Installer: baremetal: RHCOS image for bootstrap needs to be able to downloaded disconnected

[stbenjam]

Platform:

baremetal

What happened?

It's already possible to use an alternative registry for container images, as well as for the masters' RHCOS images (via baremetal platform's CacheURL).

However, the bootstrap node uses the libvirt RHCOS image, which gets downloaded over the internet:

https://github.com/openshift/installer/blob/2ec16e5336ffb15b90ac6a46eb41f43e34ec7f3f/pkg/rhcos/qemu.go#L17

The baseURI is defined in rhcos.json.

What you expected to happen?

Some mechanism to override the baseURI or entire URL for the libvirt RHCOS image. The libvirt image is cached, however it still requires hitting the external URL to get the ETag.

https://github.com/openshift/installer/blob/2ec16e5336ffb15b90ac6a46eb41f43e34ec7f3f/pkg/tfvars/libvirt/cache.go#L52-L61

As we know the SHA via rhcos.json, could we use that instead of the ETag for the cache path in $HOME/.cache/openshift-install/libvirt/image/? That way a user could prepopulate the cache.

[stbenjam]

/label platform/baremetal

[stbenjam]

https://github.com/openshift/installer/pull/2595

[hardys]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

If we could add that for both the qemu and openstack images that would probably be ideal, something like:

  platform:
    baremetal:
      bootstrapMachineOSImage: 
      machineOSImage:

Ideally this would be added along with some way to get the upstream URL for both bootimages, so the cache can be easily populated - this was discussed in https://github.com/openshift/installer/issues/1399 and AFAICT is stalled so we'd probably have to continue to check rhcos.json directly in the meantime.

[hardys]

https://github.com/openshift/installer/pull/2711

[stbenjam]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

Hm, why make it specific to baremetal? What if other platforms need to get images in a disconnected setting?

There's a global config for mirroring release image content under imageContentSources, could we put it there (or a similar field for machine OS content) so RHCOS content could be retrieved from a local mirror as well?

[kirankt]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

Hm, why make it specific to baremetal? What if other platforms need to get images in a disconnected setting?

There's a global config for mirroring release image content under imageContentSources, could we put it there (or a similar field for machine OS content) so RHCOS content could be retrieved from a local mirror as well?

@stbenjam @hardys Shouldn't this fix our issue?
https://github.com/openshift/installer/blob/master/pkg/tfvars/libvirt/libvirt.go#L38
https://github.com/openshift/installer/blob/master/pkg/tfvars/internal/cache/cache.go#L181

[stbenjam]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

Hm, why make it specific to baremetal? What if other platforms need to get images in a disconnected setting?
There's a global config for mirroring release image content under imageContentSources, could we put it there (or a similar field for machine OS content) so RHCOS content could be retrieved from a local mirror as well?

@stbenjam @hardys Shouldn't this fix our issue?
/pkg/tfvars/libvirt/libvirt.go@master#L38
/pkg/tfvars/internal/cache/cache.go@master#L181

That doesn't give us any mechanism to override the bootstrap image itself, that code just caches a downloaded copy of the image on the local filesystem where the installer is run.

So, you could pre-populate that cache directory, but in the Hive case I think that's kind of tricky. We'd have to mount some shared volume in the pod. It'd be much easier to override the bootstrap and masters images URL's to point to a local HTTP server with environment variables, or better as part of the install-config

[cgwalters]

FWIW at some point we are likely to ship something like a "raw bootimage inside a container" to fix https://github.com/openshift/os/issues/381

However, that still leaves the question of provisioning the bootstrap.

[kirankt]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

Hm, why make it specific to baremetal? What if other platforms need to get images in a disconnected setting?

This was specifically mentioned by @abhinavdahiya that they don't have an use case for other platforms. The idea of env var was a no-no as well, so it was suggested to use the platform config section to add a new entry there.

There's a global config for mirroring release image content under imageContentSources, could we put it there (or a similar field for machine OS content) so RHCOS content could be retrieved from a local mirror as well?

Can we combine the ideas of using imageContentSources as well as using the baremetal platform config section to override the bootstrap machine OS image? That way, we'll have the image mirrored locally and they using the config setting, point to that URL?

Or we just iterate through the imageContentSources list and look for the qemu entry. Ugly perhaps.

[hardys]

Can we combine the ideas of using imageContentSources as well as using the baremetal platform config section to override the bootstrap machine OS image? That way, we'll have the image mirrored locally and they using the config setting, point to that URL?

+1 on this idea, if we could optionally point to mirrored bootimages for both the bootstrap and cluster images that would be ideal, but this doesn't resolve the concern from @abhinavdahiya re exposing this only for the baremetal platform so I guess we need some further feedback on that.

[stbenjam]

I chatted briefly with @abhinavdahiya about this, and it sounds like one possibility may be to add some install-config overrides to point to a locally cached image URL, but that these should be exposed only in the baremetal platform config section, not for all platforms.

Hm, why make it specific to baremetal? What if other platforms need to get images in a disconnected setting?

This was specifically mentioned by @abhinavdahiya that they don't have an use case for other platforms. The idea of env var was a no-no as well, so it was suggested to use the platform config section to add a new entry there.

I’m fine if it has to live in the platform but seems like the installer team is backing themselves into a corner. Local image mirrors seems useful for any current or future ipi platform that doesn’t have rhcos preloaded (openstack, libvirt, vsphere, ovirt).

[tomassedovic]

I think the OpenStack platform could use this too.

We could implement the disconnected install by uploading the RHCOS image into the OpenStack image store (glance) as a prerequisite and instructing the installer to use it via the OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE env var.

But I suspect that var was meant for dev only and should not be required in the disconnected case. If so, we would need an alternative way for getting the image as well.

[kirankt]

I think the OpenStack platform could use this too.

We could implement the disconnected install by uploading the RHCOS image into the OpenStack image store (glance) as a prerequisite and instructing the installer to use it via the OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE env var.

But I suspect that var was meant for dev only and should not be required in the disconnected case. If so, we would need an alternative way for getting the image as well.

@abhinavdahiya Since there seems to be interest in other platforms as well, can we come to an agreement about adding this feature widely, rather than just making it live in baremetal platform only? We can probably even do away with the lone env variable if we make this widely available. Thoughts?

[abhinavdahiya]

The long term plan for installer to be support/control the boot-image for bootstrap-host only. And the boot-image for cluster nodes must be derived from the release-image.. see https://github.com/openshift/os/issues/381

Therefore we support one ENV OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE with vague API that it controls the boot-image and doesn't make the distinction between the bootstrap and control-plane etc..

So therefore we cannot add the OPENSHIFT_INSTALL_BOOTSTRAP_OS_IMAGE_OVERRIDE or such.

We could implement the disconnected install by uploading the RHCOS image into the OpenStack image store (glance) as a prerequisite and instructing the installer to use it via the OPENSHIFT_INSTALL_OS_IMAGE_OVERRIDE env var.

If we need to support the override in API, we should be more precise, if it's glance image, so the API should be that, so that we can verify the inputs.

Also I think supporting URL + glance image is kinda not great because the user can host the URL locally and the installer can continue to create the glance image...

Since there seems to be interest in other platforms as well, can we come to an agreement about adding this feature widely, rather than just making it live in baremetal platform only?

depends on what you are proposing?

iterate through the imageContentSources list and look for the qemu entry

i'm sorry that goes against the more desirable boot-image from release image and I don't think we should follow this path.

[stbenjam]

iterate through the imageContentSources list and look for the qemu entry

i'm sorry that goes against the more desirable boot-image from release image and I don't think we should follow this path.

@abhinavdahiya For our purposes, we are not intending to change which image is being used, but rather where it's obtained from. My understanding is in the OpenStack case, this would not be changing where in glance the image is obtained from, but rather where the image is obtained to upload to glance (i.e., baseURI in rhcos.json).

For a disconnected install, we can use oc adm release mirror to put the container images up on a mirror, and then use imageContentSources to override the path those are downloaded from during an install to point to somewhere locally.

There's no equivalent option for RHCOS images. We really need the ability to change the source from https://releases-art-rhcos.svc.ci.openshift.org to an HTTP server that's availably locally, so this idea of using imageContentSources seems (to me) to go along with the approach of coupling the image with a release, rather than offering an alternative approach.

[abhinavdahiya]

so this idea of using imageContentSources seems (to me) to go along with the approach of coupling the image with a release, rather than offering an alternative approach.

we already have a way to pull container images in disconnected env and creating another mirror fetch for boot-image is not ideal, we know how to get container images from different mirror we don't need another parallel to pull random-files from mirrors too.

[stbenjam]

so this idea of using imageContentSources seems (to me) to go along with the approach of coupling the image with a release, rather than offering an alternative approach.
we already have a way to pull container images in disconnected env and creating another mirror fetch for boot-image is not ideal, we know how to get container images from different mirror we don't need another parallel to pull random-files from mirrors too.

Right, but disconnected container images isn't useful if you can't also get the RHCOS images in a disconnected way for platforms that need this (openstack, baremetal IPI at least)

We're not creating another thing, I'm proposing using the existing thing (imageContentSources) or something similar to ensure if there's a matching configuration for RHCOS, then we would obtain the RHCOS image from there instead.

Maybe something like this:

- source: https://releases-art-rhcos.svc.ci.openshift.org/art/storage/
  mirrors:
  - http://local-mirror.com/rhcos/

[abhinavdahiya]

Right, but disconnected container images isn't useful if you can't also get the RHCOS images in a disconnected way for platforms that need this (openstack, baremetal IPI at least)

that's what i'm saying we need to work towards https://github.com/openshift/os/issues/381

We're not creating another thing, I'm proposing using the existing thing (imageContentSources) or something similar to ensure if there's a matching configuration for RHCOS, then we would obtain the RHCOS image from there instead.

You are creating an new thing.. https://github.com/openshift/installer/blob/119a65ae70800135b83d1e8c36aeb904104c2735/pkg/types/installconfig.go#L100-L102

The goal of that field and work flow is to provide alternate source for container images..
and we want it to extent to alternate source for HTTP blobs..

disconnected fetching content in form of container images is already supported transparently and re-using that mechanism to get the RHCOS image in running cluster is a lot more desirable and overloading this one-off.

[cgwalters]

Note that ship bootimages via the release image can only work after we do something like https://github.com/openshift/installer/pull/1286 - since otherwise where is the image for the bootstrap going to come from?

Or alternatively, we could have a separate public bootimage just for bootstrap which could be revved less frequently, and pivot from it.

I'm just saying that until we land a lot of work, we're going to get continual demand for short-term band-aids, and it's not clear to me that skipping the band-aids is worth it.

[abhinavdahiya]

Note that ship bootimages via the release image can only work after we do something like #1286 - since otherwise where is the image for the bootstrap going to come from?
Or alternatively, we could have a separate public bootimage just for bootstrap which could be revved less frequently, and pivot from it.

I think we are more concerned about the cluster nodes.. and why I don't think bootstrap-host needs to be handled similarly https://github.com/openshift/installer/issues/2542#issuecomment-550009668

I'm just saying that until we land a lot of work, we're going to get continual demand for short-term band-aids, and it's not clear to me that skipping the band-aids is worth it.

I'm not against for the time being fixes, but would like changes that are still useful in the desired future.

[stbenjam]

disconnected fetching content in form of container images is already supported transparently and re-using that mechanism to get the RHCOS image in running cluster is a lot more desirable and overloading this one-off.

What is the mechanism for disconnected fetching of container images if it's not imageContentSources? Maybe I'm missing some information.

Whether it's a new thing or not seems to be a semantic difference, imageContentSources exists, and is used to override where the installer fetches things from, I thought it could be modified for a similar purpose. Or maybe a totally new httpContentSources that works the same way is appropriate.

My main concern was that I don't think this should be embedded in the baremetal platform as asked earlier, as it's generally relevant to others.

If we just need a band aid short term, couldn't we take the original approach of an env var (https://github.com/openshift/installer/pull/2595)? It a lot simpler and could be removed later.

[kirankt]

disconnected fetching content in form of container images is already supported transparently and re-using that mechanism to get the RHCOS image in running cluster is a lot more desirable and overloading this one-off.

What is the mechanism for disconnected fetching of container images if it's not imageContentSources? Maybe I'm missing some information.

@abhinavdahiya When you mention transparent disconnected fetching of images, you're not referring to image caching are you?
e.g.
https://github.com/openshift/installer/blob/fefa982755d49c07b8a3e6d9e24c42f7e7e74248/pkg/tfvars/internal/cache/cache.go#L181

If that's the case, @stbenjam mentioned earlier that it causes complications with the Hive.

Whether it's a new thing or not seems to be a semantic difference, imageContentSources exists, and is used to override where the installer fetches things from, I thought it could be modified for a similar purpose. Or maybe a totally new httpContentSources that works the same way is appropriate.

My main concern was that I don't think this should be embedded in the baremetal platform as asked earlier, as it's generally relevant to others.

If we just need a band aid short term, couldn't we take the original approach of an env var (#2595)? It a lot simpler and could be removed later.

[stbenjam]

@abhinavdahiya Could we get some clarification about what approach would be acceptable to the installer team? We must have to have a way to override the location bootstrap RHCOS is downloaded from.

[stbenjam]

To summarize, I believe the 3 options we've proposed are:

1. An environment variable for bootstrap, OPENSHIFT_INSTALL_BOOTSTRAP_OS_IMAGE_OVERRIDE

2. Make use of imageContentSources or add an httpContentSources option, which will do URL matching and could override the baseURI used in rhcos.json.

3. Override the bootstrap URL by adding an explicit configuration item in the baremetal platform config

Is that correct? Keep in mind, this will need to be backportable to 4.3. 1 and 3 are probably the least risky to backport. I'm not thrilled about 3, as being able to override HTTP sources is generally applicable to other platforms (e.g. disconnected openstack which downloads the images from the baseURI locations and pushes them to glance).

[abhinavdahiya]

3. Override the bootstrap URL by adding an explicit configuration item in the baremetal platform config

personally i think this is the only short-term solution if you want to _support_ a way to be disconnected for boot-images. we can't have users set ENV for their actual installs.

Is that correct? Keep in mind, this will need to be backportable to 4.3. 1 and 3 are probably the least risky to backport. I'm not thrilled about 3, as being able to override HTTP sources is generally applicable to other platforms (e.g. disconnected openstack which downloads the images from the baseURI locations and pushes them to glance).

[hardys]

This was closed via #2757

[hardys]

/close

[openshift-ci-robot]

@hardys: Closing this issue.

In response to this:

/close

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