[Bigdata-developers] After a timeout I get only timeouts

[Daniel H. <da...@de...>]

Hi,

I, running an experiment with 583 millions of triples loaded into 
Blazegraph 2.1.0. I have 500 queries generated randomly with similar 
complexity. I started running these queries with a timeout of 120 
seconds in the http client. The first queries get small times around 2 
seconds, except some that gets around 40 seconds. However, in query 37 I 
got a timeout. Then, all the following queries get timeouts.

I guessed that this behavior was because the server was working in the 
previous query when the following queries arrive. That is, the server 
does not notice that the client have a timeout, so it is not waiting for 
a result.

I found the timeout option in the documentation. Thus, now I'm running 
queries with the option &timeout=1 to check if this behavior was because 
running queries simultaneously. I starting getting only results in less 
than 1 second, and some trunked results with an internal timeout error 
message that truncate the JSON output. However, after some queries I get 
the timeout in the client again, and then all the following queries get 
timeout.

Now I guess that a GC job that avoid receiving more queries by the 
server. I set the parameter -Xmx6g in the java command. The machine have 
32GB of RAM and 6 cores. I do not put more memory in the heap, because 
the documentation does not recommend it. However, top says that the 
process has VIRT=6913m RES=781m and CPU=104%. That is, the process is 
underusing the machine resources.

I found that I can use the option analytic to using the system heap 
instead of the java heap. The documentation said that this will solve 
the GC issue.

Do you think that am I right in suppositions about the GC?

Cheers,
Daniel