nodejs-dns-performance

A sample node app based on node USDT build to demonstrate per request DNS performance.

This is a work in process to support a future blog post on https://venshare.com/

simple usage

1. On a linux machine install bpftrace. https://github.com/iovisor/bpftrace/blob/master/INSTALL.md

2. Download and unzip the unofficial USDT build https://unofficial-builds.nodejs.org/download/release/v14.15.0/

   $ curl -L https://unofficial-builds.nodejs.org/download/release/v14.15.0/node-v14.15.0-linux-x64-usdt.tar.gz > node.tar.gz
   $ tar xvzf node.tar.gz
   

3. Run the server.js in this folder with the build

   ./v14.15.0/node-v14.15.0-linux-x64-usdt/bin/node server.js
   

4. Attach the bpf script to the node process select the correct one for your OS. If a script isn't available see modifying the bt script below.

   $ sudo bpftrace -p $(pgrep node) dns-trace-fedora.bt     
   

5. Run some load on the server this uses Apache bench but you can also open a browser

   ab -n10 http://localhost:3000/
   

6. In the script screen you should see content similar too

   Attaching 8 probes...
   01:16:38  GET 127.0.0.1/
   DNS Lookup skateipsum.com 12203     211 ms 
   DNS Lookup www.random.org 12203      22 ms 
   Total Request Time:    555 ms 
   ...
   

kubernetes usage

This demo should work on any kubernetes clusters but these steps will take you through running the code on a Free kubernetes cluster on IBM Cloud.

1. Deploy the sample app to the default namespace your cluster

   $ kubectl apply -f deployment.yaml
   

2. The deployment also container a nodeport service. Validate the the service has been exposed. Get the public node IP and the port of the service.

   $ ibmcloud ks worker ls --cluster $CLUSTER_NAME
   ID                                                       Public IP        Private IP       Flavor   State    Status   Zone    Version   
   kube-buem3v1f086vb3t9m4g0-bpftracedem-default-0000003f   159.122.175.48   10.144.195.187   free     normal   Ready    mil01   1.18.10_1531   
   
   $ kubctl get svc
   kubernetes                       ClusterIP   172.21.0.1     <none>        443/TCP          33m
   nodejs-dns-performance-service   NodePort    172.21.59.41   <none>        3000:31286/TCP   11m
   

3. curl the endpoint to ensure it's working

   $ curl http://159.122.175.48:31286/
   ["Skate ipsum dolor sit amet,  flail boneless ....
   

modifying the bt script

The script attaches to the uprobes in libc. This is dependant on the location of libc.so.6 on your linux machine. libc.so.6 is usually in your /usr folder and can be found with

$ sudo find /usr -name libc.so.6 

Once you have the location update the uprobe: definintions in the bt file with the correct location.