Created question in FIWARE Q/A platform on 10-05-2018 at 16:05
Please, ANSWER this question AT https://stackoverflow.com/questions/50274937/how-to-interpret-fiware-cygnus-stats-service-output

Question:
How to interpret Fiware CYGNUS stats service output?

Description:
Starting from my own installation of the following Fiware components: Orion Context Broker, CYGNUS NGSI, Fiware STH and MongoDB, after a while I got the following result consuming a stats service which I found inside CYGNUS management API.

Service: GET http://<cygnus_host>:<management_port>/v1/stats

Result:

{
"success":"true",
"stats":{
"sources":[

{ "name":"http-source", "status":"START", "setup_time":"2018-05-10T13:35:06.194Z", "num_received_events":78, "num_processed_events":78 }

],
"channels":[

{ "name":"sth-channel", "status":"START", "setup_time":"2018-05-10T13:35:06.662Z", "num_events":1, "num_puts_ok":78, "num_puts_failed":0, "num_takes_ok":77, "num_takes_failed":112 }

,

{ "name":"mongo-channel", "status":"START", "setup_time":"2018-05-10T13:35:06.662Z", "num_events":0, "num_puts_ok":78, "num_puts_failed":0, "num_takes_ok":78, "num_takes_failed":139 }

,

{ "name":"hdfs-channel", "status":"START", "setup_time":"2018-05-10T13:35:06.662Z", "num_events":1, "num_puts_ok":78, "num_puts_failed":0, "num_takes_ok":77, "num_takes_failed":35 }

],
"sinks":[

{ "name":"hdfs-sink", "status":"START", "setup_time":"2018-05-10T13:35:06.341Z", "num_processed_events":77, "num_persisted_events":0 }

,

{ "name":"mongo-sink", "status":"START", "setup_time":"2018-05-10T13:35:06.374Z", "num_processed_events":78, "num_persisted_events":78 }

,

{ "name":"sth-sink", "status":"START", "setup_time":"2018-05-10T13:35:06.380Z", "num_processed_events":78, "num_persisted_events":77 }

]
}
}

What caught my attention was the amount of num_takes_failed on each channel and here is my first question:

What exactly does this variable mean?

Looking into CYGNUS documentation I suppose that a "take" is something like a retry of a certain action in Flume Mongo channel but which action is that?

I looked at the MongoDB log files and did not find anything related to a connection saturation or similar problem, which brings me to my second question.

Should I worry about this statistic? If yes, how do I solve this problem?

Thank you very much in advance for any help.