This is in reference to http://groups.google.com/group/clojure/browse_frm/thread/d6deac0c34d0ce28/5c1e11ec2bd52bde.
Hi everyone! I have hacked the Clojure core to add durability to refs. The syntax to create these is (dref <val> <key> <path>), where <key> and <path> are strings. Then you use them just like refs. Creating a dref creates a global identity, such that subsequent dref calls to the same key and path will get the same dref. On subsequent dref calls, the <val> will be ignored and the persisted value used. This includes in subsequent VM instances. Get it here: git://github.com/kwanalyssa/clojure.git 1. <path> refers to BDB JE databases which get created in the "data" directory of your project. 2. BDB JE is used. I'm ignorant of IP and licensing issues. Making BDB JE core to Clojure is probably an issue. 3. Currently only a subset of Clojure primitives types is supported. No BigDecimal or Ratio yet. See the comprehensive list (and serialization mappings) at the bottom of src/jvm/clojure/lang/ DRef.java. BDB JE TupleBindings are used. Submissions welcome, especially for the persistent data structures. 4. How do we approach the problem of storing objects with lexical environments? 5. Unit tests welcome! I didn't do TDD since the work is in Java and there's no Java-level tests in the project. Please add your own in test/clojure/test_clojure/drefs.clj. I'm new to concurrency, so tests along those lines would be awesome! 6. The ACID part is not really guaranteed!!! STM is currently one- phase-commit. I inserted two-phase-commits to the data stores in the middle of the one-phase-commit. There's the remote possibility that STM in-memory changes fail AFTER writing to disk. It's REALLY remote, but it is possible. STM would have to be made 2PC to make this airtight. That's way beyond my current grasp of both concurrency and Clojure implementation. 7. I was aiming for an API where <path> is optional. However, I didn't want to stray from the ref API, which has variable arity. Suggestions on how to reconcile the two are welcome! 8. To maintain global identity, I use a static cache, which requires non-hard references to avoid OOM issues. This is my first time doing this, so please check my code to make sure that I'm doing it right. I'm using SoftReferences, though WeakReferences may be better for real- life usage patterns. Let me know! Please dig in! Feedback appreciated! Alyssa Kwan -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
