Re: In-memory Fuseki keeps growing memory indefinitely even if idle

[Andy Seaborne]

On 27/07/2021 14:19, Marco Fiocco wrote:
Hello,

I'm running a in-memory Fuseki 3.16 server and I see that the allocated memory 
keeps growing linearly indefinitely even if idle.

That is strange because if there are no requests, it does no work.

Initially I reserved 1GB of memory and I've noticed that the process gets OOM 
killed every 2 hours.

What pattern of usage is it getting?
 > Now I've allocated 2GB because I've read somewhere that 2GB is the 
minimum for Java heaps. Is that true?

It's not that simple - you have an in-memory dataset so the space needed 
is proportional to the amount of data.

I'm waiting to see if it will get again.
Is this a bug or there is a better way to config it?

If you don't need the union graph, "rdf:type ja:MemoryDataset" is a 
better in-memory choice. It has a smaller foot print and (I guess in 
your setup you delete data as well as add it?) managed DELETE and PUT 
better for GSP.  TDB, in-memory is primarily a testing configuration.



My Fuseki config is:

@prefix fuseki:  <http://jena.apache.org/fuseki#> .
@prefix rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#> .
@prefix tdb:     <http://jena.hpl.hp.com/2008/tdb#> .
@prefix ja:      <http://jena.hpl.hp.com/2005/11/Assembler#> .
@prefix :        <#> .

[] rdf:type fuseki:Server .

<#service> rdf:type fuseki:Service ;
     rdfs:label          "Dataset with SHACL validation" ;
     fuseki:name         "ds" ;                                                 
                                                              # See the endpoint url in 
build.gradle
     fuseki:serviceReadWriteGraphStore "data" ;                                 
                                                      # SPARQL Graph store protocol (read 
and write)
     fuseki:endpoint    [ fuseki:operation fuseki:query ;       fuseki:name 
"sparql"  ] ;     # SPARQL query service
     fuseki:endpoint    [ fuseki:operation fuseki:shacl ;       fuseki:name 
"shacl" ] ;               # SHACL query service
     fuseki:dataset      <#dataset> .

## In memory TDB with union graph.
<#dataset> rdf:type   tdb:DatasetTDB ;
   tdb:location "--mem--" ;
   # Query timeout on this dataset (1s, 1000 milliseconds)
   ja:context [ ja:cxtName "arq:queryTimeout" ; ja:cxtValue "1000" ] ;
   # Make the default graph be the union of all named graphs.
   tdb:unionDefaultGraph true .

Thanks
Marco