One document matched: draft-murray-cdni-triggers-00.txt
Network Working Group R. Murray
Internet-Draft B. Niven-Jenkins
Intended status: Standards Track Velocix (Alcatel-Lucent)
Expires: September 1, 2012 February 29, 2012
CDN Interconnect Triggers
draft-murray-cdni-triggers-00
Abstract
This document proposes a mechanism for a CDN to trigger activity in
an interconnected CDN that is configured to deliver content on its
behalf. The upstream CDN can use this mechanism to request that the
downstream CDN pre-positions metadata or content, or that it re-
validate or purge metadata or content. The upstream CDN can monitor
the status of activity that it has triggered in the downstream CDN.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on September 1, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Model for CDNI Triggers . . . . . . . . . . . . . . . . . . . 5
3. Collections of Trigger Status Resources . . . . . . . . . . . 7
4. CDNI Trigger interface . . . . . . . . . . . . . . . . . . . . 8
4.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 9
4.2. Checking Status . . . . . . . . . . . . . . . . . . . . . 10
4.2.1. Polling Trigger Status Resource collections . . . . . 10
4.2.2. Polling Trigger Status Resources . . . . . . . . . . . 10
4.3. Deleting Triggers . . . . . . . . . . . . . . . . . . . . 10
4.4. Expiry of Trigger Status Resources . . . . . . . . . . . . 11
5. Properties of Triggers . . . . . . . . . . . . . . . . . . . . 11
5.1. Properties of Trigger Requests . . . . . . . . . . . . . . 11
5.1.1. Content URLs . . . . . . . . . . . . . . . . . . . . . 12
5.2. Properties of Trigger Status Resources . . . . . . . . . . 12
5.3. Properties of Trigger Collections . . . . . . . . . . . . 13
5.4. Trigger Resource Simple Data Type Descriptions . . . . . . 14
5.4.1. TriggerType . . . . . . . . . . . . . . . . . . . . . 14
5.4.2. TriggerStatus . . . . . . . . . . . . . . . . . . . . 14
5.4.3. URLs . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.4.4. UrlPatterns . . . . . . . . . . . . . . . . . . . . . 14
5.4.5. AbsoluteTime . . . . . . . . . . . . . . . . . . . . . 15
6. JSON Encoding of Objects . . . . . . . . . . . . . . . . . . . 15
6.1. JSON Encoding of Embedded Types . . . . . . . . . . . . . 16
6.1.1. TriggerType . . . . . . . . . . . . . . . . . . . . . 16
6.1.2. TriggerStatus . . . . . . . . . . . . . . . . . . . . 16
6.1.3. Metadata and Content References . . . . . . . . . . . 16
6.1.4. Pattern . . . . . . . . . . . . . . . . . . . . . . . 16
6.1.5. Relationship . . . . . . . . . . . . . . . . . . . . . 17
6.2. MIME Media Types . . . . . . . . . . . . . . . . . . . . . 18
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 18
7.1.1. Preposition . . . . . . . . . . . . . . . . . . . . . 19
7.1.2. Invalidate . . . . . . . . . . . . . . . . . . . . . . 21
7.2. Examining Trigger Status . . . . . . . . . . . . . . . . . 22
7.2.1. Collection of All Triggers . . . . . . . . . . . . . . 22
7.2.2. Filtered Collections of Triggers . . . . . . . . . . . 23
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7.2.3. Trigger Status Resources . . . . . . . . . . . . . . . 25
7.2.4. Polling for Change . . . . . . . . . . . . . . . . . . 28
7.2.5. Cancelling or Removing a Trigger . . . . . . . . . . . 30
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
9. Security Considerations . . . . . . . . . . . . . . . . . . . 32
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
11.1. Normative References . . . . . . . . . . . . . . . . . . . 32
11.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
[I-D.ietf-cdni-problem-statement] introduces the Problem scope for
CDN Interconnection (CDNI) and lists the four categories of
interfaces that may be used to compose a CDNI solution (Control,
Metadata, Request Routing, Logging).
[I-D.davie-cdni-framework] expands on the information provided in
[I-D.ietf-cdni-problem-statement] and describes each of the
interfaces and the relationships between them in more detail.
This draft concentrates on the "High" and "Medium" priority
requirements for the CDNI Control Interface identified in section 4
of [I-D.ietf-cdni-requirements], reproduced here for convenience:
CNTL-1 [HIGH] The CDNI Control interface shall allow the Upstream
CDN to request that the Downstream CDN (and, if cascaded CDNs are
supported by the solution, that the potential cascaded Downstream
CDNs) perform the following actions on an object or object set:
* Mark an object(s) and/or its CDNI metadata as "stale" and
revalidate them before they are delivered again.
* Delete an object(s) and/or its CDNI metadata from the CDN
surrogates and any storage. Only the object(s) and CDNI
metadata that pertain to the requesting Upstream CDN are
allowed to be purged.
CNTL-2 [HIGH] The CDNI Control interface shall allow the
downstream CDN to report on the completion of these actions (by
itself, and if cascaded CDNs are supported by the solution, by
potential cascaded Downstream CDNs), in a manner appropriate for
the action (e.g. synchronously or asynchronously).
CNTL-3 [HIGH] The CDNI Control interface shall support initiation
and control by the Upstream CDN of pre-positioned CDNI metadata
acquisition by the Downstream CDN.
CNTL-4 [MED] The CDNI Control interface should support initiation
and control by the Upstream CDN of pre-positioned content
acquisition by the Downstream CDN.
This document does not consider those parts of the control interface
that relate to configuration, bootstrapping or authentication of CDN
Interconnect interfaces.
o Section 2 outlines the model for the Trigger Interface at a high
level.
o Section 3 describes collections of Trigger Resources.
o Section 4 defines the RESTful web service provided by dCDN.
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o Section 5 lists properties of Trigger Requests and Status
Resources.
o Section 6 defines a JSON encoding for Trigger Requests and Status
Resources.
o Section 7 contains example messages.
1.1. Terminology
This document reuses the terminology defined in
[I-D.ietf-cdni-problem-statement].
2. Model for CDNI Triggers
A trigger, sent from uCDN to dCDN, is a request for dCDN to do some
work relating to data originating from uCDN.
The trigger may request action on either metadata or on content, it
specifies one of the following actions:
o preposition - used to instruct dCDN to fetch metadata from uCDN,
or content from any origin including uCDN.
o invalidate - used to instruct dCDN to revalidate specific metadata
or content before re-using it.
o purge - used to instruct dCDN to delete specific metadata or
content.
The CDNI trigger interface is a RESTful web service offered by dCDN.
It allows creation and deletion of triggers, and tracking of the
triggered activity. When dCDN accepts a trigger it creates a
resource describing status of the triggered activity, a Trigger
Status Resource. The uCDN may poll Trigger Status Resources to
monitor progress.
Requests to invalidate and purge metadata or content apply to all
variants of that data with a given URI.
The dCDN maintains a collection of Trigger Status Resources for each
uCDN, each uCDN only has access to its own collection and the
location of that collection is shared when CDN interconnection is
established.
To trigger activity in dCDN, uCDN will POST to the collection of
Trigger Status Resources. If dCDN accepts the trigger, it creates a
new Trigger Status Resource and returns its location to uCDN. To
monitor progress, uCDN may GET the Trigger Status Resource. To
cancel a trigger, or remove a trigger from the collection once its
activity has been completed, uCDN may DELETE the Trigger Status
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Resource.
In addition to the collection of all Trigger Status Resources for
uCDN, uCDN shall have access to filtered views of that collection.
These filtered views are defined in Section 3 and include collections
of active and completed triggers. These collections provide a
mechanism for polling the status of multiple jobs.
Figure 1 is an example showing the basic message flow used by the
uCDN to trigger activity in dCDN, and for uCDN to discover the status
of that activity. Only successful triggering is shown. Examples of
the messages are given in Section 7.
uCDN dCDN
| (1) POST http://dcdn.example.com/triggers/uCDN |
[ ] --------------------------------------------------> [ ]--+
| [ ] | (2)
| (3) HTTP 201 Response [ ]<-+
[ ] <-------------------------------------------------- [ ]
| Loc: http://dcdn.example.com/triggers/uCDN/123 |
| |
. . .
. . .
. . .
| |
| (4) GET http://dcdn.example.com/triggers/uCDN/123 |
[ ] --------------------------------------------------> [ ]
| [ ]
| (5) HTTP 200 Trigger Status Resource [ ]
[ ] <-------------------------------------------------- [ ]
| |
| |
Figure 1: Basic CDNI Message Flow for Triggers
The steps in Figure 1 are:
1. uCDN triggers action in dCDN by posting to a collection of
Trigger Status Resources,
"http://dcdn.example.com/triggers/uCDN". The URL of this was
given to uCDN when the trigger interface was established.
2. dCDN authenticates the request, validates the trigger and if it
accepts the request, creates a new Trigger Status Resource.
Timing of the activity in dCDN is under dCDN's control. Progress
will be reported in the newly created Trigger Status Resource
which uCDN may poll.
3. dCDN responds to uCDN with an HTTP 201 response status, and the
location of the Trigger Status Resource.
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4. uCDN may repeatedly poll the Trigger Status Resource in dCDN.
5. dCDN responds with the Trigger Status Resource, describing
progress or results of the triggered activity.
The remainder of this document describes the messages, Trigger Status
Resources, and collections of Trigger Status Resources in more
detail.
3. Collections of Trigger Status Resources
As described in Section 2, Trigger Status Resources exist in dCDN to
report the status of activity triggered by each uCDN.
A collection of Trigger Status Resources is a resource that contains
a reference to each Trigger Status Resource in that collection.
To trigger activity in dCDN, uCDN creates a new Trigger Status
Resource by posting to dCDN's collection of uCDN's Trigger Status
Resources. The URL of each Trigger Status Resource is generated by
the dCDN when it accepts the trigger, and returned to uCDN. This
immediately enables uCDN to check the status of that trigger.
The dCDN must present a different set of Trigger Status Resources to
each interconnected uCDN, only Trigger Status Resources belonging to
a uCDN shall be visible to it. The dCDN may, for example, achieve
this by offering different collection URLs to uCDNs, or by filtering
the response based on the client uCDN.
The dCDN resource representing the collection of all uCDN's Trigger
Status Resources is accessible to uCDN. This collection lists all
uCDN triggers that have been accepted by dCDN, and have not yet been
deleted by uCDN or expired and removed by dCDN.
In order to allow uCDN to check status of multiple jobs in a single
request, dCDN shall also maintain collections representing filtered
views of the collection of all Trigger Status Resources. The
filtered collections are:
o Pending - Trigger Status Resources for triggers that have been
accepted, but not yet acted upon.
o Active - Trigger Status Resources for triggered activity that is
currently being processed in dCDN.
o Complete - Trigger Status Resources representing activity that
completed successfully.
o Failed - Trigger Status Resources representing activity that
failed.
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4. CDNI Trigger interface
This section describes an interface to enable an upstream CDN to
trigger defined activities in a downstream CDN. The interface is
intended to be independent of the set of activities defined now, or
that may be defined in future.
The CDNI Trigger interface is built on the principles of RESTful web
services. Requests are made over HTTP, and the HTTP Method defines
the operation the request would like to perform. The corresponding
HTTP Response returns the status of the operation in the HTTP Status
Code and returns the current representation of the resource (if
appropriate) in the Response Body. HTTP Responses from servers
implementing the CDNI Triggers interface that contain a response body
SHOULD include an ETag to enable validation of cached versions of
returned resources.
Servers implementing the CDNI Trigger interface MUST support the HTTP
GET, HEAD, POST and DELETE methods. The only representation
specified in this document is JSON.
Trigger Requests are POSTed to a URI in dCDN. If the trigger is
accepted by dCDN, it creates a Trigger Status Resource and returns
its URI to dCDN in an HTTP 201 response. The triggered activity can
then be monitored by uCDN using that resource and the collections
described in Section 3.
The URI that Trigger Requests should be POSTed to needs to be either
discovered by or configured in the upstream CDN. Performing a GET on
that URI retrieves a collection of the URIs of all Trigger Status
Resources. The URI of each Trigger Status Resource is also returned
to uCDN when it is created. This means all Trigger Status Resources
can be discovered, so CDNI Trigger servers are free to assign
whatever structure they desire to the URIs for CDNI Trigger
resources. CDNI Trigger clients MUST NOT make any assumptions
regarding the structure of CDNI Trigger URIs or the mapping between
CDNI Trigger objects and their associated URIs. Therefore any URIs
present in the examples below are purely illustrative and are not
intended to impose a definitive structure on CDNI Trigger interface
implementations.
The CDNI Trigger interface builds on top of HTTP, so CDNI Trigger
servers may make use of any HTTP feature when implementing the CDNI
Trigger interface. For example, a CDNI Trigger server may make use
of HTTP's caching mechanisms to indicate that the returned response/
representation has not been modified since it was last returned,
reducing the processing needed to determine whether the status of
triggered activity has changed.
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This specification is neutral with regard to the transport below the
HTTP layer. For example, is anticipated that decisions on use of
HTTPS for other CDNI interfaces will be adopted for Triggers.
Discovery of the CDNI Triggers Interface is outside the scope of this
document. It is anticipated that a common mechanism for discovery of
all CDNI interfaces will be defined.
4.1. Creating Triggers
To create a new trigger, uCDN makes an HTTP POST to the unfiltered
collection of its triggers. The request body of that POST is a
Trigger Request.
dCDN validates and authenticates that request, if it is malformed or
uCDN does not have sufficient access rights it MAY reject the request
immediately. In this case, it SHALL respond with an appropriate 4xx
HTTP error code and no resource shall be created on dCDN.
If the request is accepted, uCDN SHALL create a new Trigger Status
Resource. The HTTP response to dCDN SHALL have status code 201 and
the URI of the Trigger Status Resource in the Location header field.
The HTTP response MAY include the content of the newly created
Trigger Status Resource, this is recommended particularly in cases
where the trigger has completed immediately.
Once a Trigger Status Resource has been created dCDN MUST NOT re-use
its location, even after that resource has been removed through
deletion or expiry.
The "request" property of the Trigger Status Resource SHALL contain
the information posted in the body of the Trigger Request. Note that
this need not be a byte-for-byte copy. For example, in the JSON
representation the dCDN may re-serialise the information differently.
If the trigger is queued by dCDN for later action, the "status"
property of the Trigger Status Resource SHALL be "pending". Once
trigger processing has started the "status" SHALL be "active".
A trigger may result in no activity in dCDN if, for example, it is an
invalidate or purge request for data the dCDN has not acquired, or a
prepopulate request for data it has already acquired. In this case,
the "status" of the Trigger Status Resource shall be "complete" and
the Trigger Status Resource shall be added to the dCDN collection of
Complete Triggers.
Once created, Trigger Status Resources may be deleted by uCDN but not
modified. The dCDN MUST reject PUT and POST requests from uCDN to
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Trigger Status Resources using HTTP status code 403.
4.2. Checking Status
The uCDN has two ways to check progress of activity it has triggered
in dCDN, described in the following sections.
Because the triggers protocol is based on HTTP, Entity Tags may be
used by the uCDN as cache validators, as defined in section 3.11 of
[RFC2616], to cheaply check for change in status of a resource or
collection of resources.
The dCDN should set the cache control headers for responses to GETs
for Trigger Status Resources and Collections to indicate the
frequency it would like uCDN to poll at.
4.2.1. Polling Trigger Status Resource collections
uCDN can fetch the collection of its Trigger Status Resources, or
filtered views of that collection.
This makes it possible to poll status of all triggered activity in a
single request. If dCDN moves a Trigger Status Resource from the
Active to the Completed collection, uCDN may chose to fetch the
result of that activity.
When polling in this way, uCDN may choose to use HTTP Entity Tags to
monitor for change, rather than repeatedly fetching the whole
collection.
4.2.2. Polling Trigger Status Resources
uCDN has a reference (URI provided by the dCDN) for each Trigger
Status Resource it has created, it may fetch that resource at any
time.
This may be used to retrieve progress information, and to fetch the
result of triggered activity.
4.3. Deleting Triggers
The uCDN MAY delete Trigger Status Resources at any time, using the
HTTP DELETE method.
Once deleted, the references to a Trigger Status Resource MUST be
removed from all Trigger Status Resource collections.
If a "pending" Trigger Status Resource is deleted, dCDN SHOULD NOT
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start processing of that activity. Deleting a "pending" trigger does
not however guarantee that it is not started because, once it has
triggered activity, uCDN cannot control the timing of that activity.
Processing may, for example, start after the DELETE is sent by uCDN
and before the DELETE is processed by dCDN.
If an "active" Trigger Status Resource is deleted, dCDN MAY stop
processing the triggered activity. However, as with deletion of a
"pending" trigger, dCDN does not guarantee this.
Deletion of a "complete" or "failed" Trigger Status Resource requires
no processing in dCDN other than deletion of the resource.
4.4. Expiry of Trigger Status Resources
The dCDN MAY choose to automatically delete Trigger Status Resources
some time after they become completed or failed. In this case, dCDN
will remove the resource and respond to subsequent requests for it
with HTTP status 404 or 410.
If dCDN performs this housekeeping, it MUST have reported the length
of time after which completed Trigger Status Resources become stale
via a property of the collection of all Trigger Status Resources. It
is recommended that Trigger Status Resources are automatically
deleted 24 hours after they become completed or failed.
To ensure it has access to the status of its completed and failed
triggers, it is recommended that uCDN's polling interval is half the
time after which records for completed activity will be considered
stale.
5. Properties of Triggers
5.1. Properties of Trigger Requests
Properties of Trigger Requests are defined in the following
subsections.
Property: type
Description: This property defines the type of the trigger:
Type: TriggerType
Mandatory: Yes
Property: metadata.urls
Description: The uCDN URL for the metadata the trigger applies
to.
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Type: URLs
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty.
Property: content.urls
Description: URLs of content data the trigger applies to, see
Section 5.1.1.
Type: URLs
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty.
Property: metadata.patterns
Description: The metadata the trigger applies to.
Type: UrlPatterns
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty, and metadata.patterns MUST NOT
be present if the TriggerType is Preposition.
Property: content.patterns
Description: The content data the trigger applies to.
Type: UrlPatterns
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty, and content.patterns MUST NOT be
present if the TriggerType is Preposition.
5.1.1. Content URLs
Once interfaces for metadata and request routing interfaces have been
agreed, it will be possible to define a way to make reference to
content. That form of reference will be used in Trigger Requests.
Some possible options for content references are:
o Canonical URL - a reference to the content that is shared by all
Interconnected CDNs. A potential problem is that the URL visible
to dCDN may have been modified by uCDN during request redirection.
o Origin URL - the URL from which dCDN acquired the content. May be
different in each CDN as each dCDN may use its uCDN as the origin.
o Metadata URL - some portion of the metadata served to uCDN by dCDN
will describe content, it would be possible to refer to content
fetched as a result of that metadata description.
If the Content URL is modifed by uCDN, it is uCDN's responsibility to
translate and pass-on Trigger Requests relating to that content using
appropriately modified Content URLs.
5.2. Properties of Trigger Status Resources
Property: trigger
Description: The properties of trigger request that created
this record.
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Type: TriggerRequest
Mandatory: Yes
Property: ctime
Description: Time at which the request was received by dCDN.
Time is local to dCDN, there is no requirement to synchronise
clocks between interconnected CDNs.
Type: AbsoluteTime
Mandatory: Yes
Property: mtime
Description: Time at which the resource was last modified.
Time is local to dCDN, there is no requirement to synchronise
clocks between interconnected CDNs.
Type: AbsoluteTime
Mandatory: Yes
Property: etime
Description: Estimate of the time at which dCDN expects to
complete the activity. Time is local to dCDN, there is no
requirement to synchronise clocks between interconnected CDNs.
Type: AbsoluteTime
Mandatory: No
Property: status
Description: Current status of the triggered activity.
Type: TriggerStatus
Mandatory: Yes
Property: error
Description: Error indication.
Type: (To be decided - a set of standard error conditions needs
to be defined. The namespace for these errors codes should
allow vendor-defined error codes for extension of the protocol.
This may allow, for example, for the definition of more
specific error codes when two CDNs supplied by the same vendor
are interconnected.)
Mandatory: No, and only allowed when "status" is "Failed".
5.3. Properties of Trigger Collections
Property: links
Description: References to Trigger Status Resources in the
collection.
Type: List of Relationships.
Mandatory: Yes
Property: staleresourcetime
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Description: The length of time for which dCDN guarantees to
keep a completed Trigger Status Resource. After this time,
dCDN MAY delete the resource and all references to it from
collections.
Type: Integer, time in seconds.
Mandatory: Yes, in the collection of all Trigger Status
Resources if dCDN deletes stale entries. If the property is
present in the filtered collections, it MUST have the same
value as in the collection of all Trigger Status Resources.
5.4. Trigger Resource Simple Data Type Descriptions
This section describes the simpler data types that are used for
properties of Trigger Status resources.
5.4.1. TriggerType
This type defines the type of action being triggered, permitted
actions are:
o Preposition - a request for dCDN to acquire metadata or content.
o Invalidate - a request for dCDN to invalidate metadata or content.
After servicing this request the dCDN will not use the specified
data without first re-validating it using, for example, an "If-
None-Match" HTTP request. The dCDN need not erase the associated
data.
o Purge - a request for dCDN to erase metadata or content. After
servicing the request, the specified data must not be held on
dCDN.
5.4.2. TriggerStatus
This type describes the current status of a Trigger, possible values
are:
o Pending - the trigger has not yet been acted upon.
o Active - the trigger is currently being acted upon.
o Complete - the triggered activity completed successfully.
o Failed - the triggered activity could not be completed.
5.4.3. URLs
This type describes a set of references to metadata or content, it is
simply a list of absolute URLs.
5.4.4. UrlPatterns
This type describes a reference to a set of metadata or content. It
is a set of 'pattern.string' properties each of which has an optional
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'pattern.flags'.
The intention is to align this with the pattern matching capabilities
of the CDNI metadata interface, once defined. This current
definition is based on that in [I-D.jenkins-cdni-metadata].
Property: pattern.string
Description: String to match against the URL of metadata or
content, i.e. a [RFC3986] path-absolute.
Type: Pattern
Mandatory: Yes
Property: pattern.flags
Description: Flags to control the pattern match.
Type: PatternFlags
Mandatory: No (default Case-sensitive infix matching)
5.4.5. AbsoluteTime
Times are expressed in seconds since the UNIX epoch.
6. JSON Encoding of Objects
This encoding is based on that described in
[I-D.jenkins-cdni-metadata], but has been reproduced here while
metadata work is in progress. Once that work is complete, the
authors would look to align with the structure of the metadata draft
and make reference to common definitions as appropriate.
The "base" encoding for a CDNI Trigger object is a JSON object
containing a dictionary of (key,value) pairs where the keys are the
property names and the values are the associated property values.
The keys of the dictionary are the names of the properties associated
with the object and are therefore dependent on the specific object
being encoded (i.e. dependent on the MIME Media Type of the returned
resource). Likewise, the values associated with each key are
dependent on the specific object being encoded (i.e. dependent on the
MIME Media Type of the returned resource).
Dictionary keys in JSON are case sensitive and therefore any
dictionary key defined by this document (for example the names of
CDNI Triggers object properties) MUST always be represented in
lowercase.
In addition to the properties of the object, the following additional
keys may be present.
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Key: base
Description: Provides a prefix for any relative URLs in the
object. This is similar to the XML base tag [XML-BASE]. If
absent, all URLs in the remainder of the document must be
absolute URLs.
Type: URI
Mandatory: No
Key: links
Description: The relationships of this object to other
addressable objects.
Type: List of Relationships.
Mandatory: Yes
6.1. JSON Encoding of Embedded Types
6.1.1. TriggerType
Key: type
Description: One of "preposition", "invalidate" or "purge".
Type: string
Mandatory: Yes
6.1.2. TriggerStatus
Key: status
Description: One of "pending", "active", "failed", "complete"
Type: string
Mandatory: Yes
6.1.3. Metadata and Content References
Keys: metadata.urls, content.urls
Description: A list of URLs of the addressable objects being
referenced.
Type: URLs
Mandatory: No
Keys: metadata.patterns, content.patterns
Description: A list of patterns to match against URLs of
objects being referenced.
Type: list of Patterns
Mandatory: No
6.1.4. Pattern
JSON: A dictionary with two keys, "pattern.string" and
"pattern.flags":
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Key: pattern.string
Description: The string to match URLs against.
Type: string
Mandatory: Yes
Key: pattern.flags
Description: A number calculated by adding together the values
associated with each flag that is set.
+ 1 - Case-insensitive
+ 2 - Prefix
+ 4 - Suffix
Type: integer
Mandatory: Yes
Example of case-insensitive prefix match against
"http://www.example.com/trailers/":
{
"pattern.string": "http://www.example.com/trailers",
"pattern.flags": 3
}
6.1.5. Relationship
JSON: A dictionary with the following keys:
o href - The URI of the of the addressable object being referenced.
o rel - The Relationship between the referring object and the object
it is referencing.
o type - The MIME Media Type of the referenced object. See
Section 6.2 for the MIME Media Types of objects specified in this
document.
o title - An optional title for the Relationship/link.
Note: The above structure follows the pattern of atom:link in
[RFC4287].
Example Relationship to a CDNI Trigger Resource within a CDNI Trigger
Collection:
{
"href": "http://triggers.cdni.example.com/trigger/12345",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
}
The format of relationship values is expected to align with other
CDNI interfaces. For example, rather than use simple names (like
"Trigger" in this case), there may be a namespace that allows well-
known and proprietary values to co-exist.
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6.2. MIME Media Types
Table 1 lists the MIME Media Type for each trigger object (resource)
that is retrievable through the CDNI Trigger interface.
Note: A prefix of "vnd.cdni" is used, however it is expected that a
more appropriate prefix will be used if the CDNI WG accepts this
document.
+-------------------+-----------------------------------------------+
| Data Object | MIME Media Type |
+-------------------+-----------------------------------------------+
| TriggerStatus | application/ |
| | vnd.cdni.control.trigger.status+json |
| TriggerCollection | application/ |
| | vnd.cdni.control.trigger.collection+json |
+-------------------+-----------------------------------------------+
Table 1: MIME Media Types for CDNI Trigger resources
7. Examples
The following sections provide examples of different CDNI Trigger
objects encoded as JSON.
No authentication is shown in the following illustrative examples, it
is anticipated that authentication mechanisms will be aligned with
other CDNI Interfaces as and when those mechanisms are defined.
Discovery of the triggers interface is out of scope of this document.
In an implementation, all URLs are under control of dCDN and the uCDN
must not attempt to ascribe any meaning to individual elements of the
path. In examples in this section, the following URLs are used as
the location of the collections of triggers:
o Collection of all Triggers belonging to one uCDN:
http://dcdn.example.com/triggers
o Filtered collections:
Pending: http://dcdn.example.com/triggers/pending
Active: http://dcdn.example.com/triggers/active
Complete: http://dcdn.example.com/triggers/complete
Failed: http://dcdn.example.com/triggers/failed
7.1. Creating Triggers
Examples of uCDN triggering activity in dCDN:
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7.1.1. Preposition
An example of a preposition request, a POST to the "AllTriggers"
collection.
Note that a preposition request must not include any
"metadata.patterns" or "content.patterns":
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REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/vnd.cdni.control.trigger.request+json
Content-Length: 277
{
"type": "preposition",
"metadata.urls" : [ "http://metadata.example.com/a/b/c" ],
"content.urls" : [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Length: 472
Content-Type: application/vnd.cdni.control.trigger.status+json
Location: http://dcdn.example.com/triggers/0
Server: example-server/0.1
{
"ctime": 1330543067,
"etime": 1330543073,
"mtime": 1330543067,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
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7.1.2. Invalidate
An example of an invalidate request, another POST to the
"AllTriggers" collection. This instructs dCDN to re-validate the
content at "http://www.example.com/a/index.html", as well as any
metadata and content whose URLs are prefixed by
"http://metadata.example.com/a/b/" and "http://www.example.com/a/b/"
respectively, using case-insensitive matching.
REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/vnd.cdni.control.trigger.request+json
Content-Length: 337
{
"type": "invalidate",
"metadata.patterns" : [
{ "pattern.string" : "http://metadata.example.com/a/b/",
"pattern.flags" : 3 }
],
"content.urls" : [ "http://www.example.com/a/index.html" ],
"content.patterns" : [
{ "pattern.string" : "http://www.example.com/a/b/",
"pattern.flags" : 3 }
]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Length: 596
Content-Type: application/vnd.cdni.control.trigger.status+json
Location: http://dcdn.example.com/triggers/1
Server: example-server/0.1
{
"ctime": 1330543067,
"etime": 1330543073,
"mtime": 1330543067,
"status": "pending",
"trigger": {
"content.patterns": [
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{
"pattern.flags": 3,
"pattern.string": "http://www.example.com/a/b/"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern.flags": 3,
"pattern.string": "http://metadata.example.com/a/b/"
}
],
"type": "invalidate"
}
}
7.2. Examining Trigger Status
Once triggers have been created, uCDN can check their status as shown
in these examples.
7.2.1. Collection of All Triggers
The uCDN can fetch the set of all the triggers it has created and
which have not yet been deleted or removed as expired. After
creation of the "preposition" and "invalidate" triggers shown above,
this collection might look as follows:
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REQUEST:
GET /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 418
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "-1621644187315998047"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [
{
"href": "http://dcdn.example.com/triggers/0",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
},
{
"href": "http://dcdn.example.com/triggers/1",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
}
],
"staleresourcetime": 86400
}
7.2.2. Filtered Collections of Triggers
The filtered collections are also available to uCDN. Before dCDN
starts processing the two triggers shown above, both will appear in
the collection of Pending Triggers, for example:
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REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 418
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "8328231265607503653"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [
{
"href": "http://dcdn.example.com/triggers/0",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
},
{
"href": "http://dcdn.example.com/triggers/1",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
}
],
"staleresourcetime": 86400
}
At this point, if no other triggers had been created, the other
filtered views of the triggers would be empty. For example:
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REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 53
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "-654105208640281650"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [],
"staleresourcetime": 86400
}
7.2.3. Trigger Status Resources
The Trigger Status Resources can also be examined for detail about
individual triggers. For example, for the "preposition" and
"invalidate" triggers from previous examples:
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REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 472
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "-3658577240367174361"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.status+json
{
"ctime": 1330543067,
"etime": 1330543073,
"mtime": 1330543067,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
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REQUEST:
GET /triggers/1 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 596
Expires: Wed, 29 Feb 2012 19:18:48 GMT
Server: example-server/0.1
ETag: "-603388197619127031"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:48 GMT
Content-Type: application/vnd.cdni.control.trigger.status+json
{
"ctime": 1330543067,
"etime": 1330543073,
"mtime": 1330543067,
"status": "pending",
"trigger": {
"content.patterns": [
{
"pattern.flags": 3,
"pattern.string": "http://www.example.com/a/b/"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern.flags": 3,
"pattern.string": "http://metadata.example.com/a/b/"
}
],
"type": "invalidate"
}
}
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7.2.4. Polling for Change
The uCDN may use the Entity Tags of collections or resources when
polling for change in status, as shown in the following examples:
REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "8328231265607503653"
RESPONSE:
HTTP/1.1 304 Not Modified
Content-Length: 0
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "8328231265607503653"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "-3658577240367174361"
RESPONSE:
HTTP/1.1 304 Not Modified
Content-Length: 0
Expires: Wed, 29 Feb 2012 19:18:47 GMT
Server: example-server/0.1
ETag: "-3658577240367174361"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:47 GMT
Content-Type: application/vnd.cdni.control.trigger.status+json
When the triggered activity is complete, the contents of the filtered
collections will be updated, along with their Entity Tags. For
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example, when the two example triggers are complete, the collections
of pending and complete triggers may look like:
REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 53
Expires: Wed, 29 Feb 2012 19:18:56 GMT
Server: example-server/0.1
ETag: "-7056231826368088123"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:56 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [],
"staleresourcetime": 86400
}
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REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 418
Expires: Wed, 29 Feb 2012 19:18:56 GMT
Server: example-server/0.1
ETag: "1388228818267892536"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:56 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [
{
"href": "http://dcdn.example.com/triggers/0",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
},
{
"href": "http://dcdn.example.com/triggers/1",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
}
],
"staleresourcetime": 86400
}
7.2.5. Cancelling or Removing a Trigger
To request dCDN to cancel a Trigger, uCDN may delete the Trigger
Resource. It may also delete completed and failed triggers to reduce
the size of the collections. For example, to remove the
"preposition" request from earlier examples:
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REQUEST:
DELETE /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 204 No Content
Date: Wed, 29 Feb 2012 19:17:56 GMT
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Server: example-server/0.1
This would, for example, cause the collection of completed triggers
shown in the example above to be updated to:
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 237
Expires: Wed, 29 Feb 2012 19:18:57 GMT
Server: example-server/0.1
ETag: "-8850203857096517156"
Cache-Control: max-age=60
Date: Wed, 29 Feb 2012 19:17:57 GMT
Content-Type: application/vnd.cdni.control.trigger.collection+json
{
"links": [
{
"href": "http://dcdn.example.com/triggers/1",
"rel": "Trigger",
"type": "application/vnd.cdni.control.trigger.status+json"
}
],
"staleresourcetime": 86400
}
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8. IANA Considerations
TBD.
9. Security Considerations
The dCDN must ensure that each uCDN only has access to its own
Trigger Status Resources.
It is anticipated that a common authentication mechanism will be used
by this and other CDNI Interconnect interfaces, the mechanism must
exist but is not identified in this document.
The dCDN must ensure that activity triggered by uCDN only affects
metadata or content originating from that uCDN.
10. Acknowledgements
TBD.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
11.2. Informative References
[I-D.davie-cdni-framework]
Davie, B. and L. Peterson, "Framework for CDN
Interconnection", draft-davie-cdni-framework-01 (work in
progress), October 2011.
[I-D.ietf-cdni-problem-statement]
Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
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Statement", draft-ietf-cdni-problem-statement-03 (work in
progress), January 2012.
[I-D.ietf-cdni-requirements]
Leung, K. and Y. Lee, "Content Distribution Network
Interconnection (CDNI) Requirements",
draft-ietf-cdni-requirements-02 (work in progress),
December 2011.
[I-D.jenkins-cdni-metadata]
Niven-Jenkins, B., Ferguson, D., and G. Watson, "CDN
Interconnect Metadata", draft-jenkins-cdni-metadata-00
(work in progress), September 2011.
[RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, December 2005.
[XML-BASE]
Marsh, J., Ed. and R. Tobin, Ed., "XML Base (Second
Edition) - http://www.w3.org/TR/xmlbase/", January 2009.
Authors' Addresses
Rob Murray
Velocix (Alcatel-Lucent)
326 Cambridge Science Park
Milton Road, Cambridge CB4 0WG
UK
Email: rmurray@velocix.com
Ben Niven-Jenkins
Velocix (Alcatel-Lucent)
326 Cambridge Science Park
Milton Road, Cambridge CB4 0WG
UK
Email: ben@velocix.com
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