how do I pipe in file content as args to kubectl?

Question

I wish to run k6 in a container with some simple javascript load from local file system, It seems the below had some syntax error

$ cat simple.js
import http from 'k6/http';
import { sleep } from 'k6';
export const options = {
  vus: 10,
  duration: '30s',
};
export default function () {
  http.get('http://100.96.1.79:8080');
  sleep(1);
}

$kubectl run k6 --image=grafana/k6 -- run - <simple.js 
//OR
$kubectl run k6 --image=grafana/k6 run - <simple.js

in the k6 pod log, I got

│ time="2023-02-16T12:12:05Z" level=error msg="could not initialize '-': could not load JS test 'file:///-': no exported functions in s │

I guess this means the simple.js is not really passed to k6 this way?

thank you!

Answer 1

I think you can't pipe (host) files into Kubernetes containers this way.

One way that it should work is to:

1. Create a ConfigMap to represent your file
2. Apply a Pod config that mounts the ConfigMap file

NAMESPACE="..." # Or default

kubectl create configmap simple \
--from-file=${PWD}/simple.js \
--namespace=${NAMESPACE}

kubectl get configmap/simple \
--output=yaml \
--namespace=${NAMESPACE}

Yields:

apiVersion: v1
kind: ConfigMap
metadata:
  name: simple
data:
  simple.js: |
    import http from 'k6/http';
    import { sleep } from 'k6';

    export default function () {
      http.get('http://test.k6.io');
      sleep(1);
    }

NOTE You could just create e.g. configmap.yaml with the above YAML content and apply it.

Then with pod.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: simple
spec:
  containers:
    - name: simple
      image: docker.io/grafana/k6
      args:
      - run
      - /m/simple.js
      volumeMounts:
      - name: simple
        mountPath: /m
  volumes:
    - name: simple
      configMap:
        name: simple

Apply it:

kubectl apply \
--filename=${PWD}/pod.yaml \
--namespace=${NAMESPACE}

Then, finally:

kubectl logs pod/simple \
--namespace=${NAMESPACE}

Yields:

          /\      |‾‾| /‾‾/   /‾‾/   
     /\  /  \     |  |/  /   /  /    
    /  \/    \    |     (   /   ‾‾\  
   /          \   |  |\  \ |  (‾)  | 
  / __________ \  |__| \__\ \_____/ .io

  execution: local
     script: /m/simple.js
     output: -

  scenarios: (100.00%) 1 scenario, 1 max VUs, 10m30s max duration (incl. graceful stop):
           * default: 1 iterations for each of 1 VUs (maxDuration: 10m0s, gracefulStop: 30s)


running (00m01.0s), 1/1 VUs, 0 complete and 0 interrupted iterations
default   [   0% ] 1 VUs  00m01.0s/10m0s  0/1 iters, 1 per VU

running (00m01.4s), 0/1 VUs, 1 complete and 0 interrupted iterations
default ✓ [ 100% ] 1 VUs  00m01.4s/10m0s  1/1 iters, 1 per VU

     data_received..................: 17 kB 12 kB/s
     data_sent......................: 542 B 378 B/s
     http_req_blocked...............: avg=128.38ms min=81.34ms med=128.38ms max=175.42ms p(90)=166.01ms p(95)=170.72ms
     http_req_connecting............: avg=83.12ms  min=79.98ms med=83.12ms  max=86.27ms  p(90)=85.64ms  p(95)=85.95ms 
     http_req_duration..............: avg=88.61ms  min=81.28ms med=88.61ms  max=95.94ms  p(90)=94.47ms  p(95)=95.2ms  
       { expected_response:true }...: avg=88.61ms  min=81.28ms med=88.61ms  max=95.94ms  p(90)=94.47ms  p(95)=95.2ms  
     http_req_failed................: 0.00% ✓ 0        ✗ 2  
     http_req_receiving.............: avg=102.59µs min=67.99µs med=102.59µs max=137.19µs p(90)=130.27µs p(95)=133.73µs
     http_req_sending...............: avg=67.76µs  min=40.46µs med=67.76µs  max=95.05µs  p(90)=89.6µs   p(95)=92.32µs 
     http_req_tls_handshaking.......: avg=44.54ms  min=0s      med=44.54ms  max=89.08ms  p(90)=80.17ms  p(95)=84.62ms 
     http_req_waiting...............: avg=88.44ms  min=81.05ms med=88.44ms  max=95.83ms  p(90)=94.35ms  p(95)=95.09ms 
     http_reqs......................: 2     1.394078/s
     iteration_duration.............: avg=1.43s    min=1.43s   med=1.43s    max=1.43s    p(90)=1.43s    p(95)=1.43s   
     iterations.....................: 1     0.697039/s
     vus............................: 1     min=1      max=1
     vus_max........................: 1     min=1      max=1

Tidy:

kubectl delete \
--filename=${PWD}/pod.yaml \
--namespace=${NAMESPACE}

kubectl delete configmap/simple \
--namespace=${NAMESPACE}

kubectl delete namespace/${NAMESPACE}