Qian Zhang created MESOS-7828:
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Summary: Current approach to parse protobuf enum from JSON does
not support upgrades
Key: MESOS-7828
URL: https://issues.apache.org/jira/browse/MESOS-7828
Project: Mesos
Issue Type: Bug
Reporter: Qian Zhang
Assignee: Qian Zhang
To use protobuf enum in a backwards compatible way, [the suggestion on the
protobuf mailing
list|https://groups.google.com/forum/#!msg/protobuf/NhUjBfDyGmY/pf294zMi2bIJ]
is to use optional enum fields and include an UNKNOWN value as the first entry
in the enum list (and/or explicitly specifying it as the default). This can
handle the case of parsing protobuf message from a serialized string, but it
can not handle the case of parsing protobuf message from JSON.
E.g., when I access master endpoint with an inexistent enum, I will get an
error:
{code}
$ curl -X POST -H "Content-Type: application/json" -d '{"type": "xxx"}'
127.0.0.1:5050/api/v1
Failed to convert JSON into Call protobuf: Failed to find enum for 'xxx'%
{code}
In the {{Call}} protobuf message, the enum {{Type}} already has a default value
{{UNKNOWN}} (see
[here|https://github.com/apache/mesos/blob/1.3.0/include/mesos/v1/master/master.proto#L45]
for details) and the field {{Call.type}} is optional, but the above curl
command will still fail. The root cause is, in the code
[here|https://github.com/apache/mesos/blob/1.3.0/3rdparty/stout/include/stout/protobuf.hpp#L449:L454]
when we try to get the enum value for the string "xxx", it will fail since
there is no any enum value corresponding to "xxx".
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