binary compatibility between versions 2.x and 3.x

[Jeff Olson]

I've read through the release documents for Protocol Buffers v3.0.0 but I can't find any statements regrading binary compatibility with version 2.6.1 (or earlier). There are a couple of things I'd like to know:

1. If I dump a 3.0.0 version of the com.google.protobuf/protobuf-java.jar in a project the depends on java classes generated by protoc v2.6.1 (or v2.5.0) will everything still work? That is, is the java runtime backwards compatible?
2. Is the binary wire format the same for purely proto2 messages? If I serialize messages generated from proto2 sources using the 3.0.0 java runtime will clients using protobuf v2.6.1 be able to decode the messages correctly?

Thanks,

Jeff

[Feng Xiao]

On Thu, Aug 11, 2016 at 12:21 PM, Jeff Olson <jeff.d...@gmail.com> wrote:

I've read through the release documents for Protocol Buffers v3.0.0 but I can't find any statements regrading binary compatibility with version 2.6.1 (or earlier). There are a couple of things I'd like to know:

1. If I dump a 3.0.0 version of the com.google.protobuf/protobuf-java.jar in a project the depends on java classes generated by protoc v2.6.1 (or v2.5.0) will everything still work? That is, is the java runtime backwards compatible?

Unfortunately no. The 3.0.0 version protobuf-java.jar will not work with java classes generated by protoc v2.6.1 (or v2.5.0). For those who can not upgrade to 3.0 directly, we are considering releasing a 2.7 version which provides the following compatibility guarantees:

1. 2.7 protobuf-java.jar will be compatible with java classes generated by protoc 2.6.1 and protoc 2.5.0.

2. 3.0 protobuf-java.jar will be compatible with java classes generated by protoc 2.7

I.e., it allows you to upgrade to 3.0 in two steps: upgrade to 2.7, and after all your dependencies are upgraded to either 2.7 or 3.0, you can upgrade to 3.0 as well. It's not an ideal solution, but we hope it can help ease the migration pain for some users. I'm testing this 2.7 version in a github branch right now: https://github.com/google/protobuf/tree/2.7.0. If you are interested, feel free to test it and any feedback is welcome.

 

1. Is the binary wire format the same for purely proto2 messages? If I serialize messages generated from proto2 sources using the 3.0.0 java runtime will clients using protobuf v2.6.1 be able to decode the messages correctly?

Yes. The wire format stays the same as long as you are using the proto2 syntax version.

Thanks,

Jeff

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[Scott Sue]

Hi Feng,

Is this still the case considering that 3.2.0 is out that allows the version number to be used by protoc?

General
	* Added protoc version number to protoc plugin protocol. It can be used by
	protoc plugin to detect which version of protoc is used with the plugin and
	mitigate known problems in certain version of protoc.

Regards,

Scott

On Saturday, August 13, 2016 at 8:00:23 AM UTC+8, Feng Xiao wrote:

On Thu, Aug 11, 2016 at 12:21 PM, Jeff Olson <jeff.d...@gmail.com> wrote:

I've read through the release documents for Protocol Buffers v3.0.0 but I can't find any statements regrading binary compatibility with version 2.6.1 (or earlier). There are a couple of things I'd like to know:

1. If I dump a 3.0.0 version of the com.google.protobuf/protobuf-java.jar in a project the depends on java classes generated by protoc v2.6.1 (or v2.5.0) will everything still work? That is, is the java runtime backwards compatible?

Unfortunately no. The 3.0.0 version protobuf-java.jar will not work with java classes generated by protoc v2.6.1 (or v2.5.0). For those who can not upgrade to 3.0 directly, we are considering releasing a 2.7 version which provides the following compatibility guarantees:

1. 2.7 protobuf-java.jar will be compatible with java classes generated by protoc 2.6.1 and protoc 2.5.0.

2. 3.0 protobuf-java.jar will be compatible with java classes generated by protoc 2.7

I.e., it allows you to upgrade to 3.0 in two steps: upgrade to 2.7, and after all your dependencies are upgraded to either 2.7 or 3.0, you can upgrade to 3.0 as well. It's not an ideal solution, but we hope it can help ease the migration pain for some users. I'm testing this 2.7 version in a github branch right now: https://github.com/google/protobuf/tree/2.7.0. If you are interested, feel free to test it and any feedback is welcome.

 

1. Is the binary wire format the same for purely proto2 messages? If I serialize messages generated from proto2 sources using the 3.0.0 java runtime will clients using protobuf v2.6.1 be able to decode the messages correctly?

Yes. The wire format stays the same as long as you are using the proto2 syntax version.

Thanks,

Jeff

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[Feng Xiao]

On Thu, Apr 20, 2017 at 3:55 AM, Scott Sue <scot...@celer-tech.com> wrote:

Hi Feng,

Is this still the case considering that 3.2.0 is out that allows the version number to be used by protoc?

Not sure what you are asking, but 3.0.0 generated code should work with 3.2.0 runtime and 3.2.0 protoc will work with any old version plugins.

 

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[Scott Sue]

Hi Feng,

Apologies, what I was meaning was that with the introduction of protobuf 3.2.0 now, is 3.2.0 binary compatible with protobuf 2.5.0?  Or does you original message reply still hold true?

Regards,

Scott

SCOTT SUE

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[Feng Xiao]

On Thu, Apr 20, 2017 at 6:01 PM, Scott Sue <scot...@celer-tech.com> wrote:

Hi Feng,

Apologies, what I was meaning was that with the introduction of protobuf 3.2.0 now, is 3.2.0 binary compatible with protobuf 2.5.0?  Or does you original message reply still hold true?

No, 3.2.0 runtime is not binary compatible with 2.5.0 generated code. It is only binary compatible with older 3.x version generated code, such as 3.0, or 3.1.

[madhav goyal]

Hey Feng, Can you please tell what's the incompatibility between protoc_linux.2.5 and protobuf-java_3.x? I upgraded protobuf-java to 3.5 and tried to use it with protoc_linux.2.5 and I was able to compile, read/write with no issues. 

$protoc_linux --version

libprotoc 2.5.0

<dependency>

                <groupId>com.google.protobuf</groupId>

                <artifactId>protobuf-java</artifactId>

                <version>3.5.0</version>

</dependency>

[André Pinto]

I have the same question.

protobuf-java 3.7.1 seems to be compatible with Protobuf generated with protoc 2.5.0.

Is there any official statement about the compatibility of the protobuf-java library against different protobuf versions?

[Adam Cozzette]

Any mixing of 2.x and 3.x is not supported; you might get lucky and have it work, but I wouldn't recommend doing that because no one has attempted to make that work safely. As long as all your code is at 3.0 or higher, you can freely mix 3.x versions as long as you follow the rule that the runtime library version is at least as high as the protoc version of the newest generated code (i.e. no generated code newer than the runtime library).

To view this discussion on the web visit https://groups.google.com/d/msgid/protobuf/d7971524-638e-4a45-967a-fd9a1b233615%40googlegroups.com.

[Xuelin Fan]

So there is no formal compatibility document between 2.6 and 3.x ?  Then how to upgrade? also seem 2.7 is not a stable version