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impala-refresher.go
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impala-refresher.go
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/*
Copyright 2013 Cloudera, inc
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package main
import (
"fmt"
"os"
"time"
"os/exec"
"strings"
"errors"
"flag"
)
type ImpalaNode struct {
// Host name of Impala daemon
hostName string
// Has this node been refreshed?
refreshed bool
// Any error that may have occurred during refresh
refreshError error
// Total time taken to refresh
totalRefreshTime time.Duration
}
/*
Uses the exec library to open impala-shell in order
to manually refresh an Impala table.
*/
func ExecuteRefresh(node *ImpalaNode, tableName string, timeout int, finishRefresh chan<- *ImpalaNode) {
// Construct the refresh command using the impala-shell
refreshCommand := exec.Command("impala-shell", "-i", node.hostName,
"-q", "refresh " + tableName + "; DESCRIBE " + tableName)
// Execute a goroutine to block waiting for the command output
startTime := time.Now()
refreshFinished := make(chan error)
go func() {
output, err := refreshCommand.Output()
// Confirm that the table was successfully refreshed
if (!strings.Contains(string(output), "Successfully refreshed table") && err == nil) {
err = errors.New(node.hostName + "'s catalog did not refresh")
}
refreshFinished <- err
}()
// Wait for the refresh to finish, timeout after 1 minute.
select {
// Waits for refresh command to finish
case err := <-refreshFinished:
node.totalRefreshTime = (time.Now().Sub(startTime))
// Check for any errors (exit 1+)
if (err != nil) {
fmt.Println(err)
node.refreshed = false
node.refreshError = err
} else {
node.refreshed = true
}
finishRefresh <- node
// Timeout channel
case <-time.After(time.Second * time.Duration(timeout)):
// Kill the process
refreshCommand.Process.Kill()
fmt.Println("Node " + node.hostName + " timed out!")
node.refreshed = false
finishRefresh <- node
}
}
/*
Wait for a node to finish from the queue
*/
func WaitForNode(finishRefresh <-chan *ImpalaNode, allNodesRefreshed *bool) {
node := <-finishRefresh
if (!node.refreshed) {
fmt.Println(node.hostName + " failed to refresh!")
*allNodesRefreshed = false
} else {
fmt.Println(node.hostName + " refreshed successfully! Took: " +
node.totalRefreshTime.String())
}
}
/*
Refresh all of the supplied Impala daemon's metadata
concurrently. If all nodes refreshed, return true
*/
func RefreshNodes(nodes []*ImpalaNode, tableName string, timeout int, concurrency int) bool {
inFlight := 0
finishRefresh := make(chan *ImpalaNode)
allNodesRefreshed := true
for index, node := range nodes {
// Execute a node refresh, and increment inFlight refreshes by 1
fmt.Println("Refreshing " + node.hostName + "'s metadata...")
go ExecuteRefresh(node, tableName, timeout, finishRefresh)
inFlight++
// If we've reach the concurrency level, wait for a node to finish
// and decrement the inFlight nodes value. If we're all out of nodes
// to execute, wait for the rest of them to finish.
if (inFlight == concurrency || index == len(nodes) - 1) {
if (!(index == len(nodes) -1)) {
WaitForNode(finishRefresh, &allNodesRefreshed)
} else {
for i:= 0; i < inFlight; i++ {
WaitForNode(finishRefresh, &allNodesRefreshed)
}
}
inFlight--
}
}
return allNodesRefreshed
}
/*
Checks if this system has the Impala Shell
*/
func HasImpalaShell() bool {
_, err := exec.LookPath("impala-shell")
return err == nil
}
/*
Main Function
*/
func main() {
// Argument parsing
timeout := flag.Int("timeout", 60, "Refresh timeout in seconds")
tableName := flag.String("table", "","Table to refresh")
nodeList := flag.String("nodes", "","Comma separated list of impala daemons to refresh")
concurrency := flag.Int("concurrency", 0, "Max number of refreshes to perform concurrently (0: unlimited)")
flag.Parse()
// Check to make sure required arguments were supplied
if (*tableName == "" || *nodeList == "") {
flag.Usage()
os.Exit(1)
}
// Check if we have the Impala Shell
if (!HasImpalaShell()) {
fmt.Println("Impala shell (impala-shell) is required!")
os.Exit(1)
}
var nodes []*ImpalaNode
for _, nodeArg := range strings.Split(*nodeList, ",") {
nodes = append(nodes, &ImpalaNode{strings.Trim(nodeArg, " "), false, nil, time.Duration(0)})
}
allNodesRefreshed := RefreshNodes(nodes, *tableName, *timeout, *concurrency)
// If all nodes refreshed successfully, exit ok
if (allNodesRefreshed) {
os.Exit(0)
} else {
os.Exit(1)
}
}