Taming the dragon: using llnode to debug your Node.js application

• autocannon

  14 7,917 5.7 JavaScript

  fast HTTP/1.1 benchmarking tool written in Node.js

  To make things interesting, let’s send some requests to this server with autocannon:

• SaaSHub

  www.saashub.com featured

  SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives

  

• llnode

  2 1,154 0.0 C++

  An lldb plugin for Node.js and V8, which enables inspection of JavaScript states for insights into Node.js processes and their core dumps.

  

  The result shows us that there's an array holding a lot (156027) of objects, and is probably the reason we have so many Visit objects in memory (spoiler: it is, look at line 13 and 16 of our server). Unfortunately, llnode can't tell where this array is located yet, but there's an open issue to add this feature in the future.

• lldb-mi

  12 167 2.4 C++

  LLDB's machine interface driver

  

  Fortunately, we can use this same technique with our Node.js applications! This is possible through llnode: a LLDB plugin which enables us to inspect Node.js core dumps. With llnode, we can inspect objects in the memory and look at the complete backtrace of the program, including native (C++) frames and JavaScript frames. It can be used on a running Node.js application or through a core dump.

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