How to Import KFServing Client Package in Golang

Question

We are using KFServing in our kubernetes cluster. The project provides InferenceService struct and clientset in the folder pkg/.

How to import these packages under pkg/client? My code is as below:

package main
import (
    "fmt"
    kfs 
   "github.com/kubeflow/kfserving/pkg/client/clientset/versioned"
)

func main() {
   var clientset   *kfs.Cientset
   clientset = kfs.NewForConfig(nil)
   fmt.Println(clientset)
}
           

Try go mod tidy i got (I need dev on specified version v0.5.1):

    main imports
    github.com/kubeflow/kfserving/pkg/client/clientset/versioned 
    imports
    k8s.io/client-go/discovery imports
    github.com/googleapis/gnostic/OpenAPIv2: 
     module github.com/googleapis/gnostic@latest found (v0.5.5), 
     but does not contain package 
     github.com/googleapis/gnostic/OpenAPIv2
     main imports
    github.com/kubeflow/kfserving/pkg/client/clientset/versioned 
    imports
    ...

Try compiling these code i got:

  a lot of errors .....

After go get github.com/kubeflow/kfserving I got:

Then I changed the go.mod and reconfiged the kfseving version from v0.6.0 to v0.5.1 and then recompile these code, still got below error:

go build .
 go: github.com/kubeflow/[email protected]: missing go.sum entry; to add it:
    go mod download github.com/kubeflow/kfserving

contens of go.mod:

module main

go 1.16

require github.com/kubeflow/kfserving v0.5.1 // indirect

UPDATE
for kfserving v0.4.0 everything works well

Answer 1

Looking at the kfserving go.mod file at v0.5.1, I see a big block of replace directives. By design, replace directives “only apply in the main module's go.mod file and are ignored in other modules”, so it looks like kfserving has some technical debt here that they're passing on to you.

I started with an empty go.mod file and pasted in those replace directives. Then:

$ go get -d github.com/kubeflow/kfserving/pkg/client/clientset/[email protected]
go get: added github.com/PuerkitoBio/purell v1.1.1
…
go get: added sigs.k8s.io/yaml v1.2.0

The .go source file needed a few fixes for typos and mismatched types. I fudged it to:

package main

import (
    "fmt"

    kfs "github.com/kubeflow/kfserving/pkg/client/clientset/versioned"
)

func main() {
    var clientset *kfs.Clientset
    clientset = kfs.NewForConfigOrDie(nil)
    fmt.Println(clientset)
}

and then go build . succeeds:

$ go build -o /dev/null .

Now I'll run go mod tidy to clean up the go.mod and go.sum files:

$ go mod tidy
go: downloading github.com/stretchr/testify v1.5.1
…
go: downloading github.com/jmespath/go-jmespath v0.3.0

---

But wait! I've still got all of the technical debt from kfserving/go.mod — without any comments explaining the choice of versions! — and I'm passing that technical debt on to any downstream users. Let's see if I can improve the situation while I'm here.

Go 1.16 handles the exclude directive a lot better than previous Go versions did, so maybe I can use a couple of targeted exclude directives instead of the (rather large) replace hammer.

I'll start by committing the fixes so far. (If nothing else, I want to be able to git diff the requirements to see what has changed.)

$ git add *.go go.mod go.sum

$ git commit -m 'fixed kfserving build'
[main fd93b1d] fixed kfserving build
 3 files changed, 1643 insertions(+), 2 deletions(-)
 create mode 100644 go.sum

I notice that all of the replace directives apply to k8s.io paths, so I'll list the current versions of those paths to see what needs to be fixed:

$ go list -m k8s.io/...
k8s.io/api v0.19.2 => k8s.io/api v0.19.2
k8s.io/apiextensions-apiserver v0.19.2 => k8s.io/apiextensions-apiserver v0.19.2
k8s.io/apimachinery v0.19.2 => k8s.io/apimachinery v0.19.2
k8s.io/apiserver v0.19.2 => k8s.io/apiserver v0.19.2
k8s.io/client-go v11.0.1-0.20190805182717-6502b5e7b1b5+incompatible => k8s.io/client-go v0.19.2
k8s.io/cloud-provider v0.19.2 => k8s.io/cloud-provider v0.19.2
k8s.io/code-generator v0.19.2 => k8s.io/code-generator v0.19.2
k8s.io/component-base v0.19.2 => k8s.io/component-base v0.19.2
k8s.io/csi-translation-lib v0.19.2 => k8s.io/csi-translation-lib v0.19.2
k8s.io/gengo v0.0.0-20200428234225-8167cfdcfc14
k8s.io/klog v1.0.0 => k8s.io/klog v1.0.0
k8s.io/klog/v2 v2.2.0
k8s.io/kube-openapi v0.0.0-20200805222855-6aeccd4b50c6
k8s.io/legacy-cloud-providers v0.17.4 => k8s.io/legacy-cloud-providers v0.19.2
k8s.io/test-infra v0.0.0-20200803112140-d8aa4e063646 => k8s.io/test-infra v0.0.0-20200803112140-d8aa4e063646
k8s.io/utils v0.0.0-20200912215256-4140de9c8800 => k8s.io/utils v0.0.0-20200324210504-a9aa75ae1b89

Most of those look fine, but there are three mismatched versions:

k8s.io/client-go v11.0.1-0.20190805182717-6502b5e7b1b5+incompatible => k8s.io/client-go v0.19.2
…
k8s.io/legacy-cloud-providers v0.17.4 => k8s.io/legacy-cloud-providers v0.19.2
…
k8s.io/utils v0.0.0-20200912215256-4140de9c8800 => k8s.io/utils v0.0.0-20200324210504-a9aa75ae1b89

legacy-cloud-providers just needs an upgrade, so that should be easy enough to fix with go get — but it's not relevant to this package anyway so I can just let it float to whatever version it ends up at. I'll cut down the replace directives to just the two remaining modules and see how far I get:

replace (
    k8s.io/client-go => k8s.io/client-go v0.19.2
    k8s.io/utils => k8s.io/utils v0.0.0-20200324210504-a9aa75ae1b89
)

Now:

$ go mod tidy

$ go build -o /dev/null .

Ok, so the build is still good — I've made incremental progress, so I'll lock that in:

$ git add go.mod go.sum

$ git commit -m 'go.mod: remove irrelevant replacements'
[main cdbc1db] go.mod: remove irrelevant replacements
 3 files changed, 456 insertions(+), 43 deletions(-)
 rewrite go.mod (85%)
 create mode 100755 m

Now let's try notching out the bad client-go versions with exclude directives:

$ go mod edit -exclude=k8s.io/[email protected]+incompatible

$ go list -m k8s.io/client-go
k8s.io/client-go v9.0.0+incompatible => k8s.io/client-go v0.19.2

$ go mod edit -exclude=k8s.io/[email protected]+incompatible

$ go list -m k8s.io/client-go
k8s.io/client-go v0.19.2 => k8s.io/client-go v0.19.2

Now I'm at the client-go version I needed, so I can drop that replace directive:

$ go mod edit -dropreplace=k8s.io/client-go

$ go mod tidy

$ go build -o /dev/null .

And again lock it in:

$ git add go.mod go.sum

$ git commit -m 'go.mod: use exclude instead of replace to notch out unwanted client-go versions'
[main de69965] go.mod: use exclude instead of replace to notch out unwanted client-go versions
 2 files changed, 21 insertions(+), 3 deletions(-)

Now let's see what's going on with this k8s.io/utils replacement. I suspect that it isn't really needed — the version will be upgraded a bit, but I'm betting it won't break the build. And, indeed, it seems to be fine:

$ go list -m k8s.io/utils
k8s.io/utils v0.0.0-20200912215256-4140de9c8800 => k8s.io/utils v0.0.0-20200324210504-a9aa75ae1b89

$ go mod edit -dropreplace=k8s.io/utils

$ go mod tidy

$ go build -o /dev/null .

$ go list -m k8s.io/utils
k8s.io/utils v0.0.0-20200912215256-4140de9c8800

---

So now I've successfully reduced that big nest of replace directives from kfserving to just a couple of exclude directives targeted retracted versions of k8s.io/client-go. Here's my whole go.mod file at the end of this process:

module example.com/m

go 1.16

exclude (
    k8s.io/client-go v11.0.1-0.20190805182717-6502b5e7b1b5+incompatible
    k8s.io/client-go v9.0.0+incompatible
)

require github.com/kubeflow/kfserving v0.5.1