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PresenceChannel aims to be a generic system for allow the server, and end-users, to track the number and identity of users performing a specific task on the site. For example, it might be used to track who is currently 'replying' to a specific topic, editing a specific wiki post, etc.
A few key pieces of information about the system:
- PresenceChannels are identified by a name of the format `/prefix/blah`, where `prefix` has been configured by some core/plugin implementation, and `blah` can be any string the implementation wants to use.
- Presence is a boolean thing - each user is either present, or not present. If a user has multiple clients 'present' in a channel, they will be deduplicated so that the user is only counted once
- Developers can configure the existence and configuration of channels 'just in time' using a callback. The result of this is cached for 2 minutes.
- Configuration of a channel can specify permissions in a similar way to MessageBus (public boolean, a list of allowed_user_ids, and a list of allowed_group_ids). A channel can also be placed in 'count_only' mode, where the identity of present users is not revealed to end-users.
- The backend implementation uses redis lua scripts, and is designed to scale well. In the future, hard limits may be introduced on the maximum number of users that can be present in a channel.
- Clients can enter/leave at will. If a client has not marked itself 'present' in the last 60 seconds, they will automatically 'leave' the channel. The JS implementation takes care of this regular check-in.
- On the client-side, PresenceChannel instances can be fetched from the `presence` ember service. Each PresenceChannel can be used entered/left/subscribed/unsubscribed, and the service will automatically deduplicate information before interacting with the server.
- When a client joins a PresenceChannel, the JS implementation will automatically make a GET request for the current channel state. To avoid this, the channel state can be serialized into one of your existing endpoints, and then passed to the `subscribe` method on the channel.
- The PresenceChannel JS object is an ember object. The `users` and `count` property can be used directly in ember templates, and in computed properties.
- It is important to make sure that you `unsubscribe()` and `leave()` any PresenceChannel objects after use
An example implementation may look something like this. On the server:
```ruby
register_presence_channel_prefix("site") do |channel|
next nil unless channel == "/site/online"
PresenceChannel::Config.new(public: true)
end
```
And on the client, a component could be implemented like this:
```javascript
import Component from "@ember/component";
import { inject as service } from "@ember/service";
export default Component.extend({
presence: service(),
init() {
this._super(...arguments);
this.set("presenceChannel", this.presence.getChannel("/site/online"));
},
didInsertElement() {
this.presenceChannel.enter();
this.presenceChannel.subscribe();
},
willDestroyElement() {
this.presenceChannel.leave();
this.presenceChannel.unsubscribe();
},
});
```
With this template:
```handlebars
Online: {{presenceChannel.count}}
<ul>
{{#each presenceChannel.users as |user|}}
<li>{{avatar user imageSize="tiny"}} {{user.username}}</li>
{{/each}}
</ul>
```
287 lines
10 KiB
Ruby
287 lines
10 KiB
Ruby
# frozen_string_literal: true
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require 'rails_helper'
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require 'presence_channel'
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describe PresenceChannel do
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fab!(:user) { Fabricate(:user) }
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fab!(:group) { Fabricate(:group).tap { |g| g.add(user) } }
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fab!(:user2) { Fabricate(:user) }
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before do
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PresenceChannel.clear_all!
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secure_user = Fabricate(:user)
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secure_group = Fabricate(:group)
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PresenceChannel.register_prefix("test") do |channel|
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case channel
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when /\A\/test\/public\d*\z/
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PresenceChannel::Config.new(public: true)
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when "/test/secureuser"
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PresenceChannel::Config.new(allowed_user_ids: [ secure_user.id ])
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when "/test/securegroup"
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PresenceChannel::Config.new(allowed_group_ids: [ secure_group.id ])
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when "/test/alloweduser"
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PresenceChannel::Config.new(allowed_user_ids: [ user.id ])
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when "/test/allowedgroup"
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PresenceChannel::Config.new(allowed_group_ids: [ group.id ])
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when "/test/noaccess"
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PresenceChannel::Config.new
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when "/test/countonly"
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PresenceChannel::Config.new(count_only: true, public: true)
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else
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nil
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end
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end
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end
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after do
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PresenceChannel.clear_all!
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PresenceChannel.unregister_prefix('test')
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end
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it "can perform basic channel functionality" do
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channel1 = PresenceChannel.new("/test/public1")
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channel2 = PresenceChannel.new("/test/public1")
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channel3 = PresenceChannel.new("/test/public1")
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expect(channel3.user_ids).to eq([])
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channel1.present(user_id: user.id, client_id: 1)
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channel2.present(user_id: user.id, client_id: 2)
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expect(channel3.user_ids).to eq([user.id])
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expect(channel3.count).to eq(1)
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channel1.leave(user_id: user.id, client_id: 2)
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expect(channel3.user_ids).to eq([user.id])
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expect(channel3.count).to eq(1)
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channel2.leave(user_id: user.id, client_id: 1)
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expect(channel3.user_ids).to eq([])
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expect(channel3.count).to eq(0)
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end
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it "can automatically expire users" do
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channel = PresenceChannel.new("/test/public1")
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channel.present(user_id: user.id, client_id: 76)
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channel.present(user_id: user.id, client_id: 77)
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expect(channel.count).to eq(1)
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freeze_time Time.zone.now + 1 + PresenceChannel::DEFAULT_TIMEOUT
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expect(channel.count).to eq(0)
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end
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it "correctly sends messages to message bus" do
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channel = PresenceChannel.new("/test/public1")
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.present(user_id: user.id, client_id: "a")
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end
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data = messages.map(&:data)
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expect(data.count).to eq(1)
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expect(data[0].keys).to contain_exactly("entering_users")
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expect(data[0]["entering_users"].map { |u| u[:id] }).to contain_exactly(user.id)
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freeze_time Time.zone.now + 1 + PresenceChannel::DEFAULT_TIMEOUT
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.auto_leave
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end
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data = messages.map(&:data)
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expect(data.count).to eq(1)
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expect(data[0].keys).to contain_exactly("leaving_user_ids")
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expect(data[0]["leaving_user_ids"]).to contain_exactly(user.id)
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end
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it "can track active channels, and auto_leave_all successfully" do
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channel1 = PresenceChannel.new("/test/public1")
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channel2 = PresenceChannel.new("/test/public2")
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channel1.present(user_id: user.id, client_id: "a")
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channel2.present(user_id: user.id, client_id: "a")
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start_time = Time.zone.now
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freeze_time start_time + PresenceChannel::DEFAULT_TIMEOUT / 2
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channel2.present(user_id: user2.id, client_id: "b")
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freeze_time start_time + PresenceChannel::DEFAULT_TIMEOUT + 1
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messages = MessageBus.track_publish do
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PresenceChannel.auto_leave_all
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end
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expect(messages.map { |m| [ m.channel, m.data ] }).to contain_exactly(
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["/presence/test/public1", { "leaving_user_ids" => [user.id] }],
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["/presence/test/public2", { "leaving_user_ids" => [user.id] }]
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)
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expect(channel1.user_ids).to eq([])
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expect(channel2.user_ids).to eq([user2.id])
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end
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it 'only sends one `enter` and `leave` message' do
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channel = PresenceChannel.new("/test/public1")
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.present(user_id: user.id, client_id: "a")
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channel.present(user_id: user.id, client_id: "a")
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channel.present(user_id: user.id, client_id: "b")
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end
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data = messages.map(&:data)
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expect(data.count).to eq(1)
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expect(data[0].keys).to contain_exactly("entering_users")
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expect(data[0]["entering_users"].map { |u| u[:id] }).to contain_exactly(user.id)
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.leave(user_id: user.id, client_id: "a")
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channel.leave(user_id: user.id, client_id: "a")
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channel.leave(user_id: user.id, client_id: "b")
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end
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data = messages.map(&:data)
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expect(data.count).to eq(1)
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expect(data[0].keys).to contain_exactly("leaving_user_ids")
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expect(data[0]["leaving_user_ids"]).to contain_exactly(user.id)
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end
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it "will return the messagebus last_id in the state payload" do
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channel = PresenceChannel.new("/test/public1")
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channel.present(user_id: user.id, client_id: "a")
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channel.present(user_id: user2.id, client_id: "a")
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state = channel.state
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expect(state.user_ids).to contain_exactly(user.id, user2.id)
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expect(state.count).to eq(2)
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expect(state.message_bus_last_id).to eq(MessageBus.last_id(channel.message_bus_channel_name))
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end
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it "sets an expiry on all channel-specific keys" do
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r = Discourse.redis.without_namespace
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channel = PresenceChannel.new("/test/public1")
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channel.present(user_id: user.id, client_id: "a")
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channels_ttl = r.ttl(PresenceChannel.redis_key_channel_list)
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expect(channels_ttl).to eq(-1) # Persistent
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initial_zlist_ttl = r.ttl(channel.send(:redis_key_zlist))
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initial_hash_ttl = r.ttl(channel.send(:redis_key_hash))
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expect(initial_zlist_ttl).to be_between(PresenceChannel::GC_SECONDS, PresenceChannel::GC_SECONDS + 5.minutes)
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expect(initial_hash_ttl).to be_between(PresenceChannel::GC_SECONDS, PresenceChannel::GC_SECONDS + 5.minutes)
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freeze_time 1.minute.from_now
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# PresenceChannel#present is responsible for bumping ttl
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channel.present(user_id: user.id, client_id: "a")
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new_zlist_ttl = r.ttl(channel.send(:redis_key_zlist))
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new_hash_ttl = r.ttl(channel.send(:redis_key_hash))
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expect(new_zlist_ttl).to be > initial_zlist_ttl
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expect(new_hash_ttl).to be > initial_hash_ttl
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end
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it 'handles security correctly for anon' do
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expect(PresenceChannel.new("/test/public1").can_enter?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/secureuser").can_enter?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/securegroup").can_enter?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/noaccess").can_enter?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/public1").can_view?(user_id: nil)).to eq(true)
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expect(PresenceChannel.new("/test/secureuser").can_view?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/securegroup").can_view?(user_id: nil)).to eq(false)
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expect(PresenceChannel.new("/test/noaccess").can_view?(user_id: nil)).to eq(false)
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end
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it 'handles security correctly for a user' do
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expect(PresenceChannel.new("/test/secureuser").can_enter?(user_id: user.id)).to eq(false)
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expect(PresenceChannel.new("/test/securegroup").can_enter?(user_id: user.id)).to eq(false)
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expect(PresenceChannel.new("/test/alloweduser").can_enter?(user_id: user.id)).to eq(true)
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expect(PresenceChannel.new("/test/allowedgroup").can_enter?(user_id: user.id)).to eq(true)
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expect(PresenceChannel.new("/test/noaccess").can_enter?(user_id: user.id)).to eq(false)
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expect(PresenceChannel.new("/test/secureuser").can_view?(user_id: user.id)).to eq(false)
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expect(PresenceChannel.new("/test/securegroup").can_view?(user_id: user.id)).to eq(false)
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expect(PresenceChannel.new("/test/alloweduser").can_view?(user_id: user.id)).to eq(true)
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expect(PresenceChannel.new("/test/allowedgroup").can_view?(user_id: user.id)).to eq(true)
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expect(PresenceChannel.new("/test/noaccess").can_view?(user_id: user.id)).to eq(false)
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end
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it 'publishes messages with appropriate security' do
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channel = PresenceChannel.new("/test/alloweduser")
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.present(user_id: user.id, client_id: "a")
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end
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expect(messages.count).to eq(1)
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expect(messages[0].user_ids).to eq([user.id])
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channel = PresenceChannel.new("/test/allowedgroup")
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.present(user_id: user.id, client_id: "a")
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end
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expect(messages.count).to eq(1)
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expect(messages[0].group_ids).to eq([group.id])
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end
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it 'publishes messages correctly in count_only mode' do
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channel = PresenceChannel.new("/test/countonly")
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.present(user_id: user.id, client_id: "a")
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end
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expect(messages.count).to eq(1)
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expect(messages[0].data).to eq({
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"count_delta" => 1
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})
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messages = MessageBus.track_publish(channel.message_bus_channel_name) do
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channel.leave(user_id: user.id, client_id: "a")
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end
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expect(messages.count).to eq(1)
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expect(messages[0].data).to eq({
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"count_delta" => -1
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})
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end
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it "sets a mutex when the change involves publishing messages" do
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channel = PresenceChannel.new("/test/public1")
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messages_published = 0
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channel.define_singleton_method(:publish_message) do |*args, **kwargs|
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val = PresenceChannel.redis.get(redis_key_mutex)
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raise "Mutex was not set" if val.nil?
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messages_published += 1
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end
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redis_key_mutex = Discourse.redis.namespace_key("_presence_/test/public1_mutex")
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# Enter and leave
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expect(PresenceChannel.redis.get(redis_key_mutex)).to eq(nil)
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channel.present(user_id: user.id, client_id: 'a')
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expect(PresenceChannel.redis.get(redis_key_mutex)).to eq(nil)
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channel.leave(user_id: user.id, client_id: 'a')
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expect(PresenceChannel.redis.get(redis_key_mutex)).to eq(nil)
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expect(messages_published).to eq(2)
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# Enter and auto_leave
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channel.present(user_id: user.id, client_id: 'a')
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expect(PresenceChannel.redis.get(redis_key_mutex)).to eq(nil)
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freeze_time 1.hour.from_now
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channel.auto_leave
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expect(PresenceChannel.redis.get(redis_key_mutex)).to eq(nil)
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expect(messages_published).to eq(4)
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end
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end
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