pubsub-module.rst

================== 
PubSub Sync Module
==================

.. versionadded:: Nautilus

.. contents::

This sync module provides a publish and subscribe mechanism for the object store modification
events. Events are published into predefined topics. Topics can be subscribed to, and events
can be pulled from them. Events need to be acked. Also, events will expire and disappear
after a period of time. 

A push notification mechanism exists too, currently supporting HTTP,
AMQP0.9.1 and Kafka endpoints. In this case, the events are pushed to an endpoint on top of storing them in Ceph. If events should only be pushed to an endpoint
and do not need to be stored in Ceph, the `Bucket Notification`_ mechanism should be used instead of pubsub sync module. 

A user can create different topics. A topic entity is defined by its user and its name. A
user can only manage its own topics, and can only subscribe to events published by buckets
it owns.

In order to publish events for specific bucket a notification entity needs to be created. A
notification can be created on a subset of event types, or for all event types (default).
There can be multiple notifications for any specific topic, and the same topic could be used for multiple notifications.

A subscription to a topic can also be defined. There can be multiple subscriptions for any
specific topic.

REST API has been defined to provide configuration and control interfaces for the pubsub
mechanisms. This API has two flavors, one is S3-compatible and one is not. The two flavors can be used
together, although it is recommended to use the S3-compatible one. 
The S3-compatible API is similar to the one used in the bucket notification mechanism.

Events are stored as RGW objects in a special bucket, under a special user. Events cannot
be accessed directly, but need to be pulled and acked using the new REST API.

.. toctree::
   :maxdepth: 1

   S3 Bucket Notification Compatibility <s3-notification-compatibility>

PubSub Zone Configuration
-------------------------

The pubsub sync module requires the creation of a new zone in a :ref:`multisite` environment...
First, a master zone must exist (see: :ref:`master-zone-label`), 
then a secondary zone should be created (see :ref:`secondary-zone-label`).
In the creation of the secondary zone, its tier type must be set to ``pubsub``:

::

   # radosgw-admin zone create --rgw-zonegroup={zone-group-name} \
                               --rgw-zone={zone-name} \
                               --endpoints={http://fqdn}[,{http://fqdn}] \
                               --sync-from-all=0 \
                               --sync-from={master-zone-name} \
                               --tier-type=pubsub


PubSub Zone Configuration Parameters
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                
::

   {
       "tenant": <tenant>,             # default: <empty>
       "uid": <uid>,                   # default: "pubsub"
       "data_bucket_prefix": <prefix>  # default: "pubsub-"
       "data_oid_prefix": <prefix>     #
       "events_retention_days": <days> # default: 7
   }

* ``tenant`` (string)

The tenant of the pubsub control user.

* ``uid`` (string)

The uid of the pubsub control user.

* ``data_bucket_prefix`` (string)

The prefix of the bucket name that will be created to store events for specific topic.

* ``data_oid_prefix`` (string)

The oid prefix for the stored events.

* ``events_retention_days`` (integer)

How many days to keep events that weren't acked.

Configuring Parameters via CLI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The tier configuration could be set using the following command:

::

   # radosgw-admin zone modify --rgw-zonegroup={zone-group-name} \
                                --rgw-zone={zone-name} \
                                --tier-config={key}={val}[,{key}={val}]

Where the ``key`` in the configuration specifies the configuration variable that needs to be updated (from the list above), and
the ``val`` specifies its new value. For example, setting the pubsub control user ``uid`` to ``user_ps``:

::

   # radosgw-admin zone modify --rgw-zonegroup={zone-group-name} \
                                --rgw-zone={zone-name} \
                                --tier-config=uid=pubsub

A configuration field can be removed by using ``--tier-config-rm={key}``.


Topic and Subscription Management via CLI
-----------------------------------------

Configuration of all topics of a user could be fetched using the following command:
   
::
   
   # radosgw-admin topic list --uid={user-id}


Configuration of a specific topic could be fetched using:

::
   
   # radosgw-admin topic get --uid={user-id} --topic={topic-name}


And removed using:

::
   
   # radosgw-admin topic rm --uid={user-id} --topic={topic-name}


Configuration of a subscription could be fetched using:

::
   
   # radosgw-admin subscription get --uid={user-id} --subscription={topic-name}

And removed using:

::
   
   # radosgw-admin subscription rm --uid={user-id} --subscription={topic-name}


To fetch all of the events stored in a subcription, use:

::
   
   # radosgw-admin subscription pull --uid={user-id} --subscription={topic-name} [--marker={last-marker}]


To ack (and remove) an event from a subscription, use:

::
   
   # radosgw-admin subscription ack --uid={user-id} --subscription={topic-name} --event-id={event-id}


PubSub Performance Stats
-------------------------
Same counters are shared between the pubsub sync module and the notification mechanism.

- ``pubsub_event_triggered``: running counter of events with at lease one topic associated with them
- ``pubsub_event_lost``: running counter of events that had topics and subscriptions associated with them but that were not stored or pushed to any of the subscriptions
- ``pubsub_store_ok``: running counter, for all subscriptions, of stored events 
- ``pubsub_store_fail``: running counter, for all subscriptions, of events failed to be stored
- ``pubsub_push_ok``: running counter, for all subscriptions, of events successfully pushed to their endpoint
- ``pubsub_push_fail``: running counter, for all subscriptions, of events failed to be pushed to their endpoint
- ``pubsub_push_pending``: gauge value of events pushed to an endpoint but not acked or nacked yet

.. note:: 

    ``pubsub_event_triggered`` and ``pubsub_event_lost`` are incremented per event, while: 
    ``pubsub_store_ok``, ``pubsub_store_fail``, ``pubsub_push_ok``, ``pubsub_push_fail``, are incremented per store/push action on each subscriptions.

PubSub REST API
---------------

.. tip:: PubSub REST calls, and only them, should be sent to an RGW which belong to a PubSub zone

Topics
~~~~~~
 
.. _radosgw-create-a-topic:

Create a Topic
``````````````

This will create a new topic. Topic creation is needed both for both flavors of the API.
Optionally the topic could be provided with push endpoint parameters that would be used later
when an S3-compatible notification is created.
Upon successful request, the response will include the topic ARN that could be later used to reference this topic in an S3-compatible notification request. 
To update a topic, use the same command used for topic creation, with the topic name of an existing topic and different endpoint values.

.. tip:: Any S3-compatible notification already associated with the topic needs to be re-created for the topic update to take effect 

::

   PUT /topics/<topic-name>[?OpaqueData=<opaque data>][&push-endpoint=<endpoint>[&amqp-exchange=<exchange>][&amqp-ack-level=none|broker|routable][&verify-ssl=true|false][&kafka-ack-level=none|broker][&use-ssl=true|false][&ca-location=<file path>]]

Request parameters:

- push-endpoint: URI of an endpoint to send push notification to
- OpaqueData: opaque data is set in the topic configuration and added to all notifications triggered by the ropic

The endpoint URI may include parameters depending with the type of endpoint:

- HTTP endpoint 

 - URI: ``http[s]://<fqdn>[:<port]``
 - port defaults to: 80/443 for HTTP/S accordingly
 - verify-ssl: indicate whether the server certificate is validated by the client or not ("true" by default)

- AMQP0.9.1 endpoint

 - URI: ``amqp://[<user>:<password>@]<fqdn>[:<port>][/<vhost>]``
 - user/password defaults to: guest/guest
 - user/password may only be provided over HTTPS. Topic creation request will be rejected if not
 - port defaults to: 5672
 - vhost defaults to: "/"
 - amqp-exchange: the exchanges must exist and be able to route messages based on topics (mandatory parameter for AMQP0.9.1). Different topics pointing to the same endpoint must use the same exchange
 - amqp-ack-level: no end2end acking is required, as messages may persist in the broker before delivered into their final destination. Three ack methods exist:

  - "none": message is considered "delivered" if sent to broker
  - "broker": message is considered "delivered" if acked by broker (default)
  - "routable": message is considered "delivered" if broker can route to a consumer

.. tip:: The topic-name (see :ref:`radosgw-create-a-topic`) is used for the AMQP topic ("routing key" for a topic exchange)

- Kafka endpoint 

 - URI: ``kafka://[<user>:<password>@]<fqdn>[:<port]``
 - if ``use-ssl`` is set to "true", secure connection will be used for connecting with the broker ("false" by default)
 - if ``ca-location`` is provided, and secure connection is used, the specified CA will be used, instead of the default one, to authenticate the broker
 - user/password may only be provided over HTTPS. Topic creation request will be rejected if not
 - user/password may only be provided together with ``use-ssl``, connection to the broker would fail if not
 - port defaults to: 9092
 - kafka-ack-level: no end2end acking is required, as messages may persist in the broker before delivered into their final destination. Two ack methods exist:

  - "none": message is considered "delivered" if sent to broker
  - "broker": message is considered "delivered" if acked by broker (default)

The topic ARN in the response will have the following format:

::

   arn:aws:sns:<zone-group>:<tenant>:<topic>

Get Topic Information
`````````````````````

Returns information about specific topic. This includes subscriptions to that topic, and push-endpoint information, if provided.

::

   GET /topics/<topic-name>

Response will have the following format (JSON):

::

   {
       "topic":{
           "user":"",
           "name":"",
           "dest":{
               "bucket_name":"",
               "oid_prefix":"",
               "push_endpoint":"",
               "push_endpoint_args":"",
               "push_endpoint_topic":""
           },
           "arn":""
           "opaqueData":""
       },
       "subs":[]
   }             

- topic.user: name of the user that created the topic
- name: name of the topic
- dest.bucket_name: not used
- dest.oid_prefix: not used
- dest.push_endpoint: in case of S3-compliant notifications, this value will be used as the push-endpoint URL
- if push-endpoint URL contain user/password information, request must be made over HTTPS. Topic get request will be rejected if not 
- dest.push_endpoint_args: in case of S3-compliant notifications, this value will be used as the push-endpoint args
- dest.push_endpoint_topic: in case of S3-compliant notifications, this value will hold the topic name as sent to the endpoint (may be different than the internal topic name)
- topic.arn: topic ARN
- subs: list of subscriptions associated with this topic

Delete Topic
````````````

::

   DELETE /topics/<topic-name>

Delete the specified topic.

List Topics
```````````

List all topics that user defined.

::

   GET /topics
 
- if push-endpoint URL contain user/password information, in any of the topic, request must be made over HTTPS. Topic list request will be rejected if not 

S3-Compliant Notifications
~~~~~~~~~~~~~~~~~~~~~~~~~~

Detailed under: `Bucket Operations`_.

.. note:: 

    - Notification creation will also create a subscription for pushing/pulling events
    - The generated subscription's name will have the same as the notification Id, and could be used later to fetch and ack events with the subscription API.
    - Notification deletion will deletes all generated subscriptions
    - In case that bucket deletion implicitly deletes the notification, 
      the associated subscription will not be deleted automatically (any events of the deleted bucket could still be access),
      and will have to be deleted explicitly with the subscription deletion API
    - Filtering based on metadata (which is an extension to S3) is not supported, and such rules will be ignored
    - Filtering based on tags (which is an extension to S3) is not supported, and such rules will be ignored


Non S3-Compliant Notifications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Create a Notification
`````````````````````

This will create a publisher for a specific bucket into a topic.

::

   PUT /notifications/bucket/<bucket>?topic=<topic-name>[&events=<event>[,<event>]]

Request parameters:

- topic-name: name of topic
- event: event type (string), one of: ``OBJECT_CREATE``, ``OBJECT_DELETE``, ``DELETE_MARKER_CREATE``
 
Delete Notification Information
```````````````````````````````

Delete publisher from a specific bucket into a specific topic.

::

   DELETE /notifications/bucket/<bucket>?topic=<topic-name>

Request parameters:

- topic-name: name of topic

.. note:: When the bucket is deleted, any notification defined on it is also deleted

List Notifications
``````````````````

List all topics with associated events defined on a bucket.

::

   GET /notifications/bucket/<bucket>

Response will have the following format (JSON):

::

   {"topics":[
      {
         "topic":{
            "user":"",
            "name":"",
            "dest":{
               "bucket_name":"",
               "oid_prefix":"",
               "push_endpoint":"",
               "push_endpoint_args":"",
               "push_endpoint_topic":""
            }
            "arn":""
         },
         "events":[]
      }
    ]}            

Subscriptions
~~~~~~~~~~~~~

Create a Subscription
`````````````````````

Creates a new subscription.

::

   PUT /subscriptions/<sub-name>?topic=<topic-name>[?push-endpoint=<endpoint>[&amqp-exchange=<exchange>][&amqp-ack-level=none|broker|routable][&verify-ssl=true|false][&kafka-ack-level=none|broker][&ca-location=<file path>]]

Request parameters:

- topic-name: name of topic
- push-endpoint: URI of endpoint to send push notification to

The endpoint URI may include parameters depending with the type of endpoint:

- HTTP endpoint 

 - URI: ``http[s]://<fqdn>[:<port]``
 - port defaults to: 80/443 for HTTP/S accordingly
 - verify-ssl: indicate whether the server certificate is validated by the client or not ("true" by default)

- AMQP0.9.1 endpoint

 - URI: ``amqp://[<user>:<password>@]<fqdn>[:<port>][/<vhost>]``
 - user/password defaults to : guest/guest
 - port defaults to: 5672
 - vhost defaults to: "/"
 - amqp-exchange: the exchanges must exist and be able to route messages based on topics (mandatory parameter for AMQP0.9.1)
 - amqp-ack-level: no end2end acking is required, as messages may persist in the broker before delivered into their final destination. Three ack methods exist:

  - "none": message is considered "delivered" if sent to broker
  - "broker": message is considered "delivered" if acked by broker (default)
  - "routable": message is considered "delivered" if broker can route to a consumer

- Kafka endpoint 

 - URI: ``kafka://[<user>:<password>@]<fqdn>[:<port]``
 - if ``ca-location`` is provided, secure connection will be used for connection with the broker
 - user/password may only be provided over HTTPS. Topic creation request will be rejected if not
 - user/password may only be provided together with ``ca-location``. Topic creation request will be rejected if not
 - port defaults to: 9092
 - kafka-ack-level: no end2end acking is required, as messages may persist in the broker before delivered into their final destination. Two ack methods exist:

  - "none": message is considered "delivered" if sent to broker
  - "broker": message is considered "delivered" if acked by broker (default)


Get Subscription Information
````````````````````````````

Returns information about specific subscription.

::

   GET /subscriptions/<sub-name>

Response will have the following format (JSON):

::

   {
       "user":"",
       "name":"",
       "topic":"",
       "dest":{
           "bucket_name":"",
           "oid_prefix":"",
           "push_endpoint":"",
           "push_endpoint_args":"",
           "push_endpoint_topic":""
       }
       "s3_id":""
   }             

- user: name of the user that created the subscription
- name: name of the subscription
- topic: name of the topic the subscription is associated with
- dest.bucket_name: name of the bucket storing the events
- dest.oid_prefix: oid prefix for the events stored in the bucket
- dest.push_endpoint: in case of S3-compliant notifications, this value will be used as the push-endpoint URL
- if push-endpoint URL contain user/password information, request must be made over HTTPS. Topic get request will be rejected if not 
- dest.push_endpoint_args: in case of S3-compliant notifications, this value will be used as the push-endpoint args
- dest.push_endpoint_topic: in case of S3-compliant notifications, this value will hold the topic name as sent to the endpoint (may be different than the internal topic name)
- s3_id: in case of S3-compliant notifications, this will hold the notification name that created the subscription

Delete Subscription
```````````````````

Removes a subscription.

::

   DELETE /subscriptions/<sub-name>

Events
~~~~~~

Pull Events
```````````

Pull events sent to a specific subscription.

::

   GET /subscriptions/<sub-name>?events[&max-entries=<max-entries>][&marker=<marker>]

Request parameters:

- marker: pagination marker for list of events, if not specified will start from the oldest
- max-entries: max number of events to return

The response will hold information on the current marker and whether there are more events not fetched:

::

   {"next_marker":"","is_truncated":"",...}


The actual content of the response is depended with how the subscription was created.
In case that the subscription was created via an S3-compatible notification, 
the events will have an S3-compatible record format (JSON):

::

   {"Records":[  
       {
           "eventVersion":"2.1"
           "eventSource":"aws:s3",
           "awsRegion":"",
           "eventTime":"",
           "eventName":"",
           "userIdentity":{  
               "principalId":""
           },
           "requestParameters":{
               "sourceIPAddress":""
           },
           "responseElements":{
               "x-amz-request-id":"",
               "x-amz-id-2":""
           },
           "s3":{
               "s3SchemaVersion":"1.0",
               "configurationId":"",
               "bucket":{
                   "name":"",
                   "ownerIdentity":{
                       "principalId":""
                   },
                   "arn":"",
                   "id":""
               },
               "object":{
                   "key":"",
                   "size":"0",
                   "eTag":"",
                   "versionId":"",
                   "sequencer":"",
                   "metadata":[],
                   "tags":[]
               }
           },
           "eventId":"",
           "opaqueData":"",
       }
   ]}

- awsRegion: zonegroup
- eventTime: timestamp indicating when the event was triggered
- eventName: either ``s3:ObjectCreated:``, or ``s3:ObjectRemoved:``
- userIdentity: not supported 
- requestParameters: not supported
- responseElements: not supported
- s3.configurationId: notification ID that created the subscription for the event
- s3.bucket.name: name of the bucket
- s3.bucket.ownerIdentity.principalId: owner of the bucket
- s3.bucket.arn: ARN of the bucket
- s3.bucket.id: Id of the bucket (an extension to the S3 notification API)
- s3.object.key: object key
- s3.object.size: not supported
- s3.object.eTag: object etag
- s3.object.version: object version in case of versioned bucket
- s3.object.sequencer: monotonically increasing identifier of the change per object (hexadecimal format)
- s3.object.metadata: not supported (an extension to the S3 notification API)
- s3.object.tags: not supported (an extension to the S3 notification API)
- s3.eventId: unique ID of the event, that could be used for acking (an extension to the S3 notification API)
- s3.opaqueData: opaque data is set in the topic configuration and added to all notifications triggered by the ropic (an extension to the S3 notification API)

In case that the subscription was not created via a non S3-compatible notification, 
the events will have the following event format (JSON):

::

    {"events":[
       {
           "id":"",
           "event":"",
           "timestamp":"",
           "info":{
               "attrs":{
                   "mtime":""
               },
               "bucket":{
                   "bucket_id":"",
                   "name":"",
                   "tenant":""
               },
               "key":{
                   "instance":"",
                   "name":""
               }
           }
       }
   ]}

- id: unique ID of the event, that could be used for acking
- event: one of: ``OBJECT_CREATE``, ``OBJECT_DELETE``, ``DELETE_MARKER_CREATE``
- timestamp: timestamp indicating when the event was sent
- info.attrs.mtime: timestamp indicating when the event was triggered
- info.bucket.bucket_id: id of the bucket
- info.bucket.name: name of the bucket
- info.bucket.tenant: tenant the bucket belongs to
- info.key.instance: object version in case of versioned bucket
- info.key.name: object key

Ack Event
`````````

Ack event so that it can be removed from the subscription history.

::

   POST /subscriptions/<sub-name>?ack&event-id=<event-id>

Request parameters:

- event-id: id of event to be acked

.. _Bucket Notification : ../notifications
.. _Bucket Operations: ../s3/bucketops