficient?  Specifically, suppose my query returns 100,000 results
> and I page through batches of 1000 at a time (making 100 executes of the
> query). Will it internally retrieve all the results each time (but pass only
> the desired set of 1000 or so to me)? Or will it optimize queries to avoid
> the duplication?  I presume the latter. :)
>
> Can IndexedSlicesQuery's setStartKey method be used for the same effect?
>
>   Thanks,  Don
>

Re: Hector Problem Basic one

[Patricio Echagüe]

Hi, Hector does not retry on a down server. In the unit tests where you have
just one server, Hector will pass the exception to the client.

Can you tell us please what your test looks like ?

2011/10/12 Wangpei (Peter) 

>  I only saw this error message when all Cassandra nodes are down.
>
> How you get the Cluster and how you set the hosts?
>
> ** **
>
> *发件人:* CASSANDRA learner [mailto:cassandralear...@gmail.com]
> *发送时间:* 2011年10月12日 14:30
> *收件人:* user@cassandra.apache.org
> *主题:* Re: Hector Problem Basic one
>
> ** **
>
> Thanks for the reply ben.
>
> Actually The problem is, I could not able to run a basic hector example
> from eclipse. Its throwing "me.prettyprint.hector.api.
>
> exceptions.HectorException: All host pools marked
> > down. Retry burden pushed out to client
>
> "
> Can you please let me know why i am getting this
>
> 
>
> On Tue, Oct 11, 2011 at 3:54 PM, Ben Ashton  wrote:*
> ***
>
> Hey,
>
> We had this one, even tho in the hector documentation it says that it
> retry s failed servers even 30 by default, it doesn't.
>
> Once we explicitly set it to X seconds, when ever there is a failure,
> ie with network (AWS), it will retry and add it back into the pool.
>
> Ben
>
>
> On 11 October 2011 11:09, CASSANDRA learner 
> wrote:
> > Hi Every One,
> >
> > Actually I was using cassandra long time back and when i tried today, I
> am
> > getting a problem from eclipse. When i am trying to run a basic hector
> > (java) example, I am getting an exception
> > me.prettyprint.hector.api.exceptions.HectorException: All host pools
> marked
> > down. Retry burden pushed out to client. . But My server is up. Node tool
> > also whows that it is up. I donno what happens..
> >
> > 1.)Is it any thing to do with JMX port.
> > 2.) What is the storage port in casandra.yaml and jmx port in
> > cassandra-env.sh
> >
> >
> >
>
> ** **
>

Hector has a website

[Patricio Echagüe]

Hi, I wanted to let you all know that Hector client has a website.

http://hector-client.org

There are links to documentation, Javadoc and resources from the community.

If you have a personal blog and want us to include the link, let us know.

Feedback is always welcome.

Thanks!

Hector Team.

Re: Write everywhere, read anywhere

[Patricio Echagüe]

On Wed, Aug 3, 2011 at 4:00 PM, Philippe  wrote:

> Hello,
> I have a 3-node, RF=3, cluster configured to write at CL.ALL and read at
> CL.ONE. When I take one of the nodes down, writes fail which is what I
> expect.
> When I run a repair, I see data being streamed from those column
> families... that I didn't expect. How can the nodes diverge ? Does this mean
> that reading at CL.ONE may return inconsistent data ?
>

we abort the mutation before hand when there are enough replicas alive. If a
mutation went through and in the middle of it a replica goes down, in that
case you can write to some nodes and the request will Timeout.
In that case the CL.ONE may return inconsistence data.

>
> Question 2 : I've doing this rather than CL.QUORUM because I've been
> expecting CL.ONE to return data faster than CL.QUORUM. Is that a good
> assumption ? Yes, it's ok for writes to be down for a while.
>

When you hit a node that own the piece of data, CL.ONE will be faster as you
don't have to wait for a read across the network to reach another node.
For CL.QUORUM we fire reads in parallel to all the replicas and wait until
completing quorum. If I'm not wrong, in some cases the difference may be
negligible for CL.ONE and CL.QUORUM when you hit a coordinator that doesn't
own the data since you are going  over the network anyway (assuming all
nodes take the same time to reply)

>
> Thanks
>

Re: Counter Column in Cassandra

[Patricio Echagüe]

It's a column whose content represents a distributed counter.

http://wiki.apache.org/cassandra/Counters

On Mon, Jun 13, 2011 at 8:29 AM, Sijie YANG  wrote:

> Hi, All
>
> I am newbie to cassandra. I have a simple question but don't find any clear
> answer by searching google:
> What's the meaning of counter column in Cassandra?
>
> Best
>
>
>

Re: Site Not Surviving a Single Cassandra Node Crash

[Patricio Echagüe]

What is the consistency level you are using ?

And as Ed said, if you can provide the stacktrace that would help too.

On Sat, Apr 9, 2011 at 7:02 PM, aaron morton wrote:

> btw, the nodes are a tad out of balance was that deliberate ?
>
> http://wiki.apache.org/cassandra/Operations#Token_selection
> http://wiki.apache.org/cassandra/Operations#Load_balancing
>
>
> Aaron
>
> On 10 Apr 2011, at 08:44, Ed Anuff wrote:
>
> Sounds like the problem might be on the hector side.  Lots of hector
> users on this list, but usually not a bad idea to ask on
> hector-us...@googlegroups.com (cc'd).
>
> The jetty servers stopping responding is a bit vague, somewhere in
> your logs is an error message that should shed some light on where
> things are going awry.  If you can find the exception that's being
> thrown in hector and post that, it'd make it much easier to help you
> out.
>
> Ed
>
> On Sat, Apr 9, 2011 at 12:11 PM, Vram Kouramajian
>  wrote:
>
> The hector clients are used as part of our jetty servers. And, the
>
> jetty servers stop responding when one of the Cassandra nodes go down.
>
>
> Vram
>
>
> On Sat, Apr 9, 2011 at 11:54 AM, Joe Stump  wrote:
>
> Did the Cassandra cluster go down or did you start getting failures from
> the client when it routed queries to the downed node? The key in the client
> is to keep working around the ring if the initial node is down.
>
>
> --Joe
>
>
> On Apr 9, 2011, at 12:52 PM, Vram Kouramajian wrote:
>
>
> We have a 5 Cassandra nodes with the following configuration:
>
>
> Casandra Version: 0.6.11
>
> Number of Nodes: 5
>
> Replication Factor: 3
>
> Client: Hector 0.6.0-14
>
> Write Consistency Level: Quorum
>
> Read Consistency Level: Quorum
>
> Ring Topology:
>
>   OwnsRange  Ring
>
>
> 132756707369141912386052673276321963528
>
> 192.168.89.153Up 4.15 GB   33.87%
>
> 20237398133070283622632741498697119875 |<--|
>
> 192.168.89.155Up 5.17 GB   18.29%
>
> 51358066040236348437506517944084891398 |   ^
>
> 192.168.89.154Up 7.41 GB   33.97%
>
> 109158969152851862753910401160326064203v   |
>
> 192.168.89.152Up 5.07 GB   6.34%
>
> 119944993359936402983569623214763193674|   ^
>
> 192.168.89.151Up 4.22 GB   7.53%
>
> 132756707369141912386052673276321963528|-->|
>
>
> We believe that our setup should survive the crash of one of the
>
> Cassandra nodes. But, we had few crashes and the system stopped
>
> functioning until we brought back the Cassandra nodes.
>
>
> Any clues?
>
>
> Vram
>
>
>
>
>
>

Re: Re: Re: Re: Quorum, Hector, and datacenter preference

[Patricio Echagüe]

Glad it worked

2011/3/25 

> very cool. thanks for the info. this is exactly what we need.
>
>
> On Mar 25, 2011 8:22am, Patricio Echagüe  wrote:
> >
> > It's a cassandra consistency level
> > On Mar 24, 2011 11:44 PM, jonathan.co...@gmail.com> wrote:> Patricio -
> > >
> > > I haven't heard of local_quorum. Is that a cassandra setting or
> something
> >
> > > you specify in the client?
> > >
> > > On Mar 24, 2011 8:44pm, Patricio Echagüe patric...@gmail.com> wrote:
> > >> Doesn't CL=LOCAL_QUORUM solve your problem?
> >
> > >
> > >> On Thu, Mar 24, 2011 at 9:33 AM, jonathan.co...@gmail.com> wrote:
> > >
> > >
> > >> Hi Nate -
> > >
> > >> That sounds really promising and I'm looking forward to trying that
> out.
> >
> > >
> > >> My original question came up while thinking how to achieve quorum
> (with
> > >> rf=3) with a loss of 1 of 2 data centers. My logic was that if you had
> 2
> > >> replicas in the same data center where the client originally written
> to,
> >
> > >> then that client is guaranteed to be able to satisfy quorum, even if
> the
> > >> other data center is unreachable.
> > >
> > >
> > >
> > >> But I think there is no way to guarantee where the first write is
> written
> >
> > >> to. That would be based on the token range, which could very well be
> in
> > >> any data center.
> > >
> > >> Jon
> > >
> > >
> > >
> > >
> > >
> > >
> > >> On Mar 24, 2011 3:05pm, Nate McCall n...@datastax.com> wrote:
> >
> > >> > We have a load balancing policy which selects the host best on
> latency
> > >> >
> > >> > and uses a Phi convict algorithm in a method similar to
> DynamicSnitch.
> > >
> > >
> > >> >
> >
> > >> > Using this policy, you would inherently get the closest replica
> > >> >
> > >> > whenever possible as that would most likely be the best performing.
> > >> >
> > >> >
> > >> >
> >
> > >> > This policy is still in trunk and 0.7.0 tip. We should have a new
> > >
> > >
> > >> >
> > >> > release out containing the above in the next few days.
> > >> >
> > >> >
> >
> > >> >
> > >> > On Thu, Mar 24, 2011 at 8:46 AM, Jonathan Colby
> > >> >
> > >> > jonathan.co...@gmail.com> wrote:
> > >
> > >
> > >> >
> >
> > >> > > Indeed I found the big flaw in my own logic. Even writing to
> > >> the "local" cassandra nodes does not guarantee where the replicas will
>
> > >> end up. The decision where to write the first replica is based on the
> >
> > >> token ring, which is spread out on all nodes regardless of datacenter.
>
> > >> right ?
> > >
> > >
> > >> >
> > >> > >
> > >> >
> > >> > > On Mar 24, 2011, at 2:02 PM, Jonathan Colby wrote:
> >
> > >> >
> > >> > >
> > >> >
> > >> > >> Hi -
> > >> >
> > >> > >>
> > >> >
> > >> > >> Our cluster is spread between 2 datacenters. We have a
> >
> > >> straight-forward IP assignment so that OldNetworkTopology
> (rackinferring
> > >> snitch) works well. We have cassandra clients written in Hector in
> each
> > >> of those data centers. The Hector clients all have a list of all
> >
> > >> cassandra nodes across both data centers. RF=3.
> > >
> > >
> > >> >
> > >> > >>
> > >> >
> > >> > >> Is there an order as to which data center gets the first write?
> In
> >
> > >> other words, would (or can) the Hector client do its first write to
> the
> > >> cassandra nodes in its own data center?
> > >
> > >
> > >> >
> > >> > >>
> > >> >
> > >> > >> It would be ideal it Hector chose the "local" cassandra nodes.
> That
> >
> > >> way, if one data center is unreachable, the Quorum of replicas in
> > >> cassandra is still reached (because it was written to the working data
>
> > >> center first).
> > >
> > >
> > >> >
> >
> > >> > >>
> > >> >
> > >> > >> Otherwise, if the cassandra writes are really random from the
> Hector
> > >> client point-of-view, a data center outage would result in a read
> failure
> >
> > >> for any data that has 2 replicas in the lost data center.
> > >
> > >
> > >> >
> > >> > >>
> > >> >
> > >> > >> Is anyone doing this? Is there a flaw in my logic?
> >
> > >> >
> > >> > >>
> > >> >
> > >> > >>
> > >> >
> > >> > >
> > >> >
> > >> > >
> > >> >
> > >
> > >
> > >
> > >
> > >
> >
> > >
> >
> >
>

Re: is it possible to mutate Columns and CounterColumn in the same batch mutation?

[Patricio Echagüe]

thank you both. That makes Hector design much easier as well.

On Fri, Mar 25, 2011 at 2:50 AM, Sylvain Lebresne wrote:

> 2011/3/25 Jonathan Ellis :
> > You can't have them both in the same Mutation struct, but you can have
> > them in the map>> that is the "batch."
>
> Actually you can't, because we created a different thrift structure
> (CounteMutation) to hold
> counter mutations. Looking back, we really just did that to have a
> totally separate API for
> counters, but not sure that was a good idea. I've created
> CASSANDRA-2384 to merge
> CounterMutation into Mutation.
>
> --
> Sylvain
>
> > 2011/3/24 Patricio Echagüe :
> >> Hi folks, I'm modeling the partitioned counters into Hector and given
> the
> >> non-inheritance of Thrift, I don't see how to add a ColumnCounter and a
> >> Column in the same batch mutation.
> >> Is it possible do achieve? or are both in fact different mutations?
> >> Thanks
> >
> >
> >
> > --
> > Jonathan Ellis
> > Project Chair, Apache Cassandra
> > co-founder of DataStax, the source for professional Cassandra support
> > http://www.datastax.com
> >
>

Re: weird cassandra issue

[Patricio Echagüe]

could you paste the code that does that?

On Fri, Mar 25, 2011 at 6:47 AM, Anurag Gujral wrote:

> Hi All,
>   I am using cassandra 0.7.3 and thrift 0.0.5 when I am trying to
> write to cassandra using batch_mutate I get the following error:
> InvalidRequestException(why:Key may not be empty)
> at
> org.apache.cassandra.thrift.Cassandra$batch_mutate_result.read(Cassandra.java:16007)
> at
> org.apache.cassandra.thrift.Cassandra$Client.recv_batch_mutate(Cassandra.java:894)
> at
> org.apache.cassandra.thrift.Cassandra$Client.batch_mutate(Cassandra.java:868)
> Please let me know if you guys know about it. I am passing the correct key
> and it is not null.
>
> Thanks
> Anurag
>

is it possible to mutate Columns and CounterColumn in the same batch mutation?

[Patricio Echagüe]

Hi folks, I'm modeling the partitioned counters into Hector and given the
non-inheritance of Thrift, I don't see how to add a ColumnCounter and a
Column in the same batch mutation.

Is it possible do achieve? or are both in fact different mutations?

Thanks

Re: Re: Quorum, Hector, and datacenter preference

[Patricio Echagüe]

Doesn't CL=LOCAL_QUORUM solve your problem?

On Thu, Mar 24, 2011 at 9:33 AM,  wrote:

> Hi Nate -
>
> That sounds really promising and I'm looking forward to trying that out.
>
> My original question came up while thinking how to achieve quorum (with
> rf=3) with a loss of 1 of 2 data centers. My logic was that if you had 2
> replicas in the same data center where the client originally written to,
> then that client is guaranteed to be able to satisfy quorum, even if the
> other data center is unreachable.
>
> But I think there is no way to guarantee where the first write is written
> to. That would be based on the token range, which could very well be in any
> data center.
>
> Jon
>
>
>
>
> On Mar 24, 2011 3:05pm, Nate McCall  wrote:
> > We have a load balancing policy which selects the host best on latency
> >
> > and uses a Phi convict algorithm in a method similar to DynamicSnitch.
> >
> > Using this policy, you would inherently get the closest replica
> >
> > whenever possible as that would most likely be the best performing.
> >
> >
> >
> > This policy is still in trunk and 0.7.0 tip. We should have a new
> >
> > release out containing the above in the next few days.
> >
> >
> >
> > On Thu, Mar 24, 2011 at 8:46 AM, Jonathan Colby
> >
> > jonathan.co...@gmail.com> wrote:
> >
> > > Indeed I found the big flaw in my own logic.   Even writing to the
> "local" cassandra nodes does not guarantee where the replicas will end up.
> The decision where to write the first replica is based on the token ring,
> which is spread out on all nodes regardless of datacenter.   right ?
> >
> > >
> >
> > > On Mar 24, 2011, at 2:02 PM, Jonathan Colby wrote:
> >
> > >
> >
> > >> Hi -
> >
> > >>
> >
> > >> Our cluster is spread between 2 datacenters.   We have a
> straight-forward IP assignment so that OldNetworkTopology (rackinferring
> snitch) works well.We have cassandra clients written in Hector in each
> of those data centers.   The Hector clients all have a list of all cassandra
> nodes across both data centers.  RF=3.
> >
> > >>
> >
> > >> Is there an order as to which data center gets the first write?In
> other words, would (or can) the Hector client do its first write to the
> cassandra nodes in its own data center?
> >
> > >>
> >
> > >> It would be ideal it Hector chose the "local" cassandra nodes.  That
> way, if one data center is unreachable, the Quorum of replicas in cassandra
> is still reached (because it was written to the working data center first).
> >
> > >>
> >
> > >> Otherwise, if the cassandra writes are really random from the Hector
> client point-of-view, a data center outage would result in a read failure
> for any data that has 2 replicas in the lost data center.
> >
> > >>
> >
> > >> Is anyone doing this?  Is there a flaw in my logic?
> >
> > >>
> >
> > >>
> >
> > >
> >
> > >
> >
>

Re: unique key generation

[Patricio Echagüe]

If you are a Hector user, TimeUUIDUtils can be used to create Time UUIDs.

https://github.com/rantav/hector/blob/master/core/src/main/java/me/prettyprint/cassandra/utils/TimeUUIDUtils.java


On Mon, Feb 7, 2011 at 2:11 PM, Kallin Nagelberg  wrote:

> Maybe I can just use java5's UUID.. Need to research how this is
> effective across multiple clients..
>
> On Mon, Feb 7, 2011 at 4:57 PM, Kallin Nagelberg
>  wrote:
> > Hey,
> >
> > I am developing a session management system using Cassandra and need
> > to generate unique sessionIDs (cassandra columnfamily keys). Does
> > anyone know of an elegant/simple way to accomplish this? I am not sure
> > about using time based uuids on the client as there a chance that
> > multiple clients could generate the same ID. I've heard suggestions of
> > using zookeeper as a source for the IDs, but was just hoping that
> > there might be something simpler for my purposes.
> >
> > Thanks,
> > -Kal
> >
>

Re: TSocket timing out

[Patricio Echagüe]

The recommendation is to wait few milliseconds and retry.

For Example if you use Hector ( I don't think it is your case), Hector will
retry to different nodes in your cluster and the retry mechanisms is tunable
as well.

On Sat, Jan 29, 2011 at 2:20 PM, buddhasystem  wrote:

>
> When I do a lot of inserts into my cluster (>10k at a time) I get timeouts
> from Thrift, the TScoket.py module.
>
> What do I do?
>
> Thanks,
>
> Maxim
>
> --
> View this message in context:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/TSocket-timing-out-tp5973548p5973548.html
> Sent from the cassandra-u...@incubator.apache.org mailing list archive at
> Nabble.com.
>

Re: Basic question on a write operation immediately followed by a read

[Patricio Echagüe]

Roshan, when a client invoke a write, the write goes first to commit log and
later to memtable. After that it returns to the client.

After it reaches the memtable, that data is ready to be read.

The reads consolidates de data from the memtables and sstables unless there
is a hit in the row cache.

does it help?

On Mon, Jan 24, 2011 at 8:57 PM, Roshan Dawrani wrote:

> Thanks for your inputs, Victor.
>
> In my app, it's a bit event driven.
>
> We do writes and fire events and listeners then read - so we can't predict
> how soon the reads will come. Sometimes they came too fast, which is better
> for our app, if we can have a Cassandra DB level understanding that they
> won't miss the writes, if they come too fast :-)
>
> Or, if there is anything we should do to make sure that reads happen in an
> assured manner.
>
>
> On Tue, Jan 25, 2011 at 10:22 AM, Victor Kabdebon <
> victor.kabde...@gmail.com> wrote:
>
>> Again don't take it as a 100% sure answer because it is not an area that I
>> have really explored.
>>
>> So yes I think that reads are made from Memtables.
>> Theoretically yes, however it is very unlikely : your get must be build
>> and send before the commitlog updates the Memtable (which is like inserting
>> in a Memtable, a matter of microseconds).
>> Possible configuration : Just wait a second or so to do your "get" query
>> (I imagine that it works after one second because you don't report this
>> problem)... Other than that no not really. I have not done any application
>> with those time constraints.
>>
>> Best regards,
>> Victor Kabdebon
>>
>> 2011/1/24 Roshan Dawrani 
>>
>>> On Tue, Jan 25, 2011 at 9:57 AM, Victor Kabdebon <
>>> victor.kabde...@gmail.com> wrote:
>>>
>>>  As far as I remember, please correct me if I am wrong, on a one node
 cluster :
 First Commitlog is updated then almost immediatly after order is send to
 the memtable to add this new insert. You might have a very short delay
 between the two. I don't know your configuration but especially if you
 insert from a distant server to a node you should look at their sync..
 Otherwise if it doesn't appear I can offer no explanation for this
 behavior...

>>>
>>> As of now, I am on an app server with an embedded cassandra server, so no
>>> possibility of clocks out-of-sync.
>>>
>>> So, I understand from you that client call returns after updating the
>>> commit log and updates to memtables are async after that - with
>>> how-much-ever short a delay tried by Cassandra?
>>>
>>> And the reads are always off memtables?
>>>
>>> So, theoretically, there is a possibility of a read missing a write
>>> because it has not come to memtables from the commit log yet?
>>>
>>> Is there anything that I can tell about my configuration that would help?
>>>
>>
>>
>

Re: Converting a TimeUUID to a long (timestamp) and vice-versa

[Patricio Echagüe]

Roshan, the first 64 bits does contain the version. The method
UUID.timestamp() indeed takes it out before returning. You are right in that
point. I based my comment on the UUID spec.

What I am not convinced is that the framework should provide support to
create an almost identical UUID where only the timestamp is the same
(between the two UUIDs).

UUID.equals() and UUID.compareTo() does compare the whole bit set to say
that two objects are the same. It does compare the first 64 bits to avoid
comparing the rest in case the most significant bits already show a
difference.

But coming to your point, should Hector provide that kind of support or do
you feel that the problem you have is specific to your application ?

I feel like UUID is as it says an Unique Identifier and creating a sort-of
UUID based on a previous timestamp disregarding the least significant bits
is not the right support Hector should expose.

Thoughts?

On Wed, Jan 5, 2011 at 6:30 PM, Roshan Dawrani wrote:

> Hi Patricio,
>
> Thanks for your comment. Replying inline.
>
> 2011/1/5 Patricio Echagüe 
>
> Roshan, just a comment in your solution. The time returned is not a simple
>> long. It also contains some bits indicating the version.
>
>
> I don't think so. The version bits from the most significant 64 bits of the
> UUID are not used in creating timestamp() value. It uses only time_low,
> time_mid and time_hi fields of the UUID and not version, as documented here:
>
> http://download.oracle.com/javase/1.5.0/docs/api/java/util/UUID.html#timestamp%28%29.
>
>
> When the same timestamp comes back and I call
> TimeUUIDUtils.getTimeUUID(tmp), it internally puts the version back in it
> and makes it a Time UUID.
>
>
>> On the other hand, you are assuming that the same machine is processing
>> your request and recreating a UUID base on a long you provide. The
>> clockseqAndNode id will vary if another machine takes care of the request
>> (referring to your use case) .
>>
>
> When I recreate my UUID using the timestamp() value, my requirement is not
> to arrive at the exactly same UUID from which timestamp() was derived in the
> first place. I need a recreated UUID *that should be equivalent in terms
> of its time value* - so that filtering the time-sorted columns using this
> time UUID works fine. So, if the lower order 64 bits (clockseq + node)
> become different, I don't think it is of any concern because the UUID
> comparison first goes by most significant 64 bits, i.e. the time value and
> that should settle the time comparison in my use case.
>
>
>> Is it possible for you to send the UUID to the view? I think that would be
>> the correct behavior as a simple long does not contain enough information to
>> recreate the original UUID.
>>
>
> In my use case, the non-Java clients will be receiving a number of such
> UUIDs then and they will have to sort them chronologically. I wanted to
> avoid bits based UUID comparison in these clients. Long timestamp() value is
> perfect for such ordering of data elements and I send much lesser amount of
> data over the wire.
>
>
>>  Does it make sense?
>>
>
> Nearly everything makes sense to me :-)
>
> --
> Roshan
> Blog: http://roshandawrani.wordpress.com/
> Twitter: @roshandawrani <http://twitter.com/roshandawrani>
> Skype: roshandawrani
>
>


-- 
Patricio.-

Re: Converting a TimeUUID to a long (timestamp) and vice-versa

[Patricio Echagüe]

Roshan, just a comment in your solution. The time returned is not a simple
long. It also contains some bits indicating the version.
On the other hand, you are assuming that the same machine is processing your
request and recreating a UUID base on a long you provide. The
clockseqAndNode id will vary if another machine takes care of the request
(referring to your use case) .

Is it possible for you to send the UUID to the view? I think that would be
the correct behavior as a simple long does not contain enough information to
recreate the original UUID.

Does it make sense?

On Wed, Jan 5, 2011 at 8:36 AM, Nate McCall  wrote:

> It was our original intention on discussing this feature was to have
> back-and-forth conversion from timestamps (we were modelling similar
> functionality in Pycassa). It's lack of inclusion may have just been
> an oversight. We will add this in Hector trunk shortly - thanks for
> the complete code sample.
>
>
>
> On Tue, Jan 4, 2011 at 10:06 PM, Roshan Dawrani 
> wrote:
> > Ok, found the solution - finally ! - by applying opposite of what
> > createTime() does in TimeUUIDUtils. Ideally I would have preferred for
> this
> > solution to come from Hector API, so I didn't have to be tied to the
> private
> > createTime() implementation.
> >
> > 
> > import java.util.UUID;
> > import me.prettyprint.cassandra.utils.TimeUUIDUtils;
> >
> > public class TryHector {
> > public static void main(String[] args) throws Exception {
> > final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH =
> > 0x01b21dd213814000L;
> >
> > UUID u1 = TimeUUIDUtils.getUniqueTimeUUIDinMillis();
> > final long t1 = u1.timestamp();
> >
> > long tmp = (t1 - NUM_100NS_INTERVALS_SINCE_UUID_EPOCH) / 1;
> >
> > UUID u2 = TimeUUIDUtils.getTimeUUID(tmp);
> > long t2 = u2.timestamp();
> >
> > System.out.println(u2.equals(u1));
> > System.out.println(t2 == t1);
> > }
> >
> > }
> >  
> >
> >
> > On Wed, Jan 5, 2011 at 8:15 AM, Roshan Dawrani 
> > wrote:
> >>
> >> If I use com.eaio.uuid.UUID directly, then I am able to do what I need
> >> (attached a Java program for the same), but unfortunately I need to deal
> >> with java.util.UUID in my application and I don't have its equivalent
> >> com.eaio.uuid.UUID at the point where I need the timestamp value.
> >>
> >> Any suggestion on how I can achieve the equivalent using Hector
> library's
> >> TimeUUIDUtils?
> >>
> >> On Wed, Jan 5, 2011 at 7:21 AM, Roshan Dawrani  >
> >> wrote:
> >>>
> >>> Hi Victor / Patricio,
> >>>
> >>> I have been using Hector library's TimeUUIDUtils. I also just looked at
> >>> TimeUUIDUtilsTest also but didn't find anything similar being tested
> there.
> >>>
> >>> Here is what I am trying and it's not working - I am creating a Time
> >>> UUID, extracting its timestamp value and with that I create another
> Time
> >>> UUID and I am expecting both time UUIDs to have the same timestamp()
> value -
> >>> am I doing / expecting something wrong here?:
> >>>
> >>> ===
> >>> import java.util.UUID;
> >>> import me.prettyprint.cassandra.utils.TimeUUIDUtils;
> >>>
> >>> public class TryHector {
> >>> public static void main(String[] args) throws Exception {
> >>> UUID someUUID = TimeUUIDUtils.getUniqueTimeUUIDinMillis();
> >>> long timestamp1 = someUUID.timestamp();
> >>>
> >>> UUID otherUUID = TimeUUIDUtils.getTimeUUID(timestamp1);
> >>> long timestamp2 = otherUUID.timestamp();
> >>>
> >>> System.out.println(timestamp1);
> >>> System.out.println(timestamp2);
> >>> }
> >>> }
> >>> ===
> >>>
> >>> I have to create the timestamp() equivalent of my time UUIDs so I can
> >>> send it to my UI client, for which it will be simpler to compare "long"
> >>> timestamp than comparing UUIDs. Then for the "long" timestamp chosen by
> the
> >>> client, I need to re-create the equivalent time UUID and go and filter
> the

Re: Converting a TimeUUID to a long (timestamp) and vice-versa

[Patricio Echagüe]

In Hector framework, take a look at TimeUUIDUtils.java

You can create a UUID using   TimeUUIDUtils.getTimeUUID(long time); or
TimeUUIDUtils.getTimeUUID(ClockResolution clock)

and later on, TimeUUIDUtils.getTimeFromUUID(..) or just UUID.timestamp();

There are some example in TimeUUIDUtilsTest.java

Let me know if it helps.



On Tue, Jan 4, 2011 at 10:27 AM, Roshan Dawrani wrote:

> Hello Victor,
>
> It is actually not that I need the 2 UUIDs to be exactly same - they need
> to be same timestamp wise.
>
> So, what I need is to extract the timestamp portion from a time UUID (say,
> U1) and then later in the cycle, use the same long timestamp value to
> re-create a UUID (say, U2) that is equivalent of the previous one in terms
> of its timestamp portion - i.e., I should be able to give this U2 and filter
> the data from a column family - and it should be same as if I had used the
> original UUID U1.
>
> Does it make any more sense than before? Any way I can do that?
>
> rgds,
> Roshan
>
>
> On Tue, Jan 4, 2011 at 11:46 PM, Victor Kabdebon <
> victor.kabde...@gmail.com> wrote:
>
>> Hello Roshan,
>>
>> Well it is normal to do not be able to get the exact same UUID from a
>> timestamp, it is its purpose.
>> When you create an UUID you have in fact two information : random 64 bits
>> number - 64 bits timestamp. You put that together and you have your uuid.
>> .
>> So unless you save your random number two UUID for the same milli( or
>> micro) second are different.
>>
>> Best regards,
>> Victor K.
>> http://www.voxnucleus.fr
>>
>> 2011/1/4 Roshan Dawrani 
>>
>> Hi,
>>> I am having a little difficulty converting a time UUID to its timestamp
>>> equivalent and back. Can someone please help?
>>>
>>> Here is what I am trying. Is it not the right way to do it?
>>>
>>> ===
>>> UUID someUUID = TimeUUIDUtils.getUniqueTimeUUIDinMillis();
>>>
>>> long time = someUUID.timestamp(); /* convery from UUID to a long
>>> timestamp */
>>> UUID otherUUID = TimeUUIDUtils.getTimeUUID(time); /* do the
>>> reverse and get back the UUID from timestamp */
>>>
>>> System.out.println(someUUID); /* someUUID and otherUUID should be
>>> same, but are different */
>>> System.out.println(otherUUID);
>>> ===
>>>
>>> --
>>> Roshan
>>> Blog: http://roshandawrani.wordpress.com/
>>> Twitter: @roshandawrani 
>>> Skype: roshandawrani
>>>
>>>
>>
>
>
> --
> Roshan
> Blog: http://roshandawrani.wordpress.com/
> Twitter: @roshandawrani 
> Skype: roshandawrani
>
>


-- 
Patricio.-

Re: Any GUI for Cassandra database on Windows?

[Patricio Echagüe]

The error you mentioned sounds like one of the server/client is using
TFramedTransport and the other one TSocket. I saw the same error when that
happened.

On Mon, Dec 27, 2010 at 9:15 PM, Roshan Dawrani wrote:

> Sorry. Will do that.
>
> I am using Cassandra 0.7.0-rc2.
>
> I will try this DB client. Thanks.
>
>
> On Tue, Dec 28, 2010 at 10:41 AM, Narendra Sharma <
> narendra.sha...@gmail.com> wrote:
>
>> Please do mention the Cassandra version you are using in all ur queries.
>> It helps.
>>
>> Try https://github.com/driftx/chiton
>>
>> Thanks,
>> Naren
>>
>>
>> On Mon, Dec 27, 2010 at 7:37 PM, Roshan Dawrani 
>> wrote:
>>
>>> Hi,
>>>
>>> Is there a GUI client for a Cassandra database for a Windows based setup?
>>>
>>> I tried the one available at http://code.google.com/p/cassandra-gui/,
>>> but it always fails to connect with "error: Cannot read. Remote site has
>>> closed. Tried to read 4 bytes, but only got 0 bytes."
>>>
>>> --
>>> Roshan
>>> Blog: http://roshandawrani.wordpress.com/
>>> Twitter: @roshandawrani 
>>> Skype: roshandawrani
>>>
>>>
>>
>


-- 
Patricio.-

Re: Is it possible to read from one row, several SuperColumns with all their Columns in one call?

[Patricio Echagüe]

Hey thanks Aaron. It finally worked. The API reference looked a bit
confusing to me.

I used (as you suggested):
ColumnParent parent = new ColumnParent(
);
SlicePredicate sp = new SlicePredicate();
sp.setColumn_names( );

after calling get_slice() as result, i got the super columns I
passed in the list with ALLl their columns in one call.

so now, just IF I WANTED TO, would it be possible to get just a subset
of columns contained in those supercolumns instead of all of them
assuming that the amount of columns are lot and for performance issues
i want to avoid moving a lot of data over the network?

2010/7/22 Patricio Echagüe :
> Hi Aaron, the problem I have is that those UUIDs are random numbers.
> 2,3,4 are not sequential unfortunately. I don't think there is an API
> like mutiget_slice for key but for Super Column names.
>
> Is there any other way to specify a list of super column names to read
> where those names are not sequential?
>
> thanks
>
>
> On Wed, Jul 21, 2010 at 5:58 PM, Aaron Morton  wrote:
>> Take a look at the  get_slice  function http://wiki.apache.org/cassandra/API
>>
>> You could send one with a ColumnParent that only specifies the ColumnFamily
>> and a SlicePredicate with a SliceRange where the start and finish values are
>> empty strings. Set the count to an appropriate level to get them all (e.g.
>> 1000) or make multiple calls.
>>
>>
>> Aaron
>>
>>
>> On 22 Jul, 2010,at 12:05 PM, Patricio Echagüe  wrote:
>>
>> Hi all, apologize before hand if this question sounds a bit dumb but I
>> don't see what API I should use (if there is any)
>>
>> this is my model:
>>
>> row key A:
>> SC_UUID_1:
>> Col1, Col2, Col3
>> SC_UUID_2:
>> Col1, Col2, Col3
>> SC_UUID_3:
>> Col1, Col2, Col3
>> SC_UUID_4:
>> Col1, Col2, Col3
>> SC_UUID_5:
>> Col1, Col2, Col3
>>
>> SC_UUID(i) are random UUIDs.
>>
>> Is there any way to read in one call from row A, the SC 2,3,4 with all
>> their columns? The amount of columns in every SuperColumn is not big
>> at all. normally less than 20.
>>
>> Thanks
>> --
>> Patricio-
>>
>
>
>
> --
> Patricio.-
>



-- 
Patricio.-

Re: Is it possible to read from one row, several SuperColumns with all their Columns in one call?

[Patricio Echagüe]

Hi Aaron, the problem I have is that those UUIDs are random numbers.
2,3,4 are not sequential unfortunately. I don't think there is an API
like mutiget_slice for key but for Super Column names.

Is there any other way to specify a list of super column names to read
where those names are not sequential?

thanks


On Wed, Jul 21, 2010 at 5:58 PM, Aaron Morton  wrote:
> Take a look at the  get_slice  function http://wiki.apache.org/cassandra/API
>
> You could send one with a ColumnParent that only specifies the ColumnFamily
> and a SlicePredicate with a SliceRange where the start and finish values are
> empty strings. Set the count to an appropriate level to get them all (e.g.
> 1000) or make multiple calls.
>
>
> Aaron
>
>
> On 22 Jul, 2010,at 12:05 PM, Patricio Echagüe  wrote:
>
> Hi all, apologize before hand if this question sounds a bit dumb but I
> don't see what API I should use (if there is any)
>
> this is my model:
>
> row key A:
> SC_UUID_1:
> Col1, Col2, Col3
> SC_UUID_2:
> Col1, Col2, Col3
> SC_UUID_3:
> Col1, Col2, Col3
> SC_UUID_4:
> Col1, Col2, Col3
> SC_UUID_5:
> Col1, Col2, Col3
>
> SC_UUID(i) are random UUIDs.
>
> Is there any way to read in one call from row A, the SC 2,3,4 with all
> their columns? The amount of columns in every SuperColumn is not big
> at all. normally less than 20.
>
> Thanks
> --
> Patricio-
>



-- 
Patricio.-

Is it possible to read from one row, several SuperColumns with all their Columns in one call?

[Patricio Echagüe]

Hi all, apologize before hand if this question sounds a bit dumb but I
don't see what API I should use (if there is any)

this is my model:

row key A:
 SC_UUID_1:
 Col1, Col2, Col3
 SC_UUID_2:
 Col1, Col2, Col3
 SC_UUID_3:
 Col1, Col2, Col3
 SC_UUID_4:
 Col1, Col2, Col3
 SC_UUID_5:
 Col1, Col2, Col3

SC_UUID(i) are random UUIDs.

Is there any way to read in one call from row A, the SC 2,3,4 with all
their columns? The amount of columns in every SuperColumn is not big
at all. normally less than 20.

Thanks
-- 
Patricio.-

Re: Understanding atomicity in Cassandra

[Patricio Echagüe]

Hi, regarding the retrying strategy, I understand that it might make
sense assuming that the client can actually perform a retry.

We are trying to build a fault tolerance solution based on Cassandra.
In some scenarios, the client machine can go down during a
transaction.

Would it be bad design to store all the data that need to be
consistent under one big key? In this case the batch_mutate operations
will not be big since just a small part is updated/add at a time. But
at least we know that the operation either succeeded or failed.

We basically have:

CF: usernames (similar to Twitter model)
SCF: User_tree (it has all the information related to the user)

Thanks

On Mon, Jul 19, 2010 at 9:40 PM, Alex Yiu  wrote:
>
> Hi, Stuart,
> If I may paraphrase what Jonathan said, typically your batch_mutate
> operation is idempotent.
> That is, you can replay / retry the same operation within a short timeframe
> without any undesirable side effect.
> The assumption behind the "short timeframe" here refers to: there is no
> other concurrent writer trying to write anything conflicting in an
> interleaving fashion.
> Imagine that if there was another writer trying to write:
>>  "some-uuid-1": {
>>    "path": "/foo/bar",
>>    "size": 10
>>  },
> ...
>> {
>>  "/foo/bar": {
>>    "uuid": "some-uuid-1"
>>  },
> Then, there is a chance of 4 write operations (two writes for "/a/b/c" into
> 2 CFs and two writes for "/foo/bar" into 2) would interleave each other and
> create an undesirable result.
> I guess that is not a likely situation in your case.
> Hopefully, my email helps.
> See also:
> http://wiki.apache.org/cassandra/FAQ#batch_mutate_atomic
>
> Regards,
> Alex Yiu
>
>
> On Fri, Jul 9, 2010 at 11:50 AM, Jonathan Ellis  wrote:
>>
>> typically you will update both as part of a batch_mutate, and if it
>> fails, retry the operation.  re-writing any part that succeeded will
>> be harmless.
>>
>> On Thu, Jul 8, 2010 at 11:13 AM, Stuart Langridge
>>  wrote:
>> > Hi, Cassandra people!
>> >
>> > We're looking at Cassandra as a possible replacement for some parts of
>> > our database structures, and on an early look I'm a bit confused about
>> > atomicity guarantees and rollbacks and such, so I wanted to ask what
>> > standard practice is for dealing with the sorts of situation I outline
>> > below.
>> >
>> > Imagine that we're storing information about files. Each file has a path
>> > and a uuid, and sometimes we need to look up stuff about a file by its
>> > path and sometimes by its uuid. The best way to do this, as I understand
>> > it, is to store the data in Cassandra twice: once indexed by nodeid and
>> > once by path. So, I have two ColumnFamilies, one indexed by uuid:
>> >
>> > {
>> >  "some-uuid-1": {
>> >    "path": "/a/b/c",
>> >    "size": 10
>> >  },
>> >  "some-uuid-2" {
>> >    ...
>> >  },
>> >  ...
>> > }
>> >
>> > and one indexed by path
>> >
>> > {
>> >  "/a/b/c": {
>> >    "uuid": "some-uuid-1",
>> >    "size": 10
>> >  },
>> >  "/d/e/f" {
>> >    ...
>> >  },
>> >  ...
>> > }
>> >
>> > So, first, do please correct me if I've misunderstood the terminology
>> > here (and I've shown a "short form" of ColumnFamily here, as per
>> > http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model).
>> >
>> > The thing I don't quite get is: what happens when I want to add a new
>> > file? I need to add it to both these ColumnFamilies, but there's no "add
>> > it to both" atomic operation. What's the way that people handle the
>> > situation where I add to the first CF and then my program crashes, so I
>> > never added to the second? (Assume that there is lots more data than
>> > I've outlined above, so that "put it all in one SuperColumnFamily,
>> > because that can be updated atomically" won't work because it would end
>> > up with our entire database in one SCF). Should we add to one, and then
>> > if we fail to add to the other for some reason continually retry until
>> > it works? Have a "garbage collection" procedure which finds
>> > discrepancies between indexes like this and fixes them up and run it
>> > from cron? We'd love to hear some advice on how to do this, or if we're
>> > modelling the data in the wrong way and there's a better way which
>> > avoids these problems!
>> >
>> > sil
>> >
>> >
>> >
>>
>>
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of Riptano, the source for professional Cassandra support
>> http://riptano.com
>
>



-- 
Patricio.-

Re: Is there any way to detect when a node is down so I can failover more effectively?

[Patricio Echagüe]

Thanks Johathan

On Wed, Jun 2, 2010 at 11:17 PM, Jonathan Ellis  wrote:

> you're overcomplicating things.
>
> just connect to *a* node, and if it happens to be down, try a different
> one.
>
> nodes being down should be a rare event, not a normal condition.  no
> need to optimize for it so much.
>
> also see http://wiki.apache.org/cassandra/FAQ#node_clients_connect_to
>
> 2010/6/1 Patricio Echagüe :
> > Hi all, I'm using Hector framework to interact with Cassandra and at
> trying
> > to handle failover more effectively I found it a bit complicated to fetch
> > all cassandra nodes that are up and running.
> >
> > My goal is to keep an up-to-date list of active/up Cassandra servers to
> > provide HEctor every time I need to execute against the db.
> >
> > I've seen this Thrift  method: get_string_property("token map") but it
> > returns the nodes in the ring no matter is the node is down.
> >
> >
> >
> > Any advice?
> >
> > --
> > Patricio.-
> >
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com
>



-- 
Patricio.-

Is there any way to detect when a node is down so I can failover more effectively?

[Patricio Echagüe]

Hi all, I'm using Hector framework to interact with Cassandra and at trying
to handle failover more effectively I found it a bit complicated to fetch
all cassandra nodes that are up and running.

My goal is to keep an up-to-date list of active/up Cassandra servers to
provide HEctor every time I need to execute against the db.

I've seen this Thrift  method: get_string_property("token map") but it
returns the nodes in the ring no matter is the node is down.



Any advice?

-- 
Patricio.-

Help to understand a strange behavior with DCQUORUM

[Patricio Echagüe]

Hi all, I need to help to understand how DCQUORUM works.

This is my setup:

- Cluster with 3 Cassandra Nodes
- RF = 3
- ReplicatePlacementStrategy = RackUnawareStrategy

My test:
- I write/read with DCQUORUM

Results:
- While the 3 nodes are UP, all my writes and read succeed. (the nodes are
reached, and the third one -to complete the RF=3- is done my replication,
right?)
- When I killed one node, the test FAILED with UnavailableException
- When I performed the same test but with QUORUM instead of DCQUORUM, It
succeeded.

Could someone explain please why reads and writes with DCQUORUM worked fine
while the 3 nodes were up and running but failed when 1 was down even thouch
I have only one Data Center?

Thanks in advance

-- 
Patricio.-

Re: Basic Architecture Question

[Patricio Echagüe]

Roger, if you include the last read key as the start key for the next API
call, will that retrieve the same key/row twice?

The documentation says that both keys (start, finish) are included.
Thanks

On Thu, Apr 29, 2010 at 1:31 PM, Brandon Williams  wrote:

> On Thu, Apr 29, 2010 at 10:19 AM, David Boxenhorn wrote:
>
>> So now we can do any kind of range queries, not just "for getting all
>> keys" as Jesse said?
>>
>
> With RP, the key ranges are based on the MD5 sum of the key, so it's really
> only useful for getting all keys, or obtaining a semi-random row.
>
> -Brandon
>



-- 
Patricio.-

Re: Consistency Level of CLI

[Patricio Echagüe]

Hi all, is there any documentation for:

 ConsistencyLevel.DCQUORUM  and  ConsistencyLevel.DCQUORUMSYNC ?

DC = Data Center ?

Thanks

On Thu, Feb 25, 2010 at 12:12 PM, Masood Mortazavi <
masoodmortaz...@gmail.com> wrote:

> From the code, it appears that for "get" the default is ONE.
>   Column column = thriftClient_.get(tableName, key, path,
> ConsistencyLevel.ONE).column
> - m.
>
>
> On Thu, Feb 25, 2010 at 11:08 AM, Masood Mortazavi <
> masoodmortaz...@gmail.com> wrote:
>
>>
>>
>> What is the write and read consistency level for the CLI tool
>> "cassandra-cli" ?
>>
>> Do the "set" and "get" commands in the "cli" allow the Consistency Level
>> to be specified for a given "set" or "get"?
>>
>> Is there a current specification of CLI anywhere on the wiki?
>>
>> ( How are JIRA's related to the CLI tagged in the JIRA system assuming
>> they are "tagged" separately? In other words, is there an identifier for
>> them? )
>>
>> Regards,
>> m.
>>
>> ==
>> The Cassandra "API" describes write and read consistency levels as
>> follows:
>> http://wiki.apache.org/cassandra/API
>> Write
>>
>> *Level*
>>
>> *Behavior*
>>
>> ZERO
>>
>> Ensure nothing. A write happens asynchronously in background
>>
>> ANY
>>
>> (Coming in 0.6) Ensure that the write has been written to at least 1 node,
>> including hinted recipients.
>>
>> ONE
>>
>> Ensure that the write has been written to at least 1 node's commit log and
>> memory table before responding to the client.
>>
>> QUORUM
>>
>> Ensure that the write has been written to  / 2 + 1nodes 
>> before responding to the client.
>>
>> ALL
>>
>> Ensure that the write is written to all  nodes before
>> responding to the client. Any unresponsive nodes will fail the operation.
>>
>> Read
>>
>> *Level*
>>
>> *Behavior*
>>
>> ZERO
>>
>> Not supported, because it doesn't make sense.
>>
>> ANY
>>
>> Not supported. You probably want ONE instead.
>>
>> ONE
>>
>> Will return the record returned by the first node to respond. A
>> consistency check is always done in a background thread to fix any
>> consistency issues when ConsistencyLevel.ONE is used. This means
>> subsequent calls will have correct data even if the initial read gets an
>> older value. (This is called read repair.)
>>
>> QUORUM
>>
>> Will query all storage nodes and return the record with the most recent
>> timestamp once it has at least a majority of replicas reported. Again, the
>> remaining replicas will be checked in the background.
>>
>> ALL
>>
>> Will query all storage nodes and return the record with the most recent
>> timestamp once all nodes have replied. Any unresponsive nodes will fail the
>> operatio
>>
>>
>


-- 
Patricio.-