Use getent instead of nslookup for starting scripts

[jinfwhuang]

The nslookup only exit with status 0 with successful lookup of dns record for both forward and backward lookups. It would mean that the cluster's DNS setup has to support. getent only performs a forward lookup.

#76

[codecov-commenter]

Codecov Report

Merging #243 (f25be3b) into master (c62716b) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##           master     #243   +/-   ##
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  Coverage   86.00%   86.00%           
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  Files          11       11           
  Lines        1572     1572           
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  Hits         1352     1352           
  Misses        147      147           
  Partials       73       73           

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[amuraru]

@jinfwhuang can you please rebase your patch on top of latest master? thanks

[jinfwhuang]

@amuraru Updated this PR.

[derekm]

I think the claim that nslookup requires both forward A/AAAA records and reverse PTR records is false.

Rather, nslookup uses DNS-only lookups and does not return entries from /etc/hosts. Whereas, getent hosts does resolution according to Name Service Switch configuration.

This being the case, using nslookup does hinder /etc/hosts-only deployments.

[amuraru]

@derekm thanks for your analysis.
I don't have a strong opinion for this patch - we've seen this on some of our clusters but those are not critical atm so we can drop this.

[jinfwhuang]

I think getent is simpler than nslookup. It works for more cases. Why not?

[anishakj]

@jinfwhuang Are you still facing issues with nslookup?

[jinfwhuang]

@jinfwhuang Are you still facing issues with nslookup?

We have been running our zookeeper clusters with the patch in the past year.

[anishakj]

@jinfwhuang Are you still facing issues with nslookup?

We have been running our zookeeper clusters with the patch in the past year.

@jinfwhuang Could you please sign-off the commit?

[jinfwhuang]

Looks good to me

[anishakj]

Looks good to me

@jinfwhuang If you see DCO check is failing, because commits are not signed off

[jinfwhuang]

Looks good to me

@jinfwhuang If you see DCO check is failing, because commits are not signed off

Okay. Updated the commit.

Question, why was signoff necessary for this project?

[anishakj]

Looks good to me

@jinfwhuang If you see DCO check is failing, because commits are not signed off

Okay. Updated the commit.

Question, why was signoff necessary for this project?

In Pravega, we are using DCO instead of CLA, so authors acknowledge and retain their copyrights

[anishakj]

LGTM

[derekm]

It will be nice to help a user get off of a private fork!

[amuraru]

@jinfwhuang I still see a reference to nslookup here

zookeeper-operator/docker/bin/zookeeperStart.sh

Line 77 in c4113df

elif nslookup $DOMAIN | grep -q "server can't find $DOMAIN"; then

Should this be updated as well?
thanks