PiezÄ«me. tulk.: raksta autors - SAP inženieris Erkans Erols - dalÄs ar savu pÄtÄ«jumu par komandas darbÄ«bas mehÄnismiem kubectl exec, tik pazÄ«stams visiem, kas strÄdÄ ar Kubernetes. ViÅÅ” pavada visu algoritmu ar Kubernetes pirmkoda (un saistÄ«to projektu) sarakstiem, kas ļauj izprast tÄmu tik dziļi, cik nepiecieÅ”ams.
KÄdu piektdienu pie manis pienÄca kolÄÄ£is un jautÄja, kÄ izpildÄ«t komandu podÄ, izmantojot klients aiziet. Es nevarÄju viÅam atbildÄt un pÄkÅ”Åi sapratu, ka neko nezinu par darbÄ«bas mehÄnismu kubectl exec. JÄ, man bija zinÄmi priekÅ”stati par tÄs struktÅ«ru, taÄu nebiju 100% pÄrliecinÄts par to pareizÄ«bu un tÄpÄc nolÄmu Å”o jautÄjumu risinÄt. IzpÄtot emuÄrus, dokumentÄciju un pirmkodu, es uzzinÄju daudz jauna, un Å”ajÄ rakstÄ vÄlos dalÄ«ties ar saviem atklÄjumiem un izpratni. Ja kaut kas nav kÄrtÄ«bÄ, lÅ«dzu, sazinieties ar mani pa tÄlr Twitter.
TreniÅÅ”
Lai izveidotu kopu MacBook datorÄ, es klonÄju ecomm-integration-ballerina/kubernetes-cluster. PÄc tam es izlaboju mezglu IP adreses kubelet konfigurÄcijÄ, jo noklusÄjuma iestatÄ«jumi neļÄva kubectl exec. JÅ«s varat lasÄ«t vairÄk par galveno iemeslu Å”eit.
Jebkura automaŔīna = mans MacBook
GalvenÄ mezgla IP = 192.168.205.10
Darbinieka mezgla IP = 192.168.205.11
API servera ports = 6443
Komponenti
kubectl exec process: Kad mÄs izpildÄm ākubectl exec...ā, process tiek sÄkts. To var izdarÄ«t jebkurÄ datorÄ ar piekļuvi K8s API serverim. PiezÄ«me Tulk.: TÄlÄk konsoles sarakstos autors izmanto komentÄru ājebkura maŔīnaā, kas nozÄ«mÄ, ka turpmÄkÄs komandas var izpildÄ«t jebkurÄ Å”ÄdÄ iekÄrtÄ ar piekļuvi Kubernetes.
api serveris: galvenÄ mezgla komponents, kas nodroÅ”ina piekļuvi Kubernetes API. Å Ä« ir Kubernetes vadÄ«bas plaknes priekÅ”gals.
kubelet: aÄ£ents, kas darbojas katrÄ klastera mezglÄ. Tas nodroÅ”ina konteineru darbÄ«bu podÄ.
konteinera izpildlaiks (konteinera izpildlaiks): programmatÅ«ra, kas ir atbildÄ«ga par konteineru darbinÄÅ”anu. PiemÄri: Docker, CRI-O, konteineriā¦
kodols: OS kodols darbinieka mezglÄ; ir atbildÄ«gs par procesu vadÄ«bu.
mÄrÄ·is (mÄrÄ·is) konteiners: konteiners, kas ir daļa no pod un darbojas vienÄ no darbinieka mezgliem.
Ko es atklÄju
1. Klienta puses darbība
Izveidojiet aplikumu nosaukumvietÄ default:
// any machine
$ kubectl run exec-test-nginx --image=nginx
PÄc tam izpildÄm komandu exec un gaidÄm 5000 sekundes turpmÄkiem novÄrojumiem:
// any machine
$ kubectl exec -it exec-test-nginx-6558988d5-fgxgg -- sh
# sleep 5000
ParÄdÄs kubectl process (mÅ«su gadÄ«jumÄ ar pid = 8507):
MÄs varam arÄ« novÄrot pieprasÄ«jumu api servera pusÄ:
handler.go:143] kube-apiserver: POST "/api/v1/namespaces/default/pods/exec-test-nginx-6558988d5-fgxgg/exec" satisfied by gorestful with webservice /api/v1
upgradeaware.go:261] Connecting to backend proxy (intercepting redirects) https://192.168.205.11:10250/exec/default/exec-test-nginx-6558988d5-fgxgg/exec-test-nginx?command=sh&input=1&output=1&tty=1
Headers: map[Connection:[Upgrade] Content-Length:[0] Upgrade:[SPDY/3.1] User-Agent:[kubectl/v1.12.10 (darwin/amd64) kubernetes/e3c1340] X-Forwarded-For:[192.168.205.1] X-Stream-Protocol-Version:[v4.channel.k8s.io v3.channel.k8s.io v2.channel.k8s.io channel.k8s.io]]
Å emiet vÄrÄ, ka HTTP pieprasÄ«jums ietver pieprasÄ«jumu mainÄ«t protokolu. SPDY ļauj multipleksÄt atseviŔķas stdin/stdout/stderr/spdy-error "straumes", izmantojot vienu TCP savienojumu.
API serveris saÅem pieprasÄ«jumu un pÄrvÄrÅ” to par PodExecOptions:
// PodExecOptions is the query options to a Pod's remote exec call
type PodExecOptions struct {
metav1.TypeMeta
// Stdin if true indicates that stdin is to be redirected for the exec call
Stdin bool
// Stdout if true indicates that stdout is to be redirected for the exec call
Stdout bool
// Stderr if true indicates that stderr is to be redirected for the exec call
Stderr bool
// TTY if true indicates that a tty will be allocated for the exec call
TTY bool
// Container in which to execute the command.
Container string
// Command is the remote command to execute; argv array; not executed within a shell.
Command []string
}
Lai veiktu nepiecieÅ”amÄs darbÄ«bas, api-serverim ir jÄzina, ar kuru pod tam ir jÄsazinÄs:
// ExecLocation returns the exec URL for a pod container. If opts.Container is blank
// and only one container is present in the pod, that container is used.
func ExecLocation(
getter ResourceGetter,
connInfo client.ConnectionInfoGetter,
ctx context.Context,
name string,
opts *api.PodExecOptions,
) (*url.URL, http.RoundTripper, error) {
return streamLocation(getter, connInfo, ctx, name, opts, opts.Container, "exec")
}
Protams, dati par galapunktu tiek Åemti no informÄcijas par mezglu:
nodeName := types.NodeName(pod.Spec.NodeName)
if len(nodeName) == 0 {
// If pod has not been assigned a host, return an empty location
return nil, nil, errors.NewBadRequest(fmt.Sprintf("pod %s does not have a host assigned", name))
}
nodeInfo, err := connInfo.GetConnectionInfo(ctx, nodeName)
UrrÄ! Kubelet tagad ir ports (node.Status.DaemonEndpoints.KubeletEndpoint.Port), ar kuru API serveris var izveidot savienojumu:
// GetConnectionInfo retrieves connection info from the status of a Node API object.
func (k *NodeConnectionInfoGetter) GetConnectionInfo(ctx context.Context, nodeName types.NodeName) (*ConnectionInfo, error) {
node, err := k.nodes.Get(ctx, string(nodeName), metav1.GetOptions{})
if err != nil {
return nil, err
}
// Find a kubelet-reported address, using preferred address type
host, err := nodeutil.GetPreferredNodeAddress(node, k.preferredAddressTypes)
if err != nil {
return nil, err
}
// Use the kubelet-reported port, if present
port := int(node.Status.DaemonEndpoints.KubeletEndpoint.Port)
if port <= 0 {
port = k.defaultPort
}
return &ConnectionInfo{
Scheme: k.scheme,
Hostname: host,
Port: strconv.Itoa(port),
Transport: k.transport,
}, nil
}
Å ie savienojumi tiek izveidoti ar kubelet HTTPS galapunktu. PÄc noklusÄjuma apiserver nepÄrbauda kubelet sertifikÄtu, kas padara savienojumu neaizsargÄtu pret MITM (man-in-the-middle) uzbrukumiem un nedroÅ”s par darbu neuzticamos un/vai publiskos tÄ«klos.
Tagad API serveris zina galapunktu un izveido savienojumu:
// Connect returns a handler for the pod exec proxy
func (r *ExecREST) Connect(ctx context.Context, name string, opts runtime.Object, responder rest.Responder) (http.Handler, error) {
execOpts, ok := opts.(*api.PodExecOptions)
if !ok {
return nil, fmt.Errorf("invalid options object: %#v", opts)
}
location, transport, err := pod.ExecLocation(r.Store, r.KubeletConn, ctx, name, execOpts)
if err != nil {
return nil, err
}
return newThrottledUpgradeAwareProxyHandler(location, transport, false, true, true, responder), nil
}
PirmkÄrt, mÄs noskaidrojam darbinieka mezgla IP. MÅ«su gadÄ«jumÄ tas ir 192.168.205.11:
// any machine
$ kubectl get nodes k8s-node-1 -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-node-1 Ready <none> 9h v1.15.3 192.168.205.11 <none> Ubuntu 16.04.6 LTS 4.4.0-159-generic docker://17.3.3
PÄc tam iestatiet kubelet portu (mÅ«su gadÄ«jumÄ 10250):
// any machine
$ kubectl get nodes k8s-node-1 -o jsonpath='{.status.daemonEndpoints.kubeletEndpoint}'
map[Port:10250]
Tagad ir pienÄcis laiks pÄrbaudÄ«t tÄ«klu. Vai ir savienojums ar darbinieka mezglu (192.168.205.11)? Tas ir! Ja nokauj procesu exec, tas pazudÄ«s, tÄpÄc es zinu, ka savienojumu izveidoja api-serveris izpildÄ«tÄs komandas exec rezultÄtÄ.
Bet pagaidiet: kÄ Kubelet to panÄca? Kubelet ir dÄmons, kas nodroÅ”ina piekļuvi API, izmantojot api servera pieprasÄ«jumu portu:
// Server is the library interface to serve the stream requests.
type Server interface {
http.Handler
// Get the serving URL for the requests.
// Requests must not be nil. Responses may be nil iff an error is returned.
GetExec(*runtimeapi.ExecRequest) (*runtimeapi.ExecResponse, error)
GetAttach(req *runtimeapi.AttachRequest) (*runtimeapi.AttachResponse, error)
GetPortForward(*runtimeapi.PortForwardRequest) (*runtimeapi.PortForwardResponse, error)
// Start the server.
// addr is the address to serve on (address:port) stayUp indicates whether the server should
// listen until Stop() is called, or automatically stop after all expected connections are
// closed. Calling Get{Exec,Attach,PortForward} increments the expected connection count.
// Function does not return until the server is stopped.
Start(stayUp bool) error
// Stop the server, and terminate any open connections.
Stop() error
}
Kubelet ievieÅ” saskarni RuntimeServiceClient, kas ir daļa no konteinera izpildlaika saskarnes (mÄs par to rakstÄ«jÄm vairÄk, piemÄram, Å”eit ā apm. tulk.):
GarÅ” saraksts no cri-api kubernetes/kubernetes
// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
type RuntimeServiceClient interface {
// Version returns the runtime name, runtime version, and runtime API version.
Version(ctx context.Context, in *VersionRequest, opts ...grpc.CallOption) (*VersionResponse, error)
// RunPodSandbox creates and starts a pod-level sandbox. Runtimes must ensure
// the sandbox is in the ready state on success.
RunPodSandbox(ctx context.Context, in *RunPodSandboxRequest, opts ...grpc.CallOption) (*RunPodSandboxResponse, error)
// StopPodSandbox stops any running process that is part of the sandbox and
// reclaims network resources (e.g., IP addresses) allocated to the sandbox.
// If there are any running containers in the sandbox, they must be forcibly
// terminated.
// This call is idempotent, and must not return an error if all relevant
// resources have already been reclaimed. kubelet will call StopPodSandbox
// at least once before calling RemovePodSandbox. It will also attempt to
// reclaim resources eagerly, as soon as a sandbox is not needed. Hence,
// multiple StopPodSandbox calls are expected.
StopPodSandbox(ctx context.Context, in *StopPodSandboxRequest, opts ...grpc.CallOption) (*StopPodSandboxResponse, error)
// RemovePodSandbox removes the sandbox. If there are any running containers
// in the sandbox, they must be forcibly terminated and removed.
// This call is idempotent, and must not return an error if the sandbox has
// already been removed.
RemovePodSandbox(ctx context.Context, in *RemovePodSandboxRequest, opts ...grpc.CallOption) (*RemovePodSandboxResponse, error)
// PodSandboxStatus returns the status of the PodSandbox. If the PodSandbox is not
// present, returns an error.
PodSandboxStatus(ctx context.Context, in *PodSandboxStatusRequest, opts ...grpc.CallOption) (*PodSandboxStatusResponse, error)
// ListPodSandbox returns a list of PodSandboxes.
ListPodSandbox(ctx context.Context, in *ListPodSandboxRequest, opts ...grpc.CallOption) (*ListPodSandboxResponse, error)
// CreateContainer creates a new container in specified PodSandbox
CreateContainer(ctx context.Context, in *CreateContainerRequest, opts ...grpc.CallOption) (*CreateContainerResponse, error)
// StartContainer starts the container.
StartContainer(ctx context.Context, in *StartContainerRequest, opts ...grpc.CallOption) (*StartContainerResponse, error)
// StopContainer stops a running container with a grace period (i.e., timeout).
// This call is idempotent, and must not return an error if the container has
// already been stopped.
// TODO: what must the runtime do after the grace period is reached?
StopContainer(ctx context.Context, in *StopContainerRequest, opts ...grpc.CallOption) (*StopContainerResponse, error)
// RemoveContainer removes the container. If the container is running, the
// container must be forcibly removed.
// This call is idempotent, and must not return an error if the container has
// already been removed.
RemoveContainer(ctx context.Context, in *RemoveContainerRequest, opts ...grpc.CallOption) (*RemoveContainerResponse, error)
// ListContainers lists all containers by filters.
ListContainers(ctx context.Context, in *ListContainersRequest, opts ...grpc.CallOption) (*ListContainersResponse, error)
// ContainerStatus returns status of the container. If the container is not
// present, returns an error.
ContainerStatus(ctx context.Context, in *ContainerStatusRequest, opts ...grpc.CallOption) (*ContainerStatusResponse, error)
// UpdateContainerResources updates ContainerConfig of the container.
UpdateContainerResources(ctx context.Context, in *UpdateContainerResourcesRequest, opts ...grpc.CallOption) (*UpdateContainerResourcesResponse, error)
// ReopenContainerLog asks runtime to reopen the stdout/stderr log file
// for the container. This is often called after the log file has been
// rotated. If the container is not running, container runtime can choose
// to either create a new log file and return nil, or return an error.
// Once it returns error, new container log file MUST NOT be created.
ReopenContainerLog(ctx context.Context, in *ReopenContainerLogRequest, opts ...grpc.CallOption) (*ReopenContainerLogResponse, error)
// ExecSync runs a command in a container synchronously.
ExecSync(ctx context.Context, in *ExecSyncRequest, opts ...grpc.CallOption) (*ExecSyncResponse, error)
// Exec prepares a streaming endpoint to execute a command in the container.
Exec(ctx context.Context, in *ExecRequest, opts ...grpc.CallOption) (*ExecResponse, error)
// Attach prepares a streaming endpoint to attach to a running container.
Attach(ctx context.Context, in *AttachRequest, opts ...grpc.CallOption) (*AttachResponse, error)
// PortForward prepares a streaming endpoint to forward ports from a PodSandbox.
PortForward(ctx context.Context, in *PortForwardRequest, opts ...grpc.CallOption) (*PortForwardResponse, error)
// ContainerStats returns stats of the container. If the container does not
// exist, the call returns an error.
ContainerStats(ctx context.Context, in *ContainerStatsRequest, opts ...grpc.CallOption) (*ContainerStatsResponse, error)
// ListContainerStats returns stats of all running containers.
ListContainerStats(ctx context.Context, in *ListContainerStatsRequest, opts ...grpc.CallOption) (*ListContainerStatsResponse, error)
// UpdateRuntimeConfig updates the runtime configuration based on the given request.
UpdateRuntimeConfig(ctx context.Context, in *UpdateRuntimeConfigRequest, opts ...grpc.CallOption) (*UpdateRuntimeConfigResponse, error)
// Status returns the status of the runtime.
Status(ctx context.Context, in *StatusRequest, opts ...grpc.CallOption) (*StatusResponse, error)
}
Container Runtime ir atbildīgs par ievieŔanu RuntimeServiceServer:
GarÅ” saraksts no cri-api kubernetes/kubernetes
// RuntimeServiceServer is the server API for RuntimeService service.
type RuntimeServiceServer interface {
// Version returns the runtime name, runtime version, and runtime API version.
Version(context.Context, *VersionRequest) (*VersionResponse, error)
// RunPodSandbox creates and starts a pod-level sandbox. Runtimes must ensure
// the sandbox is in the ready state on success.
RunPodSandbox(context.Context, *RunPodSandboxRequest) (*RunPodSandboxResponse, error)
// StopPodSandbox stops any running process that is part of the sandbox and
// reclaims network resources (e.g., IP addresses) allocated to the sandbox.
// If there are any running containers in the sandbox, they must be forcibly
// terminated.
// This call is idempotent, and must not return an error if all relevant
// resources have already been reclaimed. kubelet will call StopPodSandbox
// at least once before calling RemovePodSandbox. It will also attempt to
// reclaim resources eagerly, as soon as a sandbox is not needed. Hence,
// multiple StopPodSandbox calls are expected.
StopPodSandbox(context.Context, *StopPodSandboxRequest) (*StopPodSandboxResponse, error)
// RemovePodSandbox removes the sandbox. If there are any running containers
// in the sandbox, they must be forcibly terminated and removed.
// This call is idempotent, and must not return an error if the sandbox has
// already been removed.
RemovePodSandbox(context.Context, *RemovePodSandboxRequest) (*RemovePodSandboxResponse, error)
// PodSandboxStatus returns the status of the PodSandbox. If the PodSandbox is not
// present, returns an error.
PodSandboxStatus(context.Context, *PodSandboxStatusRequest) (*PodSandboxStatusResponse, error)
// ListPodSandbox returns a list of PodSandboxes.
ListPodSandbox(context.Context, *ListPodSandboxRequest) (*ListPodSandboxResponse, error)
// CreateContainer creates a new container in specified PodSandbox
CreateContainer(context.Context, *CreateContainerRequest) (*CreateContainerResponse, error)
// StartContainer starts the container.
StartContainer(context.Context, *StartContainerRequest) (*StartContainerResponse, error)
// StopContainer stops a running container with a grace period (i.e., timeout).
// This call is idempotent, and must not return an error if the container has
// already been stopped.
// TODO: what must the runtime do after the grace period is reached?
StopContainer(context.Context, *StopContainerRequest) (*StopContainerResponse, error)
// RemoveContainer removes the container. If the container is running, the
// container must be forcibly removed.
// This call is idempotent, and must not return an error if the container has
// already been removed.
RemoveContainer(context.Context, *RemoveContainerRequest) (*RemoveContainerResponse, error)
// ListContainers lists all containers by filters.
ListContainers(context.Context, *ListContainersRequest) (*ListContainersResponse, error)
// ContainerStatus returns status of the container. If the container is not
// present, returns an error.
ContainerStatus(context.Context, *ContainerStatusRequest) (*ContainerStatusResponse, error)
// UpdateContainerResources updates ContainerConfig of the container.
UpdateContainerResources(context.Context, *UpdateContainerResourcesRequest) (*UpdateContainerResourcesResponse, error)
// ReopenContainerLog asks runtime to reopen the stdout/stderr log file
// for the container. This is often called after the log file has been
// rotated. If the container is not running, container runtime can choose
// to either create a new log file and return nil, or return an error.
// Once it returns error, new container log file MUST NOT be created.
ReopenContainerLog(context.Context, *ReopenContainerLogRequest) (*ReopenContainerLogResponse, error)
// ExecSync runs a command in a container synchronously.
ExecSync(context.Context, *ExecSyncRequest) (*ExecSyncResponse, error)
// Exec prepares a streaming endpoint to execute a command in the container.
Exec(context.Context, *ExecRequest) (*ExecResponse, error)
// Attach prepares a streaming endpoint to attach to a running container.
Attach(context.Context, *AttachRequest) (*AttachResponse, error)
// PortForward prepares a streaming endpoint to forward ports from a PodSandbox.
PortForward(context.Context, *PortForwardRequest) (*PortForwardResponse, error)
// ContainerStats returns stats of the container. If the container does not
// exist, the call returns an error.
ContainerStats(context.Context, *ContainerStatsRequest) (*ContainerStatsResponse, error)
// ListContainerStats returns stats of all running containers.
ListContainerStats(context.Context, *ListContainerStatsRequest) (*ListContainerStatsResponse, error)
// UpdateRuntimeConfig updates the runtime configuration based on the given request.
UpdateRuntimeConfig(context.Context, *UpdateRuntimeConfigRequest) (*UpdateRuntimeConfigResponse, error)
// Status returns the status of the runtime.
Status(context.Context, *StatusRequest) (*StatusResponse, error)
}
Ja tÄ, mums vajadzÄtu redzÄt savienojumu starp kubelet un konteinera izpildlaiku, vai ne? PÄrbaudÄ«sim.
Palaidiet Å”o komandu pirms un pÄc exec komandas un apskatiet atŔķirÄ«bas. ManÄ gadÄ«jumÄ atŔķirÄ«ba ir:
// worker node
$ ss -a -p |grep kubelet
...
u_str ESTAB 0 0 * 157937 * 157387 users:(("kubelet",pid=5714,fd=33))
...
Hmm... Jauns savienojums caur unix ligzdÄm starp kubeletu (pid=5714) un kaut ko nezinÄmu. Kas tas varÄtu bÅ«t? TieÅ”i tÄ, tas ir Docker (pid=1186)!
Kubectl vai api-serveris nevar palaist neko darbinieka mezglos. Kubelet var palaist, taÄu tas arÄ« mijiedarbojas ar konteinera izpildlaiku, lai veiktu Ŕīs darbÄ«bas.