[ASYNC-145] mix throws assertion error when many channels are added to a mix. Created: 08/Sep/15  Updated: 14/Feb/17

Status: Open
Project: core.async
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Angus Fletcher Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: mix
Environment:

Found in core.async version 0.1.346.0-17112a-alpha


Attachments: Text File 0001-Change-channel-to-sliding-buffer-090815.patch     Text File 0001-Change-channel-to-sliding-buffer.patch    
Patch: Code

 Description   

When a large number of channels is added to a mix simultaneously, this error is thrown:

java.lang.AssertionError: Assert failed: No more than 1024 pending puts are allowed on a single channel. Consider using a windowed buffer.

We can reproduce the issue with the following in a REPL:

user> (require '[clojure.core.async :as a])
nil
user> (defn mixtest []
(let [out (a/chan 1024)
mix (a/mix out)]
(dotimes [i 2048]
(let [chan (a/chan)]
(a/admix mix chan)
(a/put! chan i)))))

(mixtest)
#'user/mixtestAssertionError Assert failed: No more than 1024 pending puts are allowed on a single channel. Consider using a windowed buffer.
(< (.size puts) impl/MAX-QUEUE-SIZE) clojure.core.async.impl.channels.ManyToManyChannel (channels.clj:150)
user>

This is a consequence of the use of an unbuffered channel in the mix implementation. Since the channel's function is just to update the mix's internal data structure, using a windowed buffered channel appears to clear up this issue. Patch 0001-Change-channel-to-sliding-buffer.patch contains the proposed solution.



 Comments   
Comment by Angus Fletcher [ 08/Sep/15 2:32 PM ]

Update patch to include cljs fix as well.

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