Any command to get active namenode for nameservice in hadoop? - hadoop

Question

The command:
hdfs haadmin -getServiceState machine-98
Works only if you know the machine name. Is there any command like:
hdfs haadmin -getServiceState <nameservice>
which can tell you the IP/hostname of the active namenode?

Answer 1

To print out the namenodes use this command:
hdfs getconf -namenodes
To print out the secondary namenodes:
hdfs getconf -secondaryNameNodes
To print out the backup namenodes:
hdfs getconf -backupNodes
Note: These commands were tested using Hadoop 2.4.0.
Update 10-31-2014:
Here is a python script that will read the NameNodes involved in Hadoop HA from the config file and determine which of them is active by using the hdfs haadmin command. This script is not fully tested as I do not have HA configured. Only tested the parsing using a sample file based on the Hadoop HA Documentation. Feel free to use and modify as needed.
#!/usr/bin/env python
# coding: UTF-8
import xml.etree.ElementTree as ET
import subprocess as SP
if __name__ == "__main__":
hdfsSiteConfigFile = "/etc/hadoop/conf/hdfs-site.xml"
tree = ET.parse(hdfsSiteConfigFile)
root = tree.getroot()
hasHadoopHAElement = False
activeNameNode = None
for property in root:
if "dfs.ha.namenodes" in property.find("name").text:
hasHadoopHAElement = True
nameserviceId = property.find("name").text[len("dfs.ha.namenodes")+1:]
nameNodes = property.find("value").text.split(",")
for node in nameNodes:
#get the namenode machine address then check if it is active node
for n in root:
prefix = "dfs.namenode.rpc-address." + nameserviceId + "."
elementText = n.find("name").text
if prefix in elementText:
nodeAddress = n.find("value").text.split(":")[0]
args = ["hdfs haadmin -getServiceState " + node]
p = SP.Popen(args, shell=True, stdout=SP.PIPE, stderr=SP.PIPE)
for line in p.stdout.readlines():
if "active" in line.lower():
print "Active NameNode: " + node
break;
for err in p.stderr.readlines():
print "Error executing Hadoop HA command: ",err
break
if not hasHadoopHAElement:
print "Hadoop High-Availability configuration not found!"

Answer 2

Found this:
https://gist.github.com/cnauroth/7ff52e9f80e7d856ddb3
This works out of the box on my CDH5 namenodes, although I'm not sure other hadoop distributions will have http://namenode:50070/jmx available - if not, I think it can be added by deploying Jolokia.
Example:
curl 'http://namenode1.example.com:50070/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus'
{
"beans" : [ {
"name" : "Hadoop:service=NameNode,name=NameNodeStatus",
"modelerType" : "org.apache.hadoop.hdfs.server.namenode.NameNode",
"State" : "active",
"NNRole" : "NameNode",
"HostAndPort" : "namenode1.example.com:8020",
"SecurityEnabled" : true,
"LastHATransitionTime" : 1436283324548
} ]
So by firing off one http request to each namenode (this should be quick) we can figure out which one is the active one.
It's also worth noting that if you talk WebHDFS REST API to an inactive namenode you will get a 403 Forbidden and the following JSON:
{"RemoteException":{"exception":"StandbyException","javaClassName":"org.apache.hadoop.ipc.StandbyException","message":"Operation category READ is not supported in state standby"}}

Answer 3

In a High Availability Hadoop cluster, there will be 2 namenodes - one active and one standby.
To find the active namenode, we can try executing the test hdfs command on each of the namenodes and find the active name node corresponding to the successful run.
Below command executes successfully if the name node is active and fails if it is a standby node.
hadoop fs -test -e hdfs://<Name node>/
Unix script
active_node=''
if hadoop fs -test -e hdfs://<NameNode-1>/ ; then
active_node='<NameNode-1>'
elif hadoop fs -test -e hdfs://<NameNode-2>/ ; then
active_node='<NameNode-2>'
fi
echo "Active Dev Name node : $active_node"

Answer 4

You can do it in bash with hdfs cli calls, too. With the noted caveat that this takes a bit more time since it's a few calls to the API in succession, but this may be preferable to using a python script for some.
This was tested with Hadoop 2.6.0
get_active_nn(){
ha_name=$1 #Needs the NameServiceID
ha_ns_nodes=$(hdfs getconf -confKey dfs.ha.namenodes.${ha_name})
active=""
for node in $(echo ${ha_ns_nodes//,/ }); do
state=$(hdfs haadmin -getServiceState $node)
if [ "$state" == "active" ]; then
active=$(hdfs getconf -confKey dfs.namenode.rpc-address.${ha_name}.${node})
break
fi
done
if [ -z "$active" ]; then
>&2 echo "ERROR: no active namenode found for ${ha_name}"
exit 1
else
echo $active
fi
}

Answer 5

After reading all the existing answers none seemed to combine the three steps of:
Identifying the namenodes from the cluster.
Resolving the node names to host:port.
Checking the status of each node (without requiring
cluster admin privs).
Solution below combines hdfs getconf calls and JMX service call for node status.
#!/usr/bin/env python
from subprocess import check_output
import urllib, json, sys
def get_name_nodes(clusterName):
ha_ns_nodes=check_output(['hdfs', 'getconf', '-confKey',
'dfs.ha.namenodes.' + clusterName])
nodes = ha_ns_nodes.strip().split(',')
nodeHosts = []
for n in nodes:
nodeHosts.append(get_node_hostport(clusterName, n))
return nodeHosts
def get_node_hostport(clusterName, nodename):
hostPort=check_output(
['hdfs','getconf','-confKey',
'dfs.namenode.rpc-address.{0}.{1}'.format(clusterName, nodename)])
return hostPort.strip()
def is_node_active(nn):
jmxPort = 50070
host, port = nn.split(':')
url = "http://{0}:{1}/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus".format(
host, jmxPort)
nnstatus = urllib.urlopen(url)
parsed = json.load(nnstatus)
return parsed.get('beans', [{}])[0].get('State', '') == 'active'
def get_active_namenode(clusterName):
for n in get_name_nodes(clusterName):
if is_node_active(n):
return n
clusterName = (sys.argv[1] if len(sys.argv) > 1 else None)
if not clusterName:
raise Exception("Specify cluster name.")
print 'Cluster: {0}'.format(clusterName)
print "Nodes: {0}".format(get_name_nodes(clusterName))
print "Active Name Node: {0}".format(get_active_namenode(clusterName))

Answer 6

From java api, you can use HAUtil.getAddressOfActive(fileSystem).

Answer 7

You can do a curl command to find out the Active and secondary Namenode
for example
curl -u username -H "X-Requested-By: ambari" -X GET
http://cluster-hostname:8080/api/v1/clusters//services/HDFS
Regards

Answer 8

I found the below when i simply typed 'hdfs' and found a couple of helpful commands, which could be useful for someone who could maybe come here seeking for help.
hdfs getconf -namenodes
This above command will give you the service id of the namenode. Say, hn1.hadoop.com
hdfs getconf -secondaryNameNodes
This above command will give you the service id of the available secondary namenodes. Say , hn2.hadoop.com
hdfs getconf -backupNodes
This above command will get you the service id of backup nodes, if any.
hdfs getconf -nnRpcAddresses
This above command will give you info of name service id along with rpc port number. Say, hn1.hadoop.com:8020
You're Welcome :)

Answer 9

In HDFS 2.6.0 the one that worked for me
ubuntu#platform2:~$ hdfs getconf -confKey dfs.ha.namenodes.arkin-platform-cluster
nn1,nn2
ubuntu#platform2:~$ sudo -u hdfs hdfs haadmin -getServiceState nn1
standby
ubuntu#platform2:~$ sudo -u hdfs hdfs haadmin -getServiceState nn2
active

Answer 10

Here is example of bash code that returns active name node even if you do not have local hadoop installation.
It also works faster as curl calls are usually faster than hadoop.
Checked on Cloudera 7.1
#!/bin/bash
export nameNode1=myNameNode1
export nameNode2=myNameNode2
active_node=''
T1=`curl --silent --insecure -request GET https://${nameNode1}:9871/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus | grep "\"State\" : \"active\"" | wc -l`
if [ $T1 == 1 ]
then
active_node=${nameNode1}
else
T1=`curl --silent --insecure -request GET https://${nameNode2}:9871/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus | grep "\"State\" : \"active\"" | wc -l`
if [ $T1 == 1 ]
then
active_node=${nameNode2}
fi
fi
echo "Active Dev Name node : $active_node"

Answer 11

#!/usr/bin/python
import subprocess
import sys
import os, errno
def getActiveNameNode () :
cmd_string="hdfs getconf -namenodes"
process = subprocess.Popen(cmd_string, shell=True, stdout=subprocess.PIPE)
out, err = process.communicate()
NameNodes = out
Value = NameNodes.split(" ")
for val in Value :
cmd_str="hadoop fs -test -e hdfs://"+val
process = subprocess.Popen(cmd_str, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = process.communicate()
if (err != "") :
return val
def main():
out = getActiveNameNode()
print(out)
if __name__ == '__main__':
main()

Answer 12

You can simply use the below command. I have tested this in hadoop 3.0 You can check the reference here -
hdfs haadmin -getAllServiceState
It returns the state of all the NameNodes.

Answer 13

more /etc/hadoop/conf/hdfs-site.xml
<property>
<name>dfs.ha.namenodes.nameservice1</name>
<value>namenode1353,namenode1357</value>
</property>
hdfs#:/home/ubuntu$ hdfs haadmin -getServiceState namenode1353
active
hdfs#:/home/ubuntu$ hdfs haadmin -getServiceState namenode1357
standby