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1 | 1 | # messaging-postgres
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2 | 2 |
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3 |
| -Postgres messaging for Eventide |
| 3 | +Eventide messaging for Postgres |
4 | 4 |
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5 |
| -## Summary |
| 5 | +## Documentation |
6 | 6 |
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7 |
| -The `messaging-postgres` library contains primitives for writing and reading messages, as well as message handlers and mixins for message schemas and stream name utilities. |
8 |
| - |
9 |
| -## Example |
10 |
| - |
11 |
| -```ruby |
12 |
| -account_id = ‘123’ |
13 |
| - |
14 |
| -deposit = Deposit.new |
15 |
| -deposit.account_id = account_id |
16 |
| -deposit.amount = 11 |
17 |
| - |
18 |
| -stream_name = StreamName.stream_name(account_id, 'account') |
19 |
| -# => 'account-123' |
20 |
| - |
21 |
| -Messaging::Postgres::Write.(deposit, stream_name) |
22 |
| - |
23 |
| -Messaging::Postgres::Read.(stream_name) do |message_data| |
24 |
| - AccountComponent::Handlers::Command.(message_data) |
25 |
| -end |
26 |
| -``` |
27 |
| - |
28 |
| -## Elements |
29 |
| - |
30 |
| -### Handlers |
31 |
| - |
32 |
| -A Handler is the mechanism that receives messages, and takes action based on them. |
33 |
| - |
34 |
| -By including `Messaging::Handle`, a class becomes a handler. By including `Messaging::Postgres::StreamName` the handler class receives some useful utilities for composing stream names from constituent parts (category and an entity's ID), and for declaring a the category name that the handler is concerned with (eg: `account`, `fundsTransfer`, `userProfile`, etc). |
35 |
| - |
36 |
| -```ruby |
37 |
| -module AccountComponent |
38 |
| - module Handlers |
39 |
| - class Commands |
40 |
| - include Messaging::Handle |
41 |
| - include Messaging::Postgres::StreamName |
42 |
| - |
43 |
| - category :account |
44 |
| - |
45 |
| - handle Deposit do |deposit| |
46 |
| - account_id = deposit.account_id |
47 |
| - |
48 |
| - time = clock.iso8601 |
49 |
| - |
50 |
| - deposited = Deposited.follow(deposit) |
51 |
| - |
52 |
| - stream_name = stream_name(account_id) |
53 |
| - |
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| - write.(deposited, stream_name, expected_version: version) |
55 |
| - end |
56 |
| - end |
57 |
| - end |
58 |
| -end |
59 |
| -``` |
60 |
| - |
61 |
| -### Messages |
62 |
| - |
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| -Messages are typically simplistic data structures that carry instructions and responses to and from services. |
64 |
| - |
65 |
| -By including `Messaging::Message`, a message class can declare attributes that will become part of a message's payload. |
66 |
| - |
67 |
| -```ruby |
68 |
| -module AccountComponent |
69 |
| - module Messages |
70 |
| - module Commands |
71 |
| - class Deposit |
72 |
| - include Messaging::Message |
73 |
| - |
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| - attribute :deposit_id, String |
75 |
| - attribute :account_id, String |
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| - attribute :amount, Numeric |
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| - attribute :time, String |
78 |
| - end |
79 |
| - end |
80 |
| - end |
81 |
| -end |
82 |
| - |
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| -deposit = AccountComponent::Messages::Commands::Deposit.new |
84 |
| - |
85 |
| -deposit.deposit_id = Identifier::UUID::Random.get |
86 |
| -deposit.account_id = account_id |
87 |
| -deposit.amount = 11 |
88 |
| -deposit.time = clock.iso8601 |
89 |
| -``` |
90 |
| - |
91 |
| -### Reading Messages |
92 |
| - |
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| -The `Messaging::Postgres::Read` class provides access to streams stored in Postgres. The reader takes a block that receives raw _message data_, and executes the block for each message data received. |
94 |
| - |
95 |
| -```ruby |
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| -stream_name = 'account-123' |
97 |
| - |
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| -Messaging::Postgres::Read.(stream_name) do |message_data| |
99 |
| - puts message_data.type |
100 |
| -end |
101 |
| -``` |
102 |
| - |
103 |
| -### Writing Messages |
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| - |
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| -The `Messaging::Postgres::Write` class writes a message to a stream. The message is converted to raw _message data_ first, then written to the data store. |
106 |
| - |
107 |
| -```ruby |
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| -deposit = AccountComponent::Messages::Commands::Deposit.new |
109 |
| - |
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| -deposit.deposit_id = Identifier::UUID::Random.get |
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| -deposit.account_id = account_id |
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| -deposit.amount = 11 |
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| -deposit.time = clock.iso8601 |
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| - |
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| -stream_name = 'account-123' |
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| - |
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| -Messaging::Postgres::Write.(deposit, stream_name) |
118 |
| -``` |
119 |
| - |
120 |
| -## Detailed Examples |
121 |
| - |
122 |
| -For a more in-depth example of the use of this library, see the example projects in the Eventide Examples org on GitHub: https://github.com/eventide-examples |
123 |
| - |
124 |
| -## Complete Documentation |
125 |
| - |
126 |
| -The complete Eventide project documentation can be found at http://eventide-project.org |
| 7 | +See the [Eventide documentation site](http://docs.eventide-project.org) for more information, examples, and user guides. |
127 | 8 |
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128 | 9 | ## License
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129 | 10 |
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