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https://issues.apache.org/jira/browse/HADOOP-8232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242565#comment-13242565
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Steve Loughran commented on HADOOP-8232:
----------------------------------------
Test with table mapping pointing to a table that does not exist relative to the
directory where the hadoop command is being invoked from:
{code}
bash hadoop-dist/target/hadoop-3.0.0-SNAPSHOT/bin/hadoop --config
/Users/slo/Java/Hadoop/github/hadoop-patches/misc/topology/missing-table
org.apache.hadoop.net.TopologyTool test 4 home extra
net.topology.node.switch.mapping.impl=org.apache.hadoop.net.TableMapping
Caching wrapper class = class org.apache.hadoop.net.TableMapping
Instance information: cached switch mapping relaying to TableMapping with table
"table.txt"
Path: /Users/slo/Java/Hadoop/github/trunk/table.txt
Map size: 0
Topology is not considered single-switch
Resolving 4
2012-03-30 18:22:03,831 WARN net.TableMapping (TableMapping.java:load(113)) -
table.txt cannot be read. /default-rack will be returned.
java.io.FileNotFoundException: table.txt (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:120)
at java.io.FileInputStream.<init>(FileInputStream.java:79)
at java.io.FileReader.<init>(FileReader.java:41)
at
org.apache.hadoop.net.TableMapping$RawTableMapping.load(TableMapping.java:98)
at
org.apache.hadoop.net.TableMapping$RawTableMapping.resolve(TableMapping.java:132)
at
org.apache.hadoop.net.CachedDNSToSwitchMapping.resolve(CachedDNSToSwitchMapping.java:119)
at
org.apache.hadoop.net.TopologyTool.resolveHostnames(TopologyTool.java:189)
at org.apache.hadoop.net.TopologyTool.run(TopologyTool.java:103)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84)
at org.apache.hadoop.net.TopologyTool.main(TopologyTool.java:228)
Hostname "4" resolved to "/default-rack" in 15.548 milliseconds
Resolving home
Hostname "home" resolved to "/default-rack" in 6.812 milliseconds
Resolving extra
Hostname "extra" resolved to "/default-rack" in 0.702 milliseconds
Final topology:
Mapping: cached switch mapping relaying to TableMapping with table "table.txt"
Path: /Users/slo/Java/Hadoop/github/trunk/table.txt
Map size: 0
Known mappings:
home -> /default-rack
extra -> /default-rack
4 -> /default-rack
Nodes: 3
Switches: 1
{code}
The error message is printed inside the TableMapping, and is not visible to the
caller. It could be improved by listing the absolute path to the table.
> Provide a command line entry point to view/test topology options
> ----------------------------------------------------------------
>
> Key: HADOOP-8232
> URL: https://issues.apache.org/jira/browse/HADOOP-8232
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: util
> Affects Versions: 0.23.1
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Minor
> Attachments: HADOOP-8232.patch
>
>
> Add a new command line entry point "topo" with commands for preflight
> checking of a clusters topology setup.
> The initial operations would be to list the implementation class of the
> mapper, and attempt to load it, resolve a set of supplied hostnames, then
> dump the topology map after the resolution process.
> Target audience:
> # ops teams trying to get a new/changed script working before deploying it on
> a cluster.
> # someone trying to write their first script.
> Resolve and list the rack mappings of the given host
> {code}
> hadoop topo test [host1] [host2] ...
> {code}
> This would load the hostnames from a given file, resolve all of them and list
> the results:
> {code}
> hadoop topo testfile filename
> {code}
> This version is intended for the ops team who have a list of hostnames, IP
> addresses.
> * Rather than just list them, the ops team may want to mandate that there
> were no /default-rack mappings found, as that is invariably a sign that the
> script isn't handling a hostname properly.
> * No attempt to be clever and do IP address resolution, FQDN to hostname
> mapping, etc.
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