Github user mattyb149 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2443#discussion_r164563821
--- Diff:
nifi-nar-bundles/nifi-mongodb-bundle/nifi-mongodb-processors/src/main/java/org/apache/nifi/processors/mongodb/GetMongo.java
---
@@ -302,15 +348,19 @@ public void process(OutputStream out) throws
IOException {
}
}
- session.commit();
+ if (input != null) {
+ session.transfer(input, REL_ORIGINAL);
--- End diff --
If you set Query Location to Query Parameter, but there are input flow
files, then the "original" relationship might be a bit confusing. If I schedule
GetMongo to run once a second, and upstream it is generating flow files once
every 2 seconds, then if using Query Parameter, the first GetMongo will not
output along the "original" relationship, but the second one will, causing
twice as many success FlowFiles as originals. This is in line with the
documented behavior, but it seems a bit awkward to me, what do you think?
An alternative is to not run if there is an incoming connection but no flow
file, basically the processor behaves in an event-driven fashion if there is an
incoming connection, or a timer-driven fashion if there is no incoming
(non-loop) connection. ExecuteSQL has this code at the beginning of onTrigger():
```
FlowFile fileToProcess = null;
if (context.hasIncomingConnection()) {
fileToProcess = session.get();
// If we have no FlowFile, and all incoming connections are self-loops
then we can continue on.
// However, if we have no FlowFile and we have connections coming from
other Processors, then
// we know that we should run only if we have a FlowFile.
if (fileToProcess == null && context.hasNonLoopConnection()) {
return;
}
}
```
You could do other runtime checking (unfortunately, connections are not
currently known to the `ValidationContext` or `ProcessorInitializationContext`
so must be done in onTrigger) such as making sure that if there is an incoming
connection, then the Query Location must be Body, if that's the kind of
behavior you want. Thoughts?
---
