Re: Cassandra (2.0.4) pagination and total records?
With Cassandra 2.0.x and Java driver 2.0.0 you can set the fetch size on
the query and then use Resulset.iterator(). It will iterate over your data
set by loading batches of size = fetch size
Le 18 mars 2014 01:39, Philip G g...@gpcentre.net a écrit :
Thanks for the links.
As I'm messing around with CQL, I'm realizing Cassandra isn't going to do
what I need. Quite simply, here's a basic layout of my table:
myTable (
visit_dt timestamp,
cid ascii,
company text,
// ... other stuff
primary key (visit_dt, cid)
);
index on (company)
My query starts off with visit_dt IN ('2014-01-17'). In Cassandra, I
essentially get back just 1 wide row (but shows as many within CQL3). I can
filter that via AND company='my company' due to the index. However, if I
LIMIT 10; there isn't a way to get the next 10 records as token() only
works on the partition key, and each row has the same partition key.
Or am I missing something? Is there a way I've not discovered to get the
next 10 on a single wide row?
---
Philip
g...@gpcentre.net
http://www.gpcentre.net/
On Mon, Mar 17, 2014 at 5:12 PM, Tupshin Harper tups...@tupshin.comwrote:
Read the automatic paging portion of this post :
http://www.datastax.com/dev/blog/client-side-improvements-in-cassandra-2-0
On Mar 17, 2014 8:09 PM, Philip G g...@gpcentre.net wrote:
On Mon, Mar 17, 2014 at 4:54 PM, Robert Coli rc...@eventbrite.comwrote:
The form of your question suggests you are Doing It Wrong, FWIW.
Okay, let me ask different question: how do you go about data browsing
in a CQL3 table? Especially in situations were a single query could return
a couple thousand records, and we want to limit it by a 100 at a time.
Please, feel free to point me in the right direction, if necessary. I
admit I'm still figuring out Cassandra/CQL. But my knowledge has been
exponentially expanding on a daily basis. I want to understand this more,
and possible solution to problems I'm running into migrating from a RDBMS
(mssql) to Cassandra. I've figured out a lot of stuff, but have not quite
resolved this use-case.
Thanks,
---
Philip
g...@gpcentre.net
http://www.gpcentre.net/
Re: Cassandra DSC 2.0.5 not starting - * could not access pidfile for Cassandra
For others who get stuck with this in future, here is fix that worked for
me:
http://askubuntu.com/questions/435749/cant-start-an-application-as-service-but-running-as-standalone-process-simply
On Tue, Mar 11, 2014 at 9:24 PM, Michael Shuler mich...@pbandjelly.orgwrote:
On 03/11/2014 08:47 AM, Ken Hancock wrote:
See http://www.rudder-project.org/redmine/issues/2941 for the mess that
has been created regarding java JRE dependencies.
That's a good example of the cluster.. so many thanks to the Oracle legal
department for disallowing redistribution..
FWIW, I maintain my own apt repository for oracle-java7-{jre,jdk,etc}
packages. If you want to build proper deb packages for Debian/Ubuntu (I'm
sure there's a similar project for RPM-based distros) (there is also some
sort of Ubuntu PPA that does a similar build, but I don't do random PPAs):
git clone https://github.com/rraptorr/oracle-java7.git
cd oracle-java7
sh ./prepare.sh
dpkg-buildpackage -uc -us
and install the packages in that you want (just the jre, the jdk if you
are building/testing, etc.)
Throw 'em in an apt repo for installation on many machines :)
--
Michael
Re: Relation between Atomic Batches and Consistency Level
Okay your question is clear to me know. My understanding, after talking this through with some of the engineers here, is that we have 2 levels of success with batches: 1) Did the batch make it to the batch log table? [yes or no] - yes = success - no = not success 2) Did each statement in the batch succeed? [yes or no] - yes = success - no = not success - the case you are interested in. If 1 and 2 are both successful - you will receive a success message if 1 is successful but 2 is not successful (your case) - you will receive a message stating the batch succeeded but not all replicas are live yet - in this case, the batch will be retried by Cassandra. This is the target scenario for atomic batches (to take the burden off of the client app to monitor, maintain, and retry batches) - i am going to test this, was shooting for last night but didn't get to it, to see what actually happens inside the batch - you could test this scenario with a trace to see what occurs (i.e. if statement 1 fails is statement 2 tried) if 1 is not successful then the batch fails - this is because it couldn't make it to the batchlog table for execution Hope this helps. I believe this is the best i can do for you at the moment. Thanks, Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 http://www.linkedin.com/in/jlacefield http://www.datastax.com/what-we-offer/products-services/training/virtual-training On Mon, Mar 17, 2014 at 4:05 PM, Drew Kutcharian d...@venarc.com wrote: I have read that blog post which actually was the source of the initial confusion ;) If I write normally (no batch) at Quorum, then a hinted write wouldn't count as a valid write so the write wouldn't succeed, which means I would have to retry. That's a pretty well defined outcome. Now if I write a logged batch at Quorum, then a by definition, a hinted write shouldn't be considered a valid response, no? - Drew On Mar 17, 2014, at 11:23 AM, Jonathan Lacefield jlacefi...@datastax.com wrote: Hello, Have you seen this blog post, it's old but still relevant. I think it will answer your questions. http://www.datastax.com/dev/blog/atomic-batches-in-cassandra-1-2. I think the answer lies in how Cassandra defines a batch In the context of a Cassandra batch operation, atomic means that if any of the batchsucceeds, all of it will. My understanding is that in your scenario if either statement succeeded, you batch would succeed. So #1 would get hinted and #2 would be applied, assuming no other failure events occur, like the coordinator fails, the client fails, etc. Hope that helps. Thanks, Jonathan Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 http://www.linkedin.com/in/jlacefield http://www.datastax.com/what-we-offer/products-services/training/virtual-training On Mon, Mar 17, 2014 at 1:38 PM, Drew Kutcharian d...@venarc.com wrote: Hi Jonathan, I'm still a bit unclear on this. Say I have two CQL3 tables: - user (replication of 3) - user_email_index (replication of 3) Now I create a new logged batch at quorum consistency level and put two inserts in there: #1 Insert into the user table with partition key of a timeuuid of the user #2 Insert into the user_email_index with partition key of user's email address As you can see, there is a chance that these two insert statements will be executed on two different nodes because they are keyed by different partition keys. So based on the docs for Logged Batches, a batch will be applied eventually in an all or nothing fashion. So my question is, what happens if insert #1 fails (say replicas are unavailable), would insert #2 get applied? Would the whole thing be rejected and return an error to the client? PS. I'm aware of the isolation guarantees and that's not an issue. All I need to make sure is that if the first the statement failed, the whole batch needs to fail. Thanks, Drew On Mar 17, 2014, at 5:33 AM, Jonathan Lacefield jlacefi...@datastax.com wrote: Hello, Consistency is declared at the statement level, i.e. batch level when writing, but enforced at each batch row level. My understanding is that each batch (and all of it's contents) will be controlled through a specific CL declaration. So batch A could use a CL of QUORUM while batch B could use a CL of ONE. The detail that may help sort this out for you is that batch statements do not provide isolation guarantees: www.datastax.com/documentation/cql/3.0/cql/cql_reference/batch_r.html. This means that you write the batch as a batch but the reads are per row. If you are reading records contained in the batch, you will read results of partially updated batches. Taking this into account for your second question, you should expect that your read CL will preform as it would for any individual row mutation. Hope this helps. Jonathan Jonathan Lacefield Solutions
Re: Problems with adding datacenter and schema version disagreement
Ok, i've dropped all system keyspaces, rebuild cluster and recover schema, now everything looks ok. But main goal of operations was to add new datacenter to cluster. After starting node in new cluster two schema versions appear, one version is held by 6 nodes of first datacenter, second one is in newly added node in new datacenter. Sth like this: nodetool status Datacenter: datacenter1 === Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- AddressLoad Tokens Owns Host ID Rack UN 192.168.1.1 50.19 GB 1 0,5% c9323f38-d9c4-4a69-96e3-76cd4e1a204e rack1 UN 192.168.1.2 54.83 GB 1 0,3% ad1de2a9-2149-4f4a-aec6-5087d9d3acbb rack1 UN 192.168.1.3 51.14 GB 1 0,6% 0ceef523-93fe-4684-ba4b-4383106fe3d1 rack1 UN 192.168.1.4 54.31 GB 1 0,7% 39d15471-456d-44da-bdc8-221f3c212c78 rack1 UN 192.168.1.5 53.36 GB 1 0,3% 7fed25a5-e018-43df-b234-47c2f118879b rack1 UN 192.168.1.6 39.89 GB 1 0,1% 9f54fad6-949a-4fa9-80da-87efd62f3260 rack1 Datacenter: DC1 === Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- AddressLoad Tokens Owns Host ID Rack UN 192.168.1.7 100.77 KB 256 97,4% ddb1f913-d075-4840-9665-3ba64eda0558 RAC1 describe cluster; Cluster Information: Name: Metadata Cluster Snitch: org.apache.cassandra.locator.GossipingPropertyFileSnitch Partitioner: org.apache.cassandra.dht.RandomPartitioner Schema versions: 8fe34841-4f2a-3c05-97f2-15dd413d71dc: [192.168.1.7] 4ad381b6-df5a-3cbc-ba5a-0234b74d2383: [192.168.1.1, 192.168.1.2, 192.168.1.3, 192.168.1.4, 192.168.1.5, 192.168.1.6] All keyspaces are now configured to keep data in datacenter1. I assume, that It's not correct behaviour, is it true? Could you help me, how can I safely add new DC to the cluster? Regards Aleksander 2014-03-14 18:28 GMT+01:00 olek.stas...@gmail.com olek.stas...@gmail.com: Ok, I'll do this during the weekend, I'll give you a feedback on Monday. Regards Aleksander 14 mar 2014 18:15 Robert Coli rc...@eventbrite.com napisał(a): On Fri, Mar 14, 2014 at 12:40 AM, olek.stas...@gmail.com olek.stas...@gmail.com wrote: OK, I see, so the data files stay in place, i have to just stop cassandra on whole cluster, remove system schema and then start cluster and recreate all keyspaces with all column families? Data will be than loaded automatically from existing ssstables, right? Right. If you have clients reading while loading the schema, they may get exceptions. So one more question: what about KS system_traces? should it be removed and recreted? What data it's holding? It's holding data about tracing, a profiling feature. It's safe to nuke. =Rob
Re: Problems with adding datacenter and schema version disagreement
Oh, one more question: what should be configuration for storing system_traces keyspace? Should it be replicated or stored locally? Regards Olek 2014-03-18 16:47 GMT+01:00 olek.stas...@gmail.com olek.stas...@gmail.com: Ok, i've dropped all system keyspaces, rebuild cluster and recover schema, now everything looks ok. But main goal of operations was to add new datacenter to cluster. After starting node in new cluster two schema versions appear, one version is held by 6 nodes of first datacenter, second one is in newly added node in new datacenter. Sth like this: nodetool status Datacenter: datacenter1 === Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- AddressLoad Tokens Owns Host ID Rack UN 192.168.1.1 50.19 GB 1 0,5% c9323f38-d9c4-4a69-96e3-76cd4e1a204e rack1 UN 192.168.1.2 54.83 GB 1 0,3% ad1de2a9-2149-4f4a-aec6-5087d9d3acbb rack1 UN 192.168.1.3 51.14 GB 1 0,6% 0ceef523-93fe-4684-ba4b-4383106fe3d1 rack1 UN 192.168.1.4 54.31 GB 1 0,7% 39d15471-456d-44da-bdc8-221f3c212c78 rack1 UN 192.168.1.5 53.36 GB 1 0,3% 7fed25a5-e018-43df-b234-47c2f118879b rack1 UN 192.168.1.6 39.89 GB 1 0,1% 9f54fad6-949a-4fa9-80da-87efd62f3260 rack1 Datacenter: DC1 === Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- AddressLoad Tokens Owns Host ID Rack UN 192.168.1.7 100.77 KB 256 97,4% ddb1f913-d075-4840-9665-3ba64eda0558 RAC1 describe cluster; Cluster Information: Name: Metadata Cluster Snitch: org.apache.cassandra.locator.GossipingPropertyFileSnitch Partitioner: org.apache.cassandra.dht.RandomPartitioner Schema versions: 8fe34841-4f2a-3c05-97f2-15dd413d71dc: [192.168.1.7] 4ad381b6-df5a-3cbc-ba5a-0234b74d2383: [192.168.1.1, 192.168.1.2, 192.168.1.3, 192.168.1.4, 192.168.1.5, 192.168.1.6] All keyspaces are now configured to keep data in datacenter1. I assume, that It's not correct behaviour, is it true? Could you help me, how can I safely add new DC to the cluster? Regards Aleksander 2014-03-14 18:28 GMT+01:00 olek.stas...@gmail.com olek.stas...@gmail.com: Ok, I'll do this during the weekend, I'll give you a feedback on Monday. Regards Aleksander 14 mar 2014 18:15 Robert Coli rc...@eventbrite.com napisał(a): On Fri, Mar 14, 2014 at 12:40 AM, olek.stas...@gmail.com olek.stas...@gmail.com wrote: OK, I see, so the data files stay in place, i have to just stop cassandra on whole cluster, remove system schema and then start cluster and recreate all keyspaces with all column families? Data will be than loaded automatically from existing ssstables, right? Right. If you have clients reading while loading the schema, they may get exceptions. So one more question: what about KS system_traces? should it be removed and recreted? What data it's holding? It's holding data about tracing, a profiling feature. It's safe to nuke. =Rob
Re: Relation between Atomic Batches and Consistency Level
Alright, this is much better. The main thing I’m trying to figure out is that if there is a way to stop the batch if the first statement fails or there is a better pattern/construct for Cassandra to handle that scenario. - Drew On Mar 18, 2014, at 4:46 AM, Jonathan Lacefield jlacefi...@datastax.com wrote: Okay your question is clear to me know. My understanding, after talking this through with some of the engineers here, is that we have 2 levels of success with batches: 1) Did the batch make it to the batch log table? [yes or no] - yes = success - no = not success 2) Did each statement in the batch succeed? [yes or no] - yes = success - no = not success - the case you are interested in. If 1 and 2 are both successful - you will receive a success message if 1 is successful but 2 is not successful (your case) - you will receive a message stating the batch succeeded but not all replicas are live yet - in this case, the batch will be retried by Cassandra. This is the target scenario for atomic batches (to take the burden off of the client app to monitor, maintain, and retry batches) - i am going to test this, was shooting for last night but didn't get to it, to see what actually happens inside the batch - you could test this scenario with a trace to see what occurs (i.e. if statement 1 fails is statement 2 tried) if 1 is not successful then the batch fails - this is because it couldn't make it to the batchlog table for execution Hope this helps. I believe this is the best i can do for you at the moment. Thanks, Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 On Mon, Mar 17, 2014 at 4:05 PM, Drew Kutcharian d...@venarc.com wrote: I have read that blog post which actually was the source of the initial confusion ;) If I write normally (no batch) at Quorum, then a hinted write wouldn’t count as a valid write so the write wouldn’t succeed, which means I would have to retry. That’s a pretty well defined outcome. Now if I write a logged batch at Quorum, then a by definition, a hinted write shouldn’t be considered a valid response, no? - Drew On Mar 17, 2014, at 11:23 AM, Jonathan Lacefield jlacefi...@datastax.com wrote: Hello, Have you seen this blog post, it's old but still relevant. I think it will answer your questions. http://www.datastax.com/dev/blog/atomic-batches-in-cassandra-1-2. I think the answer lies in how Cassandra defines a batch In the context of a Cassandra batch operation, atomic means that if any of the batch succeeds, all of it will. My understanding is that in your scenario if either statement succeeded, you batch would succeed. So #1 would get hinted and #2 would be applied, assuming no other failure events occur, like the coordinator fails, the client fails, etc. Hope that helps. Thanks, Jonathan Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 On Mon, Mar 17, 2014 at 1:38 PM, Drew Kutcharian d...@venarc.com wrote: Hi Jonathan, I’m still a bit unclear on this. Say I have two CQL3 tables: - user (replication of 3) - user_email_index (replication of 3) Now I create a new logged batch at quorum consistency level and put two inserts in there: #1 Insert into the “user table with partition key of a timeuuid of the user #2 Insert into the “user_email_index with partition key of user’s email address As you can see, there is a chance that these two insert statements will be executed on two different nodes because they are keyed by different partition keys. So based on the docs for Logged Batches, a batch will be applied “eventually” in an all or nothing” fashion. So my question is, what happens if insert #1 fails (say replicas are unavailable), would insert #2 get applied? Would the whole thing be rejected and return an error to the client? PS. I’m aware of the isolation guarantees and that’s not an issue. All I need to make sure is that if the first the statement failed, the whole batch needs to fail. Thanks, Drew On Mar 17, 2014, at 5:33 AM, Jonathan Lacefield jlacefi...@datastax.com wrote: Hello, Consistency is declared at the statement level, i.e. batch level when writing, but enforced at each batch row level. My understanding is that each batch (and all of it's contents) will be controlled through a specific CL declaration. So batch A could use a CL of QUORUM while batch B could use a CL of ONE. The detail that may help sort this out for you is that batch statements do not provide isolation guarantees: www.datastax.com/documentation/cql/3.0/cql/cql_reference/batch_r.html. This means that you write the batch as a batch but the reads are per row. If you are reading records contained in the batch, you will read results of partially updated batches. Taking this into
Cassandra blob storage
Hi, I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: *Currently Cassandra isn't optimized specifically for large file or BLOB storage. However, files of around 64Mb and smaller can be easily stored in the database without splitting them into smaller chunks. This is primarily due to the fact that Cassandra's public API is based on Thrift, which offers no streaming abilities; any value written or fetched has to fit in to memory.* Does the above statement still hold? Thrift supports framed data transport, does that change the above statement. If not, why does casssandra not adopt the Thrift framed data transfer support? Thanks
Re: Cassandra blob storage
You may want to look at: https://github.com/Netflix/astyanax/wiki/Chunked-Object-Store -brian --- Brian O'Neill Chief Technology Officer Health Market Science The Science of Better Results 2700 Horizon Drive King of Prussia, PA 19406 M: 215.588.6024 @boneill42 http://www.twitter.com/boneill42 healthmarketscience.com This information transmitted in this email message is for the intended recipient only and may contain confidential and/or privileged material. If you received this email in error and are not the intended recipient, or the person responsible to deliver it to the intended recipient, please contact the sender at the email above and delete this email and any attachments and destroy any copies thereof. Any review, retransmission, dissemination, copying or other use of, or taking any action in reliance upon, this information by persons or entities other than the intended recipient is strictly prohibited. From: prem yadav ipremya...@gmail.com Reply-To: user@cassandra.apache.org Date: Tuesday, March 18, 2014 at 1:41 PM To: user@cassandra.apache.org Subject: Cassandra blob storage Hi, I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: Currently Cassandra isn't optimized specifically for large file or BLOB storage. However, files of around 64Mb and smaller can be easily stored in the database without splitting them into smaller chunks. This is primarily due to the fact that Cassandra's public API is based on Thrift, which offers no streaming abilities; any value written or fetched has to fit in to memory. Does the above statement still hold? Thrift supports framed data transport, does that change the above statement. If not, why does casssandra not adopt the Thrift framed data transfer support? Thanks
Re: Cassandra blob storage
Thanks Brian, I have seen that. Its more of a workaround and a hack. Of course a great solution. But my question is more about why Cassandra itself can't support that. Give then Thrift supports frames. Thanks. On Tue, Mar 18, 2014 at 5:55 PM, Brian O'Neill b...@alumni.brown.eduwrote: You may want to look at: https://github.com/Netflix/astyanax/wiki/Chunked-Object-Store -brian --- Brian O'Neill Chief Technology Officer *Health Market Science* *The Science of Better Results* 2700 Horizon Drive * King of Prussia, PA * 19406 M: 215.588.6024 * @boneill42 http://www.twitter.com/boneill42 * healthmarketscience.com This information transmitted in this email message is for the intended recipient only and may contain confidential and/or privileged material. If you received this email in error and are not the intended recipient, or the person responsible to deliver it to the intended recipient, please contact the sender at the email above and delete this email and any attachments and destroy any copies thereof. Any review, retransmission, dissemination, copying or other use of, or taking any action in reliance upon, this information by persons or entities other than the intended recipient is strictly prohibited. From: prem yadav ipremya...@gmail.com Reply-To: user@cassandra.apache.org Date: Tuesday, March 18, 2014 at 1:41 PM To: user@cassandra.apache.org Subject: Cassandra blob storage Hi, I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: *Currently Cassandra isn't optimized specifically for large file or BLOB storage. However, files of around 64Mb and smaller can be easily stored in the database without splitting them into smaller chunks. This is primarily due to the fact that Cassandra's public API is based on Thrift, which offers no streaming abilities; any value written or fetched has to fit in to memory.* Does the above statement still hold? Thrift supports framed data transport, does that change the above statement. If not, why does casssandra not adopt the Thrift framed data transfer support? Thanks
Re: Cassandra blob storage
For large volume big data scenarios we don't recommend using Cassandra as a blob storage simply because of intensive IO involved during compation, repair etc. Cassandra store is only well suited for metadata type storage. However, if you are fairly low volume then it's a different story, but if you have low volume why use Cassandra :) On Tue, Mar 18, 2014 at 10:55 AM, Brian O'Neill b...@alumni.brown.eduwrote: You may want to look at: https://github.com/Netflix/astyanax/wiki/Chunked-Object-Store -brian --- Brian O'Neill Chief Technology Officer *Health Market Science* *The Science of Better Results* 2700 Horizon Drive * King of Prussia, PA * 19406 M: 215.588.6024 * @boneill42 http://www.twitter.com/boneill42 * healthmarketscience.com This information transmitted in this email message is for the intended recipient only and may contain confidential and/or privileged material. If you received this email in error and are not the intended recipient, or the person responsible to deliver it to the intended recipient, please contact the sender at the email above and delete this email and any attachments and destroy any copies thereof. Any review, retransmission, dissemination, copying or other use of, or taking any action in reliance upon, this information by persons or entities other than the intended recipient is strictly prohibited. From: prem yadav ipremya...@gmail.com Reply-To: user@cassandra.apache.org Date: Tuesday, March 18, 2014 at 1:41 PM To: user@cassandra.apache.org Subject: Cassandra blob storage Hi, I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: *Currently Cassandra isn't optimized specifically for large file or BLOB storage. However, files of around 64Mb and smaller can be easily stored in the database without splitting them into smaller chunks. This is primarily due to the fact that Cassandra's public API is based on Thrift, which offers no streaming abilities; any value written or fetched has to fit in to memory.* Does the above statement still hold? Thrift supports framed data transport, does that change the above statement. If not, why does casssandra not adopt the Thrift framed data transfer support? Thanks
How to extract information from commit log?
Hi Cassandra hackers! I have a question regarding extracting useful information from commit log. Since its a binary log, how should I extract information such as timestamp, values from it? Does anyone know any binary log reader that I can use directly to read commit log? If there is no such reader, could someone give me some advice hwo I can wrote such a reader? Particularly, I want to know the order that write operations happens at each replica(cassandra server node) along with their timestamps, Does anyone know other methods how I can get this information without instrumenting Cassandra code? Any help is appreciated! Cheers, Meng
Re: Cassandra blob storage
@Mohit Bit confused with your reply. For what use cases you find Cassandra useful then? -Vivek On Tue, Mar 18, 2014 at 11:41 PM, Mohit Anchlia mohitanch...@gmail.comwrote: For large volume big data scenarios we don't recommend using Cassandra as a blob storage simply because of intensive IO involved during compation, repair etc. Cassandra store is only well suited for metadata type storage. However, if you are fairly low volume then it's a different story, but if you have low volume why use Cassandra :) On Tue, Mar 18, 2014 at 10:55 AM, Brian O'Neill b...@alumni.brown.eduwrote: You may want to look at: https://github.com/Netflix/astyanax/wiki/Chunked-Object-Store -brian --- Brian O'Neill Chief Technology Officer *Health Market Science* *The Science of Better Results* 2700 Horizon Drive * King of Prussia, PA * 19406 M: 215.588.6024 * @boneill42 http://www.twitter.com/boneill42 * healthmarketscience.com This information transmitted in this email message is for the intended recipient only and may contain confidential and/or privileged material. If you received this email in error and are not the intended recipient, or the person responsible to deliver it to the intended recipient, please contact the sender at the email above and delete this email and any attachments and destroy any copies thereof. Any review, retransmission, dissemination, copying or other use of, or taking any action in reliance upon, this information by persons or entities other than the intended recipient is strictly prohibited. From: prem yadav ipremya...@gmail.com Reply-To: user@cassandra.apache.org Date: Tuesday, March 18, 2014 at 1:41 PM To: user@cassandra.apache.org Subject: Cassandra blob storage Hi, I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: *Currently Cassandra isn't optimized specifically for large file or BLOB storage. However, files of around 64Mb and smaller can be easily stored in the database without splitting them into smaller chunks. This is primarily due to the fact that Cassandra's public API is based on Thrift, which offers no streaming abilities; any value written or fetched has to fit in to memory. * Does the above statement still hold? Thrift supports framed data transport, does that change the above statement. If not, why does casssandra not adopt the Thrift framed data transfer support? Thanks
Re: Cassandra blob storage
On Tue, Mar 18, 2014 at 10:41 AM, prem yadav ipremya...@gmail.com wrote: I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: https://code.google.com/p/mogilefs/ Cassandra is not optimized for single values of this size. Leaving aside Thrift, trying to store 100mb in a single cell is not Cassandra's sweet spot. =Rob
Re: Cassandra blob storage
On Tue, Mar 18, 2014 at 10:41 AM, prem yadav ipremya...@gmail.com wrote: I have been spending some time looking into whether large files(100mb) can be stores in Cassandra. As per Cassandra faq: https://code.google.com/p/mogilefs/ Cassandra is not optimized for single values of this size. Leaving aside Thrift, trying to store 100mb in a single cell is not Cassandra's sweet spot. =Rob
Re: How to extract information from commit log?
Hello, Is this a one time investigative item or are you looking to set something up to do this continuously? Don't recommend trying to read the commit log. You can always use the WRITETIME function in CQL or look within SSTables via the SStable2Json utility to see write times for particular versions of partitions. Jonathan Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 http://www.linkedin.com/in/jlacefield http://www.datastax.com/what-we-offer/products-services/training/virtual-training On Tue, Mar 18, 2014 at 2:25 PM, Han,Meng meng...@ufl.edu wrote: Hi Cassandra hackers! I have a question regarding extracting useful information from commit log. Since its a binary log, how should I extract information such as timestamp, values from it? Does anyone know any binary log reader that I can use directly to read commit log? If there is no such reader, could someone give me some advice hwo I can wrote such a reader? Particularly, I want to know the order that write operations happens at each replica(cassandra server node) along with their timestamps, Does anyone know other methods how I can get this information without instrumenting Cassandra code? Any help is appreciated! Cheers, Meng
Re: Cassandra data migration from 1.9.8 to 2.0.2
On Mon, Mar 17, 2014 at 6:19 PM, Lakshmi Kanth lk.c...@gmail.com wrote: Cassandra 1.9.8 No? This version does not exist. Cassandra 2.0.2 Cassandra 2.0.x versions up to and including 2.0.5 have serious issues. Including this one, which randomly tombstones your data when you use SSTableloader. https://issues.apache.org/jira/browse/CASSANDRA-6527 (fixed in 2.0.4) This is the reason why I do not currently recommend running Cassandra 2.0.x in production. https://engineering.eventbrite.com/what-version-of-cassandra-should-i-run/ If I were you, with such small cluster sizes, I would consider the copy-all-data-to-all-nodes-and-run-cleanup method. http://www.palominodb.com/blog/2012/09/25/bulk-loading-options-cassandra =Rob
Re: How to extract information from commit log?
Hi Jonathan, Thank you for the timely reply. I am doing this experiment on a continuous basis. To be more specific, I will issue a large amount of read and write operations to a particular key in a short time interval. I'd like to know the order that write operations happens at each replica. TImestamps definitely help to determine order, but the WRITETIME and SStable2Json both looks me only return the timestamps when that key was updated the moment the WRITETIME/SStable2Json is issued. It looks like a one time thing to me. Or put in another way, if I want to get the write time for all write operations in that short invertal to determine a total order for write on that replia I have to constantly issue WRITETIME to this replica? Correct me if I am wrong here. Light me up pleease! On Tue, 18 Mar 2014 15:05:07 -0400, Jonathan Lacefield wrote: Hello, Is this a one time investigative item or are you looking to set something up to do this continuously? Don't recommend trying to read the commit log. You can always use the WRITETIME function in CQL or look within SSTables via the SStable2Json utility to see write times for particular versions of partitions. Jonathan Jonathan Lacefield Solutions Architect, DataStax (404) 822 3487 [1] [2] On Tue, Mar 18, 2014 at 2:25 PM, Han,Meng wrote: Hi Cassandra hackers! I have a question regarding extracting useful information from commit log. Since its a binary log, how should I extract information such as timestamp, values from it? Does anyone know any binary log reader that I can use directly to read commit log? If there is no such reader, could someone give me some advice hwo I can wrote such a reader? Particularly, I want to know the order that write operations happens at each replica(cassandra server node) along with their timestamps, Does anyone know other methods how I can get this information without instrumenting Cassandra code? Any help is appreciated! Cheers, Meng Links: -- [1] http://www.linkedin.com/in/jlacefield [2] http://www.datastax.com/what-we-offer/products-services/training/virtual-training [3] mailto:meng...@ufl.edu
Re: Cassandra data migration from 1.9.8 to 2.0.2
Thanks Robert. I wrongly mentioned the source Cassandra version. Actual source version is 1.2.9. Regards, LakshmiKanth On Tue, Mar 18, 2014 at 12:06 PM, Robert Coli rc...@eventbrite.com wrote: On Mon, Mar 17, 2014 at 6:19 PM, Lakshmi Kanth lk.c...@gmail.com wrote: Cassandra 1.9.8 No? This version does not exist. Cassandra 2.0.2 Cassandra 2.0.x versions up to and including 2.0.5 have serious issues. Including this one, which randomly tombstones your data when you use SSTableloader. https://issues.apache.org/jira/browse/CASSANDRA-6527 (fixed in 2.0.4) This is the reason why I do not currently recommend running Cassandra 2.0.x in production. https://engineering.eventbrite.com/what-version-of-cassandra-should-i-run/ If I were you, with such small cluster sizes, I would consider the copy-all-data-to-all-nodes-and-run-cleanup method. http://www.palominodb.com/blog/2012/09/25/bulk-loading-options-cassandra =Rob
Re: Multi-site Active-Active replication - Preparing Sites - Cluster Name and Snitch
Thanks Jonathan, points taken onboard.
I'll be testing the GossipingPropertyFileSnitch. Just need to assess what
the impact is to a running-active cluster restarting 1 node at a time.
Given that I'm using Simple Strategy initially, I'm guessing there will be
no impact.
With regards to the non-application keyspaces,
RowKey: system_auth
= (column=durable_writes, value=true, timestamp=1394601216807000)
= (column=strategy_class,
value=org.apache.cassandra.locator.SimpleStrategy,
timestamp=1394601216807000)
= (column=strategy_options, value={replication_factor:1},
timestamp=1394601216807000)
---
RowKey: system
= (column=durable_writes, value=true, timestamp=1394601462264001)
= (column=strategy_class,
value=org.apache.cassandra.locator.LocalStrategy,
timestamp=1394601462264001)
= (column=strategy_options, value={}, timestamp=1394601462264001)
---
RowKey: system_traces
= (column=durable_writes, value=true, timestamp=1394601462327001)
= (column=strategy_class,
value=org.apache.cassandra.locator.SimpleStrategy,
timestamp=1394601462327001)
= (column=strategy_options, value={replication_factor:1},
timestamp=1394601462327001)
From what I can gather,
- system_auth only needs to be replicated if not using the allowall
authenticator.
- system_traces replication factor cannot be changed under 1.2.x (
https://issues.apache.org/jira/browse/CASSANDRA-6016)
- system keyspace is set to LocalStrategy. This should not be replicated
as it contains data relevant to the local node.
So I think if I just update the Application Keyspace, I should be okay ?
Thanks for your help.
Matt
On Tue, Mar 18, 2014 at 12:34 AM, Jonathan Lacefield
jlacefi...@datastax.com wrote:
Hello,
Please see comments under your
1) Use GossipingPropertyFileSnitc:
http://www.datastax.com/documentation/cassandra/1.2/cassandra/architecture/architectureSnitchGossipPF_c.html
-
much easier to manage
2) All nodes in the same cluster must have the same cluster name:
http://www.datastax.com/documentation/cassandra/1.2/cassandra/configuration/configCassandra_yaml_r.html
3) Run repair at the very end if you would like, rebuild should take
care of this for you. No need to do it when you are going from Simple
(with 1 DC) to Network (with 1 dc). Not sure you need to do step 2
actually.
4) Yes, all Keyspaces should be updated as a part of this process.
Hope that helps.
Jonathan Lacefield
Solutions Architect, DataStax
(404) 822 3487
http://www.linkedin.com/in/jlacefield
http://www.datastax.com/what-we-offer/products-services/training/virtual-training
On Sun, Mar 16, 2014 at 10:39 PM, Matthew Allen matthew.j.al...@gmail.com
wrote:
Hi all,
New to this list, so apologies in advance if I in inadvertently break
some of the guidelines.
We currently have 2 geographically separate Cassandra/Application
clusters (running in active/warm-standby mode), that I am looking to enable
replication between so that we can have an active/active configuration.
I've got the process working in our Labs, using
http://www.datastax.com/documentation/cassandra/1.2/cassandra/operations/ops_add_dc_to_cluster_t.htmlas
a guide, but still have many questions (to verify that what I have done
is correct), so I'm trying to break down my questions into various emails.
Our Setup
---
- Our replication factor is currently set to 5 in both sites (NSW and
VIC). Each site has 9 nodes.
- We use a read/write quorum of ONE
- We have autoNodeDiscovery set to off in our app ( in anticipation of
multi-site replication), so that it only points to its local Cassandra
cluster
- The 2 sites have a 16-20ms latency
The Plan
-
1. Update and restart each node in active Cluster (NSW) 1 at a time to
get it to use NetworkTopologySnitch in preparation of addition of standby
cluster.
- update cassandra-topologies.yaml file with settings as below so NSW
Cluster is aware of NSW only
- update cassandra.yaml to use PropertyFileSnitch
- restart node
# Cassandra Node IP=Data Center:Rack
xxx.yy.zzz.144=DC_NSW:rack1
xxx.yy.zzz.145=DC_NSW:rack1
xxx.yy.zzz.146=DC_NSW:rack1
xxx.yy.zzz.147=DC_NSW:rack1
xxx.yy.zzz.148=DC_NSW:rack1
... and so forth for 9 nodes
2. Update App Keyspace to use NetworkTopologySnitch with {'DC_NSW':5}
3. Stop and blow away the standby cluster (VIC) and start afresh,
- assign new tokens NSW+100
- set auto_bootstrap: false
- update seeds to point to mixture of VIC and NSW nodes.
- update cassandra-topologies.yaml file with below so VIC Cluster is
aware of VIC and NSW.
- Leave cassandra cluster down
# Cassandra Node IP=Data Center:Rack
xxx.yy.zzz.144=DC_NSW:rack1
xxx.yy.zzz.145=DC_NSW:rack1
xxx.yy.zzz.146=DC_NSW:rack1
xxx.yy.zzz.147=DC_NSW:rack1
xxx.yy.zzz.148=DC_NSW:rack1
... and so forth for 9 nodes
aaa.bb.ccc.144=DC_VIC:rack1
Multi-site Active-Active replication - Maintenance Commands
Hi all, We currently run a script that runs the following on our separate clusters each night. The script operates on 3 nodes (out of 9) a night to minimize impact to the cluster. repair -pr compact cleanup These separate clusters are going to start replicating between each other within a few weeks. I (may) have (mis)read that when using multiple data-centers, that a repair, instead of a repair -pr should be used. I'm reluctant to do this, as when we initially used to run a repair, we would suffer hung repairs and an increased load on the hosts due to multiple ranges being repaired at the same time. So going forward to a multi-dc cluster, we intend to run the following -local repair -pr compact cleanup Is there a definitive answer for this ? Thanks Matt
Setting up Cassandra across private network
I'm currently using Cassandra 1.23 and I'm trying to set up a cluster on the private network, so that nodes can communicate through eth4 inet address instead of eth0 inet address. My current yaml file specify eth4 address in the seed field. However the the rpc address is set to 0.0.0.0. Both listen address and broadcast address are not set. Then I got error message: ERROR 22:52:21,936 Exception encountered during startup java.lang.RuntimeException: No other nodes seen! Unable to bootstrap.If you intended to start a single-node cluster, you should make sure your broadcast_address (or listen_address) is listed as a seed. Otherwise, you need to determine why the seed being contacted has no knowledge of the rest of the cluster. Usually, this can be solved by giving all nodes the same seed list. My guess is the nodes were not be able to communicate with each other but some unspecified field is resolved to eth0 address. Could it be the problem with broadcast/listen address? My nodes share filesystem through NFS so if eth4 address needs to be specified receptively on each node then separate config file will be necessary.
Is it safe to remove (pid file folder) /var/run/cassandra
Is it safe to remove (pid file folder)* /var/run/cassandra* if I think it has got wrong permissions, will it be recreated by process as before ? folder permissions seem to be incorrect immediately after I installed dsc20 due to this sudo service cassandra start fails saying - * could not access pidfile for Cassandra. So is it safe to delete pid file folder(*/var/run/cassandra)* when cassandra is not running ?
Re: Is it safe to remove (pid file folder) /var/run/cassandra
I've verified that problem is solvable by deleting * /var/run/cassandra*folder on my test server. Should I remove the pid folder from my new production server ? On Wed, Mar 19, 2014 at 10:54 AM, user 01 user...@gmail.com wrote: Is it safe to remove (pid file folder)* /var/run/cassandra* if I think it has got wrong permissions, will it be recreated by process as before ? folder permissions seem to be incorrect immediately after I installed dsc20 due to this sudo service cassandra start fails saying - * could not access pidfile for Cassandra. So is it safe to delete pid file folder(*/var/run/cassandra)* when cassandra is not running ?
