MQTT on Pulsar (MoP)

MQTT-on-Pulsar (aka MoP) is developed to support MQTT protocol natively on Apache Pulsar. Currently, only MQTT 3.1.1 supported.

Get started

Download or build MoP protocol handler

1. Clone the MoP project from GitHub to your local.

   git clone https://github.com/streamnative/mop.git
   cd mop

2. Build the project.

   mvn clean install -DskipTests

3. The NAR file can be found at this location.

   ./mqtt-impl/target/pulsar-protocol-handler-mqtt-${version}.nar

Install MoP protocol handler

Configure the Pulsar broker to run the MoP protocol handler as a plugin by adding configurations to the Pulsar configuration file, such as broker.conf or standalone.conf.

1. Set the configuration of the MoP protocol handler.

   Add the following properties and set their values in the Pulsar configuration file, such as conf/broker.conf or conf/standalone.conf.

   Property	Suggested value	Default value
   messagingProtocols	mqtt	null
   protocolHandlerDirectory	Location of MoP NAR file	./protocols

   Example

   messagingProtocols=mqtt
   protocolHandlerDirectory=./protocols
   

2. Set the MQTT server listeners.

   Example

   mqttListeners=mqtt://127.0.0.1:1883
   advertisedAddress=127.0.0.1
   

   Note

   The default hostname of advertisedAddress is InetAddress.getLocalHost().getHostName(). If you'd like to config this, please keep the same as Pulsar broker's advertisedAddress.

Load MoP protocol handler

After you install the MoP protocol handler to Pulsar broker, you can restart the Pulsar brokers to load the MoP protocol handler.

How to use Proxy

To use the proxy, follow the following steps. For detailed steps, refer to Deploy a cluster on bare metal.

1. Prepare a ZooKeeper cluster.

2. Initialize the cluster metadata.

3. Prepare a BookKeeper cluster.

4. Copy the pulsar-protocol-handler-mqtt-${version}.nar to the $PULSAR_HOME/protocols directory.

5. Start the Pulsar broker.

   Here is an example of the Pulsar broker configuration.

   messagingProtocols=mqtt
   protocolHandlerDirectory=./protocols
   brokerServicePort=6651
   mqttListeners=mqtt://127.0.0.1:1883
   advertisedAddress=127.0.0.1
   
   mqttProxyEnabled=true
   mqttProxyPort=5682

Verify MoP protocol handler

There are many MQTT client that can be used to verify the MoP protocol handler, such as MQTTBox, MQTT Toolbox. You can choose a CLI tool or interface tool to verify the MoP protocol handler.

The following example shows how to verify the MoP protocol handler with FuseSource MqttClient.

1. Add the dependency.

   <dependency>
       <groupId>org.fusesource.mqtt-client</groupId>
       <artifactId>mqtt-client</artifactId>
       <version>1.16</version>
   </dependency>

2. Publish messages and consume messages.

   MQTT mqtt = new MQTT();
   mqtt.setHost("127.0.0.1", 1883);
   BlockingConnection connection = mqtt.blockingConnection();
   connection.connect();
   Topic[] topics = { new Topic("persistent://public/default/my-topic", QoS.AT_LEAST_ONCE) };
   connection.subscribe(topics);
   
   // publish message
   connection.publish("persistent://public/default/my-topic", "Hello MOP!".getBytes(), QoS.AT_LEAST_ONCE, false);
   
   // receive message
   Message received = connection.receive();

Security

Enabling Authentication

MoP currently supports basic and token authentication methods. The token authentication method works with any of the token based Pulsar authentication providers such as the built-in JWT provider and external token authentication providers like biscuit-pulsar.

To use authentication for MQTT connections your Pulsar cluster must already have authentication enabled with your chosen authentication provider(s) configured.

You can then enable MQTT authentication with the following configuration properties:

mqttAuthenticationEnabled=true
mqttAuthenticationMethods=token

mqttAuthenticationMethods can be set to a comma delimited list if you wish to enable multiple authentication providers. MoP will attempt each in order when authenticating client connections.

With authentication enabled MoP will not allow anonymous connections currently.

Authenticating client connections

Basic Authentication

Set the MQTT username and password client settings.

Token Authentication

Set the MQTT password to the token body, currently username will be disregarded but MUST be set to some value as this is required by the MQTT specification.

Enabling Authorization

MoP currently supports authorization. When authorization enabled, MoP will check the authenticated role if it has the ability to pub/sub topics, eg: When sending messages, you need to have the produce permission of the topic. When subscribing to a topic, you need to have the consume permission of the topic. You can reference here to grant permissions.

You can then enable MQTT authorization with the following configuration properties:

mqttAuthorizationEnabled=true

If MoP proxy enabled, following configuration needs to be configured and brokerClientAuthenticationParameters should configure lookup permission at least:

brokerClientAuthenticationPlugin=org.apache.pulsar.client.impl.auth.AuthenticationBasic
brokerClientAuthenticationParameters={"userId":"superUser","password":"superPass"}

Enabling TLS

MoP currently supports TLS transport encryption.

Generate crt and key file :

openssl genrsa 2048 > server.key
chmod 400 server.key
openssl req -new -x509 -nodes -sha256 -days 365 -key server.key -out server.crt

TLS with broker

1. Config mqtt broker to load tls config.

...
tlsEnabled=true
mqttListeners=mqtt+ssl://127.0.0.1:8883
tlsCertificateFilePath=/xxx/server.crt
tlsKeyFilePath=/xxx/server.key
...

2. Config client to load tls config.

MQTT mqtt = new MQTT();
// default tls port
mqtt.setHost(URI.create("ssl://127.0.0.1:8883")); 
File crtFile = new File("server.crt");
Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream(crtFile));
KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
keyStore.load(null, null);
keyStore.setCertificateEntry("server", certificate);
TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
trustManagerFactory.init(keyStore);
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, trustManagerFactory.getTrustManagers(), null);
mqtt.setSslContext(sslContext);
BlockingConnection connection = mqtt.blockingConnection();
connection.connect();
...

TLS with proxy

1. Config mqtt broker to load tls config.

...
mqttProxyEnable=true
mqttProxyTlsEnabled=true
tlsCertificateFilePath=/xxx/server.crt
tlsKeyFilePath=/xxx/server.key
...

2. Config client to load tls config.

MQTT mqtt = new MQTT();
// default proxy tls port
mqtt.setHost(URI.create("ssl://127.0.0.1:5683")); 
File crtFile = new File("server.crt");
Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream(crtFile));
KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
keyStore.load(null, null);
keyStore.setCertificateEntry("server", certificate);
TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
trustManagerFactory.init(keyStore);
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, trustManagerFactory.getTrustManagers(), null);
mqtt.setSslContext(sslContext);
BlockingConnection connection = mqtt.blockingConnection();
connection.connect();
...

TLS PSK with broker

Please reference here to learn more about TLS-PSK.

1. Config mqtt broker to load tls psk config.

...
tlsPskEnabled=true
mqttListeners=mqtt+ssl+psk://127.0.0.1:8884
// any string can be specified
tlsPskIdentityHint=alpha
// identity is semicolon list of string with identity:secret format
tlsPskIdentity=mqtt:mqtt123
...

Optional configs

Config key	Comment
tlsPskIdentityFile	When you want identities in a single file with many pairs, you can config this. Identities will load from both tlsPskIdentity and tlsPskIdentityFile
tlsProtocols	TLS PSK protocols, default are [ TLSv1, TLSv1.1, TLSv1.2 ]
tlsCiphers	TLS PSK ciphers, default are [ TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305_SHA256, TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA, TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA, TLS_PSK_WITH_AES_128_CBC_SHA, TLS_PSK_WITH_AES_256_CBC_SHA ]

2. As current known mqtt Java client does not support TLS-PSK, it's better to verify this by mosquitto cli

# Default with tlsv1.2
mosquitto_pub --psk-identity mqtt --psk 6d717474313233 -p 8884 -t "/a/b/c" -m "hello mqtt"

# Test with tlsv1.1
mosquitto_pub --psk-identity mqtt --psk 6d717474313233 -p 8884 -t "/a/b/c" -m "hello mqtt" --tls-version tlsv1.1

# Test with tlsv1
mosquitto_pub --psk-identity mqtt --psk 6d717474313233 -p 8884 -t "/a/b/c" -m "hello mqtt" --tls-version tlsv1

• Download mosquitto with Mac version.
• The secret mqtt123 is converted to 6d717474313233 using Hex Code Converter

TLS PSK with proxy

1. Config mqtt proxy to load tls psk config.

...
mqttProxyEnable=true
mqttProxyTlsPskEnabled=true
// default tls psk port
mqttProxyTlsPskPort=5684
// any string can be specified
tlsPskIdentityHint=alpha
// identity is semicolon list of string with identity:secret format
tlsPskIdentity=mqtt:mqtt123
...

2. Test with mosquitto cli

mosquitto_pub --psk-identity mqtt --psk 6d717474313233 -p 5684 -t "/a/b/c" -m "hello mqtt"

Topic Names & Filters

For Apache Pulsar, The topic name consists of 4 parts:

<domain>://<tenant>/<namespace>/<local-name>

And / is not allowed in the local topic name. But for the MQTT topic name can have multiple levels such as:

/a/b/c/d/e/f

MoP mapping the MQTT topic name to Pulsar topic name as follows:

1. If the MQTT topic name does not start with the topic domain, MoP treats the URL encoded MQTT topic name as the Pulsar local topic name, and the default tenant and default namespace will be used to map the Pulsar topic name.
2. If the MQTT topic name starts with the topic domain, MoP will treat the first level topic name as the tenant and the second level topic name as the namespace and the remaining topic name levels will be covert as the local topic name with URL encoded.

Examples:

MQTT topic name	Apache Pulsar topic name
/a/b/c	persistent://public/default/%2Fa%2Fb%2Fc
a	persistent://public/default/a
persistent://my-tenant/my-ns/a/b/c	persistent://my-tenant/my-ns/a%2Fb%2Fc
persistent://my-tenant/my-ns/a	persistent://my-tenant/my-ns/a
non-persistent://my-tenant/my-ns/a	non-persistent://my-tenant/my-ns/a
non-persistent://my-tenant/my-ns/a/b/c	non-persistent://my-tenant/my-ns/a%2Fb%2Fc

So if you want to consume messages by Pulsar Client from the topic /a/b/c, the topic name for the Pulsar consumer should be persistent://public/default/%2Fa%2Fb%2Fc. If you want to consume messages from a Pulsar topic by the MQTT client, use the Pulsar topic name as the MQTT topic name directly.

MoP topic supports single-level wildcard + and multi-level wildcard #. The topic name filter also follows the above topic name mapping rules.

1. If the topic filter starts with the topic domain, MoP only filters the topic under the namespace that the topic filter provided.
2. If the topic filter does not start with the topic domain, MoP only filters the topic name under the default namespace.

Examples:

MQTT topic name	Topic filter	Is match
/a/b/c	/a/+/c	Yes
/a/b/c	/a/#	Yes
/a/b/c	a/#	No
/a/b/c	persistent://my-tenant/my-namespace//a/#	No
/a/b/c	persistent://public/default//a/#	Yes
persistent://public/default/a/b/c	persistent://public/default/a/#	Yes
persistent://public/default/a/b/c	persistent://public/default/a/+/c	Yes
persistent://public/default/a/b/c	persistent://public/default//a/+/c	No
persistent://public/default/a/b/c	persistent://my-tenant/my-namespace/a/+/c	No

Notice:

The default tenant and the default namespace for the MoP are configurable, by default, the default tenant is public and the default namespace is default.

Metrics

MoP will uniformly output its own metrics to Prometheus.

Name	Type	Description
mop_active_client_count	Gauge	The active client count
mop_total_client_count	Counter	The total client count
mop_maximum_client_count	Counter	The maximum client count
mop_sub_count	Gauge	The subscription count
mop_send_count	Counter	The total send msg count
mop_send_bytes	Counter	The total send msg in bytes
mop_received_count	Counter	The total received msg count
mop_received_bytes	Counter	The total received msg in bytes

MoP can also expose metrics through the http interface. Add below configs first and then restart pulsar broker.

additionalServlets=mqtt-servlet
additionalServletDirectory=[protocolHandlerDir]

Then you can obtain mop information in json format through /mop-stats:

curl http://pulsar-broker-webservice-address:port/mop-stats/
{"cluster":"test","subscriptions":{"subs":["/a/b/c"],"count":1},"clients":{"total":1,"maximum":1,"active":0,"active_clients":[]},"namespace":"default","messages":{"received_bytes":57351,"received_count":10,"send_count":20,"send_bytes":60235},"version":"2.9.0-SNAPSHOT","tenant":"public","uptime":"46 seconds"}

MoP available configurations

Please refer here

Project maintainers

• @Technoboy-
• @mattisonchao
• @codelipenghui