anchor.diff:  - Snapshot: Peer state that can be stored whenever a barrier alignment has occurred.
   - Channel: Network messaging channel. Channel may become blocked waiting for channel alignment.
   
  -===== ABS Execution Example
  +==== ABS Execution Example
   
   **Step 1:**
   Coordinator peer emits barrier with epoch 3 after the coordinator period passes.
  
positive.code: Aeron is the primary messaging transport layer. The transport layer is
  pluggable, though we don't support any other transports at this time.
  
  ==== Asynchronous Barrier Snapshotting
  
  Asynchronous Barrier Snapshotting (ABS) provides fault tolerance and exactly once processing by 
  inserting and tracking barriers that flow through the Directed Acyclic Graph (DAG). 
  
  ===== Motivation
  
  ABS improves performance by reducing acking overhead present in Onyx 0.9, and allows for exactly
  once aggregations which do not require message de-duplication. In ABS,
  consistent state snapshots can be made by tracking and aligning the barriers,
  and snapshotting state at appropriate points of barrier alignment.
  
  ===== Concepts
  
  Onyx 0.10.0 and above uses the Asynchronous Barrier Snapshotting method described in
  http://arxiv.org/abs/1506.08603[Lightweight Asynchronous Snapshots for Distributed Dataflows, Carbone et al.], and 
  
negative.code: :agg1 synchronizes on epoch 3, snapshots state to durable storage, and re-emits the barrier to :output.
  image::https://raw.githubusercontent.com/onyx-platform/onyx/0.10.x/doc/user-guide/abs/barrier-example-1/step4.png[Coordinator emits epoch 3]
  
  === Phases of Execution
  
  A batch of segments runs through the phases and execution states http://www.onyxplatform.org/docs/cheat-sheet/latest/#/task-states[described here in the cheat sheet].
  
  === The Log
  
  This design centers around a totally ordered sequence of commands using
  a log structure. The log acts as an immutable history and arbiter. It's
  