A short post to help others avoid some frustration in using a typical counter pattern when implementing code in RxJava.

Often in Couchbase one uses an atomic counter to keep track of the number of documents of a certain type.

It's easy enough to create or increment these counters:


bucket.async().counter(docType + "::Count", 1, 1);

When you come to read the counter though, if you try and do a standard:


bucket.async().get(docType + "::Count");

The best that the SDK can know (given that we have different types of JsonDocument classes) is that the return type will be of Observable<Document>.

If we KNOW that we are getting a counter we should use the different method signature that allows us to specify the return class. For a counter, this is:


bucket.async()
    .get(docType + "::Count", JsonLongDocument.class);

We can see here that the class of the returned document type is specified. This lets us then treat the counter object correctly and extract its value for further processing.