Re: Repair has now effect
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 h...@filez.com 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
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: Hector Problem Basic one
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) peter.wang...@huawei.com 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 b...@bossastudios.com 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 cassandralear...@gmail.com 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 ** **
Re: Efficiency of hector's setRowCount
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 dsm...@likewise.com 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 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: Efficiency of hector's setRowCount (and setStartKey!)
On Thu, Oct 13, 2011 at 9:39 AM, Don Smith dsm...@likewise.com 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;
IndexedSlicesQueryString, String, String
indexedSlicesQuery =
HFactory.createIndexedSlicesQuery(keyspace,
stringSerializer, stringSerializer, stringSerializer);
indexedSlicesQuery.addEqualsExpression(user, username);
indexedSlicesQuery.setColumnNames(source,ip);
indexedSlicesQuery.setColumnFamily(ourColumnFamilyName);
indexedSlicesQuery.setStartKey(startKey);
//
indexedSlicesQuery.setRowCount(batchSize);
QueryResultOrderedRowsString, String,
String result =indexedSlicesQuery.execute();
OrderedRowsString,String,String rows =
result.get();
for(RowString,String,String 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 dsm...@likewise.com 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: Write everywhere, read anywhere
On Wed, Aug 3, 2011 at 4:00 PM, Philippe watche...@gmail.com 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
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 iyan...@gmail.com 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
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 aa...@thelastpickle.comwrote: 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 vram.kouramaj...@gmail.com 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 j...@joestump.net 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: Quorum, Hector, and datacenter preference
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?
is it possible to mutate Columns and CounterColumn in the same batch mutation?
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: TSocket timing out
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 potek...@bnl.gov 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
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 roshandawr...@gmail.comwrote: 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 roshandawr...@gmail.com 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
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 n...@riptano.com 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 roshandawr...@gmail.com
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 roshandawr...@gmail.com
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 roshandawr...@gmail.com
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
data from Cassandra database.
--
Roshan
Blog: http://roshandawrani.wordpress.com/
Twitter: @roshandawrani
Skype: roshandawrani
On Wed, Jan 5, 2011 at 1:32 AM, Victor Kabdebon
victor.kabde...@gmail.com wrote:
Hi Roshan,
Sorry I misunderstood your problem.It is weird that it doesn't work,
it
works for me...
As Patricio pointed out use hector standard way of creating TimeUUID
and tell us if it still doesn't work.
Maybe you can paste here some of the code you use to query your
columns
too.
Victor K.
http://www.voxnucleus.fr
2011/1/4 Patricio Echagüe patric...@gmail.com
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
Re: Converting a TimeUUID to a long (timestamp) and vice-versa
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 roshandawr...@gmail.comwrote: Hi Patricio, Thanks for your comment. Replying inline. 2011/1/5 Patricio Echagüe patric...@gmail.com 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
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 roshandawr...@gmail.comwrote: 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 roshandawr...@gmail.com 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 http://twitter.com/roshandawrani Skype: roshandawrani -- Roshan Blog: http://roshandawrani.wordpress.com/ Twitter: @roshandawrani http://twitter.com/roshandawrani Skype: roshandawrani -- Patricio.-
Re: Any GUI for Cassandra database on Windows?
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 roshandawr...@gmail.comwrote: 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 roshandawr...@gmail.comwrote: 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 http://twitter.com/roshandawrani Skype: roshandawrani -- Patricio.-
Re: Is it possible to read from one row, several SuperColumns with all their Columns in one call?
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 aa...@thelastpickle.com 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 patric...@gmail.com 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.-
Re: Is it possible to read from one row, several SuperColumns with all their Columns in one call?
Hey thanks Aaron. It finally worked. The API reference looked a bit confusing to me. I used (as you suggested): ColumnParent parent = new ColumnParent( ColumnFamily name); SlicePredicate sp = new SlicePredicate(); sp.setColumn_names( list of super column 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 patric...@gmail.com: 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 aa...@thelastpickle.com 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 patric...@gmail.com 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: Understanding atomicity in Cassandra
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 bigcontentf...@gmail.com 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 jbel...@gmail.com 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
stuart.langri...@canonical.com 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?
Thanks Johathan On Wed, Jun 2, 2010 at 11:17 PM, Jonathan Ellis jbel...@gmail.com 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 patric...@gmail.com: 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?
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
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
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 dri...@gmail.com wrote: On Thu, Apr 29, 2010 at 10:19 AM, David Boxenhorn da...@lookin2.comwrote: 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.-
