readNamespacedPodLog with follow=true

[cabrinoob]

I have a problem with the usage of readNamespacedPodLog with the follow parameter set to true.

This function returns a Promise (BlueBird). I'd like to display the logs in real time of a pod in my Angular app but I have no idea of how to use the promise of a streamed response ...

I tried this :

import * as rxnode from 'rx-node' 
...
let logs = await this.k8sApi.readNamespacedPodLog(podName,this.ns,containerName,true)
rxnode.fromReadableStream(logs.response).subscribe((i)={
 ...
})

I saw in the source code that the Promise returns a http.ClientResponse which extends an IncomingMessage which extends a stream.Readable which implements NodeJS.ReadableStream. So thats why I though using .fromReadableStream with the rx-node librarie ... But it does'nt work.

Do you have any advice of how I can use this method (in streaming way) with Javascript?

Thank you

[brendandburns]

The stream should implements events, so you can run:

stream.on('data', (chunk) => { ... })

[cabrinoob]

@brendanburns
Hi,
Do you have a snippet because I'am doing like this :

let obj = await this.k8sApi.readNamespacedPodLog(podName,this.ns,containername,true)
obj.response.on('data',(chunk) => {
    console.log(chunk.toString())
})

And it does'nt work. I'am stucked on the await. I cannot figure out how to mix promise and stream ...

[brendanburns]

I'll try to repro/write an example today... Thanks for the patience!

…

On Fri, Sep 28, 2018, 7:35 AM cabrinoob ***@***.***> wrote: @brendanburns <https://github.com/brendanburns> Hi, Do you have a snippet because I'am doing like this : let obj = await this.k8sApi.readNamespacedPodLog(podName,this.ns,containername,true) obj.response.on('data',(chunk) => { console.log(chunk.toString()) }) And it does'nt work. I'am stucked on the await. I cannot figure out how to mix promise and stream ... — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#110 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABOYXt7bkCADVNhzuWuAnUtz3ByuUMEQks5ufjPNgaJpZM4W61P8> .

[marvinosswald]

this issue over at the python client matches with my observations, the promise never resolves with follow true

kubernetes-client/python#199

[brendandburns]

Edit: This example is incorrect, see below

Yeah, I think what you need to do is:

const promise =  this.k8sApi.readNamespacedPodLog(podName,this.ns,containername,true);
obj.response.on('data',(chunk) => {
    console.log(chunk.toString())
})
const obj = await promise;

This is because the log with follow=true never closes the TCP stream, so the promise never completes.

But if you await after you register the event listener, you should get events...

[dkapanidis]

I don't get the example, how is obj used before it is initialized?

I get ReferenceError: obj is not defined trying this

Yeah, I think what you need to do is:

const promise =  this.k8sApi.readNamespacedPodLog(podName,this.ns,containername,true);
obj.response.on('data',(chunk) => {
    console.log(chunk.toString())
})
const obj = await promise;

This is because the log with follow=true never closes the TCP stream, so the promise never completes.

But if you await after you register the event listener, you should get events...

[brendandburns]

Ah, sorry, you are correct, I was skimming and not paying careful enough attention to the code.

I think that this will require a different solution, which probably involves writing some custom code.

Sorry for the mislead.

[juliahw]

@cabrinoob Did you ever find a workaround? I'm stuck on the same issue.

[cabrinoob]

@juliahw : No. I think i'll try to take a look at socket.io with a nodeJS backend or whatever. But for me, this cannot work as expected directly using a promise that returns a stream

[juliahw]

Ok :( I think the GoDaddy Kubernetes client might be able to do this, so I'll give it a go. It's too bad we can't use the officially supported library.

[cabrinoob]

Yes, it could be nice to have the .getStream() implementation of godaddy watch()

[borremosch]

I was facing the same issue and have written a FollowLogs class to be able to follow logs. It is included in #214.

[cabrinoob]

Hi @borremosch, thank you for your PR. Do you have a code sample that shows how to use your class ?

I rapidely read your code and I was asking myself a question : You only specify namespace and podname to get logs, but what if you have a multicontainer pod ? You have to specify the container name too isn't it?

Thank you

[borremosch]

Hey @cabrinoob, you can put the class anywhere in your codebase. A specific container can be specified in the option parameter like so:

new FollowLogs(kubeConfig).followPodLog(
  'pod',
  'namespace',
  newLogs => console.log(newLogs),
  err => console.log(err),
  { container: 'main' }
);