istio

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// Copyright Istio Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package app
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import (
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	"fmt"
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	"io"
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	"net/http"
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	"time"
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	"github.com/spf13/cobra"
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	"istio.io/istio/pkg/log"
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)
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var (
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	timeoutSeconds       int
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	requestTimeoutMillis int
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	periodMillis         int
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	url                  string
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	waitCmd = &cobra.Command{
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		Use:   "wait",
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		Short: "Waits until the Envoy proxy is ready",
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		RunE: func(c *cobra.Command, args []string) error {
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			client := &http.Client{
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				Timeout: time.Duration(requestTimeoutMillis) * time.Millisecond,
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			}
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			log.Infof("Waiting for Envoy proxy to be ready (timeout: %d seconds)...", timeoutSeconds)
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			var err error
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			timeout := time.After(time.Duration(timeoutSeconds) * time.Second)
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			for {
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				select {
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				case <-timeout:
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					return fmt.Errorf("timeout waiting for Envoy proxy to become ready. Last error: %v", err)
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				case <-time.After(time.Duration(periodMillis) * time.Millisecond):
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					err = checkIfReady(client, url)
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					if err == nil {
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						log.Infof("Envoy is ready!")
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						return nil
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					}
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					log.Debugf("Not ready yet: %v", err)
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				}
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			}
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		},
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	}
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)
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func checkIfReady(client *http.Client, url string) error {
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	req, err := http.NewRequest(http.MethodGet, url, nil)
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	if err != nil {
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		return err
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	}
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	resp, err := client.Do(req)
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	if err != nil {
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		return err
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	}
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	defer resp.Body.Close()
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	_, err = io.ReadAll(resp.Body)
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	if err != nil {
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		return err
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	}
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	if resp.StatusCode != http.StatusOK {
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		return fmt.Errorf("HTTP status code %v", resp.StatusCode)
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	}
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	return nil
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}
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func init() {
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	waitCmd.PersistentFlags().IntVar(&timeoutSeconds, "timeoutSeconds", 60, "maximum number of seconds to wait for Envoy to be ready")
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	waitCmd.PersistentFlags().IntVar(&requestTimeoutMillis, "requestTimeoutMillis", 500, "number of milliseconds to wait for response")
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	waitCmd.PersistentFlags().IntVar(&periodMillis, "periodMillis", 500, "number of milliseconds to wait between attempts")
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	waitCmd.PersistentFlags().StringVar(&url, "url", "http://localhost:15021/healthz/ready", "URL to use in requests")
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}
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