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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11010) Update to Protobuf 3 in trunk
Date Fri, 14 Oct 2016 20:24:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11010?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15576383#comment-15576383

Chris Douglas commented on HDFS-11010:

bq. Let me ask the question in a different way, what about PB 3 is concerning to you ?
Some of its incompatibilities with 2.x, such as [dropping unknown fields|https://developers.google.com/protocol-buffers/docs/proto3#updating]
from records. Any component that proxies records must have an updated version of the schema,
or it will silently drop data and convert unknown values to defaults. Unknown enum value handling
has changed. There's no mention of the [convenient|https://developers.google.com/protocol-buffers/docs/proto#updating]
"Embedded messages are compatible with bytes if the bytes contain an encoded version of the
message" semantics in proto3.

If unknown fields are dropped, then applications proxying tokens and other data between servers
will effectively corrupt those messages, unless we make everything opaque {{bytes}}, which-
absent the convenient, prenominate semantics managing the conversion- obviate the compatibility
machinery that is the whole point of PB. Google is removing the features that justified choosing
PB over its alternatives. Since we can't require that our applications compile (or link) against
our updated schema, this creates a problem that PB was supposed to solve.

> Update to Protobuf 3 in trunk
> -----------------------------
>                 Key: HDFS-11010
>                 URL: https://issues.apache.org/jira/browse/HDFS-11010
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ipc
>    Affects Versions: 3.0.0-alpha2
>            Reporter: Anu Engineer
> This JIRA is to propose that we should move to protobuf 3 from protobuf 2.5. This allows
us to stay with the newer versions of the protobuf.

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