>From: Unidata User Support <address@hidden> >Organization: UCAR/Unidata >Keywords: 200303151644.h2FGivB2018646 IDD NLDN LDM-6 Hi David et. al., I have been working with Gilbert Sebenste of Northern Illinois University <address@hidden> to get NIU upgraded to the latest release candidate of LDM-6 (an as yet unannounced version of the LDM). During this process, I asked Gilbert to consolidate all of his IDD ingest on a single machine so that only one machine from NIU would report real time statistics back to the UPC. One result of this is his request for weather2.admin.niu.edu to be allowed to receive NLDN data: From: Gilbert Sebenste <address@hidden> Date: Fri, 14 Mar 2003 23:28:54 -0500 (EST) To: address@hidden "Also...I need to have striker.atmos.albany.edu allow weather2.admin.niu.edu to feed NLDN from it. I can't remember who controls this now...but if the responsible person reads this, can you allow me in (I'm trying to feed from you now)? Thanks much!" I figured that since Gilbert forgot who to send this request to, I should chime in. The second topic I wanted to discuss is SUNY Albany upgrading its LDM servers to LDM-6. We have been running the latest release candidate, LDM-6.0.2, _hard_ on several machines in the UPC and around the US and world, and the results look very good. Until Steve Emmerson told me about a problem with ldmsend, I was all set to announce LDM-6.0.2 to the community this weekend. Now, I will wait until all known bugs are fixed. Nonetheless, I want to encourage you to upgrade to LDM-6.0.2 _IF_ you do not use ldmsend for any activities. If you do, or if you would rather wait until we have solved all known bugs, it would be wise to wait. The following is the note I have been sending to top level IDD relay sites regarding upgrading to LDM-6. It will be included in the general announcement of LDM-6 availability, so you will be seeing it again in a few days: Notes: - The online documentation for LDM was just put on the my.unidata web site yesterday. It may undergo some touching up in the next few days. LDM 6 offers a number of new ideas that we are excited about. Here's an overview: o request lines to the same host in ldmd.conf are no longer accumulated into a single rpc.ldmd invocation. This allows a user to split feeds without having to create machine name aliases in /etc/hosts. o the size of the HEREIS - COMINGSOON "fence" is now user configurable. In LDM-5, all products smaller than 16384 bytes would be sent using the HEREIS protocol. In LDM-6, this "fence" is settable on a per-request line basis. The default for the "fence" size is now essentially infinity (actually, it is size of a uint). You specify the "fence" size as the 4th parameter on an ldmd.conf request line. LDM-6 understands a couple of mnemonics for minimim and maximum "fence" sizes: request IDS|DDPLUS ".*" my.upstream.site PRIMARY (or PRI) request IDS|DDPLUS ".*" my.upstream.site ALTERNATE (or ALT) or equivalently: request IDS|DDPLUS ".*" my.upstream.site MAXIMIM (or MAX) request IDS|DDPLUS ".*" my.upstream.site MINIMUM (or MIN) We think that the PRI (uint_max) and ALT (zero) values are basically all that a site will ever need/use, but the values are configurable nonetheless. o products sent with the COMINGSOON/BLKDATA protocol are sent in one chunk after a transaction is made between the client and server in which the client says that it wants the product. In LDM-5, the same client/server transaction was made and then the product was sent in 16384 BLKDATA chunks. o LDM-6 is backward/forward compatible with LDM-5. LDM-5 clients can receive data from LDM-6 servers, and LDM-6 clients can receive data from LDM-5 servers. When LDM-5 talks to LDM-6, it does so using LDM-5 protocols. LDM-6 running LDM-5 protocols is more efficient than LDM-5. o LDM-6 can use the same product queue that LDM-5 uses. This allows a site to install the new version and start running without remaking the product queue. o LDM-6 is much more capable of delivering data to electronically remote sites. One site we have been using for testing is located on the edge of the Amazon in Belem, Brazil. o LDM-6's ldmadmin now does several things for you that you had to do by hand in LDM-5: o put you in the ~ldm directory at LDM startup o create the ~ldm/logs/ldmd.log file if it does not already exist o determine your machine's hostname using a 'uname -n'. If this does not result in a fully qualified hostname, ldmadmin will complain and not start the LDM. In this case, you need to edit ldmadmin and set the hostname: change: chop($hostname = `uname -n`); # $hostname = "your.hostname.here"; to: # chop($hostname = `uname -n`); $hostname = "yourown.hostname.edu"; o LDM-6's ldmadmin now waits until the rpc.ldmd processes have all exited before returning you to the Unix command prompt o LDM-6 now understands CONDUIT and CRAFT as the NMC2 and NEXRD2 streams. o Some early tests using synthesized data showed that LDM-6 was capable of moving 8.4 times more data than LDM-5. The increase in "efficiency" using real data has, however, not yet been quantified, but qualitatively we can assure that the increase in "efficiency" is real. For reference, the early tests that showed the 8.4 times increase was conducted between a machine here at the UPC, and a Linux PC running at the Universidade Federal do Para in Belem, Brazil using synthetic products that were each 200KB in size. Also, during the test, the client LDM did not write into a product queue. N.B. (nota bene/yo): During stress testing of the LDM-6, we learned that there is a class of "pathological" regular expressions that adversly affect the performance of LDM servers. Steve sent a note to ldm-users explaining how to identify pathological cases, and what to do to correct these. Unfortunately, it is the client requesting data that has control over these regular expressions, so if you find these in your ldmd.log files, you will need to contact the downstream host's administrator and ask him/her to correct the pattern. Steve has included a new function in LDM-6, regex, that can be used to test regular expressions for pathologicalness ;-). Check the regex man page for more information after you install LDM-6. To upgrade to LDM-6, then you should do the following: 1) make backup copies of your ~ldm/etc/ldmd.conf file(s). While you are at it, you could make a backup copy of your ~ldm/etc/pqact.conf file, but this is optional since it will not be affected by moving to LDM-6. 2) FTP LDM-6 release candidate 6.0.2: <login as 'ldm'> cd ~ldm ftp ftp.unidata.ucar.edu <user> anonymous <pass> your_full_email_address cd pub/ldm/test binary get ldm-6.0.2.tar.Z quit zcat ldm-6.0.2.tar.Z | tar xvf - 3) build LDM-6. Note that LDM-6 is built with '-O' optimization turned on. If you want to build otherwise, you will want to set the Unix environment variable CFLAGS _before_ you run configure. Also, you should define the Unix environment variable LDMHOME _before_ you run configure: setenv LDMHOME your_ldm_home_directory cd ~ldm/ldm-6.0.2/src ./configure make && make install 4) finish the LDM install as 'root': sudo make install_setuids 5) adjust entries in ldmadmin to match those from your existing ldmadin. This should boil down to you changing the product queue size; the number of log files that you want to keep online (we keep 14 on our IDD machines); uncommenting out the entry for udunits if you are running things like gribtonc; filling in your full hostname if a 'uname -n' does not return a fully qualified hostname; etc. 6) shutdown your current LDM waiting for all LDM processes to exit. This step is easier in LDM-6 since ldmadmin won't return you to the Unix/Linux prompt before processes have exited. 7) add the execution of the real time statistics routine, rtstats to your ~ldm/etc/ldmd.conf file: add: exec "rtstats -h rtstats.unidata.ucar.edu" somewhere in the list of 'exec's at the top of ldmd.conf 8) change the runtime link to point at ldm-6.0 cd ~ldm rm runtime && ln -s ldm-6.0.2 runtime 9) verify that your operating system has finished flushing the LDM queue from memory to disk. I found that this was an important step in getting things to work smoothly on thelma. I did the verification by watching the iostat listing of top. As soon as it quites down, you are ready to go. Our experience is that the larger the queue, the longer this step takes. We even added a 'sync' call from ldmadmin to tell the OS to sync to disk before shutting down LDM processes. 10) start LDM-6: rehash <- C shell only ldmadmin start I think I have covered all bases in this note, but you never know. After your LDM-6 is up and running, and you are reporting real time statistics, you can review latencies, datastream volumes, datastream product numbers, and topology at: http://www.unidata.ucar.edu/staff/chiz/rtstats This web page will likely change in the future, but it is very useful right now. If you would help doing the upgrade or have any questions, just let us know. Tom Yoksas
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