Node.js Metrics

This page describes Node.js process metrics that are specific to the Node.js Agent.

You can view the metrics under these paths in the Metric Browser navigation tree:

  • By tier at Application Infrastructure Performance > <TierName> > Node.js.
  • By node at Application Infrastructure Performance > <TierName> > Individual Nodes > Nodejs_<NodeName> > Node.js.

CPU Usage Metric

  • CPU Usage: % busy

Memory Metrics

Garbage Collection

  • Full GC Per Min: Number of full garbage collection cycles per minute that the V8 JavaScript runtime has performed in the selected time range.
  • Incremental GC Per Min: Number of incremental garbage collection cycles per minute that the V8 JavaScript runtime has performed in the selected time range.

Memory

  • Heap size changed: Total amount of memory reclaimed by the full and incremental garbage collection cycles (as a percentage) in the selected time range.
  • Current usage (V8 heap used in MB): Total size of the heap at the current time point. This reports how much memory the node process is using for data storage.
  • RSS: Resident Set Size of the Node process. This reports the amount of memory (heap and stack) allocated for the process and in RAM, not swapped out.

I/O Metrics

Disk

  • KB read per second: KB read from disk per second for the selected time range.
  • KB written per second: KB written to disk per second for the selected time range.

Network

  • Incoming: KB/sec received for the selected time range.
  • Outgoing: KB/sec sent for the selected time range.

Socket.io Metrics

  • Number of Connections: Number of currently open Socket.IO connections.
  • Total Number of Connections: Number of connections that have been opened since the application started.
  • Number of Messages Sent/Received: Number of messages that have been exchanged between the application and all connected Socket.IO clients.
  • Size of Messages Sent/Received: Average size, in characters, of the messages exchanged. The underlying transport is text only, so non-string messages are JSON.serialized to determine their size.

Event Loop Metrics

  • Average IO Time: Average number of milliseconds per event loop tick spent processing IO callbacks.
  • Average Tick Length: Average amount of milliseconds between event loop ticks.
  • Maximum Tick Length: Shortest amount of milliseconds between event loop ticks.
  • Minimum Tick Length: Longest amount of milliseconds between event loop ticks.
  • Tick Count: Number of times the event loop was ticked.