fix(matrix-algorithms): Consistent use of maximum visited nodes limit

[aoles]

Apply the limit on the number of visited nodes which is specified in the config file to all matrix algorithms.

Pull Request Checklist

• 1. I have rebased the latest version of the master branch into my feature branch and all conflicts
  have been resolved.
• 2. I have added information about the change/addition to functionality to the CHANGELOG.md file under the
  [Unreleased] heading.
• 3. I have documented my code using JDocs tags.
• 4. I have removed unnecessary commented out code, imports and System.out.println statements.
• 5. I have written JUnit tests for any new methods/classes and ensured that they pass.
• 6. I have created API tests for any new functionality exposed to the API.
• 7. If changes/additions are made to the ors-config.json file, I have added these to the ors config documentation
  along with a short description of what it is for, and documented this in the Pull Request (below).
• 8. I have built graphs with my code of the Heidelberg.osm.gz file and run the api-tests with all test passing
• 9. I have referenced the Issue Number in the Pull Request (if the changes were from an issue).
• 10. For new features or changes involving building of graphs, I have tested on a larger dataset
  (at least Germany), and the graphs build without problems (i.e. no out-of-memory errors).
• 11. For new features or changes involving the graphbuilding process (i.e. changing encoders, updating the
  importer etc.), I have generated longer distance routes for the affected profiles with different options
  (avoid features, max weight etc.) and compared these with the routes of the same parameters and start/end
  points generated from the current live ORS.
  If there are differences then the reasoning for these MUST be documented in the pull request.
• 12. I have written in the Pull Request information about the changes made including their intended usage
  and why the change was needed.
• 13. For changes touching the API documentation, I have tested that the API playground renders correctly.

Fixes #1246.

Information about the changes

• Key functionality added: Enforce maximum_visited_nodes limit specified in the config file.

• Reason for change: The limit was not respected at all by RPHAST matrix algorithm, and not handled properly by CoreMatrix either.

Examples and reasons for differences between live ORS routes, and those generated from this pull request

Some more complex long-distance matrix queries computed with either RPHAST or CoreMatrix which have been working before might start failing with the following error:

Unable to compute a distance/duration matrix: Search exceeds the limit of visited nodes.

This can be circumvented by increasing the maximum_visited_nodes limit if server resources allow it.

[MichaelsJP]

@aoles thanks for implementing this.

[MichaelsJP]

I'd say we should have an integration/unit test in place checking, checking for this exception to be thrown. What do you think?

[MichaelsJP]

@aoles Any progress so far or anything I could help with?

[aoles]

Thanks @MichaelsJP , I'm good 😎

Implementing reasonable unit tests turned out to be more effort than originally anticipated as the tests actually revealed some issues with the current implementation 🙈 Addressing these required some smart restructuring of existing methods and classes, that's why it took a bit longer. But I'm basically done now, just going through the introduced changes the last time before pushing to make sure nothing breaks 🤞

[aoles]

Unit test for exceeding the maximum number of visited nodes in RPHAST and Core matrix algorithms are now in. Regular Dijkstra matrix algorithm is currently not covered by any unit tests at all. I will look whether we could have at least an API test for it. I believe an additional integration test apart from the unit tests makes sense anyway.

[aoles]

@MichaelsJP With the API test in place, I think we are good to go now! 🚀