Add timeout for Interactive Query

[zhanglei1949]

Following query failed on Interactive.

MATCH (p:Paper)-[:Paper_Has_Experiment]->(e:Experiment), 
      (p)-[:Paper_Has_Challenge]->(c:Challenge), 
      (p)-[:Paper_Has_Solution]->(s:Solution), 
      (p)-[:Paper_Has_Baseline]->(b:Baseline), 
      (p)-[:Paper_Has_Contribution]->(co:Contribution)
RETURN p.title AS PaperTitle, 
       e.name AS ExperimentName, 
       c.name AS ChallengeName, 
       s.name AS SolutionName, 
       b.name AS BaselineName, 
       co.summary AS ContributionSummary

[zhanglei1949]

This query actually does 5 degree bfs, including flattering the context(engine internal data structure). Causing server stuck and not responding.

[zhanglei1949]

It turns out that we could probably use seastar::with_timeout to set a timeout for the query, however, we still can not cancel the query.

And trying to set a timeout for GraphDBSession.Eval() fails, due to the underlying synchronous execution.

[zhanglei1949]

See https://groups.google.com/g/seastar-dev/c/6QA0XCFQxrk.

[zhanglei1949]

We need a timeout mechanism for Interactive; however, we can't implement it in the current circumstance, with the query execution logic is synchronous.

[zhanglei1949]

But we could set timeout at compiler, client(sdk).