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This ZooKeeper instance is not currently serving requests

When one of your zookeeper nodes is sending you this message, that means that your Zookeeper cluster hasn’t started in the right order.
 
Solution: Restart your cluster (node per node), starting from node 1 (as stated in zoo.conf)
 
This problem is easy to diagnose. When the order was wrong you will get this output:

[myserver:myuser] ~: echo stat | nc localhost 2181
This ZooKeeper instance is not currently serving requests

 
After you’ve restarted all nodes (in the correct order), you will get this output:

[myserver:myuser] ~: echo stat | nc localhost 2181 |grep Mode
Mode: follower
[myserver:myuser] ~: echo stat | nc localhost 2181 |grep Mode
Mode: leader

 
 
Hope this will help you out!

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Why no SSL!? Port is open!

Okay, this has taken me too long to not post.. So here it is..:
When your firewall is blocking SSL traffic but allowing HTTP traffic, openssl s_client will show this:

my_host:joris [/etc/stores] openssl s_client -host external_host -port 12345
CONNECTED(00000003)
write:errno=104
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no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 247 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
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Continue reading “Why no SSL!? Port is open!”