In this chapter we'll describe the concepts required for understanding Apache ActiveMQ Artemis transports and where and how they're configured.
One of the most important concepts in Apache ActiveMQ Artemis transports is the
acceptor. Let's dive straight in and take a look at an acceptor
defined in xml in the configuration file broker.xml.
<acceptors>
<acceptor name="netty">tcp://localhost:61617</acceptor>
</acceptors>
Acceptors are always defined inside an acceptors element. There can be
one or more acceptors defined in the acceptors element. There's no
upper limit to the number of acceptors per server.
Each acceptor defines a way in which connections can be made to the Apache ActiveMQ Artemis server.
In the above example we're defining an acceptor that uses
Netty to listen for connections at port
61617.
The acceptor element contains a URI that defines the kind of Acceptor
to create along with its configuration. The schema part of the URI
defines the Acceptor type which can either be tcp or vm which is
Netty or an In VM Acceptor respectively. For Netty the host and the
port of the URI define what host and port the Acceptor will bind to. For
In VM the Authority part of the URI defines a unique server id.
The acceptor can also be configured with a set of key, value pairs
used to configure the specific transport, the set of
valid key-value pairs depends on the specific transport be used and are
passed straight through to the underlying transport. These are set on the
URI as part of the query, like so:
<acceptor name="netty">tcp://localhost:61617?sslEnabled=true;key-store-path=/path</acceptor>
Whereas acceptors are used on the server to define how we accept connections, connectors are used by a client to define how it connects to a server.
Let's look at a connector defined in our broker.xml
file:
<connectors>
<connector name="netty">tcp://localhost:61617</connector>
</connectors>
Connectors can be defined inside a connectors element. There can be
one or more connectors defined in the connectors element. There's no
upper limit to the number of connectors per server.
You make ask yourself, if connectors are used by the client to make connections then why are they defined on the server? There are a couple of reasons for this:
Sometimes the server acts as a client itself when it connects to another server, for example when one server is bridged to another, or when a server takes part in a cluster. In this cases the server needs to know how to connect to other servers. That's defined by connectors.
If you're using JMS and you're using JNDI on the client to look up
your JMS connection factory instances then when creating the
ActiveMQConnectionFactory it needs to know what server that
connection factory will create connections to.
That's defined by the java.naming.provider.url element in the JNDI
context environment, e.g. jndi.properties. Behind the scenes, the
ActiveMQInitialContextFactory uses the
java.naming.provider.url to construct the transport. Here's a
simple example:
java.naming.factory.initial=org.apache.activemq.artemis.jndi.ActiveMQInitialContextFactory
connectionFactory.MyConnectionFactory=tcp://myhost:61616
How do we configure a core ClientSessionFactory with the information
that it needs to connect with a server?
Connectors are also used indirectly when directly configuring a core
ClientSessionFactory to directly talk to a server. Although in this
case there's no need to define such a connector in the server side
configuration, instead we just create the parameters and tell the
ClientSessionFactory which connector factory to use.
Here's an example of creating a ClientSessionFactory which will
connect directly to the acceptor we defined earlier in this chapter, it
uses the standard Netty TCP transport and will try and connect on port
61617 to localhost (default):
Map<String, Object> connectionParams = new HashMap<String, Object>();
connectionParams.put(org.apache.activemq.artemis.core.remoting.impl.netty.TransportConstants.PORT_PROP_NAME,
61617);
TransportConfiguration transportConfiguration =
new TransportConfiguration(
"org.apache.activemq.artemis.core.remoting.impl.netty.NettyConnectorFactory",
connectionParams);
ServerLocator locator = ActiveMQClient.createServerLocatorWithoutHA(transportConfiguration);
ClientSessionFactory sessionFactory = locator.createClientSessionFactory();
ClientSession session = sessionFactory.createSession(...);
etc
Similarly, if you're using JMS, you can configure the JMS connection
factory directly on the client side without having to define a connector
on the server side or define a connection factory in activemq-jms.xml:
Map<String, Object> connectionParams = new HashMap<String, Object>();
connectionParams.put(org.apache.activemq.artemis.core.remoting.impl.netty.TransportConstants.PORT_PROP_NAME, 61617);
TransportConfiguration transportConfiguration =
new TransportConfiguration(
"org.apache.activemq.artemis.core.remoting.impl.netty.NettyConnectorFactory",
connectionParams);
ConnectionFactory connectionFactory = ActiveMQJMSClient.createConnectionFactoryWithoutHA(JMSFactoryType.CF, transportConfiguration);
Connection jmsConnection = connectionFactory.createConnection();
etc
Out of the box, Apache ActiveMQ Artemis currently uses Netty, a high performance low level network library.
Our Netty transport can be configured in several different ways; to use old (blocking) Java IO, or NIO (non-blocking), also to use straightforward TCP sockets, SSL, or to tunnel over HTTP or HTTPS..
We believe this caters for the vast majority of transport requirements.
Apache ActiveMQ Artemis supports using a single port for all protocols, Apache ActiveMQ Artemis will automatically detect which protocol is being used CORE, AMQP, STOMP or OPENWIRE and use the appropriate Apache ActiveMQ Artemis handler. It will also detect whether protocols such as HTTP or Web Sockets are being used and also use the appropriate decoders
It is possible to limit which protocols are supported by using the
protocols parameter on the Acceptor like so:
<connector name="netty">tcp://localhost:61617?protocols=CORE,AMQP</connector>
Netty TCP is a simple unencrypted TCP sockets based transport. Netty TCP can be configured to use old blocking Java IO or non blocking Java NIO. We recommend you use the Java NIO on the server side for better scalability with many concurrent connections. However using Java old IO can sometimes give you better latency than NIO when you're not so worried about supporting many thousands of concurrent connections.
If you're running connections across an untrusted network please bear in mind this transport is unencrypted. You may want to look at the SSL or HTTPS configurations.
With the Netty TCP transport all connections are initiated from the client side. I.e. the server does not initiate any connections to the client. This works well with firewall policies that typically only allow connections to be initiated in one direction.
All the valid Netty transport keys are defined in the class
org.apache.activemq.artemis.core.remoting.impl.netty.TransportConstants. Most
parameters can be used either with acceptors or connectors, some only
work with acceptors. The following parameters can be used to configure
Netty for simple TCP:
Note
The
hostandportparameters are only used in the core API, in XML configuration these are set in the URI host and port.
host. This specifies the host name or IP address to connect to
(when configuring a connector) or to listen on (when configuring an
acceptor). The default value for this property is localhost. When
configuring acceptors, multiple hosts or IP addresses can be
specified by separating them with commas. It is also possible to
specify 0.0.0.0 to accept connection from all the host's network
interfaces. It's not valid to specify multiple addresses when
specifying the host for a connector; a connector makes a connection
to one specific address.
Note
Don't forget to specify a host name or IP address! If you want your server able to accept connections from other nodes you must specify a hostname or IP address at which the acceptor will bind and listen for incoming connections. The default is localhost which of course is not accessible from remote nodes!
port. This specified the port to connect to (when configuring a
connector) or to listen on (when configuring an acceptor). The
default value for this property is 61616.
tcpNoDelay. If this is true then Nagle's
algorithm will be
disabled. This is a Java (client) socket
option.
The default value for this property is true.
tcpSendBufferSize. This parameter determines the size of the
TCP send buffer in bytes. The default value for this property is
32768 bytes (32KiB).
TCP buffer sizes should be tuned according to the bandwidth and latency of your network. Here's a good link that explains the theory behind this.
In summary TCP send/receive buffer sizes should be calculated as:
buffer_size = bandwidth * RTT.
Where bandwidth is in bytes per second and network round trip time
(RTT) is in seconds. RTT can be easily measured using the ping
utility.
For fast networks you may want to increase the buffer sizes from the defaults.
tcpReceiveBufferSize. This parameter determines the size of the
TCP receive buffer in bytes. The default value for this property is
32768 bytes (32KiB).
batchDelay. Before writing packets to the transport, Apache ActiveMQ Artemis can
be configured to batch up writes for a maximum of batchDelay
milliseconds. This can increase overall throughput for very small
messages. It does so at the expense of an increase in average
latency for message transfer. The default value for this property is
0 ms.
directDeliver. When a message arrives on the server and is
delivered to waiting consumers, by default, the delivery is done on
the same thread as that on which the message arrived. This gives
good latency in environments with relatively small messages and a
small number of consumers, but at the cost of overall throughput and
scalability - especially on multi-core machines. If you want the
lowest latency and a possible reduction in throughput then you can
use the default value for directDeliver (i.e. true). If you are
willing to take some small extra hit on latency but want the highest
throughput set directDeliver to `false
`.
nioRemotingThreads. When configured to use NIO, Apache ActiveMQ Artemis will,
by default, use a number of threads equal to three times the number
of cores (or hyper-threads) as reported by
Runtime.getRuntime().availableProcessors() for processing incoming
packets. If you want to override this value, you can set the number
of threads by specifying this parameter. The default value for this
parameter is -1 which means use the value from
Runtime.getRuntime().availableProcessors() * 3.
localAddress. When configured a Netty Connector it is possible to
specify which local address the client will use when connecting to
the remote address. This is typically used in the Application Server
or when running Embedded to control which address is used for
outbound connections. If the local-address is not set then the
connector will use any local address available
localPort. When configured a Netty Connector it is possible to
specify which local port the client will use when connecting to the
remote address. This is typically used in the Application Server or
when running Embedded to control which port is used for outbound
connections. If the local-port default is used, which is 0, then the
connector will let the system pick up an ephemeral port. valid ports
are 0 to 65535
connectionsAllowed. This is only valid for acceptors. It limits the
number of connections which the acceptor will allow. When this limit
is reached a DEBUG level message is issued to the log, and the connection
is refused. The type of client in use will determine what happens when
the connection is refused. In the case of a core client, it will
result in a org.apache.activemq.artemis.api.core.ActiveMQConnectionTimedOutException.
Netty SSL is similar to the Netty TCP transport but it provides additional security by encrypting TCP connections using the Secure Sockets Layer SSL
Please see the examples for a full working example of using Netty SSL.
Netty SSL uses all the same properties as Netty TCP but adds the following additional properties:
sslEnabled
Must be true to enable SSL. Default is false.
keyStorePath
When used on an acceptor this is the path to the SSL key store on
the server which holds the server's certificates (whether
self-signed or signed by an authority).
When used on a connector this is the path to the client-side SSL
key store which holds the client certificates. This is only relevant
for a connector if you are using 2-way SSL (i.e. mutual
authentication). Although this value is configured on the server, it
is downloaded and used by the client. If the client needs to use a
different path from that set on the server then it can override the
server-side setting by either using the customary
"javax.net.ssl.keyStore" system property or the ActiveMQ-specific
"org.apache.activemq.ssl.keyStore" system property. The
ActiveMQ-specific system property is useful if another component on
client is already making use of the standard, Java system property.
keyStorePassword
When used on an acceptor this is the password for the server-side
keystore.
When used on a connector this is the password for the client-side
keystore. This is only relevant for a connector if you are using
2-way SSL (i.e. mutual authentication). Although this value can be
configured on the server, it is downloaded and used by the client.
If the client needs to use a different password from that set on the
server then it can override the server-side setting by either using
the customary "javax.net.ssl.keyStorePassword" system property or
the ActiveMQ-specific "org.apache.activemq.ssl.keyStorePassword"
system property. The ActiveMQ-specific system property is useful if
another component on client is already making use of the standard,
Java system property.
trustStorePath
When used on an acceptor this is the path to the server-side SSL
key store that holds the keys of all the clients that the server
trusts. This is only relevant for an acceptor if you are using
2-way SSL (i.e. mutual authentication).
When used on a connector this is the path to the client-side SSL
key store which holds the public keys of all the servers that the
client trusts. Although this value can be configured on the server,
it is downloaded and used by the client. If the client needs to use
a different path from that set on the server then it can override
the server-side setting by either using the customary
"javax.net.ssl.trustStore" system property or the ActiveMQ-specific
"org.apache.activemq.ssl.trustStore" system property. The
ActiveMQ-specific system property is useful if another component on
client is already making use of the standard, Java system property.
trustStorePassword
When used on an acceptor this is the password for the server-side
trust store. This is only relevant for an acceptor if you are
using 2-way SSL (i.e. mutual authentication).
When used on a connector this is the password for the client-side
truststore. Although this value can be configured on the server, it
is downloaded and used by the client. If the client needs to use a
different password from that set on the server then it can override
the server-side setting by either using the customary
"javax.net.ssl.trustStorePassword" system property or the
ActiveMQ-specific "org.apache.activemq.ssl.trustStorePassword"
system property. The ActiveMQ-specific system property is useful if
another component on client is already making use of the standard,
Java system property.
enabledCipherSuites
Whether used on an acceptor or connector this is a comma
separated list of cipher suites used for SSL communication. The
default value is null which means the JVM's default will be used.
enabledProtocols
Whether used on an acceptor or connector this is a comma
separated list of protocols used for SSL communication. The default
value is null which means the JVM's default will be used.
needClientAuth
This property is only for an acceptor. It tells a client
connecting to this acceptor that 2-way SSL is required. Valid values
are true or false. Default is false.
Netty HTTP tunnels packets over the HTTP protocol. It can be useful in scenarios where firewalls only allow HTTP traffic to pass.
Please see the examples for a full working example of using Netty HTTP.
Netty HTTP uses the same properties as Netty TCP but adds the following additional properties:
httpEnabled. This is now no longer needed as of version 2.4. With
single port support Apache ActiveMQ Artemis will now automatically detect if http
is being used and configure itself.
httpClientIdleTime. How long a client can be idle before
sending an empty http request to keep the connection alive
httpClientIdleScanPeriod. How often, in milliseconds, to scan
for idle clients
httpResponseTime. How long the server can wait before sending an
empty http response to keep the connection alive
httpServerScanPeriod. How often, in milliseconds, to scan for
clients needing responses
httpRequiresSessionId. If true the client will wait after the
first call to receive a session id. Used the http connector is
connecting to servlet acceptor (not recommended)