flags.go

Documentation: k8s.io/kubernetes/cmd/kubeadm/app/phases/kubelet

     1  /*
     2  Copyright 2018 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package kubelet
    18  
    19  import (
    20  	"fmt"
    21  	"os"
    22  	"path/filepath"
    23  	"strings"
    24  
    25  	"github.com/pkg/errors"
    26  
    27  	"k8s.io/klog/v2"
    28  
    29  	nodeutil "k8s.io/component-helpers/node/util"
    30  	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
    31  	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
    32  	"k8s.io/kubernetes/cmd/kubeadm/app/images"
    33  	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
    34  )
    35  
    36  type kubeletFlagsOpts struct {
    37  	nodeRegOpts              *kubeadmapi.NodeRegistrationOptions
    38  	pauseImage               string
    39  	registerTaintsUsingFlags bool
    40  }
    41  
    42  // GetNodeNameAndHostname obtains the name for this Node using the following precedence
    43  // (from lower to higher):
    44  // - actual hostname
    45  // - NodeRegistrationOptions.Name (same as "--node-name" passed to "kubeadm init/join")
    46  // - "hostname-override" flag in NodeRegistrationOptions.KubeletExtraArgs
    47  // It also returns the hostname or an error if getting the hostname failed.
    48  func GetNodeNameAndHostname(cfg *kubeadmapi.NodeRegistrationOptions) (string, string, error) {
    49  	hostname, err := nodeutil.GetHostname("")
    50  	nodeName := hostname
    51  	if cfg.Name != "" {
    52  		nodeName = cfg.Name
    53  	}
    54  	if name, idx := kubeadmapi.GetArgValue(cfg.KubeletExtraArgs, "hostname-override", -1); idx > -1 {
    55  		nodeName = name
    56  	}
    57  	return nodeName, hostname, err
    58  }
    59  
    60  // WriteKubeletDynamicEnvFile writes an environment file with dynamic flags to the kubelet.
    61  // Used at "kubeadm init" and "kubeadm join" time.
    62  func WriteKubeletDynamicEnvFile(cfg *kubeadmapi.ClusterConfiguration, nodeReg *kubeadmapi.NodeRegistrationOptions, registerTaintsUsingFlags bool, kubeletDir string) error {
    63  	flagOpts := kubeletFlagsOpts{
    64  		nodeRegOpts:              nodeReg,
    65  		pauseImage:               images.GetPauseImage(cfg),
    66  		registerTaintsUsingFlags: registerTaintsUsingFlags,
    67  	}
    68  	stringMap := buildKubeletArgs(flagOpts)
    69  	argList := kubeadmutil.ArgumentsToCommand(stringMap, nodeReg.KubeletExtraArgs)
    70  	envFileContent := fmt.Sprintf("%s=%q\n", constants.KubeletEnvFileVariableName, strings.Join(argList, " "))
    71  
    72  	return writeKubeletFlagBytesToDisk([]byte(envFileContent), kubeletDir)
    73  }
    74  
    75  // buildKubeletArgsCommon takes a kubeletFlagsOpts object and builds based on that a slice of arguments
    76  // that are common to both Linux and Windows
    77  func buildKubeletArgsCommon(opts kubeletFlagsOpts) []kubeadmapi.Arg {
    78  	kubeletFlags := []kubeadmapi.Arg{}
    79  	kubeletFlags = append(kubeletFlags, kubeadmapi.Arg{Name: "container-runtime-endpoint", Value: opts.nodeRegOpts.CRISocket})
    80  
    81  	// This flag passes the pod infra container image (e.g. "pause" image) to the kubelet
    82  	// and prevents its garbage collection
    83  	if opts.pauseImage != "" {
    84  		kubeletFlags = append(kubeletFlags, kubeadmapi.Arg{Name: "pod-infra-container-image", Value: opts.pauseImage})
    85  	}
    86  
    87  	if opts.registerTaintsUsingFlags && opts.nodeRegOpts.Taints != nil && len(opts.nodeRegOpts.Taints) > 0 {
    88  		taintStrs := []string{}
    89  		for _, taint := range opts.nodeRegOpts.Taints {
    90  			taintStrs = append(taintStrs, taint.ToString())
    91  		}
    92  		kubeletFlags = append(kubeletFlags, kubeadmapi.Arg{Name: "register-with-taints", Value: strings.Join(taintStrs, ",")})
    93  	}
    94  
    95  	// Pass the "--hostname-override" flag to the kubelet only if it's different from the hostname
    96  	nodeName, hostname, err := GetNodeNameAndHostname(opts.nodeRegOpts)
    97  	if err != nil {
    98  		klog.Warning(err)
    99  	}
   100  	if nodeName != hostname {
   101  		klog.V(1).Infof("setting kubelet hostname-override to %q", nodeName)
   102  		kubeletFlags = append(kubeletFlags, kubeadmapi.Arg{Name: "hostname-override", Value: nodeName})
   103  	}
   104  
   105  	return kubeletFlags
   106  }
   107  
   108  // writeKubeletFlagBytesToDisk writes a byte slice down to disk at the specific location of the kubelet flag overrides file
   109  func writeKubeletFlagBytesToDisk(b []byte, kubeletDir string) error {
   110  	kubeletEnvFilePath := filepath.Join(kubeletDir, constants.KubeletEnvFileName)
   111  	fmt.Printf("[kubelet-start] Writing kubelet environment file with flags to file %q\n", kubeletEnvFilePath)
   112  
   113  	// creates target folder if not already exists
   114  	if err := os.MkdirAll(kubeletDir, 0700); err != nil {
   115  		return errors.Wrapf(err, "failed to create directory %q", kubeletDir)
   116  	}
   117  	if err := os.WriteFile(kubeletEnvFilePath, b, 0644); err != nil {
   118  		return errors.Wrapf(err, "failed to write kubelet configuration to the file %q", kubeletEnvFilePath)
   119  	}
   120  	return nil
   121  }
   122  
   123  // buildKubeletArgs takes a kubeletFlagsOpts object and builds based on that a slice of arguments
   124  // that should be given to the local kubelet daemon.
   125  func buildKubeletArgs(opts kubeletFlagsOpts) []kubeadmapi.Arg {
   126  	return buildKubeletArgsCommon(opts)
   127  }
   128
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