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Messaging services

Messaging services

Aug 18, 2016

Questions

  • When we send emails to users, should we download the body of the email and send it in the email body?  Or should we tell them to visit the portal?

    • At the moment, the body of the email == the body of the message.  And files are assumed to be stored as plain text.

  •  Should notifications of this nature be implemented now or later?

    • Also, if the affected entity has child entities, should those be included in the notification?

  • How should we tie Entities to users in terms of notifications?

    • Ownership?  << It might be this.

    • Favorites? << It might be this.

    • Permissions?  << I don't think it's this.

    • Something else?  << It could be a completely new set of services, allowing users to enable/disable notification.  (Could be initialized from Favorites and Owners.)

Objects

Name

DBO

Migration

DTO

MessageContent

(Immutable after creation)

  • Primary key: ID

  • Foreign key: CreatedBy (UserGroup)

  • Foreign key: MessageBody (S3 File Handle ID)

  • Etag

  • CreatedOn

Backup via ID

Note:  Etag is required because MessageStatus is mutable.

Interface

  • ID

  • CreatedBy (principal ID)

  • S3 File Handle ID

  • CreatedOn

MessageToUser

(Immutable after creation)

  • Foreign key: ID (MessageContent)

  • Subject (nullable)

  • Self foreign key: InReplyTo (ID) (nullable)

  • Foreign key: InReplyToRootId

    • Recursive foreign key to primary key

     

Secondary to MessageContent

Implements MessageContent

  • Subject (string, optional)

  • Set of recipient IDs

  • inReplyTo (optional)

  • inReplyToRoot (optional)

MessageRecipient

(Immutable after creation)

  • Foreign key: ID (MessageContent)

  • Foreign key: Recipient ID (UserGroup)

Secondary to MessageContent

 

MessageStatus

  • Foreign key: ID (MessageContent)

  • Foreign key: Recipient ID (UserGroup)

  • States: UNREAD, READ, ARCHIVED

Secondary to MessageContent

  • ID

  • Recipient

  • State

Comment

(Immutable after creation)

  • Foreign key: ID (MessageContent)

  • Target type (Enum ObjectType)

  • Target ID

TBD:  references to other Comments in the conversation*

Secondary to MessageContent

Implements MessageContent

  • Target type

  • Target ID

MessagingSettings

Part of UserProfile

Use existing services to support this

Secondary to UserGroup

Should email be sent?
Should emailed messages be READ automatically?
Other options (as necessary)
Blacklist of blocked users
CommentVotes

  • Primary key: Message ID

  • Up votes

  • Down votes

  • Is-comment-inappropriate votes

TBD

  • ID

  • Up

  • Down

MessageBundle

 

 

Bundles the MessageToUser and Message Status

MessageRecipientSet

 

 

  • Set of recipient IDs

'* per Marcel, Comments may have a more complex set of references/relationships than Messages to Users have.  Rather than just 'inReplyTo', it might be that one Comment is an 'answer' to another comment which is a question.  Further, the multiple answers to a question may have 'previous' references which order them.

Other TODOs

Throttle message input 

  • Max 10 creations per minute

  • Max 50 recipients

When adding a new person to a conversation, the new person should get the whole history of the conversation

  • Might be implemented by forwarding ALL the previous messages 

  • OR by concatenating all previous into one new message

Configure Amazon SES

  • Automated proposal:

    • Reroute bounce and complaints to SNS

    • Have a worker subscribe to the topic via SQS

    • Have a worker disable emails to hard-bounced recipients

    • The worker may email a Google Group to notify us of anything it cannot handle

    • Also flip flags in settings for complaints

    • Store the bounce/complaint in a blob 

Add methods to send messages according to templates

  • Each individual Message should be stored in its final form.  

  • This design choice would change for very very large notification message volumes.

  • Templates:

    Password reset
    Welcome
    Delivery failure
    Entity shared
    Entity changed
    TBD

Message sender (worker)

Extend ObjectType to include a "MESSAGE" type
Have DBOMessage extend ObservableEntity
Send a change message when a message is created
Subscribe worker to the repo-changes topic
Look for MESSAGE-CREATED changes to process
The worker should always check to see if a message has already been sent, so that messages do not get resent every time the stack changes.
Whenever the message sending worker encounters an error:
Send the sender of the message a notification with the summary of delivery failures
Add CloudWatch metrics to count delivery failures
If the message cannot be sent to anyone, mark the sender as the receiver of the message so that it doesn't get reprocessed (i.e. after migration)
Process change of other ObjectTypes (i.e. ENTITY) for notifications
Needs additional state: either a link between ObjectID/Type and messageContent or ObjectID/Type and UserID (to prevent messages from being resent everytime the stack blows away the change messages)

Services

  • Sorting & Pagination

    Sort by creation date
    Sort by subject
    Sort by recipient name

 

Method

URI

Body

Parameters

Return

Description

Permission

POST

/message

MessageToUser

 

MessageToUser

Sends a message.  Note, message delivery permission is on a recipient-by-recipient basis, asynchronous to the message creation.  Unauthorized delivery may result in silent failure or a bounce message (TBD).

Authenticated User

 

Must be admin to send to AUTH_USERS

Must have SEND_MESSAGE permission on team to send to team

GET

/message/inbox

 

Sorting + pagination

Paginated results<MessageBundle>

Gets all messages the authenticated user has received

Authenticated User

GET

/message/outbox

 

Sorting + pagination

Paginated results<MessageToUser>

Gets all messages the authenticated user has sent

Authenticated User

GET

/message/{id}

 

 

MessageToUser

Gets a specific message

Sender or Receiver

POST

/message/{id}/forward

MessageRecipientSet

 

MessageToUser

Forwards a message to other recipients. This is equivalent to getting a (visible) message and POST-ing it to /message with a different set of recipients

Sender or Receiver

GET

/message/{id}/conversation

 

Sorting + pagination

Paginated results<MessageToUser>

Gets messages belonging in the same thread as the message ID.  The list is filtered according to the user's ID.

Sender or Receiver

POST

/message/{id}/conversation/forward

MessageRecipientSet

 

 

Adds the set of recipients to the conversation by marking each recipient as a receiver of each message within the conversation.

Should each recipient be sent the messages (i.e. via email)?

Or should a notification be sent instead?

Sender or Receiver

PUT

/message/status

MessageStatus

 

 

Marks a message as:

  • READ

  • UNREAD

  • ARCHIVED

Receiver

GET

/message/{id}/file

 

 

(Redirect)

Checks to see if the user can read the message and then redirects to the actual URL of the file associated with the message

Sender or Receiver

POST

/entity/{id}/message

MessageToUser

 

MessageToUser

Sends a message to the creator or administrator of the given entity. This allows users to ask for permission to see restricted entities.

Added per

Authenticated user

POST

/entity/{id}/comment

Comment

 

Comment

Method for commenting on an entity.

Authenticated user with SEND_MESSAGE permission on entity

GET

/entity/{id}/comment

 

Sorting + pagination

Paginated results<Comment>

Gets messages belonging to the thread tied to the entity.

Authenticated user with READ permission on entity