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From Giovanni Usai <giovanni.u...@francelabs.com>
Subject Best way to get Cassandra status in Bash
Date Mon, 04 Jan 2016 12:47:11 GMT
Hello,
I would gladly welcome the help of the community on the following issue 
I am having while starting Cassandra.

I am starting Cassandra by a Bash script in this way:

- $CASSANDRA_HOME/bin/cassandra -p $CASSANDRA_PID_FILE
and then, I submit some updates via
- $CASSANDRA_HOME/bin/cqlsh -f 
$DATAFARI_HOME/bin/common/config/cassandra/tables

=> First question: is it a good idea? Or, are there better ways to do 
start Cassandra?


If it is a good idea to use Bash, this is my need: when something goes 
wrong (e.g. privileges issue on  Cassandra's data directory, etc), I 
would like to detect it to be able to apply some countermeasures.

=> Second question: do you know what's the best way to get the Cassandra 
and CQLSH status from Bash (if it is possible)?

These are all the approaches that I have already tried, with no chance:
- use the return code of Cassandra script ($? Bash operator), but it 
returns all the times 0 even if something goes wrong.
- grep the Cassandra logs looking for "Exception" or "Error" (after 
redirection with &> ), but it doesn't work as they are not yet flushed 
by Cassandra (as a result, the calling bash exits).
- get the output of the Cassandra script with something like 
cassandra_return=$($CASSANDRA_HOME/bin/cassandra -p 
$CASSANDRA_PID_FILE), but the variable is empty all the times.
- detach Cassandra process from calling script with '&' operator and 
then grep the logs or get the return code, but it doesn't work neither.

Furthermore, when CQLSH script cannot connect to Cassandra, it prints 
this error on console:
Connection error: ('Unable to connect to any servers', {'127.0.0.1': 
error(111, "Tried connecting to [('127.0.0.1', 9042)]. Last error: 
Connection refused")})
and then kills the calling script.

Just for your information, we are embedding Cassandra in our open source 
product "Datafari".

Thanks for your help and
-- 

Best regards,
*Giovanni Usai
* giovanni.usai@francelabs.com <mailto:giovanni.usai@francelabs.com>


www.francelabs.com <http://www.francelabs.com/>

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1 Bd. MaƮtre Maurice Slama
06200 Nice FRANCE

Ph: +33 (0)9 72 43 72 85


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