diff --git a/README.md b/README.md new file mode 100644 index 0000000..495a5c0 --- /dev/null +++ b/README.md @@ -0,0 +1,73 @@ +# Open Cluster Framework (OCF) + +## What is the OCF? + +The Open Cluster Framework (OCF) is a collection of open standards for +high-availability (HA) clustering. + +The only standard currently in active use is: + +* The OCF Resource Agent API provides a layer of abstraction between cluster + software and the services managed by the cluster. + +## Who is the OCF? + +The OCF is maintained and distributed by +[ClusterLabs](https://www.clusterlabs.org/), a community hub for open-source, +high-availability clustering software. + +## What is the history of the OCF? + +In the early 2000s, open-source, high-availability clustering software was in +its infancy, and there were various implementations. Each needed to do things +like start and stop cluster-managed services, and each implemented this +functionality on its own. + +To reduce that duplication of effort, the OCF Project was formed, spearheaded +by Linux HA project developers Alan Robertson and Lars Marowsky-Brée, and +unveiled at the Ottawa Linux Symposium in July 2001. (1) + +The original goal was ambitious: create a set of APIs for all functionality +needed by both high-availability and high-performance-computing clusters, +provide a reference implementation, and get all open source projects on board. +The OCF became an official Working Group of the Free Standards Group. + +However, by the end of the decade, the situation had changed. The Free +Standards Group had been absorbed into the Linux Foundation, and the "working +group" ceased to exist. The field of open source HA had been winnowed to a few +projects. The high-performance computing community went its own way, and of the +APIs, only the resource agent standard was in active use. + +The narrower focus strengthened the community. At a 2015 summit (2), +participants agreed to consolidate efforts under the banner of ClusterLabs, +which took on maintenance of the OCF standards. + +(1) ["Introducing the Open Cluster Framework", Linux Journal, Sept. 3, 2002](https://www.linuxjournal.com/article/6143) + +(2) ["HA Cluster Summit 2015", plan.alteeva.ca](http://plan.alteeve.ca/index.php/HA_Cluster_Summit_2015) + +## How is this repository organized? + +The repository has these subdirectories: + +* concepts: Some background on clustering +* historical: Standards and implementations no longer used or maintained +* ra: OCF Resource Agent API + * ra/_number_: A particular (official or draft) version of the standard + * resource-agent-api.md: The standard + * ra-metadata-example.xml: Example resource agent meta-data (informational + only, not part of the standard) + * ra-api.rng: RelaxNG schema for validating resource agent meta-data + * ra/latest: Symbolic link to latest official version + * ra/next: Proposed changes that have not made it into a specific draft yet + +## How are the standards maintained? + +The standards are maintained in a +[Github repository](https://github.com/ClusterLabs/OCF-spec). + +Changes are proposed and discussed via pull requests to the repository. +Topics related to the OCF may also be discussed on the +[users@clusterlabs.org](https://lists.clusterlabs.org/mailman/listinfo/users) and +[developers@clusterlabs.org](https://lists.clusterlabs.org/mailman/listinfo/developers) +mailing lists. diff --git a/ra/next/Makefile b/ra/next/Makefile index cb079fd..03866f7 100644 --- a/ra/next/Makefile +++ b/ra/next/Makefile @@ -1,23 +1,23 @@ # Basic DocBook mangling makefile. # # BASENAME=resource-agent-api GRAMMAR=ra-api.rng -TEST_FILES=ra-metadata-example-1.0.xml ra-metadata-example.xml +TEST_FILES=ra-metadata-example.xml .PHONY: all clean %.html: %.md pandoc -f markdown -o $@ $^ %.pdf: %.md pandoc -f markdown -o $@ $^ all: $(BASENAME).pdf $(BASENAME).html clean: rm $(BASENAME).pdf $(BASENAME).html||true check: $(GRAMMAR) $(TEST_FILES) xmllint --relaxng $(GRAMMAR) --noout $(TEST_FILES) diff --git a/ra/next/ra-api.rng b/ra/next/ra-api.rng index 7934b66..154a43f 100644 --- a/ra/next/ra-api.rng +++ b/ra/next/ra-api.rng @@ -1,128 +1,141 @@ + + + + + + + - - - - - - + + + + + + + + + + + + boolean string integer select - + 0 1 diff --git a/ra/next/ra-metadata-example-1.0.xml b/ra/next/ra-metadata-example-1.0.xml deleted file mode 100644 index 71a5dd0..0000000 --- a/ra/next/ra-metadata-example-1.0.xml +++ /dev/null @@ -1,105 +0,0 @@ - - - - - - -1.0 - - - - - - - - - -The resource name is the directory where the filesystem will be actually -mounted. Please make sure it exists. - - - -Mountpoint - - - - - - - - -When mounting a filesystem on a specific mountpoint, you have to specify which -device should be mounted; this will usually be similiar to /dev/sda1 or -/dev/volumegroup/logicalvolume when using LVM. - -Device to be mounted - - - - - -You should chose a journaled filesystem for the shared storage to ensure that -the filesystem remains consistent and that it can be mounted without an -expensive fsck run; recommendations include reiserfs, ext3 and XFS. - -Type of the filesystem - - - - - -The mount options used for mounting a filesystem; normally this is set to -defaults, but you may want to modify this if you require a read-only -mount or something similar. - -Mount options for this filesystem - - - - - - - - - - - - - - - - - - - - - - - - -403 - - - diff --git a/ra/next/ra-metadata-example.xml b/ra/next/ra-metadata-example.xml index ff43c12..3f2101c 100644 --- a/ra/next/ra-metadata-example.xml +++ b/ra/next/ra-metadata-example.xml @@ -1,151 +1,193 @@ + + + - + The root element may optionally contain the resource agent's version, + which is a free-form text field. +--> + - -1.0 + +1.1 + - Filesystem matters. + This resource agent manages the example daemon, which does many wondrous + things. - + - + - - + + + -The resource name is the directory where the filesystem will be actually -mounted. Please make sure it exists. +The full path to the example daemon configuration file. - -Mountpoint + +Configuration filename - - + + - - -When mounting a filesystem on a specific mountpoint, you have to specify which -device should be mounted; this will usually be similiar to /dev/sda1 or -/dev/volumegroup/logicalvolume when using LVM. - -Device to be mounted - - + + -You should chose a journaled filesystem for the shared storage to ensure that -the filesystem remains consistent and that it can be mounted without an -expensive fsck run; recommendations include reiserfs, ext3 and XFS. +The local IP address the example daemon should bind to and accept requests on. +If omitted, the wildcard address will be used. -Type of the filesystem - +IP address + - + -The mount options used for mounting a filesystem; normally this is set to -defaults, but you may want to modify this if you require a read-only -mount or something similar. +The port number the example daemon should accept requests on. -Mount options for this filesystem - +Port number + - + + -The fstype options is used to specify file system type. +The mode the example daemon should operate in. Allowed values are "dry-run" and +"live". -Filesystem type - - + -Some archaic parameter +This parameter is no longer used. -Archaic parameter +Unused - - + + + + + -Some archaic parameter +The full path to the example daemon configuration file. -Archaic parameter +Configuration filename - - + + + + Don't use foo, it's bad. Nepoužívej foo, sic to schytáš -Some archaic parameter +Whether the example daemon should operate with foo factor -Archaic parameter +Foo factor - + - - + + + + + + + + + + - - - - - - - + + + + - + 403 diff --git a/ra/next/resource-agent-api.md b/ra/next/resource-agent-api.md index ff93f0d..55023de 100644 --- a/ra/next/resource-agent-api.md +++ b/ra/next/resource-agent-api.md @@ -1,595 +1,681 @@ **DRAFT - DRAFT - DRAFT** **JOIN THE developers@clusterlabs.org MAILING LIST AND FOLLOW PULL REQUESTS AT https://github.com/ClusterLabs/OCF-spec/ TO DISCUSS CHANGES** # Open Clustering Framework Resource Agent API -Editor: Lars Marowsky-Brée - URL: https://github.com/ClusterLabs/OCF-spec/blob/master/ra/next/resource-agent-api.md ## Abstract The Open Clustering Framework Resource Agent (RA) API provides an abstraction layer between diverse, computer-hosted resources and diverse types of software managing such resources in a clustered environment. The RA API allows resources to be managed without any modification to the actual resource providers, by providing a standardized interface to common management tasks. It also allows (but does not require) RAs to be designed without consideration of specific software that might invoke them, and thus shared by any such software. ## Status of This Memo This is an Open Cluster Framework (OCF) document produced by ClusterLabs . This document describes proposed extensions to the OCF RA API, which may be incorporated into future versions of the standard. It has not been adopted as a standard, and should be considered for discussion purposes only. ## Copyright Notice -Copyright 2002,2018 Lars Marowsky-Brée +Originally Copyright 2002,2018 Lars Marowsky-Brée +Later changes copyright 2020 the Open Cluster Framework project contributors Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license can be found at http://www.gnu.org/licenses/fdl.txt. ## Terms used in this document ### Resource A _resource_, also known as a _resource instance_, is a logical entity that provides a particular computer-hosted service. Examples of resources include a disk volume, a network address, a web server, or a virtual machine. ### Cluster A _cluster_ is a collection of one or more computers under common administration running a set of resources. ### Resource Manager A _resource manager_ (RM), also known as a _cluster resource manager_ (CRM), is software that manages resources in a cluster. ### Resource Type A _resource type_ is a name indicating the service provided by a resource. This name should be suitable for use as a file name. +A resource type beginning with a leading dot (.) is a hint to RMs and other +tools that the resource type should be omitted from lists provided in response +to user queries. + ### Resource Agent A _resource agent_ (RA) is a software application implementing the RA API for a particular resource type. An RA allows a resource manager to perform specific mangement tasks for resource instances. ### Resource Agent Provider A _resource agent provider_ is an entity supplying one or more resource agents for installation on cluster hosts. Each provider should have a unique name suitable for use as a file system directory name. +A resource agent provider beginning with a leading dot (.) is a hint to RMs and +other tools that the resource agent provider should be omitted from lists +provided in response to user queries. + A provider may choose to supply multiple, separate collections of resource agents. In this case, each collection should have a unique name, and _provider_ may refer either to the entity as a whole, or to an individual collection. Currently, there is no central registry for provider names. Providers should choose names that do not appear to be already in use for publicly available resource agents. Each provider also chooses the resource type names used for the resource agents it provides. These do not need to be unique across providers. ### Resource Name A _resource name_ is a unique identifier chosen by the cluster administrator to identify a particular resource instance. ### Resource Parameters _Resource parameters_, also known as _instance parameters_, are attributes describing a particular resource instance. Each parameter has a name and a value, which must satisfy the requirements of POSIX environment variable names and values. The resource agent defines the names, meaning, and allowed values of parameters available for its resource type. The cluster administrator specifies the particular parameters used for each resource instance. +### Role + +A _role_ is a mode of operation that a service may have, with two possible +values: _unpromoted_ and _promoted_. Resource agent support for roles is +optional. + ## API ### API Version Numbers The version number is of the form `x.y`, where `x` and `y` are positive numbers greater or equal to zero. `x` is referred to as the "major" number, and `y` as the "minor" number. The major number must be increased if a _backwards incompatible_ change is made to the API. A major number mismatch between the RA and the RM must be reported as an error by both sides. The minor number must be increased if _any_ change at all is made to the API. If the major is increased, the minor number should be reset to zero. The minor number can be used by both sides to see whether a certain additional feature is supported by the other party. ### The Resource Agent Directory Resource agents are executable files that must be made available beneath a common location on a host's file system, referred to as the _resource agent directory_. In the 1.0 version of this standard, the only acceptable location of this directory was `/usr/ocf/resource.d`. However, in practice, installations typically used the nonconforming location `/usr/lib/ocf/resource.d`. For strict compatibility with the standard, resource agents should be installed in the 1.0 location, and resource managers should look for agents there. For widest compatibility, resource agents and resource managers should allow the installer to choose the location of the directory, which should have a reasonable default, and should be identical for all resource agents and resource managers installed on a particular host. Resource managers may also choose to search multiple locations. ### The Resource Agent Directory Tree Each provider shall install its resource agents in a subdirectory of the resource agent directory, using the provider's name. This allows installation of multiple resource agents for the same type, but from different suppliers or package versions. Each resource agent should be installed as a file within the provider subdirectory, named according to the resource type. The provider subdirectory and resource agent file may be links to the actual locations. A simple example of a resource agent directory tree containing a single provider `acme` that provides resource agents `widget` and `gadget`: acme/ acme/widget acme/gadget Another example where multiple versions of acme's agents are installed: acme -> acme-2.0/ acme-1.0/ acme-1.0/widget acme-1.0/gadget acme-2.0/ acme-2.0/widget acme-2.0/gadget An example with two providers, an agent available from two providers, and an agent available under multiple names from the same provider: acme/ acme/widget acme/gadget betterco/ betterco/widget betterco/IP -> IPAddr betterco/IPAddr Resource managers may choose an agent for a specific resource type name from the available set in any manner they choose. ### Execution syntax After the RM has identified the executable to call, the RA will be called with the requested action as its sole argument. To allow for further extensions, the RA shall ignore all other arguments. ### Resource Agent Actions Resource agents must accept a single command-line argument specifying an action to be performed. RAs must be able to perform actions listed in this section as mandatory, and must advertise them as described in **Resource Agent Meta-Data**. RAs may support any additional actions, including but not limited to those listed in this section as optional. Actions must be idempotent. Invoking an already successfully performed action additional times must be successful and leave the resource instance in the requested state. For example, a start command given to a resource that has already been successfully started should return success without changing the state of the resource. An RA should not assume it is the only RA of its type running at any given time. Multiple resource instances of the same type may be running in parallel. An RA must return a well-defined status, as described under **Exit Status Codes**. This includes improper usage such as being called with an unsupported action. #### Mandatory Actions - `start` This must bring the resource instance online and makes it available for use. It should NOT terminate before the resource instance has either been fully started or an error has been encountered. It may try to implement recovery actions for certain cases of startup failures. `start` must succeed if the resource instance is already running. `start` must return an error if the resource instance is not fully started. + If the resource agent supports roles, a successful start must put the + resource in the unpromoted role. + - `stop` This must stop the resource instance. After the `stop` command has completed, no component of the resource shall remain active, and it must be possible to start it on the same node or another node, otherwise an error must be returned. The `stop` request by the RM includes the authorization to bring down the resource even by force as long as data integrity is maintained. Breaking currently active transactions should be avoided, but the request to offline the resource has higher priority than this. If this is not possible, the RA shall return an error, to allow higher-level recovery. The `stop` action should also clean up any artifacts such as leftover shared memory segments, semaphores, IPC message queues, lock files, etc. `stop` must succeed if the resource is already stopped. `stop` must return an error if the resource is not fully stopped. - `monitor` This must check the current status of the resource instance. The - thoroughness of the check is influenced by the weight of the check, as - described under **Monitor-Specific Parameters**. - - An RA may have additional instance parameters which are not strictly - required to identify the resource instance but are useful for monitoring - it. In particular, RAs may support an integer _depth_ parameter specifying - how intrusive this check is allowed to be (which values for depth are - supported and what degree of intrusiveness they correspond to is left to - the RA). + thoroughness of the check may optionally be influenced by **Check Levels**. + Service must remain available during the monitor, regardless of check + level. - `meta-data` - This must display the XML information described under + This must display the information described under **Resource Agent Meta-Data** via standard output. #### Optional Actions - `demote` - If the resource supports two modes of operation (_roles_), this action - must put the resource in the default role (the role that a start action - leaves the resource in). + If the resource agent supports roles, this action must put an active + resource in the unpromoted role. - `notify` If the resource requires special coordination when multiple instances are run simultaneously in the cluster, the resource agent should support this action, which should perform such coordination. When the RA supports this action, RMs should call the action for all active instances of this particular resource in the cluster before and after any demote, promote, start, or stop action performed on any instance of it. How the RM passes useful information to the RA when performing this action is currently left to the RM and RA, but may be formalized in a future version of this standard. - `promote` - If the resource supports roles, this action must put the resource in the - special (non-default) role. + If the resource agent supports roles, this action must put an active + resource in the promoted role. - `recover` A special case of the `start` action, this should try to recover a resource locally. It is recommended that this action is not advertised unless it is advantageous to use when compared to a stop and start action sequence. If this is not supported, it may be mapped to a stop and start action sequence by the RM. An example includes "recovering" an IP address by moving it to another interface; this is much less costly than initiating a full resource group fail-over to another node. - `reload` This should notify the resource instance of a configuration change external to the instance parameters. It should reload the configuration of the resource instance without disrupting the service. It is recommended that this action is not advertised unless it is advantageous to use when compared to a stop and start action sequence. If this is not supported, it may be mapped to a stop and start action sequence by the RM. -- `validate-all` +- `reload-params` + + This should make effective any changes in instance parameters that have been + marked as reloadable as described in **Resource Agent Meta-Data**. - This should validate the instance parameters provided. +- `validate-all` - This should perform a syntax check, and if possible a semantic check, on - the instance parameters. + This should validate the instance parameters provided. The thoroughness of + the check may optionally be influenced by **Check Levels**. ### Parameter passing The instance parameters and some additional attributes are passed in via the environment; this has been chosen because it does not reveal the parameters to an unprivileged user on the same system and environment variables can be easily accessed by all programming languages and shell scripts. The entire environment variable name space starting with `OCF_` is considered to be reserved for OCF use. #### Syntax for instance parameters They are directly converted to environment variables; the name is prefixed with `OCF_RESKEY_`. The instance parameter `force` with the value `yes` thus becomes `OCF_RESKEY_force=yes` in the environment. See the terms section on instance parameters for a more formal explanation. #### Global OCF attributes Currently, the following additional environment variables are defined: * `OCF_RA_VERSION_MAJOR` * `OCF_RA_VERSION_MINOR` Version number of the OCF Resource Agent API. If the script does not support this revision, it should report an error. See **API Version Numbers** for an explanation of the versioning scheme used. The version number is split into two numbers for ease of use in shell scripts. These two may be used by the RA to determine whether it is run under an OCF compliant RM. Example: ``` OCF_RA_VERSION_MAJOR=1 OCF_RA_VERSION_MINOR=1 ``` * `OCF_ROOT` Referring to the root of the OCF directory hierarchy. Example: `OCF_ROOT=/usr/ocf` * `OCF_RESOURCE_INSTANCE` The name of the resource instance. * `OCF_RESOURCE_TYPE` The name of the resource type being operated on. -#### Monitor-Specific Parameters +* `OCF_OUTPUT_FORMAT` + + Resource agents may optionally support multiple formats for output generated + by an action. The specific formats supported and values used to indicate + them are left to agents, but it is recommended to use "text" for readable + text output, "xml" for XML output, and "html" for HTML output. + + The `meta-data` action must support, and default to, XML output. The default + for other actions is left to agents. -Resource agents may optionally support the parameters listed here when called -with the `monitor` action. +#### Check Levels + +Resource agents may optionally support the `OCF_CHECK_LEVEL` +environment variable when called with the `monitor` or `validate-all` actions, +to allow requests for more or less intensive checks. Agents that support +`OCF_CHECK_LEVEL` may choose their own default value if it is not specified. + +Agents that support `OCF_CHECK_LEVEL` should indicate so by specifying actions +with `depth` attributes in agent meta-data, as described in +**Resource Agent Meta-Data**. - `OCF_CHECK_LEVEL` - `0` - The most lightweight check possible, which should not - have an impact on the QoS. + The most lightweight check possible. + + For `validate-all` actions, this should verify the internal consistency + (syntax and compatibility) of specified parameters, but should not + verify the local environment in any fashion. This allows tools to + validate parameters even if running on a node that will not run the + agent. + For `monitor` actions, this should not affect quality of service. Example: Check for the existence of the process. - `10` - A medium weight check, expected to be called multiple - times per minute, which should not have a noticeable - impact on the QoS. + A medium-weight check. - Example: Send a request for a static page to a - webserver. + For `validate-all` actions, this may verify the suitability of the + local environment, in addition to the internal consistency of + parameters. - - `20` + For `monitor` actions, this should be suitable for being called + multiple times per minute, with minimal impact on quality of service. + Example: Send a request for a static page to a Web server. - A heavy weight check, called infrequently, which may - impact system or service performance. + - `20` - Example: An internal consistency check to verify service - integrity. + A heavyweight check. This is expected to be called infrequently, and + may affect system or service performance. -Service must remain available during all of these operation. -All other number are reserved. + - All other numbers are reserved. It is recommended that if a requested level is not implemented, the RA should perform the next lower level supported. ### Exit Status Codes These exit status codes are identical to those documented in the LSB 5.0 Core specification for non-status "Init Script Actions" , with additional explanations of how they shall be used by RAs. -Non-zero status codes are referred to in this document as errors, however RA +Although non-zero status codes are referred to in this document as errors, RA developers should keep in mind that RMs decide whether a status code is a failure or not (for example, if a particular error is the expected situation, it may not be considered a failure). - `0` - No error, action succeeded completely + Success. The requested action finished and succeeded completely, or + for a "monitor" action, the service was found to be properly active. - `1` - Generic or unspecified error (current practice) - The "monitor" action shall return this for a crashed, hung or - otherwise non-functional resource. + Unspecified error. The action did not completely succeed for some reason, + or for a "monitor" action, the service was malfunctioning or in an + undetermined state. A more specific status code should be used if + applicable. - `2` - Invalid or excess argument(s) - Likely error code for validate-all, if the instance parameters - do not validate. Any other action is free to also return this - exit status code for this case. + Invalid parameter(s). Note: there is some variance in the actual use of + this status; it may refer to parameters that are inherently invalid (for + example, text provided for a parameter value that must be an integer), or + to parameters that are invalid in the context of the local host (for + example, a supplied file name does not exist). It is recommended to use + the latter meaning, so RMs can decide to try running the resource on a + different host after receiving this status. - `3` - Unimplemented feature - RAs should return this for unsupported actions (for example, "reload"). + Unimplemented feature. The RA does not support the requested action. - `4` - User had insufficient privilege + Insufficient privilege. The user executing the RA lacked some necessary + authorization. - `5` - Program is not installed + Not installed. Some software required for the operation of the service is + not available on the local host. - `6` - Program is not configured + Not configured. Note: there is some variance in the actual use of this + status; it may mean the service's own configuration on the local host is + invalid, or it may mean the parameters supplied to the RA are inherently + invalid. It is recommended to use the latter meaning, so that RMs may + decide to fail the action without retrying elsewhere. - `7` - Program is not running + Not running. A "monitor" action shall return this if it finds the service + to be completely stopped (if there is doubt, some other status such as 1 + should be returned). Note: A successful "stop" operation shall return 0, + not 7. + +- `8` - Note: This is not the error code to be returned by a successful - "stop" operation. A successful "stop" operation shall return 0. - The "monitor" action shall return this value only for a - _cleanly_ stopped resource. If in doubt, it should return 1. + Running promoted. A "monitor" action shall return this if the + resource agent supports roles, and the service is both properly active and + in the promoted role. Note: The LSB reserves this value for future use in + the context of init scripts, but it is used here for compatibility with + established practice. -- `8-99` +- `9` - Reserved for future LSB use + Failed promoted. A "monitor" action shall return this if the resource agent + supports roles, and the service may be in the promoted role, but it is not + functioning properly. Note: The LSB reserves this value for future use in + the context of init scripts, but it is used here for compatibility with + established practice. -- `100-149` +- `190` - Reserved for distribution use + Degraded success. A "monitor" action may return this if the service is + found to be properly active, but in such a condition that future failures + are more likely. -- `150-199` +- `191` - Reserved for application use + Degraded promoted. A "monitor" action may return this if the resource agent + supports roles, and the service is found to be properly active in the + promoted role, but in such a condition that future failures are more + likely. -- `200-254` +- Other values - Reserved + This standard does not explicitly reserve any other values. In the context + of init scripts, the LSB standard sets aside `150-199` for application use, + and reserves `8-99` for LSB use, `100-149` for distribution use, and + `200-254`. Many shells use values `129-255` to indicate termination by a + signal, which could be ambiguous when a resource agent is run via a shell. ## Relation to the LSB The RA API aims to make it possible for (but does not require) an RA to function as both an LSB-compliant init script and a cluster-aware RA. RAs may use helper functions defined for LSB init scripts. ## Resource Agent Meta-Data ### Format While the LSB uses shell script comments at the beginning of init scripts to provide meta-data, OCF RA meta-data is described using XML so that the meta-data can be: - Independent of the language the RA itself is written in, - Extensible, - Structured, and - Easy to parse from a variety of languages. -RA meta-data shall conform to the XML schema formally described at +Resource agents must at least support XML output for the `meta-data` action, +and such XML shall conform to the XML schema formally described at . ### Example An example of a valid meta-data output is provided at . ### Semantics Certain meta-data XML elements warrant further explanation: - `resource-agent`: The optional `version` attribute should describe the version of the agent itself. - `version`: This is the version of the OCF RA standard with which the RA claims compatibility. -- `longdesc` and `shortdesc`: These are hints to tools describing the purpose - of the agent. They may contain any XML, but it is strongly recommended to - limit the content to a text string. +- `longdesc`, `shortdesc`, and `desc`: These elements, wherever they occur in + meta-data, are natural-language descriptions of what is specified by their + parent element, intended as hints to tools for display to users. These + elements must contain a `lang` attribute whose value is a standard language + identifier ("BCP 47" ). + Multiple elements with different values for `lang` may be specified, to + provide translations. These elements may contain any XML, but it is strongly + recommended to limit the content to a text string. - `parameter`: - - `unique` attribute: This is a hint to RMs and other tools that the - combination of all parameters marked `unique` must be unique to the resource - type. That is, no two resource instances of the same resource type may have - the same combination of `unique` parameters. + - `unique-group` attribute: This is a hint to RMs and other tools that the + combination of all parameters with the same value should be unique to the + resource type. That is, no two instances of the same resource type should + have the same combination of these parameters. If not specified, multiple + instances of the same resource type may have the same value of this + parameter. + + Note: a boolean `unique` attribute was formerly used for a similar + purpose, but was commonly misused, and is now deprecated. An RA may + provide it for backward compatibility, but because it is only a hint in + any case, RMs and tools are free to ignore it. + - `required` attribute: This is a hint to RMs and other tools that every resource instance of this resource type must specify a value for this parameter. - - `longdesc` and `shortdesc`: The same guidance applies as described above - when these tags appear under `resource-agent`. + + - `reloadable` attribute: If set to 1, this is a hint to indicate that a + change in this attribute does not necessitate a full stop and start to + take effect, but can take effect via a `reload-params` action. + + - `deprecated` child element: When present, this element is a hint to RMs + and other tools that the parameter is supported for backward + compatibility only. + - `replaced-with` child element: This must contain a `name` attribute + with the name of another parameter that should be used instead of the + deprecated parameter. Multiple such elements maybe specified. - `action`: Resource agents should advertise each action they support, including all mandatory actions, with an `action` element. - `name` attribute (required): This is a unique identifier for the action as described in **Resource Agent Actions**. There may be multiple `action` entries with the same name and different values for other attributes (for example, to recommend different timeout and interval values for status actions of different depths). - `timeout` attribute (required): This is a hint to RMs and other tools that every resource instance of this resource type should specify a timeout equal to or greater than this value (when used with any other attribute values specified in this entry). - `interval` attribute (optional): This is a hint to RMs and other tools that every resource instance of this resource type should repeat this action at intervals equal to this value (when used with any other attribute values specified in this entry). - `depth` attribute (optional): This is a hint to RMs and other tools that this action of the resource agent utilizes the depth parameter with - this value, as described in **Resource Agent Actions**. + this value, as described in **Resource Agent Actions** and + **Check Levels**. - `role` attribute (optional): This is a hint to RMs and other tools - that this action of the resource agent recognizes this role value, - as described in **Resource Agent Actions**. + that this action of the resource agent recognizes this role value + (promoted or unpromoted). ## Contributors - James Bottomley - Greg Freemyer - Simon Horman - Ragnar Kjørstad - Lars Marowsky-Brée - Alan Robertson - Yixiong Zou - Ken Gaillot