{"id":738,"date":"2024-08-03T09:55:47","date_gmt":"2024-08-03T09:55:47","guid":{"rendered":"https:\/\/doctor-dark.co.uk\/blog\/?p=738"},"modified":"2024-08-29T12:11:45","modified_gmt":"2024-08-29T12:11:45","slug":"how-not-to-do-cluster-monitoring","status":"publish","type":"post","link":"https:\/\/doctor-dark.co.uk\/blog\/how-not-to-do-cluster-monitoring\/","title":{"rendered":"How not to do cluster monitoring."},"content":{"rendered":"\n

The world should have blinkenlights on its computer systems. That’s a given.<\/p>\n\n\n\n

I wrote a couple of things. One was a Python program that pinged the four machines forming the cluster, and displayed a red or green light on a UnicornHD HAT to show their status. It worked very nicely. Then I wrote Python code to form part of any program that would be run in parallel on the cluster, which would send a signal saying whether each core was busy or not. It worked nicely, and I now had a row of 16 LEDs, in red or green, so I could see what was going on. It was very pretty.<\/p>\n\n\n\n

Unfortunately, as it worked by sending a file by FTP every time a processor core changed between running and idle, it created a very effective Denial of Service attack on our network. Oops.<\/p>\n\n\n\n

Now that I have thought about it more carefully, I shall be constructing a much better monitoring system, which will be based on sockets. I’ve been avoiding learning how to use them for far too long, anyway…<\/p>\n\n\n\n

Later:<\/p>\n\n\n\n

I tried at least umpteen example programs using sockets, and the connections were all rejected, and I couldn’t work out how to fix that. Suggestions, anyone?<\/p>\n\n\n\n

Using a Python program to query the cluster computers took nearly six seconds to look at the 16 cores, hardly blinkenlights… A quick hack of a bash script, astonishingly, took almost as long. Back to trying to get sockets to work, then…<\/p>\n\n\n\n

Working sockets tutorial!<\/h2>\n\n\n\n

At last, I found a socket programming example that worked, here<\/a>!<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

I wanted to give Zan a tiny donation, but sadly his GoFundMe page seems defunct, and possibly the message I tried to send him also failed…<\/p>\n\n\n\n

Sadly, I was then unable to work out how to accept multiple connections from the cluster computers. <\/p>\n\n\n\n

Threading sockets programs!<\/h2>\n\n\n\n

There’s another set of client-server demos on GitHub, here<\/a>, that I tested with Marvin and two of the Oysters, to confirm that it can do what I want. I can hoik code from those while retaining the program logic, and maybe get all four Oysters to send their status to Marvin, for him to display. I am not at all bothered that I am writing control system code for the cluster, instead of getting round to some fun applications of parallelism<\/p>\n\n\n\n

\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

The world should have blinkenlights on its computer systems. That’s a given. I wrote a couple of things. One was a Python program that pinged the four machines forming the cluster, and displayed a red or green light on a UnicornHD HAT to show their status. It worked very nicely. Then I wrote Python code … Continue reading “How not to do cluster monitoring.”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20,7],"tags":[15,13,30,31,32],"class_list":["post-738","post","type-post","status-publish","format-standard","hentry","category-computing","category-raspberry-pi","tag-led","tag-raspberrypi","tag-cluster","tag-dosattack","tag-python-2"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/posts\/738","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/comments?post=738"}],"version-history":[{"count":5,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/posts\/738\/revisions"}],"predecessor-version":[{"id":754,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/posts\/738\/revisions\/754"}],"wp:attachment":[{"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/media?parent=738"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/categories?post=738"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/doctor-dark.co.uk\/blog\/wp-json\/wp\/v2\/tags?post=738"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}