http://www.datastax.com/support-forums/tags/key Software, Support, and Training for Apache Cassandra en-US Sun, 26 May 2013 08:33:32 +0000 http://bbpress.org/?v=1.0.3 q http://www.datastax.com/support-forums/search.php http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1946 Sun, 20 May 2012 20:25:21 +0000 nickmbailey 1946@http://www.datastax.com/support-forums/ <p>Glad you got everything working. I've created an internal bug to investigate SELinux on RHEL 6.0 further. If we need any further information we will update this forum post.</p> <p>Thanks for the bug report! </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1945 Sat, 19 May 2012 16:53:31 +0000 Anonymous 1945@http://www.datastax.com/support-forums/ <p>I've been able to resolve the problem, and now all agents are working - thanks for your help. The situation was that I'd disabled SSL while working on an earlier agent connection problem. Uninstalling and reinstalling the agent restored the default SSL settings, leaving the agent trying to use SSL to connect to an opscenter that was not using it.</p> <p>I appreciate very much your prompt and helpful responses. Your suggested workaround of disabling SELinux during the agent install was the key to resolution. I'm a little concerned that this was necessary, and if you need anything more to diagnose it, I'll be happy to provide it. However, my original issue is resolved. </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1943 Sat, 19 May 2012 01:05:32 +0000 nickmbailey 1943@http://www.datastax.com/support-forums/ <p>Thanks for the additional information. </p> <p>Regarding the install from the UI not working, do you know if the agent process managed to start? There are two places I would look for errors. '/var/log/opscenter-agent/installer.log' will contain the log of the installation process. If that appears normal then the normal agent log '/var/log/opscenter-agent/agent.log' should hopefully indicate any communication problems if the install succeeded and the process started.</p> <p>Any errors from those logs will help us debug, but obviously if the manual installation is working for you, you can continue to use that. </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1942 Sat, 19 May 2012 00:57:17 +0000 Anonymous 1942@http://www.datastax.com/support-forums/ <p>I had already installed the agent manually, but uninstalled it with </p> <blockquote><p>yum opscenter-agent erase</p></blockquote> <p>and cycled opscenter.</p> <p>This restored the problem. Here is additional context from the failed install:</p> <blockquote><p> 2012-05-18 17:42:47-0700 [CA_APM] INFO: Beginning install of OpsCenter agent to 138.42.81.221<br /> 2012-05-18 17:42:47-0700 [] couldn't get fingerprint for SSH key ('ssh-rsa', 'AAAAB3NzaC1yc2EAAAABIwAAAQEA3TgMr2NFv5HI5m++1ycFrJE75h6NPRW/Bg+RoMTF68jhgbr8TBRpO43gntPc5WA+CyTEV3Jj9P+xfMVccP2q/+uqHYqZU3fYxFn3Dm2WpuZh0Q8E3v7yNOolsOUarc0pZ6iFeQnaOcIv7lc9xNFURsDkcJgACejnPN9YRvozCdWw0HyzkDDLuO2HAlpySSeSk1y1mj5PEctyvMQ7o+3SIIueykiUcqelCMDFEFMvZENtWkb6TbsytTFjLg6GoWFUgImUFrrT390svSx0inz1OVl9LNpx6C0SZAuCD+FD8y7Yw6puE3TCneaP2hh3N4W6c6XTlkICqnLWZ7wTNbkxrw=='):</p> <p> /usr/share/opscenter/tmp/tmp0tSgtF: Permission denied<br /> Traceback (most recent call last):<br /> Failure: twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1. </p></blockquote> <p>I then tried your suggested workaround, and it appeared to work - the agent install finished successfully.</p> <blockquote><p> 2012-05-18 17:47:01-0700 [CA_APM] INFO: Beginning install of OpsCenter agent to 138.42.81.221<br /> 2012-05-18 17:47:32-0700 [CA_APM] INFO: Install of OpsCenter agent to 138.42.81.221 complete </p></blockquote> <p>However, opscenter didn't detect the agent, even after a recycle. I tried - and succeeded - in installing it a second time, and also recycled opscenter. It still cannot detect the agent (the opscenter console still states "1 of 2 agents connected" and shows a "Fix" link. The missing agent is on the opscenter server box itself. </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1941 Fri, 18 May 2012 17:59:27 +0000 nickmbailey 1941@http://www.datastax.com/support-forums/ <p>Have you tried installing the agents again since running the chcon command? Assuming it is still failing, attaching more context from the failure in the log may help.</p> <p>As a temporary workaround I believe you can disable selinux temporarily in order to install the agents. 'setenforce 0' should accomplish this. You may also need to restart the OpsCenter process. </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1932 Fri, 18 May 2012 00:18:28 +0000 Anonymous 1932@http://www.datastax.com/support-forums/ <p>SELinux is enabled. The chcon command you suggested gave no response, so I added the -v argument:</p> <blockquote><p> [root@bvdl-vm-01 cassandra]# sestatus<br /> SELinux status: enabled<br /> SELinuxfs mount: /selinux<br /> Current mode: enforcing<br /> Mode from config file: enforcing<br /> Policy version: 24<br /> Policy from config file: targeted<br /> [root@bvdl-vm-01 cassandra]# which chcon<br /> /usr/bin/chcon<br /> [root@bvdl-vm-01 cassandra]# which setenforce<br /> /usr/sbin/setenforce<br /> [root@bvdl-vm-01 cassandra]# chcon -vt ssh_home_t /usr/share/opscenter/tmp<br /> changing security context of `/usr/share/opscenter/tmp' </p></blockquote> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1930 Thu, 17 May 2012 01:30:47 +0000 nickmbailey 1930@http://www.datastax.com/support-forums/ <p>This also sounds like a problem with SELinux in RHEL 6.0. Can you confirm if SELinux is enabled or not?</p> <p>Assuming it is running can you run the following commands and post the output:</p> <p>which chcon<br /> which setenforce<br /> chcon -t ssh_home_t /usr/share/opscenter/tmp</p> <p>That last command is the command that should have been run during install to enable the correct SELinux permissions on the directory. The first two commands will help us debug why it may not have worked. </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-1927 Wed, 16 May 2012 23:29:50 +0000 Anonymous 1927@http://www.datastax.com/support-forums/ <p>I am having the same problem on RHEL 6.0. An attempt to install an agent with opscenter fails with the cryptic message:</p> <p>Error during agent install (c(d, f) is null).</p> <p>/var/log/opscenter/opscenterd.log contains:</p> <p>/usr/share/opscenter/tmp/tmpVtC6da: permission denied</p> <p>However, directory permissions are wide open:</p> <p>[root@bvdl-vm-01 opscenter]# ls -lt /usr/share/opscenter<br /> total 28<br /> drwxrwxrwx. 2 opscenter opscenter 4096 May 16 15:53 tmp</p> <p>and if I su to opscenter, I can update the directory without any problem. </p> http://www.datastax.com/support-forums/topic/help-me-learn#post-898 Wed, 21 Dec 2011 04:17:27 +0000 Anonymous 898@http://www.datastax.com/support-forums/ <p>Ok... So you can have a single "row" with a bunch of "columns" and no "values". I can see how this might be useful... But please elaborate on the contents of the third paragraph (Both of these column fam...). In this example, why would you want to create a setup with just a single row and a ton of columns? Why not make it a single column with a ton of rows? </p> http://www.datastax.com/support-forums/topic/help-me-learn#post-884 Tue, 20 Dec 2011 18:29:51 +0000 zznate 884@http://www.datastax.com/support-forums/ <p>To satisfy those queries you are looking at 2 column families:</p> <p>TagsByDriver<br /> - comparator would be the UTF8Type to maintain the columns sorted alphabetically by name<br /> - column name is the driver name, value could be a serialized list of 1 or more tags</p> <p>TagIndex<br /> - using, in this trivial example, LongType comparator to order the columns by tag<br /> - column name is the tag, column value the driver name</p> <p>Both of these column families need row keys still. In the above example we are treating these as indexes, taking advantage of the comparator sort order to minimize disk seeks. Cassandra can store 2 billiion columns in a single row, but because a row is the unit of distribution in the cluster, this would create hot spots where a single node would hold all the results.</p> <p>To avoid this we would have to 'bucket' results in such a way that makes them easier to break up. In the above, the row keys could be the first two characters of the name and tag number respectively. We still have some hotspot potential here, so you would want to play with this bucketing a bit depending on distribution of results. </p> <p>If you need a higher level search - say all drivers starting with N, then you would create all the 26 potential combinations and issue a multiget_slice as opposed to a get_slice (the former retrieving N keys at a time). Same with tag: for 102 to 104 you would issue a multiget_slice for 102,103,104. </p> <p>There are several other ways to do this, but this example is the most approachable, IMO. Because we are relying on a column index of the comparator, lookups - even for a large number of users in order - only consist of two disk seeks: one to locate the row, the next to seek to the column position. The read is then sequential regardless of the number of results. </p> <p>To "page" over results, use the following approach:<br /> 1. initial get_slice with a slicepredicate containing null for start and end with a limit of 2<br /> 2. use the last result of the above get_slice as the "start" for the next get_slice and set the limit to 3 (N+1)<br /> 3. skip the first result (since you displayed it last time [though seemingly dumb, this is sort of fundamental to a distributed columnar datastore where you 'don't know what you have until you have it])<br /> 4. go to step 2 with results from 3 </p> http://www.datastax.com/support-forums/topic/help-me-learn#post-882 Tue, 20 Dec 2011 17:53:09 +0000 Anonymous 882@http://www.datastax.com/support-forums/ <p>I read that already... And it gives a nice overview of the structure itself and such, but it is by no means clear. For instance, though there are secondary indexes defined in this example, it doesn't explain if those indexes let me then request sorted data in a response based on those columns. And time_ordered_blogs_by_user??? I understand that this column family has something to do with getting information sorted, but it is not explained just sort of dropped in there, and there are no code examples.</p> <p>Given that, I believe all my original questions are still valid and I still need them answered. </p> http://www.datastax.com/support-forums/topic/help-me-learn#post-879 Tue, 20 Dec 2011 16:09:21 +0000 zznate 879@http://www.datastax.com/support-forums/ <p>Read this first: <a href="http://www.datastax.com/docs/1.0/ddl/index" rel="nofollow">http://www.datastax.com/docs/1.0/ddl/index</a></p> <p>Not intended to be an RTFM, but the above should answer all your questions and give you an overview of how Cassandra stores data on disk (and taking advantage of this in your data model to minimize disk seeks). </p> <p>In short, a very good place to start. </p> <p>If you have specific questions after reading the above, I will be happy to answer them. </p> http://www.datastax.com/support-forums/topic/help-me-learn#post-875 Tue, 20 Dec 2011 06:37:06 +0000 Anonymous 875@http://www.datastax.com/support-forums/ <p>Ok... Very new to Cassandra. Still trying to wrap my head around how it works. Let me start with a super simple table.</p> <p>This is a table matching car license plates to vehicle owners. Tag numbers are unique and will be the most looked-up value so that will be my primary key. For simplicity's sake, let's also assume people's names are a single word and unique as well. I get this:</p> <p>Tag | Owner<br /> -----------<br /> 211 | Jack<br /> 112 | David<br /> 313 | Suzanne<br /> 114 | Jack<br /> 227 | Mike<br /> 472 | Adam<br /> 552 | Mike<br /> 102 | Jason</p> <p>As you can see, Jack and Mike both have two cars, and everyone else only has one.</p> <p>Now, here are my questions:</p> <p>* How would I get a list of all tag numbers in ascending order?<br /> * How would I get a list of all tag numbers held by Jack? In ascending order?<br /> * How would I get a list of all the owners in alphabetical order?<br /> * What if this was on a web page showing 2 names at a time. How do I get the next two and so on? In order?<br /> * Knowing I need the above information in the above forms in advance, how do I set this ColumnFamily (???) up in Cassandra in the most optimum fashion?</p> <p>Thanks in advance for helping out a Cassandra noob!!! </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-771 Sat, 26 Nov 2011 23:11:35 +0000 Anonymous 771@http://www.datastax.com/support-forums/ <p>OS: RHEL 6</p> <p><code>so the authorized_keys and known_hosts files need to be updated for that user (home directory: /usr/share/opscenter/</code></p> <p>ok, i will try that</p> <p>Same as stopping SELinux</p> <p>thnx :D </p> http://www.datastax.com/support-forums/topic/unable-to-install-remote-agent-couldnt-get-fingerprint-for-ssh-key#post-770 Sat, 26 Nov 2011 22:55:17 +0000 nickmbailey 770@http://www.datastax.com/support-forums/ <p>What operating system are you installing on? On RHEL/CentOS systems the opscenter process runs as the opscenter user, so the authorized_keys and known_hosts files need to be updated for that user (home directory: /usr/share/opscenter/).</p> <p>We have seen problems similar to this when installing on RHEL/CentOS with SELinux enabled. Do you have SELinux turned on? The install script attempts to set permissions on /usr/share/opscenter/tmp correctly but there may still be a problem related to that. </p>