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What a rocky start to labor day weekend

Woke up by earthquake at 7:00 AM in morning and then couldn't get to sleep. I took a bath, made my tea and started checking emails and saw that after last night deployment three storage node out of 100s of nodes were running into Full GC. What was special about the 3 nodes was that each one was in a different Data centre but it was named same app02.  This got me curious I asked the node to be taken out of rotation and take a heap dump.  Yesterday night a new release has happened and I had upgraded spymemcached library version as new relic now natively supports instrumentation on it so it was a suspect. And the hunch was a bullseye, the heap dump clearly showed it taking 1.3G and full GCs were taking 6 sec but not claiming anything.



I have a quartz job in each jvm that takes a thread dump every 5 minutes and saves last 300 of them, checking few of them quickly showed a common thread among all 3 data centres. It seems there was a long running job that was trying to replicate pending storage objects as per replication policy and it had 50M or so backlog to catchup.  It seems newrelic was holding on to all that data for the thread and not just collecting the aggregate stats, the job was running for hours causing memory to increase with each replicated file.

Now I had two options:-
  1. Rollback the library
  2. Suppress newrelic instrumentation
I thought of going option#2 as it wont require any new build, just run puppet and restart all nodes.  Boy I was wrong , newrelic has negligible documentation for the yml file.  I filed a support ticket as they have no phone support even for emergencies even though we pay thousands of dollars a month. After IPO their support team quality has also reduced, the support told me hey go and disable the class, i am like its natively supported by you so give me some hints how to do it. She told me that a OOM ticket is filed 2 versions ago so I can wait for it to be fixed, wtf. I waited 20 min for her to tell me how to disable it and no reply,  It seems even she didnt knew how to do it so she was buying time letting me hanging dry on a cloth line. I started mining the support forum and google and I tried 5-10 settings with our devops engineer and newrelic agent is stupid that it would take any wrong setting too and show it in the UI. I ended up with a settings nightmare


Finally I tried one setting which was weird but worked, I had updated library to spymemcached-2.12.1 but the setting to turn it off in newrelic was

  class_transformer:
    com.newrelic.instrumentation.spymemcached-2.12.0:
      enabled: false

notice the setting is called 2.12.0 even though my library is 2.12.1, wtf.  It was late in night for the devops engineer and I was almost 5 hours on the desk, we just patched those 3 special nodes and called it a day. The other nodes would be patched by puppet before Monday using automation. 

Today I also complete 7  years at the company :).


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