[couchdb] 01/01: Switch fabric attachment reciever to use messages instead of function closures

[va...@apache.org]

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vatamane pushed a commit to branch switch-fabric-to-use-message-based-attachment-receiver
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 8d6d2e98d22e8c142ebb1e416025e9a61779e9fd
Author: Nick Vatamaniuc <va...@apache.org>
AuthorDate: Tue Jul 17 14:53:26 2018 -0400

    Switch fabric attachment reciever to use messages instead of function closures
    
    Function closures are fragile and attachment uploads would break if
    fabric_doc_attachments is different on any of the nodes in a cluster, like it
    might happen during a roling cluster upgrade.
    
    Previously fe53e437ca5ec9d23aa1b55d7934daced157a9e3 introduced two versions of
    the module one which handles function closure, other which handled message but
    only in this commit messages are starting to be sent.
    
    To avoid breakages in attachemnt uploads during the period of a rolling cluster
    upgrade, make sure to upgrade to that commit first then upgrade to this change.
    
    Issue #1394
---
 src/fabric/src/fabric.erl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/fabric/src/fabric.erl b/src/fabric/src/fabric.erl
index 4a07271..f5c7937 100644
--- a/src/fabric/src/fabric.erl
+++ b/src/fabric/src/fabric.erl
@@ -271,13 +271,14 @@ purge_docs(_DbName, _IdsRevs) ->
     not_implemented.
 
 %% @doc spawns a process to upload attachment data and
-%%      returns a function that shards can use to communicate
-%%      with the spawned middleman process
+%%      returns a fabric attachment receiver context tuple
+%%      with the spawned middleman process, an empty binary,
+%%      or exits with an error tuple {Error, Arg}
 -spec att_receiver(#httpd{}, Length :: undefined | chunked | pos_integer() |
         {unknown_transfer_encoding, any()}) ->
-    function() | binary().
+    {fabric_attachment_receiver, pid(), chunked | pos_integer()} | binary().
 att_receiver(Req, Length) ->
-    fabric_doc_attachments:receiver(Req, Length).
+    fabric_doc_atts:receiver(Req, Length).
 
 %% @equiv all_docs(DbName, [], Callback, Acc0, QueryArgs)
 all_docs(DbName, Callback, Acc, QueryArgs) ->