Claus Stadler created JENA-1858:
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Summary: SERVICE in SPARQL blocks after a while
Key: JENA-1858
URL: https://issues.apache.org/jira/browse/JENA-1858
Project: Apache Jena
Issue Type: Bug
Components: ARQ
Affects Versions: Jena 3.14.0
Reporter: Claus Stadler
Hi once again :)
I wanted to create a quick RDF/SPARQL-based service online/offline monitoring
system just like this:
* A list of endpoints in [this
dataset|https://github.com/SmartDataAnalytics/Meta-LOD/blob/master/sparql-endpoints.ttl]
* Have a CI process run this SPARQL query and publish/commit the results to a
file
{code}
PREFIX eg: <http://www.example.org/>
PREFIX dcat: <http://www.w3.org/ns/dcat#>
CONSTRUCT {
?s eg:serviceStatus ?status
}
{
?s dcat:endpointURL ?e .
# Here we rely on jena's substitution mechanism in QueryIterService.java -
which is sufficient for my use case
SERVICE SILENT ?e {
# If the request fails, we get a single binding without any variables bound
{ SELECT ?t { ?x a ?t } LIMIT 1 }
}
BIND(IF(BOUND(?t), "online", "offline") AS ?status)
}
{code}
However, the query blocks after a while by consuming the HTTP connection pool.
I have not yet identified all sources, but one I could spot is here:
* The InputStream opened at
[Service.java#L172|https://github.com/apache/jena/blob/64253b9de5924006cdd46f1e3492a92031842d3b/jena-arq/src/main/java/org/apache/jena/sparql/engine/http/Service.java#L172]
is not in a try-catch-block, so if the subsequent XML parsing fails, then it
is never closed.
Maybe this triggers ideas of potentially other spots. I have a local jena
checkout and will try to find out whether there are any other leaks. My goal is
to have the query complete on the whole endpoint list - despite many of the
URLs actually referring to by now broken services.
I am aware of the context settings in
https://jena.apache.org/documentation/query/service.html - but I did not fiddle
with the settings - especially timeouts, as so far the issue is really the
exhaustion of the connection pool.
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