Re: On Mesos versioning and deprecation policy
+1 For the sum up. Now it is clear for me. On Sat, Oct 29, 2016 at 6:45 AM, Vinod Kone wrote: > We had an extended discussion around this in the last community sync. > Thanks for those who participated! > > To sum up the discussion: > > --> As mesos devs, we should strive to not make incompatible changes in > APIs, flags, environment variables. > > --> In the rare case where an incompatible change is preferred (e.g., code > complexity), we should give a clear 6 months heads up the users that a > breaking change is going to take place. > > --> Breaking changes do not necessitate a major version bump. This is > because we want to allow live upgrades between major versions (e.g., 1.10 > to 2.0). > > --> Compatibility guarantees do not apply to experimental features (incl. > APIs). > > --> We need to have clear documentation about procedure that devs could > follow when deprecating/removing stable features and adding experimental > features. > > --> We need to improve upgrades.md to make it easy for operators to know > what features are deprecated/removed between versions X and Y. > > --> We should decouple internal protos used by Mesos from the unversioned > protos used by driver based frameworks. > > I will spend some time in the next few weeks to create/update the > documentation reflecting these points. > > Anything else I missed? > > Thanks, > > On Sat, Oct 15, 2016 at 11:47 AM, haosdent wrote: > > > Thanks @yan's great inputs! I couldn't agree more almost of them. > > > > > Also the API is not just what the machine reads but all the > documentation > > associated with it, right? It depends on what the documentation says; > what > > the user _should_ expect. > > > > I think different users may have different expectations. And the guy who > > developed the APIs may have different understand from some users as well. > > Our documentations should cover most of cases. > > > > But in case that we didn't or forgot to write it explicitly in the > > document, should we give up to update the API? Just like user Alice said > > this is a BUG while user Bob said this is a feature. I think we still > need > > to raise it case by case to ensure most users are not affected by the > > breaking API changes. > > > > On Sat, Oct 15, 2016 at 6:55 AM, Vinod Kone > wrote: > > > > > We will chat about this in the upcoming community sync (thursday 3 PM). > > > So, please make sure to attend if you are interested. > > > > > > On Fri, Oct 14, 2016 at 3:44 PM, Yan Xu wrote: > > > > > >> > > >> On Fri, Oct 14, 2016 at 3:37 PM, Yan Xu wrote: > > >> > > >>> Thanks Alex for starting this! > > >>> > > >>> In addition to comments below, I think it'll be helpful to keep the > > >>> existing versioning doc concise and user-friendly while having a > > dedicated > > >>> doc for the "implementation details" where precise requirements and > > >>> procedures go. Maybe some duplication/cross-referencing is needed but > > Mesos > > >>> developers will find the latter much more helpful while the > > users/framework > > >>> developer will find the former easy to read. > > >>> > > >>> e.g., a similar split: > > >>> https://github.com/kubernetes/kubernetes/blob/master/docs/api.md > > >>> https://github.com/kubernetes/kubernetes/blob/master/docs/de > > >>> vel/api_changes.md (which has a lot of details on how the kubernetes > > >>> community is thinking about similar issues, which we can learn from) > > >>> > > >>> Jiang Yan Xu > > >>> > > >>> On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov > > > >>> wrote: > > >>> > > Folks, > > > > There have been a bunch of online [1, 2] and offline discussions > about > > our > > deprecation and versioning policy. I found that people—including > > myself—read the versioning doc [3] differently; moreover some > aspects > > are > > not captured there. I would like to start a discussion around this > > topic by > > sharing my confusions and suggestions. This will hopefully help us > > stay > > on > > the same page and have similar expectations. The second goal is to > > eliminate ambiguities from the versioning doc (thanks Vinod for > > volunteering to update it). > > > > >>> > > >>> +1 Let me know if there are things I can help with. > > >>> > > >>> > > > > 1. API vs. semantic changes. > > Current versioning guide treat features (e.g. flags, metrics, > > endpoints) > > and API differently: incompatible changes for the former are allowed > > after > > 6 month deprecation cycle, while for the latter they require > bumping a > > major version. I suggest we consolidate these policies. > > > > >>> > > >>> I feel that the distinction is not API vs. semantic changes, > Backwards > > >>> compatible API guarantee should imply backwards compatible semantics > > (of > > >>> the API). > > >>> i.e., if a change in API doesn't cause the message to be dropped to > the > > >>> floor but leads to behavior chan
Re: On Mesos versioning and deprecation policy
We had an extended discussion around this in the last community sync. Thanks for those who participated! To sum up the discussion: --> As mesos devs, we should strive to not make incompatible changes in APIs, flags, environment variables. --> In the rare case where an incompatible change is preferred (e.g., code complexity), we should give a clear 6 months heads up the users that a breaking change is going to take place. --> Breaking changes do not necessitate a major version bump. This is because we want to allow live upgrades between major versions (e.g., 1.10 to 2.0). --> Compatibility guarantees do not apply to experimental features (incl. APIs). --> We need to have clear documentation about procedure that devs could follow when deprecating/removing stable features and adding experimental features. --> We need to improve upgrades.md to make it easy for operators to know what features are deprecated/removed between versions X and Y. --> We should decouple internal protos used by Mesos from the unversioned protos used by driver based frameworks. I will spend some time in the next few weeks to create/update the documentation reflecting these points. Anything else I missed? Thanks, On Sat, Oct 15, 2016 at 11:47 AM, haosdent wrote: > Thanks @yan's great inputs! I couldn't agree more almost of them. > > > Also the API is not just what the machine reads but all the documentation > associated with it, right? It depends on what the documentation says; what > the user _should_ expect. > > I think different users may have different expectations. And the guy who > developed the APIs may have different understand from some users as well. > Our documentations should cover most of cases. > > But in case that we didn't or forgot to write it explicitly in the > document, should we give up to update the API? Just like user Alice said > this is a BUG while user Bob said this is a feature. I think we still need > to raise it case by case to ensure most users are not affected by the > breaking API changes. > > On Sat, Oct 15, 2016 at 6:55 AM, Vinod Kone wrote: > > > We will chat about this in the upcoming community sync (thursday 3 PM). > > So, please make sure to attend if you are interested. > > > > On Fri, Oct 14, 2016 at 3:44 PM, Yan Xu wrote: > > > >> > >> On Fri, Oct 14, 2016 at 3:37 PM, Yan Xu wrote: > >> > >>> Thanks Alex for starting this! > >>> > >>> In addition to comments below, I think it'll be helpful to keep the > >>> existing versioning doc concise and user-friendly while having a > dedicated > >>> doc for the "implementation details" where precise requirements and > >>> procedures go. Maybe some duplication/cross-referencing is needed but > Mesos > >>> developers will find the latter much more helpful while the > users/framework > >>> developer will find the former easy to read. > >>> > >>> e.g., a similar split: > >>> https://github.com/kubernetes/kubernetes/blob/master/docs/api.md > >>> https://github.com/kubernetes/kubernetes/blob/master/docs/de > >>> vel/api_changes.md (which has a lot of details on how the kubernetes > >>> community is thinking about similar issues, which we can learn from) > >>> > >>> Jiang Yan Xu > >>> > >>> On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov > >>> wrote: > >>> > Folks, > > There have been a bunch of online [1, 2] and offline discussions about > our > deprecation and versioning policy. I found that people—including > myself—read the versioning doc [3] differently; moreover some aspects > are > not captured there. I would like to start a discussion around this > topic by > sharing my confusions and suggestions. This will hopefully help us > stay > on > the same page and have similar expectations. The second goal is to > eliminate ambiguities from the versioning doc (thanks Vinod for > volunteering to update it). > > >>> > >>> +1 Let me know if there are things I can help with. > >>> > >>> > > 1. API vs. semantic changes. > Current versioning guide treat features (e.g. flags, metrics, > endpoints) > and API differently: incompatible changes for the former are allowed > after > 6 month deprecation cycle, while for the latter they require bumping a > major version. I suggest we consolidate these policies. > > >>> > >>> I feel that the distinction is not API vs. semantic changes, Backwards > >>> compatible API guarantee should imply backwards compatible semantics > (of > >>> the API). > >>> i.e., if a change in API doesn't cause the message to be dropped to the > >>> floor but leads to behavior change that causes problems in the system, > it > >>> still breaks compatibility. > >>> > >>> IMO the distinction is more between: > >>> - Compatibility between components that are impossible/very unpleasant > >>> to upgrade in lockstep - high priority for compatibility guarantee. > >>> - Compatibility between components that are generally bundled (mod
Re: On Mesos versioning and deprecation policy
Thanks @yan's great inputs! I couldn't agree more almost of them. > Also the API is not just what the machine reads but all the documentation associated with it, right? It depends on what the documentation says; what the user _should_ expect. I think different users may have different expectations. And the guy who developed the APIs may have different understand from some users as well. Our documentations should cover most of cases. But in case that we didn't or forgot to write it explicitly in the document, should we give up to update the API? Just like user Alice said this is a BUG while user Bob said this is a feature. I think we still need to raise it case by case to ensure most users are not affected by the breaking API changes. On Sat, Oct 15, 2016 at 6:55 AM, Vinod Kone wrote: > We will chat about this in the upcoming community sync (thursday 3 PM). > So, please make sure to attend if you are interested. > > On Fri, Oct 14, 2016 at 3:44 PM, Yan Xu wrote: > >> >> On Fri, Oct 14, 2016 at 3:37 PM, Yan Xu wrote: >> >>> Thanks Alex for starting this! >>> >>> In addition to comments below, I think it'll be helpful to keep the >>> existing versioning doc concise and user-friendly while having a dedicated >>> doc for the "implementation details" where precise requirements and >>> procedures go. Maybe some duplication/cross-referencing is needed but Mesos >>> developers will find the latter much more helpful while the users/framework >>> developer will find the former easy to read. >>> >>> e.g., a similar split: >>> https://github.com/kubernetes/kubernetes/blob/master/docs/api.md >>> https://github.com/kubernetes/kubernetes/blob/master/docs/de >>> vel/api_changes.md (which has a lot of details on how the kubernetes >>> community is thinking about similar issues, which we can learn from) >>> >>> Jiang Yan Xu >>> >>> On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov >>> wrote: >>> Folks, There have been a bunch of online [1, 2] and offline discussions about our deprecation and versioning policy. I found that people—including myself—read the versioning doc [3] differently; moreover some aspects are not captured there. I would like to start a discussion around this topic by sharing my confusions and suggestions. This will hopefully help us stay on the same page and have similar expectations. The second goal is to eliminate ambiguities from the versioning doc (thanks Vinod for volunteering to update it). >>> >>> +1 Let me know if there are things I can help with. >>> >>> 1. API vs. semantic changes. Current versioning guide treat features (e.g. flags, metrics, endpoints) and API differently: incompatible changes for the former are allowed after 6 month deprecation cycle, while for the latter they require bumping a major version. I suggest we consolidate these policies. >>> >>> I feel that the distinction is not API vs. semantic changes, Backwards >>> compatible API guarantee should imply backwards compatible semantics (of >>> the API). >>> i.e., if a change in API doesn't cause the message to be dropped to the >>> floor but leads to behavior change that causes problems in the system, it >>> still breaks compatibility. >>> >>> IMO the distinction is more between: >>> - Compatibility between components that are impossible/very unpleasant >>> to upgrade in lockstep - high priority for compatibility guarantee. >>> - Compatibility between components that are generally bundled (modules) >>> or things that usually aren't built into automated tooling (e.g., the >>> /state endpoint) - more relaxed for now but we should explicitly exclude >>> them from the guarantee. >>> >>> We should also define and clearly explain what changes require bumping the major version. I have no strong opinion here and would love to hear what people think. The original motivation for maintaining backwards compatibility is to make sure vN schedulers can correctly work with vN API without being updated. But what about semantic changes that do not touch the API? For example, what if we decide to send less task health updates to schedulers based on some health policy? It influences the flow of task status updates, should such change be considered compatible? Taking it to an extreme, we may not even be able to fix some bugs because someone may already rely on this behaviour! >>> >>> API changes should warrant a major version bump. Also the API is not >>> just what the machine reads but all the documentation associated with it, >>> right? It depends on what the documentation says; what the user _should_ >>> expect. >>> >>> That said, I feel that these things are hard to be talked about in the >>> abstract. Even with a guideline, we still need to make case-by-case >>> decisions. (e.g., has the documentation precisely defined this precise >>> behavior?
Re: On Mesos versioning and deprecation policy
We will chat about this in the upcoming community sync (thursday 3 PM). So, please make sure to attend if you are interested. On Fri, Oct 14, 2016 at 3:44 PM, Yan Xu wrote: > > On Fri, Oct 14, 2016 at 3:37 PM, Yan Xu wrote: > >> Thanks Alex for starting this! >> >> In addition to comments below, I think it'll be helpful to keep the >> existing versioning doc concise and user-friendly while having a dedicated >> doc for the "implementation details" where precise requirements and >> procedures go. Maybe some duplication/cross-referencing is needed but Mesos >> developers will find the latter much more helpful while the users/framework >> developer will find the former easy to read. >> >> e.g., a similar split: >> https://github.com/kubernetes/kubernetes/blob/master/docs/api.md >> https://github.com/kubernetes/kubernetes/blob/master/docs/de >> vel/api_changes.md (which has a lot of details on how the kubernetes >> community is thinking about similar issues, which we can learn from) >> >> Jiang Yan Xu >> >> On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov >> wrote: >> >>> Folks, >>> >>> There have been a bunch of online [1, 2] and offline discussions about >>> our >>> deprecation and versioning policy. I found that people—including >>> myself—read the versioning doc [3] differently; moreover some aspects are >>> not captured there. I would like to start a discussion around this topic >>> by >>> sharing my confusions and suggestions. This will hopefully help us stay >>> on >>> the same page and have similar expectations. The second goal is to >>> eliminate ambiguities from the versioning doc (thanks Vinod for >>> volunteering to update it). >>> >> >> +1 Let me know if there are things I can help with. >> >> >>> >>> 1. API vs. semantic changes. >>> Current versioning guide treat features (e.g. flags, metrics, endpoints) >>> and API differently: incompatible changes for the former are allowed >>> after >>> 6 month deprecation cycle, while for the latter they require bumping a >>> major version. I suggest we consolidate these policies. >>> >> >> I feel that the distinction is not API vs. semantic changes, Backwards >> compatible API guarantee should imply backwards compatible semantics (of >> the API). >> i.e., if a change in API doesn't cause the message to be dropped to the >> floor but leads to behavior change that causes problems in the system, it >> still breaks compatibility. >> >> IMO the distinction is more between: >> - Compatibility between components that are impossible/very unpleasant to >> upgrade in lockstep - high priority for compatibility guarantee. >> - Compatibility between components that are generally bundled (modules) >> or things that usually aren't built into automated tooling (e.g., the >> /state endpoint) - more relaxed for now but we should explicitly exclude >> them from the guarantee. >> >> >>> >>> We should also define and clearly explain what changes require bumping >>> the >>> major version. I have no strong opinion here and would love to hear what >>> people think. The original motivation for maintaining backwards >>> compatibility is to make sure vN schedulers can correctly work with vN >>> API >>> without being updated. But what about semantic changes that do not touch >>> the API? For example, what if we decide to send less task health updates >>> to >>> schedulers based on some health policy? It influences the flow of task >>> status updates, should such change be considered compatible? Taking it to >>> an extreme, we may not even be able to fix some bugs because someone may >>> already rely on this behaviour! >>> >> >> API changes should warrant a major version bump. Also the API is not just >> what the machine reads but all the documentation associated with it, right? >> It depends on what the documentation says; what the user _should_ expect. >> >> That said, I feel that these things are hard to be talked about in the >> abstract. Even with a guideline, we still need to make case-by-case >> decisions. (e.g., has the documentation precisely defined this precise >> behavior? If not, is it reasonable for the users to expect some behavior >> because it's common sense? How bad is it if some behavior just changes a >> tiny bit?) Therefore we need to make sure the process for API changes are >> more rigorously defined. >> >> Whether something is a bug depends on whether the API does what it says >> it'll do. The line may sometimes be blurry but in general I don't feel it's >> a problem. If someone is relying on the behavior that is a bug, we should >> still help them fix it but the bug shouldn't count as "our guarantee". >> >> >>> >>> Another tightly related thing we should explicitly call out is >>> upgradability and rollback capabilities inside a major release. >>> Committing >>> to this may significantly limit what we can change within a major >>> release; >>> on the other side it will give users more time and a better experience >>> about using and maintaining Mesos clust
Re: On Mesos versioning and deprecation policy
On Fri, Oct 14, 2016 at 3:37 PM, Yan Xu wrote: > Thanks Alex for starting this! > > In addition to comments below, I think it'll be helpful to keep the > existing versioning doc concise and user-friendly while having a dedicated > doc for the "implementation details" where precise requirements and > procedures go. Maybe some duplication/cross-referencing is needed but Mesos > developers will find the latter much more helpful while the users/framework > developer will find the former easy to read. > > e.g., a similar split: > https://github.com/kubernetes/kubernetes/blob/master/docs/api.md > https://github.com/kubernetes/kubernetes/blob/master/docs/de > vel/api_changes.md (which has a lot of details on how the kubernetes > community is thinking about similar issues, which we can learn from) > > Jiang Yan Xu > > On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov > wrote: > >> Folks, >> >> There have been a bunch of online [1, 2] and offline discussions about our >> deprecation and versioning policy. I found that people—including >> myself—read the versioning doc [3] differently; moreover some aspects are >> not captured there. I would like to start a discussion around this topic >> by >> sharing my confusions and suggestions. This will hopefully help us stay on >> the same page and have similar expectations. The second goal is to >> eliminate ambiguities from the versioning doc (thanks Vinod for >> volunteering to update it). >> > > +1 Let me know if there are things I can help with. > > >> >> 1. API vs. semantic changes. >> Current versioning guide treat features (e.g. flags, metrics, endpoints) >> and API differently: incompatible changes for the former are allowed after >> 6 month deprecation cycle, while for the latter they require bumping a >> major version. I suggest we consolidate these policies. >> > > I feel that the distinction is not API vs. semantic changes, Backwards > compatible API guarantee should imply backwards compatible semantics (of > the API). > i.e., if a change in API doesn't cause the message to be dropped to the > floor but leads to behavior change that causes problems in the system, it > still breaks compatibility. > > IMO the distinction is more between: > - Compatibility between components that are impossible/very unpleasant to > upgrade in lockstep - high priority for compatibility guarantee. > - Compatibility between components that are generally bundled (modules) or > things that usually aren't built into automated tooling (e.g., the /state > endpoint) - more relaxed for now but we should explicitly exclude them from > the guarantee. > > >> >> We should also define and clearly explain what changes require bumping the >> major version. I have no strong opinion here and would love to hear what >> people think. The original motivation for maintaining backwards >> compatibility is to make sure vN schedulers can correctly work with vN API >> without being updated. But what about semantic changes that do not touch >> the API? For example, what if we decide to send less task health updates >> to >> schedulers based on some health policy? It influences the flow of task >> status updates, should such change be considered compatible? Taking it to >> an extreme, we may not even be able to fix some bugs because someone may >> already rely on this behaviour! >> > > API changes should warrant a major version bump. Also the API is not just > what the machine reads but all the documentation associated with it, right? > It depends on what the documentation says; what the user _should_ expect. > > That said, I feel that these things are hard to be talked about in the > abstract. Even with a guideline, we still need to make case-by-case > decisions. (e.g., has the documentation precisely defined this precise > behavior? If not, is it reasonable for the users to expect some behavior > because it's common sense? How bad is it if some behavior just changes a > tiny bit?) Therefore we need to make sure the process for API changes are > more rigorously defined. > > Whether something is a bug depends on whether the API does what it says > it'll do. The line may sometimes be blurry but in general I don't feel it's > a problem. If someone is relying on the behavior that is a bug, we should > still help them fix it but the bug shouldn't count as "our guarantee". > > >> >> Another tightly related thing we should explicitly call out is >> upgradability and rollback capabilities inside a major release. Committing >> to this may significantly limit what we can change within a major release; >> on the other side it will give users more time and a better experience >> about using and maintaining Mesos clusters. >> > > According to the versioning doc upgradability depends on whether you > depend on deprecated/removed features. > > That paragraph should be explained more precisely: > - "deprecated" means your system won't break but warnings are shown (Maybe > we should use some standard deprecation warning key
Re: On Mesos versioning and deprecation policy
Thanks Alex for starting this! In addition to comments below, I think it'll be helpful to keep the existing versioning doc concise and user-friendly while having a dedicated doc for the "implementation details" where precise requirements and procedures go. Maybe some duplication/cross-referencing is needed but Mesos developers will find the latter much more helpful while the users/framework developer will find the former easy to read. e.g., a similar split: https://github.com/kubernetes/kubernetes/blob/master/docs/api.md https://github.com/kubernetes/kubernetes/blob/master/docs/devel/api_changes.md (which has a lot of details on how the kubernetes community is thinking about similar issues, which we can learn from) Jiang Yan Xu On Wed, Oct 12, 2016 at 9:34 AM, Alex Rukletsov wrote: > Folks, > > There have been a bunch of online [1, 2] and offline discussions about our > deprecation and versioning policy. I found that people—including > myself—read the versioning doc [3] differently; moreover some aspects are > not captured there. I would like to start a discussion around this topic by > sharing my confusions and suggestions. This will hopefully help us stay on > the same page and have similar expectations. The second goal is to > eliminate ambiguities from the versioning doc (thanks Vinod for > volunteering to update it). > +1 Let me know if there are things I can help with. > > 1. API vs. semantic changes. > Current versioning guide treat features (e.g. flags, metrics, endpoints) > and API differently: incompatible changes for the former are allowed after > 6 month deprecation cycle, while for the latter they require bumping a > major version. I suggest we consolidate these policies. > I feel that the distinction is not API vs. semantic changes, Backwards compatible API guarantee should imply backwards compatible semantics (of the API). i.e., if a change in API doesn't cause the message to be dropped to the floor but leads to behavior change that causes problems in the system, it still breaks compatibility. IMO the distinction is more between: - Compatibility between components that are impossible/very unpleasant to upgrade in lockstep - high priority for compatibility guarantee. - Compatibility between components that are generally bundled (modules) or things that usually aren't built into automated tooling (e.g., the /state endpoint) - more relaxed for now but we should explicitly exclude them from the guarantee. > > We should also define and clearly explain what changes require bumping the > major version. I have no strong opinion here and would love to hear what > people think. The original motivation for maintaining backwards > compatibility is to make sure vN schedulers can correctly work with vN API > without being updated. But what about semantic changes that do not touch > the API? For example, what if we decide to send less task health updates to > schedulers based on some health policy? It influences the flow of task > status updates, should such change be considered compatible? Taking it to > an extreme, we may not even be able to fix some bugs because someone may > already rely on this behaviour! > API changes should warrant a major version bump. Also the API is not just what the machine reads but all the documentation associated with it, right? It depends on what the documentation says; what the user _should_ expect. That said, I feel that these things are hard to be talked about in the abstract. Even with a guideline, we still need to make case-by-case decisions. (e.g., has the documentation precisely defined this precise behavior? If not, is it reasonable for the users to expect some behavior because it's common sense? How bad is it if some behavior just changes a tiny bit?) Therefore we need to make sure the process for API changes are more rigorously defined. Whether something is a bug depends on whether the API does what it says it'll do. The line may sometimes be blurry but in general I don't feel it's a problem. If someone is relying on the behavior that is a bug, we should still help them fix it but the bug shouldn't count as "our guarantee". > > Another tightly related thing we should explicitly call out is > upgradability and rollback capabilities inside a major release. Committing > to this may significantly limit what we can change within a major release; > on the other side it will give users more time and a better experience > about using and maintaining Mesos clusters. > According to the versioning doc upgradability depends on whether you depend on deprecated/removed features. That paragraph should be explained more precisely: - "deprecated" means your system won't break but warnings are shown (Maybe we should use some standard deprecation warning keywords so the operator can monitor the log for such warnings! - "removed": means it may break. If you deprecate a flag/env that interface with operator tooling in the next minor release, the operator basicall
Re: On Mesos versioning and deprecation policy
>How about splitting the unnamed version into explicit v0, v2, and internal? Currently our internal protobuf and v0 protobuf use the same unnamed version protobuf and under the same namespace (`package mesos`). If we are going to split v0 and internal, that requires copy all protobuf files under `package mesos` into `package mesos.internal` and need to change the whole code base to use the protobuf in `package mesos.internal`. But it is beneficial to do this, so that we could avoid [the hacks][1] that convert from the unversioned protobuf(v0) to the unversioned protobuf(internal). [1] https://github.com/apache/mesos/blob/fa976c22ac66ff5c905157a5a36bda1d21525b32/src/master/master.cpp#L4077-L4108 On Thu, Oct 13, 2016 at 12:34 AM, Alex Rukletsov wrote: > Folks, > > There have been a bunch of online [1, 2] and offline discussions about our > deprecation and versioning policy. I found that people—including > myself—read the versioning doc [3] differently; moreover some aspects are > not captured there. I would like to start a discussion around this topic by > sharing my confusions and suggestions. This will hopefully help us stay on > the same page and have similar expectations. The second goal is to > eliminate ambiguities from the versioning doc (thanks Vinod for > volunteering to update it). > > 1. API vs. semantic changes. > Current versioning guide treat features (e.g. flags, metrics, endpoints) > and API differently: incompatible changes for the former are allowed after > 6 month deprecation cycle, while for the latter they require bumping a > major version. I suggest we consolidate these policies. > > We should also define and clearly explain what changes require bumping the > major version. I have no strong opinion here and would love to hear what > people think. The original motivation for maintaining backwards > compatibility is to make sure vN schedulers can correctly work with vN API > without being updated. But what about semantic changes that do not touch > the API? For example, what if we decide to send less task health updates to > schedulers based on some health policy? It influences the flow of task > status updates, should such change be considered compatible? Taking it to > an extreme, we may not even be able to fix some bugs because someone may > already rely on this behaviour! > > Another tightly related thing we should explicitly call out is > upgradability and rollback capabilities inside a major release. Committing > to this may significantly limit what we can change within a major release; > on the other side it will give users more time and a better experience > about using and maintaining Mesos clusters. > > 2. Versioned vs. unversioned protobufs. > Currently we have v1 and unnamed protobufs, which simultaneously mean v0, > v2, and internal. I am sometimes confused about what is the right way to > update or introduce a field or message there, do people feel the same? How > about splitting the unnamed version into explicit v0, v2, and internal? > > Food for thought. It would be great if we can only maintain "diffs" to the > internal protobufs in the code, instead of duplicating them altogether. > > 3. API and feature labelling. > I suggest to introduce explicit labels for API and features, to ensure > users have the right assumptions about the their lifetime while engineers > have the ability to change a wip feature in an non-compatible way. I > propose the following: > API: stable, non-stable, pure (not used by Mesos components) > Feature: experimental, normal. > > Looking forward to your thoughts and suggestions. > AlexR > > [1] https://www.mail-archive.com/user@mesos.apache.org/msg08025.html > [2] https://www.mail-archive.com/dev@mesos.apache.org/msg36621.html > [3] > https://github.com/apache/mesos/blob/b2beef37f6f85a8c75e968136caa7a > 1f292ba20e/docs/versioning.md > -- Best Regards, Haosdent Huang
