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Introduction
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What's New in 2.0
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FAQ
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nats.io
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<li class="header">Concepts</li>
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What is NATS
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Subject-Based Messaging
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Publish-Subscribe
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Request-Reply
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Queue Groups
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Acknowledgements
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Sequence Numbers
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<li class="header">Developing With NATS</li>
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Introduction
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Connecting
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Connecting to the Default Server
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Connecting to a Specific Server
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Connecting to a Cluster
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Setting a Connect Timeout
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Ping/Pong Protocol
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Controlling the Client/Server Protocol
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Turning Off Echo'd Messages
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Automatic Reconnections
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Disabling Reconnect
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Set the Number of Reconnect Attempts
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Pausing Between Reconnect Attempts
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Avoiding the Thundering Herd
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Listening for Reconnect Events
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Buffering Messages During Reconnect Attempts
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Securing Connections
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Authenticating with a User and Password
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Authenticating with a Token
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Authenticating with an NKey
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Authenticating with a Credentials File
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Encrypting Connections with TLS
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Receiving Messages
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Synchronous Subscriptions
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Asynchronous Subscriptions
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Unsubscribing
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Unsubscribing After N Messages
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Replying to a Message
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Wildcard Subscriptions
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<li class="chapter " data-level="3.5.7" data-path="../receiving/queues.html">
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Queue Subscriptions
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<li class="chapter " data-level="3.5.8" data-path="../receiving/drain.html">
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Draining Messages Before Disconnect
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Structured Data
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Sending Messages
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Including a Reply Subject
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Request-Reply Semantics
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Caches, Flush and Ping
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Sending Structured Data
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<li class="chapter " data-level="3.7" data-path="../events/intro.html">
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Monitoring the Connection
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Listen for Connection Events
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<li class="chapter " data-level="3.7.2" data-path="../events/slow.html">
<a href="../events/slow.html">
Slow Consumers
</a>
</li>
</ul>
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<li class="chapter " data-level="3.8" data-path="../tutorials/intro.html">
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Tutorials
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<li class="chapter " data-level="3.8.1" data-path="../tutorials/pubsub.html">
<a href="../tutorials/pubsub.html">
Explore NATS Pub/Sub
</a>
</li>
<li class="chapter " data-level="3.8.2" data-path="../tutorials/reqreply.html">
<a href="../tutorials/reqreply.html">
Explore NATS Request/Reply
</a>
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<li class="chapter " data-level="3.8.3" data-path="../tutorials/queues.html">
<a href="../tutorials/queues.html">
Explore NATS Queueing
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<li class="chapter " data-level="3.8.4" data-path="../tutorials/custom_dialer.html">
<a href="../tutorials/custom_dialer.html">
Advanced Connect and Custom Dialer in Go
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</ul>
</li>
<li class="header">NATS Server</li>
<li class="chapter " data-level="4.1" data-path="../../nats_server/installation.html">
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Installing
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Running
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Window Service
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Clients
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Flags
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Configuration
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Securing NATS
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<a href="../../nats_server/tls.html">
Enabling TLS
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Authentication
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Tokens
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Username/Password
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TLS Authentication
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</li>
<li class="chapter " data-level="4.5.1.2.4" data-path="../../nats_server/nkey_auth.html">
<a href="../../nats_server/nkey_auth.html">
NKeys
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<li class="chapter " data-level="4.5.1.2.5" data-path="../../nats_server/accounts.html">
<a href="../../nats_server/accounts.html">
Accounts
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<a href="../../nats_server/jwt_auth.html">
JWTs
</a>
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<li class="chapter " data-level="4.5.1.2.7" data-path="../../nats_server/auth_timeout.html">
<a href="../../nats_server/auth_timeout.html">
Authentication Timeout
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.5.1.3" data-path="../../nats_server/authorization.html">
<a href="../../nats_server/authorization.html">
Authorization
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.5.2" data-path="../../nats_server/clustering.html">
<a href="../../nats_server/clustering.html">
Clustering
</a>
<ul class="articles">
<li class="chapter " data-level="4.5.2.1" data-path="../../nats_server/cluster_config.html">
<a href="../../nats_server/cluster_config.html">
Configuration
</a>
</li>
<li class="chapter " data-level="4.5.2.2" data-path="../../nats_server/cluster_tls.html">
<a href="../../nats_server/cluster_tls.html">
TLS Authentication
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.5.3" data-path="../../gateways/">
<a href="../../gateways/">
Gateways
</a>
<ul class="articles">
<li class="chapter " data-level="4.5.3.1" data-path="../../gateways/gateway.html">
<a href="../../gateways/gateway.html">
Configuration
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.5.4" data-path="../../leafnodes/">
<a href="../../leafnodes/">
Leaf Nodes
</a>
<ul class="articles">
<li class="chapter " data-level="4.5.4.1" data-path="../../leafnodes/leafnode_conf.html">
<a href="../../leafnodes/leafnode_conf.html">
Configuration
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.5.5" data-path="../../nats_server/logging.html">
<a href="../../nats_server/logging.html">
Logging
</a>
</li>
<li class="chapter " data-level="4.5.6" data-path="../../nats_server/monitoring.html">
<a href="../../nats_server/monitoring.html">
Monitoring
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="4.6" data-path="../../nats_admin/">
<a href="../../nats_admin/">
Managing A NATS Server
</a>
<ul class="articles">
<li class="chapter " data-level="4.6.1" data-path="../../nats_admin/upgrading_cluster.html">
<a href="../../nats_admin/upgrading_cluster.html">
Upgrading a Cluster
</a>
</li>
<li class="chapter " data-level="4.6.2" data-path="../../nats_admin/slow_consumers.html">
<a href="../../nats_admin/slow_consumers.html">
Slow Consumers
</a>
</li>
<li class="chapter " data-level="4.6.3" data-path="../../nats_admin/signals.html">
<a href="../../nats_admin/signals.html">
Signals
</a>
</li>
<li class="chapter " data-level="4.6.4" data-path="../../sys_accounts/">
<a href="../../sys_accounts/">
System Accounts
</a>
<ul class="articles">
<li class="chapter " data-level="4.6.4.1" data-path="../../sys_accounts/sys_accounts.html">
<a href="../../sys_accounts/sys_accounts.html">
Configuration
</a>
</li>
</ul>
</li>
</ul>
</li>
<li class="chapter " data-level="4.7" data-path="../../nats_docker/">
<a href="../../nats_docker/">
NATS and Docker
</a>
<ul class="articles">
<li class="chapter " data-level="4.7.1" data-path="../../nats_docker/tutorial.html">
<a href="../../nats_docker/tutorial.html">
Tutorial
</a>
</li>
<li class="chapter " data-level="4.7.2" data-path="../../nats_docker/docker_swarm.html">
<a href="../../nats_docker/docker_swarm.html">
Docker Swarm
</a>
</li>
</ul>
</li>
<li class="header">NATS Tools</li>
<li class="chapter " data-level="5.1" data-path="../../nats_tools/mkpasswd.html">
<a href="../../nats_tools/mkpasswd.html">
mkpasswd
</a>
</li>
<li class="chapter " data-level="5.2" data-path="../../nats_tools/nk.html">
<a href="../../nats_tools/nk.html">
nk
</a>
</li>
<li class="chapter " data-level="5.3" data-path="../../nats_tools/nsc/">
<a href="../../nats_tools/nsc/">
nsc
</a>
<ul class="articles">
<li class="chapter " data-level="5.3.1" data-path="../../nats_tools/nsc/nsc.html">
<a href="../../nats_tools/nsc/nsc.html">
Basics
</a>
</li>
<li class="chapter " data-level="5.3.2" data-path="../../nats_tools/nsc/streams.html">
<a href="../../nats_tools/nsc/streams.html">
Streams
</a>
</li>
<li class="chapter " data-level="5.3.3" data-path="../../nats_tools/nsc/services.html">
<a href="../../nats_tools/nsc/services.html">
Services
</a>
</li>
<li class="chapter " data-level="5.3.4" data-path="../../nats_tools/nsc/signing_keys.html">
<a href="../../nats_tools/nsc/signing_keys.html">
Signing Keys
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="5.4" data-path="../../nats_tools/nas/">
<a href="../../nats_tools/nas/">
nats-account-server
</a>
<ul class="articles">
<li class="chapter " data-level="5.4.1" data-path="../../nats_tools/nas/nas_conf.html">
<a href="../../nats_tools/nas/nas_conf.html">
Basics
</a>
</li>
<li class="chapter " data-level="5.4.2" data-path="../../nats_tools/nas/inspecting_jwts.html">
<a href="../../nats_tools/nas/inspecting_jwts.html">
Inspecting JWTs
</a>
</li>
<li class="chapter " data-level="5.4.3" data-path="../../nats_tools/nas/dir_store.html">
<a href="../../nats_tools/nas/dir_store.html">
Directory Store
</a>
</li>
<li class="chapter " data-level="5.4.4" data-path="../../nats_tools/nas/notifications.html">
<a href="../../nats_tools/nas/notifications.html">
Update Notifications
</a>
</li>
<li class="chapter " data-level="5.4.5" data-path="../../nats_tools/nas/mem_resolver.html">
<a href="../../nats_tools/nas/mem_resolver.html">
Memory Resolver
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="5.5" data-path="../../nats_tools/nats_top/">
<a href="../../nats_tools/nats_top/">
nats-top
</a>
<ul class="articles">
<li class="chapter " data-level="5.5.1" data-path="../../nats_tools/nats_top/tutorial.html">
<a href="../../nats_tools/nats_top/tutorial.html">
Tutorial
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="5.6" data-path="../../nats_tools/natsbench.html">
<a href="../../nats_tools/natsbench.html">
nats-bench
</a>
</li>
<li class="header">NATS Streaming Concepts</li>
<li class="chapter " data-level="6.1" data-path="../../nats_streaming/intro.html">
<a href="../../nats_streaming/intro.html">
Introduction
</a>
<ul class="articles">
<li class="chapter " data-level="6.1.1" data-path="../../nats_streaming/relation-to-nats.html">
<a href="../../nats_streaming/relation-to-nats.html">
Relation to NATS
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="6.2" data-path="../../nats_streaming/client-connections.html">
<a href="../../nats_streaming/client-connections.html">
Client Connections
</a>
</li>
<li class="chapter " data-level="6.3" data-path="../../nats_streaming/channels/channels.html">
<a href="../../nats_streaming/channels/channels.html">
Channels
</a>
<ul class="articles">
<li class="chapter " data-level="6.3.1" data-path="../../nats_streaming/channels/message-log.html">
<a href="../../nats_streaming/channels/message-log.html">
Message Log
</a>
</li>
<li class="chapter " data-level="6.3.2" data-path="../../nats_streaming/channels/subscriptions/subscriptions.html">
<a href="../../nats_streaming/channels/subscriptions/subscriptions.html">
Subscriptions
</a>
<ul class="articles">
<li class="chapter " data-level="6.3.2.1" data-path="../../nats_streaming/channels/subscriptions/regular.html">
<a href="../../nats_streaming/channels/subscriptions/regular.html">
Regular
</a>
</li>
<li class="chapter " data-level="6.3.2.2" data-path="../../nats_streaming/channels/subscriptions/durable.html">
<a href="../../nats_streaming/channels/subscriptions/durable.html">
Durable
</a>
</li>
<li class="chapter " data-level="6.3.2.3" data-path="../../nats_streaming/channels/subscriptions/queue-group.html">
<a href="../../nats_streaming/channels/subscriptions/queue-group.html">
Queue Group
</a>
</li>
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Redelivery
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Store Encryption
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Supported Stores
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Configuration
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Auto Configuration
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Active Server
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Standby Servers
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Shared State
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Failover
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Partitioning
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Introduction
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Connecting to NATS Streaming
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Receiving Messages from a Channel
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Durable Subscriptions
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Queue Subscriptions
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Acknowledgements
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The Streaming Protocol
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Running
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Configuring
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Securing
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Process Signaling
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Windows Service
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Embedding NATS Streaming Server
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Docker Swarm
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Monitoring
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Enabling
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Endpoints
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Protocol Demo
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Client Protocol
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Developing a Client
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<li class="chapter " data-level="9.3" data-path="../../nats_protocol/nats-server-protocol.html">
<a href="../../nats_protocol/nats-server-protocol.html">
NATS Cluster Protocol
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<a href="../.." >Queue Groups</a>
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<h1 id="queue-subscribers--scalability"><a name="queue-subscribers--scalability" class="plugin-anchor" href="#queue-subscribers--scalability"><i class="fa fa-link" aria-hidden="true"></i></a>Queue Subscribers &amp; Scalability</h1>
<p>NATS provides a built-in load balancing feature called distributed queues. Using queue subscribers will balance message delivery across a group of subscribers which can be used to provide application fault tolerance and scale workload processing.</p>
<p>To create a queue subscription, subscribers register a queue name. All subscribers with the same queue name form the queue group. This requires no configuration. As messages on the registered subject are published, one member of the group is chosen randomly to receive the message. Although queue groups have multiple subscribers, each message is consumed by only one.</p>
<p>One of the great features of NATS is that queue groups are defined by the application and their queue subscribers, not on the server configuration.</p>
<p>Queue subscribers are ideal for scaling services. Scale up is as simple as running another application, scale down is terminating the application with a signal that drains the in flight requests.
This flexibility and lack of any configuration changes makes NATS an excellent service communication technology that can work with all platform technologies.</p>
<div class="graphviz"><code data-viz="dot">
digraph nats_queues {
rankdir=LR
publisher [shape=box, style=&quot;rounded&quot;, label=&quot;Publisher&quot;];
subject [shape=circle, label=&quot;Queue&quot;];
sub1 [shape=box, style=&quot;rounded&quot;, label=&quot;Subscriber&quot;];
sub2 [shape=box, style=&quot;rounded&quot;, label=&quot;Subscriber&quot;];
sub3 [shape=box, style=&quot;rounded&quot;, label=&quot;Subscriber&quot;];
publisher -&gt; subject [label=&quot;msgs 1,2,3&quot;];
subject -&gt; sub1 [label=&quot;msg 2&quot;];
subject -&gt; sub2 [label=&quot;msg 1&quot;];
subject -&gt; sub3 [label=&quot;msg 3&quot;];
}
</code></div>
<p>Try NATS queue subscriptions on your own, using a live server by walking through the <a href="../tutorials/queues.html">queueing tutorial</a>.</p>
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