src/doc: add monitor janitorial list

Signed-off-by: Joao Eduardo Luis <[email protected]>

src/doc/mon-janitorial-queue.txt

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+Items to work on the monitor:
+
+Low-hanging fruit:
+
+- audit helpers that put() messages but do not get() them.
+  where possible, get rid of those put().  No one expects helpers to
+  put() messages and that may lead to double frees.
+
+Medium complexity:
+
+- get rid of QuorumServices.  It seemed like a neat idea, but we only have
+  one or two and they just add complexity and noise.
+
+Time consuming / complex:
+
+- Split the OSDMonitor.cc file into auxiliary files.  This will mean:
+
+  1. Logically split subsystems (osd crush, osd pool, ...)
+  2. Split the big badass functions, especially prepare/process_command()
+
+- Have Tracked Ops on the monitor, similarly to the OSDs.
+
+  1. Instead of passing messages back and forth, we will pass OpRequests
+  2. We may be able to get() the message when we create the OpRequest and
+     put() it upon OpRequest destruction.  This will help controlling the
+     lifespan of messages and reduce leaks.
+  3. There will be a fair amount of work changing stuff from Messages to
+     OpRequests, and we will need to make sure that we reach a format that
+     is easily supported throughout the monitor
+
+  Possible format, off the top of my head:
+
+    MonOpRequest:
+
+      int op = m->get_type();
+      Message *m = m.get();
+
+      template<typename T>
+      T* get_message() { return (T*)m.get(); }
+
+- Move to Ref'erenced messages instead of pointers all around.  This would
+  also help with the Tracked Ops thing, as we'd be able to simply ignore all
+  the get() and put() stuff behind it.