Joyent announced the offering at the Node Summit conference, being held this week in San Francisco.
One early user was Walmart, which used the tool to debug a very slow memory leak that would only become evident a week or so after starting a Node.js instance. "Memory that leaks out slowly is really dastardly, because it is too small to notice in minutes or even hours," Cantrill said. "Understanding where the memory is going is brutally hard, because you can't reproduce it in development. It has to be done in production."
Joyent first built the diagnostic toolchain to monitor Node.js deployments on Joyent's version of Solaris, called SmartOS. The toolchain runs on Joyent's hosted storage service Manta, which includes compute capabilities. A Joyent engineer developed a way to run the diagnostics on core dumps from a Linux kernel in addition to Solaris kernels, which allowed the company to open the service to a wider possible user base, Cantrill said.