[PATCH 09/17] docs: Convert 'support' page to rST
Peter Krempa
pkrempa at redhat.com
Mon Mar 7 15:59:29 UTC 2022
Signed-off-by: Peter Krempa <pkrempa at redhat.com>
---
docs/meson.build | 2 +-
docs/support.html.in | 258 -------------------------------------------
docs/support.rst | 207 ++++++++++++++++++++++++++++++++++
3 files changed, 208 insertions(+), 259 deletions(-)
delete mode 100644 docs/support.html.in
create mode 100644 docs/support.rst
diff --git a/docs/meson.build b/docs/meson.build
index d0c1217351..b3432cc6f6 100644
--- a/docs/meson.build
+++ b/docs/meson.build
@@ -63,7 +63,6 @@ docs_html_in_files = [
'remote',
'securityprocess',
'storage',
- 'support',
'testapi',
'testsuites',
'testtck',
@@ -112,6 +111,7 @@ docs_rst_files = [
'strategy',
'styleguide',
'submitting-patches',
+ 'support',
]
# list of web targets to build for docs/web rule
diff --git a/docs/support.html.in b/docs/support.html.in
deleted file mode 100644
index 38f2f906e0..0000000000
--- a/docs/support.html.in
+++ /dev/null
@@ -1,258 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml">
- <body>
- <h1>Support guarantees</h1>
-
- <ul id="toc"></ul>
-
- <p>
- This document will outline the support status / guarantees around the
- very interfaces that libvirt exposes to applications and/or system
- administrators. The intent is to help users understand what features they
- can rely upon in particular scenarios, and whether they are likely to
- suffer disruption during upgrades.
- </p>
-
- <h2><a id="publicAPI">Primary public API</a></h2>
-
- <p>
- The main public API provided by <code>libvirt.so</code> and described
- in <code>libvirt/libvirt.h</code> exposes the primary hypervisor
- agnostic management interface of libvirt. This API has the strongest
- guarantee of any part of libvirt with a promise to keep backwards
- compatibility forever. Specific details are as follows:
- </p>
-
- <dl>
- <dt>Functions</dt>
- <dd>Functions will never be removed from the public API, and will
- never have parameters added, removed or changed in their signature.
- IOW they will be ABI compatible forever. The semantics implied by
- a specific set of parameters passed to the function will remain
- unchanged. Where a parameter accepts a bitset of feature flags, or
- an enumerated value, further flags / enum values may be supported
- in the future. Where a parameter accepts one of a set of related
- constants, further constants may be supported in the future.
- </dd>
- <dt>Struct types</dt>
- <dd>Once defined in a release, struct definitions will never have any
- fields add, removed or changed in any way. Their size and layout is
- fixed forever. If a struct name starts with an underscore, it is
- considered acceptable to rename it. Applications should thus always
- use the corresponding typedef in preference to the struct name.
- </dd>
- <dt>Union types</dt>
- <dd>Once defined in a release, union definitions will never have any
- existing fields removed or changed. New union choices may be added,
- provided that they don't change the size of the existing union
- definition. If a struct name starts with an underscore, it is
- considered acceptable to rename it. Applications should thus always
- use the corresponding typedef in preference to the struct name.
- </dd>
- <dt>Type definitions</dt>
- <dd>Most custom data types used in the APIs have corresponding typedefs
- provided for their stable names. The typedefs should always be used
- in preference to the underlying data type name, as the latter are not
- guaranteed to be stable.
- </dd>
- <dt>Enumerations</dt>
- <dd>Once defined in a release, existing enumeration values will never
- be removed or renamed. New enumeration values may be introduced at
- any time. Every enumeration will have a '_LAST' value which indicates
- the current highest enumeration value, which may increase with new
- releases. If an enumeration name starts with an underscore, it is
- considered acceptable to rename it. Applications should thus always
- use the corresponding typedef in preference to the enum name.
- </dd>
- <dt>Constants</dt>
- <dd>Once defined in a release, existing constants will never be removed
- or have their value changed. Most constants are grouped into related
- sets, and within each set, new constants may be introduced. APIs which
- use the constants may thus accept or return new constant values over
- time.
- </dd>
- <dt>Symbol versions</dt>
- <dd>Where the platform library format permits, APIs defined in libvirt.so
- library will have version information associated. Each API will be
- tagged with the version in which it was introduced, and this won't
- be changed thereafter.
- </dd>
- </dl>
-
- <h2><a id="hvAPI">Hypervisor specific APIs</a></h2>
-
- <p>
- A number of hypervisor drivers provide additional libraries with hypervisor
- specific APIs, extending the core libvirt API. These add-on libraries follow
- the same general principles described above, however, they are <strong>not</strong>
- guaranteed to be preserved forever. The project reserves the right to remove
- hypervisor specific APIs in any new release, or to change their semantics.
- That said the project will endeavour to maintain API compatibility for as long
- as is practical.
- </p>
-
- <p>
- Use of some hypervisor specific APIs may result in the running guest being
- marked as "tainted" if the API is at risk of having unexpected interactions
- with normal libvirt operations. An application which chooses to make use of
- hypervisor specific APIs should validate their operation with each new release
- of libvirt and each new release of the underlying hypervisor. The semantics
- may change in unexpected ways, or have unforeseen interactions with libvirt's
- operation.
- </p>
-
- <h2><a id="apierrors">Error reporting</a></h2>
-
- <p>
- Most API calls are subject to failure and so will report error codes and
- messages. Libvirt defines error codes for a wide variety of scenarios, some
- represent very specific problems, while others are general purpose for
- broad classes of problem. Over time the error codes reported are liable
- to change, usually changing from a generic error to a more specific error.
- Thus applications should be careful about checking for & taking action
- upon specific error codes, as their behaviour may change across releases.
- </p>
-
- <h2><a id="xmlschema">XML schemas</a></h2>
-
- <p>
- The main objects exposed via the primary libvirt public API are usually
- configured via XML documents following specific schemas. The XML schemas
- are considered to be stable formats, whose compatibility will be maintained
- forever. Specific details are as follows:
- </p>
-
- <dl>
- <dt>Attributes</dt>
- <dd>Attributes defined on an XML element will never be removed or
- renamed. New attributes may be defined. If the set of valid values
- for an attribute are determined by an enumeration, the permitted
- values will never be removed or renamed, only new values defined.
- None the less, specific hypervisors may reject usage of certain
- values according to their feature set.
- </dd>
- <dt>Elements</dt>
- <dd>Elements defined will never be removed or renamed. New child
- elements may be defined at any time. In places where only a
- single instance of a named XML element is used, future versions
- may be extended to permit multiple instances of the named XML
- element to be used. An element which currently has no content
- may later gain child elements.
- </dd>
- </dl>
-
- <p>
- Some hypervisor drivers may choose to allow use of hypervisor specific
- extensions to the XML documents. These extensions will always be
- contained within a hypervisor specific XML namespace. There is generally
- no guarantee of long term support for the hypervisor specific extensions
- across releases, though the project will endeavour to preserve them as
- long as is possible. Applications choosing to use hypervisor specific
- extensions should validate their operation against new libvirt or
- hypervisor releases.
- </p>
-
- <h2><a id="configfiles">Configuration files</a></h2>
-
- <p>
- A number of programs / daemons provided libvirt rely on host filesystem
- configuration files. These configuration files are accompanied by augeas
- lens for easy manipulation by applications. There is in general no
- guarantee that parameters available in the configuration file will be
- preserved across releases, though the project will endeavour to preserve
- them as long as is possible. If a configuration option is dropped from
- the file, the augeas lens will retain the ability to read that configuration
- parameter, so that it is able to read & update historically modified
- files.
-
- The default configuration files ship with all parameters commented out
- such that a deployment relies on the built-in defaults of the application
- in question. There is no guarantee that the defaults will remain the same
- across releases. A deployment that expects a particular value for a
- configuration parameter should consider defining it explicitly, instead
- of relying on the defaults.
- </p>
-
- <h2><a id="hvdrivers">Hypervisor drivers</a></h2>
-
- <p>
- The libvirt project provides support for a wide variety of hypervisor
- drivers. These drivers target certain versions of the hypervisor's
- underlying management APIs. In general libvirt aims to work with any
- hypervisor version that is still broadly supported by its vendor.
- When a vendor discontinues support for a particular hypervisor
- version it will be dropped by libvirt. Libvirt may choose to drop
- support for a particular hypervisor version prior to the vendor
- ending support, if it deems that the likely usage is too small to
- justify the ongoing maintenance cost.
- </p>
- <p>
- Each hypervisor release will implement a distinct subset of features
- that can be expressed in the libvirt APIs and XML formats. While the
- XML schema syntax will be stable across releases, libvirt is unable
- to promise that it will always be able to support usage of the same
- features across hypervisor releases. Where a hypervisor changes the
- way a feature is implemented, the project will endeavour to adapt
- to the new implementation to provide the same semantics. In cases
- where the feature is discontinued by the hypervisor, libvirt will
- return an error indicating it is not supported. Likewise libvirt will
- make reasonable efforts to keep API calls working across hypervisor
- releases even if the underlying implementation changes. In cases where
- this is impossible, a suitable error will be reported. The list of
- APIs which have implementations <a href="hvsupport.html">is detailed separately</a>.
- </p>
-
- <h2><a id="rpcproto">RPC protocol</a></h2>
-
- <p>
- For some hypervisor drivers, the libvirt.so library communicates with
- separate libvirt daemons to perform work. This communication takes
- place over a binary RPC protocol defined by libvirt. The protocol uses
- the XDR format for data encoding, and the message packet format is
- defined in libvirt source code.
- </p>
- <p>
- Applications are encouraged to use the primary libvirt.so library which
- transparently talks to the daemons, so that they are not exposed to the
- hypervisor driver specific details. None the less, the RPC protocol
- associated with the libvirtd is considered to be a long term stable ABI.
- It will only ever have new messages added to it, existing messages will
- not be removed, nor have their contents changed. Thus if an application
- does wish to provide its own client side implementation of the RPC
- protocol this is supported, with the caveat that the application will
- loose the ability to work with certain hypervisors libvirt supports.
- The project reserves the right to define new authentication and encryption
- options for the protocol, and the defaults used in this area may change
- over time. This is particularly true of the TLS ciphers permitted. Thus
- applications choosing to implement the RPC protocol must be prepared to
- track support for new security options. If defaults are changed, however,
- it will generally be possible to reconfigure the daemon to use the old
- defaults, albeit with possible implications for system security.
- </p>
-
- <p>
- Other daemons besides, libvirtd, also use the same RPC protocol, but
- with different message types defined. These RPC protocols are all
- considered to be private implementations that are liable to change
- at any time. Applications must not attempt to talk to these other
- daemons directly.
- </p>
-
- <h2><a id="virsh">virsh client</a></h2>
-
- <p>
- The virsh program provides a simple client to interact with an arbitrary libvirt
- hypervisor connection. Since it uses the primary public API of libvirt, it should
- generally inherit the guarantees associated with that API, and with the hypervisor
- driver. The commands that virsh exposes, and the arguments they accept are all
- considered to be long term stable. Existing commands and arguments will not be
- removed or renamed. New commands and arguments may be added in new releases.
- The text output format produced by virsh commands is not generally guaranteed to
- be stable if it contains compound data (eg formatted tables or lists). Commands
- which output single data items (ie an object name, or an XML document), can be
- treated as having stable format.
- </p>
-
- </body>
-</html>
diff --git a/docs/support.rst b/docs/support.rst
new file mode 100644
index 0000000000..f285f63c55
--- /dev/null
+++ b/docs/support.rst
@@ -0,0 +1,207 @@
+==================
+Support guarantees
+==================
+
+.. contents::
+
+This document will outline the support status / guarantees around the very
+interfaces that libvirt exposes to applications and/or system administrators.
+The intent is to help users understand what features they can rely upon in
+particular scenarios, and whether they are likely to suffer disruption during
+upgrades.
+
+Primary public API
+------------------
+
+The main public API provided by ``libvirt.so`` and described in
+``libvirt/libvirt.h`` exposes the primary hypervisor agnostic management
+interface of libvirt. This API has the strongest guarantee of any part of
+libvirt with a promise to keep backwards compatibility forever. Specific details
+are as follows:
+
+Functions
+ Functions will never be removed from the public API, and will never have
+ parameters added, removed or changed in their signature. IOW they will be ABI
+ compatible forever. The semantics implied by a specific set of parameters
+ passed to the function will remain unchanged. Where a parameter accepts a
+ bitset of feature flags, or an enumerated value, further flags / enum values
+ may be supported in the future. Where a parameter accepts one of a set of
+ related constants, further constants may be supported in the future.
+Struct types
+ Once defined in a release, struct definitions will never have any fields add,
+ removed or changed in any way. Their size and layout is fixed forever. If a
+ struct name starts with an underscore, it is considered acceptable to rename
+ it. Applications should thus always use the corresponding typedef in
+ preference to the struct name.
+Union types
+ Once defined in a release, union definitions will never have any existing
+ fields removed or changed. New union choices may be added, provided that they
+ don't change the size of the existing union definition. If a struct name
+ starts with an underscore, it is considered acceptable to rename it.
+ Applications should thus always use the corresponding typedef in preference
+ to the struct name.
+Type definitions
+ Most custom data types used in the APIs have corresponding typedefs provided
+ for their stable names. The typedefs should always be used in preference to
+ the underlying data type name, as the latter are not guaranteed to be stable.
+Enumerations
+ Once defined in a release, existing enumeration values will never be removed
+ or renamed. New enumeration values may be introduced at any time. Every
+ enumeration will have a '_LAST' value which indicates the current highest
+ enumeration value, which may increase with new releases. If an enumeration
+ name starts with an underscore, it is considered acceptable to rename it.
+ Applications should thus always use the corresponding typedef in preference
+ to the enum name.
+Constants
+ Once defined in a release, existing constants will never be removed or have
+ their value changed. Most constants are grouped into related sets, and within
+ each set, new constants may be introduced. APIs which use the constants may
+ thus accept or return new constant values over time.
+Symbol versions
+ Where the platform library format permits, APIs defined in libvirt.so library
+ will have version information associated. Each API will be tagged with the
+ version in which it was introduced, and this won't be changed thereafter.
+
+Hypervisor specific APIs
+------------------------
+
+A number of hypervisor drivers provide additional libraries with hypervisor
+specific APIs, extending the core libvirt API. These add-on libraries follow the
+same general principles described above, however, they are **not** guaranteed to
+be preserved forever. The project reserves the right to remove hypervisor
+specific APIs in any new release, or to change their semantics. That said the
+project will endeavour to maintain API compatibility for as long as is
+practical.
+
+Use of some hypervisor specific APIs may result in the running guest being
+marked as "tainted" if the API is at risk of having unexpected interactions with
+normal libvirt operations. An application which chooses to make use of
+hypervisor specific APIs should validate their operation with each new release
+of libvirt and each new release of the underlying hypervisor. The semantics may
+change in unexpected ways, or have unforeseen interactions with libvirt's
+operation.
+
+Error reporting
+---------------
+
+Most API calls are subject to failure and so will report error codes and
+messages. Libvirt defines error codes for a wide variety of scenarios, some
+represent very specific problems, while others are general purpose for broad
+classes of problem. Over time the error codes reported are liable to change,
+usually changing from a generic error to a more specific error. Thus
+applications should be careful about checking for & taking action upon specific
+error codes, as their behaviour may change across releases.
+
+XML schemas
+-----------
+
+The main objects exposed via the primary libvirt public API are usually
+configured via XML documents following specific schemas. The XML schemas are
+considered to be stable formats, whose compatibility will be maintained forever.
+Specific details are as follows:
+
+Attributes
+ Attributes defined on an XML element will never be removed or renamed. New
+ attributes may be defined. If the set of valid values for an attribute are
+ determined by an enumeration, the permitted values will never be removed or
+ renamed, only new values defined. None the less, specific hypervisors may
+ reject usage of certain values according to their feature set.
+Elements
+ Elements defined will never be removed or renamed. New child elements may be
+ defined at any time. In places where only a single instance of a named XML
+ element is used, future versions may be extended to permit multiple instances
+ of the named XML element to be used. An element which currently has no
+ content may later gain child elements.
+
+Some hypervisor drivers may choose to allow use of hypervisor specific
+extensions to the XML documents. These extensions will always be contained
+within a hypervisor specific XML namespace. There is generally no guarantee of
+long term support for the hypervisor specific extensions across releases, though
+the project will endeavour to preserve them as long as is possible. Applications
+choosing to use hypervisor specific extensions should validate their operation
+against new libvirt or hypervisor releases.
+
+Configuration files
+-------------------
+
+A number of programs / daemons provided libvirt rely on host filesystem
+configuration files. These configuration files are accompanied by augeas lens
+for easy manipulation by applications. There is in general no guarantee that
+parameters available in the configuration file will be preserved across
+releases, though the project will endeavour to preserve them as long as is
+possible. If a configuration option is dropped from the file, the augeas lens
+will retain the ability to read that configuration parameter, so that it is able
+to read & update historically modified files. The default configuration files
+ship with all parameters commented out such that a deployment relies on the
+built-in defaults of the application in question. There is no guarantee that the
+defaults will remain the same across releases. A deployment that expects a
+particular value for a configuration parameter should consider defining it
+explicitly, instead of relying on the defaults.
+
+Hypervisor drivers
+------------------
+
+The libvirt project provides support for a wide variety of hypervisor drivers.
+These drivers target certain versions of the hypervisor's underlying management
+APIs. In general libvirt aims to work with any hypervisor version that is still
+broadly supported by its vendor. When a vendor discontinues support for a
+particular hypervisor version it will be dropped by libvirt. Libvirt may choose
+to drop support for a particular hypervisor version prior to the vendor ending
+support, if it deems that the likely usage is too small to justify the ongoing
+maintenance cost.
+
+Each hypervisor release will implement a distinct subset of features that can be
+expressed in the libvirt APIs and XML formats. While the XML schema syntax will
+be stable across releases, libvirt is unable to promise that it will always be
+able to support usage of the same features across hypervisor releases. Where a
+hypervisor changes the way a feature is implemented, the project will endeavour
+to adapt to the new implementation to provide the same semantics. In cases where
+the feature is discontinued by the hypervisor, libvirt will return an error
+indicating it is not supported. Likewise libvirt will make reasonable efforts to
+keep API calls working across hypervisor releases even if the underlying
+implementation changes. In cases where this is impossible, a suitable error will
+be reported. The list of APIs which have implementations `is detailed
+separately <hvsupport.html>`__.
+
+RPC protocol
+------------
+
+For some hypervisor drivers, the libvirt.so library communicates with separate
+libvirt daemons to perform work. This communication takes place over a binary
+RPC protocol defined by libvirt. The protocol uses the XDR format for data
+encoding, and the message packet format is defined in libvirt source code.
+
+Applications are encouraged to use the primary libvirt.so library which
+transparently talks to the daemons, so that they are not exposed to the
+hypervisor driver specific details. None the less, the RPC protocol associated
+with the libvirtd is considered to be a long term stable ABI. It will only ever
+have new messages added to it, existing messages will not be removed, nor have
+their contents changed. Thus if an application does wish to provide its own
+client side implementation of the RPC protocol this is supported, with the
+caveat that the application will loose the ability to work with certain
+hypervisors libvirt supports. The project reserves the right to define new
+authentication and encryption options for the protocol, and the defaults used in
+this area may change over time. This is particularly true of the TLS ciphers
+permitted. Thus applications choosing to implement the RPC protocol must be
+prepared to track support for new security options. If defaults are changed,
+however, it will generally be possible to reconfigure the daemon to use the old
+defaults, albeit with possible implications for system security.
+
+Other daemons besides, libvirtd, also use the same RPC protocol, but with
+different message types defined. These RPC protocols are all considered to be
+private implementations that are liable to change at any time. Applications must
+not attempt to talk to these other daemons directly.
+
+virsh client
+------------
+
+The virsh program provides a simple client to interact with an arbitrary libvirt
+hypervisor connection. Since it uses the primary public API of libvirt, it
+should generally inherit the guarantees associated with that API, and with the
+hypervisor driver. The commands that virsh exposes, and the arguments they
+accept are all considered to be long term stable. Existing commands and
+arguments will not be removed or renamed. New commands and arguments may be
+added in new releases. The text output format produced by virsh commands is not
+generally guaranteed to be stable if it contains compound data (eg formatted
+tables or lists). Commands which output single data items (ie an object name, or
+an XML document), can be treated as having stable format.
--
2.35.1
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