Re: [netmod] yang-instance-file include-defaults leaf
Andy Bierman <andy@yumaworks.com> Tue, 14 September 2021 17:08 UTC
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From: Andy Bierman <andy@yumaworks.com>
Date: Tue, 14 Sep 2021 10:08:36 -0700
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To: Balázs Lengyel <balazs.lengyel@ericsson.com>
Cc: "Rob Wilton (rwilton)" <rwilton@cisco.com>, NetMod WG <netmod@ietf.org>
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Subject: Re: [netmod] yang-instance-file include-defaults leaf
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Hi, I do not have time for a conference on this leaf. You think this cut-and-paste is good engineering and not confusing to users. I disagree. IMO it is less confusing to use the correct typedef and declare in your leaf description-stmt that the inclusion of defaults is not considered a retrieval, so 6243, sec 3 does not apply. Andy On Tue, Sep 14, 2021 at 8:24 AM Balázs Lengyel <balazs.lengyel@ericsson.com> wrote: > Hello, > > My view is that reusing the data ncwd:with-defaults-mode datatype, might > be acceptable, but it is wrong, because: > > 1. As opposed to what Andy has wrote the data type does reference "RFC > 6243 <https://datatracker.ietf.org/doc/html/rfc6243>; Section 3 > <https://datatracker.ietf.org/doc/html/rfc6243#section-3>." (See line > 58 in the YANG module). Section 3 contains a lot of concepts that are > inappropriate for the instance-data draft (server, data retrieval, > capabilities) > 2. The typedef’s description is "Possible modes to *report* default > data." From the 8 listed use-cases only two UC4 and UC5 is about reporting. > In UC1,UC2,UC3, UC7,UC8 the instance-data-set is usually prepared by human > SW developers which is not reporting. In UC6 we do not know whether this is > about reporting, replying, or just sending the data. > > In the instance-data draft we always avoided assumptions about who creates > the instance-data and why. There are so many potential use-cases, that they > may have very different processes creating and using the data. The data is > just present or absent. The wording in With-default RFC is too specific: > “data is reported ...”. > > 1. report-all-tagged description contains “XML attribute” which is > incorrect if we use JSON encoding. You can have an attribute in JSON, but > here specifically an XML attribute is mentioned. > 2. Rob, you stated that it is preferred to use the 2119 terms SHALL, > SHALL NOT in the enum descriptions (and I also think it is the good > solution). So, I reworded the text, that if the data node is covered by the > instance-data-set then the enum’s value MUST be adhered to. The > ncwd:with-defaults-mode datatype uses wording like “is reported”, “not > reported”. > > > > That said, if this is the cost of getting this document to the IESG, I can > accept the data-type. Please decide, so we can move forward. > I am willing to have a conference, would you arrange it? > > Regards Balazs > > > > *From:* Rob Wilton (rwilton) <rwilton@cisco.com> > *Sent:* 2021. szeptember 13., hétfő 12:05 > *To:* Andy Bierman <andy@yumaworks.com>; Balázs Lengyel < > balazs.lengyel@ericsson.com> > *Cc:* NetMod WG <netmod@ietf.org> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hi Andy, Balazs, > > > > I’m wondering whether it might be helpful to arrange a meeting to get to > consensus on this issue (which I believe is important)? > > > > The concern that I raised in my original AD review was that the data set > is allowed to be partial with the RECOMMENDATION that default values are > removed from the data set. Hence, I think that those two choices combine > to make it impossible for a consumer of an instance data file to know > whether a data node has been excluded because it contained the default > value vs it has been excluded because it not part of the data set. > > > > However, I think that Andy is potentially coming from the perspective that > if these instance data files represent configuration then understanding how > RFC 6243 with-defaults handling applies is important. To that end, I > quite like Andy’s suggestion of directly reusing the > ncwd:with-defaults-mode type, because it guarantees that the definitions > are entirely consistent, and I believe that it sufficient to address my > concern. > > leaf includes-defaults { > > type ncwd:with-defaults-mode; > > } > > Balazs, is there some way, perhaps with a tweaked description, or assigned > default value for the leaf includes-defaults leaf, that this could be made > to work for you? > > > > Thanks, > > Rob > > > > > > > > *From:* Andy Bierman <andy@yumaworks.com> > *Sent:* 10 September 2021 18:03 > *To:* Balázs Lengyel <balazs.lengyel@ericsson.com> > *Cc:* Rob Wilton (rwilton) <rwilton@cisco.com>; NetMod WG <netmod@ietf.org > > > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > > > > > On Fri, Sep 10, 2021 at 5:15 AM Balázs Lengyel < > balazs.lengyel@ericsson.com> wrote: > > See below as BALAZS4 > > > > *From:* Andy Bierman <andy@yumaworks.com> > *Sent:* 2021. szeptember 10., péntek 4:57 > *To:* Balázs Lengyel <balazs.lengyel@ericsson.com> > *Cc:* Rob Wilton (rwilton) <rwilton@cisco.com>; NetMod WG <netmod@ietf.org > > > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > > > > > On Thu, Sep 9, 2021 at 6:19 AM Balázs Lengyel <balazs.lengyel@ericsson.com> > wrote: > > Hello Andy, > > See below as BALAZS3. > > > > *From:* Andy Bierman <andy@yumaworks.com> > *Sent:* 2021. augusztus 25., szerda 18:29 > *To:* Balázs Lengyel <balazs.lengyel@ericsson.com> > *Cc:* Rob Wilton (rwilton) <rwilton@cisco.com>; NetMod WG <netmod@ietf.org > > > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > Hi, > > > > Here is the latest text. It is inconsistent with RFC 6243, section 3. > > IMO the subsections should be cited instead of the copy-and-change > approach. > > BALAZS3: The 6243 sections contain parts about “data retrieval” > “capabilities” or “conceptual data nodes set by the server” > > These parts are not relevant for many of the instance data use cases, so I > would like to stick with including text here. > > > > > > > > I guess I do not understand why the "with-defaults" leaf or at leaf > "with-defaults-mode" typedef > > cannot be used. IMO this is bad practice. Applications that already know > how to deal > > with defaults according to RFC 6243 should be supported. > > > > > > leaf includes-defaults { > > type ncwd:with-defaults-mode; > > } > > > > I do not see any text in this typedef that is server-specific. > > Andy > > BALAZS4: While I generally agree that duplication is a bad practice, I > avoided using ncwd:with-defaults-mode because: > > · It references RFC 6243 <https://datatracker.ietf.org/doc/html/rfc6243>; Section 3 <https://datatracker.ietf.org/doc/html/rfc6243#section-3> which is full of inappropriate references (server, data retrieval, capabilities) > > · The typedef’s description is "Possible modes to report default data." However, in a number of use cases (e.g., UC2 Preloading default configuration data, UC7, U8) the data is not reported. > > · report-all-tagged description contains “XML attribute” which is incorrect if we use JSON encoding > > · I prefer to use the 2119 term SHALL, SHALL NOT in the enum descriptions. > > Is this acceptable? > > > > > > > > The data type I suggested does not have any references to section 3. > > It does not have any MUST,SHOULD,MAY text at all. > > The JSON encoding in RFC 7951 supports attributes. > > > > IMO this leaf will cause a lot of confusion for users. > > includes-defaults looks like with-defaults but it isn't. > > It uses the exact same enums as with-defaults, but they mean different > things. > > > > > > Andy > > > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHOULD be included independent of > > any default values."; > > > > AB: should follow 6243, 3.1 > > } > > enum trim { > > value 2; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD > > NOT be included."; > > > > AB: should follow 6243, section 3.2 > > } > > enum explicit { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD NOT be > > included. However, if the actual value was set by > > a NETCONF client or other management application > > by the way of an explicit management operation the > > data node SHOULD be included."; > > > > AB: should follow 6243, section 3.3 > > } > > } > > description > > "As instance-data-sets MAY contain incomplete data sets, > > thus any data node MAY be absent. > > > > Providing the instance-data-set intends to contain a > > full data set, this leaf specifies whether the data set > > includes data nodes that have a default defined and > > where the actual value is the same as the default value. > > > > Data nodes that have no default values should always > > be included. > > Data nodes that have a default value, but the actual > > value is not equal to the schema defined default > > should always be included."; > > > > > > AB: The last paragraph should be removed or changed. Why are these nodes special? > > Nodes that are actually present and do not contain the YANG default > > are not relevant to this object. > > BALAZS3: OK > > > > reference > > "RFC 6243 <https://datatracker.ietf.org/doc/html/rfc6243>: With-defaults Capability for NETCONF"; > > } > > > > The best way to indicate a representation of a YANG default in the data > set is to include > > the "default" attribute in each default node. > https://datatracker.ietf.org/doc/html/rfc6243#section-6 > > This actually works for explicit mode and leaf-lists (unlike the current > solution). > > BALAZS3: OK. Added report-all-tagged enum to includes-defaults leaf. > > Here is the current proposed text: > > ------------------------------------------------------------ > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHALL be included independent of > > any default values, if the data node > > is covered by the instance-data-set."; > > } > > enum report-all-tagged { > > value 2; > > description > > "All data nodes SHALL be included independent of > > any default values if the data node > > is covered by the instance-data-set. > > Any nodes considered to be default data SHALL > > contain a 'default' attribute set to 'true'"; > > } > > enum trim { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is equal to the schema default > > value SHALL NOT be included."; > > } > > enum explicit { > > value 4; > > description > > "Data nodes where the actual value is equal to the > > schema default value SHALL NOT be included. > > However, if the actual value was set by a NETCONF > > client or other management application by the way > > of an explicit management operation, the data node > > SHALL be included, if the data node is covered by > > the instance-data-set."; > > } > > } > > description > > "An instance-data-set may contain or exclude default > > data. This leaf indicates whether default data is > > included. > > > > As instance-data-sets MAY contain incomplete data > > sets: MAY NOT cover all data nodes. A leaf or > > leaf-list MAY be absent because the instance-data-set > > does not intend to include the data node independent > > of default handling."; > > reference > > "RFC 6243: With-defaults Capability for NETCONF > > RFC 8040 :RESTCONF Protocol"; > > } > > ------------------------------------------------------------ > > > > > > On Tue, Aug 24, 2021 at 1:41 AM Balázs Lengyel < > balazs.lengyel@ericsson.com> wrote: > > Hello Andy, > > In the -17 I removed the default value for includes-defaults as you > proposed. > > > > I am not sure I understand the rest of the comments as > instance-file-format does not use the concept of “basic-mode”. It has a > single leaf to indicate what is the situation with defaults in the specific > instance-data-set. > > As this is not a live server request/reply situation we do not want to > specify a basic and additional modes, we just want to specify the handling > used for this specific instance data set. > > > > Regards Balazs > > > > *From:* Andy Bierman <andy@yumaworks.com> > *Sent:* 2021. augusztus 23., hétfő 18:58 > *To:* Balázs Lengyel <balazs.lengyel@ericsson.com> > *Cc:* Rob Wilton (rwilton) <rwilton@cisco.com>; NetMod WG <netmod@ietf.org > > > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > > > > > On Mon, Aug 23, 2021 at 5:17 AM Balázs Lengyel < > balazs.lengyel@ericsson.com> wrote: > > Hello Rob, > > I think this won’t fly. > > In sections 1.2 and 2 we state: > > *“Instance data files MAY contain partial data sets.”* > > Which is important for many use-cases. This means you cannot say that a default value will or must be included, as they might be omitted because they are not part of the partial data set. > > In a way it is difficult to separate between leaves that are missing because > > - They are not part of the partial data-set > > - They are omitted because they have the default value and one of the trim or explicit options is used > > If this becomes important the report-all options shall be used. > > > > > > > > I thought we already agreed there cannot be a default or there is no way to > > represent "no defaults added". > > > > Note that "report-all" is not useful if basic-mode=explicit, since a leaf > reporting the YANG default > > could be set by the client. Only report-all-tagged will clearly identify > defaults in this case. > > > > Also note that if basic-mode=report-all then there will be no defaults > ever reported. > > This mode means the server does not consider any node to be a default and > always returns > > every node (if with-defaults used or not). > > > > This is the reason I used the SHOULD word. > > Regards Balazs > > > > Andy > > > > > > *From:* Rob Wilton (rwilton) <rwilton@cisco.com> > *Sent:* 2021. augusztus 23., hétfő 12:27 > *To:* Balázs Lengyel <balazs.lengyel@ericsson.com>; Andy Bierman < > andy@yumaworks.com>; NetMod WG <netmod@ietf.org> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hi Balazs, Andy, Netmod, > > > > Sorry for the delayed response. I would still like to strength the > description of the defaults. E.g., RFC 6243 uses MUSTs rather than SHOULDs. > > > > Hence, I have generated some proposed alternative descriptions, that are > somewhat stricter, but also more generically focussed only on the default > values. > > > > With these definitions, I think that we could define the > “include-defaults” default value to be “explicit”, since if the leaf if not > included, then I think that this effectively what the meaning would be > anyway. > > > > > > In particular, I would propose changing the descriptions as follows: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHOULD be included independent of > > any default values."; > > } > > enum trim { > > value 2; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD > > NOT be included."; > > } > > enum explicit { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD NOT be > > included. However, if the actual value was set by > > a NETCONF client or other management application > > by the way of an explicit management operation the > > data node SHOULD be included."; > > } > > } > > > > Proposed: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "The instance data set includes all data nodes, > > including those that contain the schema default.”; > > } > > enum trim { > > value 2; > > description > > "The instance data set excludes all data nodes > > that contain the schema default."; > > } > > enum explicit { > > value 3; > > description > > "The instance data set may include some data nodes > > that match the schema default and may exclude some > > data nodes that match the schema default.”; > > } > > } > > description > > "This leaf provides an indication of how default data > > is presented within an instance data set, modelled on > > RFC 6243. > > > > Interpretation of the use of defaults depends on the > > context of what the instance data set represents. > > > > E.g., if the instance data set represents configuration, > > Then include-defaults aligns to the meaning of the > > default-handling basic modes in RFC 6243. If the > > instance data set represents operational data from the > > operational state datastore [RFC 8342], then > > include-defaults aligns to the definition of that > > datastore in RFC 8342.”; > > > > Would text along these lines work? > > > > Thanks, > > Rob > > > > > > *From:* Balázs Lengyel <balazs.lengyel@ericsson.com> > *Sent:* 28 July 2021 23:08 > *To:* Rob Wilton (rwilton) <rwilton@cisco.com>; Andy Bierman < > andy@yumaworks.com> > *Cc:* NetMod WG <netmod@ietf.org> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hello Rob, > > Removing the “default trim;” will address Andy’s comment. > > > > Your *in-use-values* is very specific to one of the use-cases: > reading/documenting operational values. It is not useful for the other > use-cases. I think the “documenting operational datastore” use-case could > be handled by indicating the *includes-defaults=report-all*. Case (i) > would contain the value case (ii) will not. > > Regards Balazs > > > > *From:* Rob Wilton (rwilton) <rwilton@cisco.com> > *Sent:* 2021. július 27., kedd 17:38 > *To:* Andy Bierman <andy@yumaworks.com>; Balázs Lengyel < > balazs.lengyel@ericsson.com> > *Cc:* NetMod WG <netmod@ietf.org> > *Subject:* RE: [netmod] yang-instance-file include-defaults leaf > > > > Hi Andy, Balazs, > > > > So, the reason that I want a flag to indicate whether default values are > in use is because of this definition of operational in RFC 8342: > > > > Requests to retrieve nodes from <operational> always return the value > > in use if the node exists, regardless of any default value specified > > in the YANG module. If no value is returned for a given node, then > > this implies that the node is not used by the device. > > > > It was written this way because otherwise a consumer of operational data > cannot differentiate between: > > (i) This value is not present because it matches the > default value specified in the YANG module, and > > (ii) This value is not present because the server has failed > to return it for some reason (e.g., perhaps the daemon that would have > provided this value is down or not available, or perhaps it is a bug, or > perhaps it is not implemented and is a missing deviation). > > > > So, I think that in some cases, the absence of a data node does not > necessarily mean that the default value is in effect, and I wanted the > instance-data document to be able to contain and correctly report this data. > > > > I think that this behaviour could be captured by a single leaf. Another > way of articulating this would be: > > > > leaf in-use-values { > > type boolean; > > default false; > > description > > “Only if set to true, the absence of a value in the > > instance data for a given data node implies that the > > node is not used rather than implicitly taking the > > default value specified by any corresponding > > ‘default’ statement specified in the YANG schema.”; > > } > > > > With this, I’m not sure whether we need the “includes-default” leaf > currently specified in the draft, but if we do, then I would think that > leaf should be entirely optional, i.e., without the default “trim”. > > > > Regards, > Rob > > > > > > *From:* Andy Bierman <andy@yumaworks.com> > *Sent:* 10 July 2021 17:41 > *To:* Rob Wilton (rwilton) <rwilton@cisco.com> > *Cc:* NetMod WG <netmod@ietf.org>; Balázs Lengyel < > balazs.lengyel@ericsson.com> > *Subject:* Re: [netmod] yang-instance-file include-defaults leaf > > > > > > > > On Fri, Jul 9, 2021 at 5:23 AM Rob Wilton (rwilton) <rwilton@cisco.com> > wrote: > > Andy, > > > > Yes, when I suggested this, I was thinking that a boolean flag might be > sufficient. My point being that automatically filtering out default values > isn’t always the right thing to do. > > > > > > > > The solution is simple. > > Get rid of the inappropriate "default trim" statement. > > > > If the leaf is present then it identifies the basic-mode that was used to > include defaults. > > If not then the information is either not known, not applicable, or > defaults were not added. > > > > The "default" statement is a bug because there is no default basic-mode. > > All of the basic-modes are in use in deployments and no camp has ever > > been able to convince the others that theirs is right. > > > > > > Andy > > > > E.g., something along these lines: > > > > leaf exclude-defaults { > > type boolean; > > default true; > > description > > “Can be used to reduce the size of the content data file. > > > > When unset or set to true, data nodes that have a default defined and > > where the actual value is the default value are excluded from the > content > > data. > > > > When set to false, data nodes with default value are not filtered, > and > > may appear in the content data.” > > } > > > > Would this satisfy your concern? > > > > Regards, > Rob > > > > > > *From:* netmod <netmod-bounces@ietf.org> *On Behalf Of *Andy Bierman > *Sent:* 08 July 2021 18:16 > *To:* NetMod WG <netmod@ietf.org> > *Subject:* [netmod] yang-instance-file include-defaults leaf > > > > Hi, > > > > The module has this object: > > > > leaf includes-defaults { > > type enumeration { > > enum report-all { > > value 1; > > description > > "All data nodes SHOULD be included independent of > > any default values."; > > } > > enum trim { > > value 2; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD > > NOT be included."; > > } > > enum explicit { > > value 3; > > description > > "Data nodes that have a default defined and where > > the actual value is the default value SHOULD NOT be > > included. However, if the actual value was set by > > a NETCONF client or other management application > > by the way of an explicit management operation the > > data node SHOULD be included."; > > } > > } > > default trim; > > > > The draft is extremely server-centric, like most IETF standards, but this > > leaf is too server-centric to ignore. > > > > Consider the possibility that the source of the file is NOT a NETCONF > server. > > This data may not be known so the default of "trim" may not be correct. > > > > IMO this leaf is noise because any tool that knows the schema will also > > know the YANG defaults. The solution is incomplete anyway because > > the presence of a leaf that has a YANG default is not enough. > > The "report-all-tagged" mode must be used to identify defaults. > > IMO this leaf should be removed, but at least add an enum called "unknown". > > > > > > Andy > > > > > >
- [netmod] yang-instance-file include-defaults leaf Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)
- Re: [netmod] yang-instance-file include-defaults … Balázs Lengyel
- Re: [netmod] yang-instance-file include-defaults … Andy Bierman
- Re: [netmod] yang-instance-file include-defaults … Benoit Claise
- Re: [netmod] yang-instance-file include-defaults … Rob Wilton (rwilton)