Messaging connections are created by specifying a broker or a list of brokers, and an optional set of connection options. The constructor prototypes for Connections are:
Connection connection();
Connection connection(const string url);
Connection connection(const string url, const string& options);
Connection connection(const string url, const Variant::Map& options);
Messaging connection URLs specify only the network host address(es). Connection options are specified separately as an options string or map. This is different from JMS Connection URLs that combine the network address and connection properties in a single string.
Connection URLs describe the broker or set of brokers to which the connection is to attach. The format of the Connection URL is defined by AMQP 0.10 Domain:connection.amqp-host-url.
amqp_url = "amqp:" prot_addr_list prot_addr_list = [prot_addr ","]* prot_addr prot_addr = tcp_prot_addr | tls_prot_addr tcp_prot_addr = tcp_id tcp_addr tcp_id = "tcp:" | "" tcp_addr = [host [":" port] ] host = <as per http://www.ietf.org/rfc/rfc3986.txt> port = number
Examples of Messaging Connection URLs
localhost localhost:5672 localhost:9999 192.168.1.2:5672 mybroker.example.com:5672 amqp:tcp:localhost:5672 tcp:locahost:5672,localhost:5800
Aspects of the connections behaviour can be controlled through specifying connection options. For example, connections can be configured to automatically reconnect if the connection to a broker is lost.
Example 1.14. Specifying Connection Options in C++, Python, and .NET
In C++, these options can be set using Connection::setOption() or by passing in a set of options to the constructor. The options can be passed in as a map or in string form:
or
Connection connection("localhost:5672");
connection.setOption("reconnect", true);
try {
connection.open();
!!! SNIP !!!
In Python, these options can be set as attributes of the connection or using named arguments in
the Connection constructor:
connection = Connection("localhost:5672", reconnect=True)
try:
connection.open()
!!! SNIP !!!
or
connection = Connection("localhost:5672")
connection.reconnect = True
try:
connection.open()
!!! SNIP !!!
In .NET, these options can be set using Connection.SetOption() or by passing in a set of options to the constructor. The options can be passed in as a map or in string form:
Connection connection= new Connection("localhost:5672", "{reconnect: true}");
try {
connection.Open();
!!! SNIP !!!
or
Connection connection = new Connection("localhost:5672");
connection.SetOption("reconnect", true);
try {
connection.Open();
!!! SNIP !!!
See the reference documentation for details in each language.
The following table lists the supported connection options.
Table 1.4. Connection Options
| option name | value type | semantics |
|---|---|---|
username
| string | The username to use when authenticating to the broker. |
password
| string | The password to use when authenticating to the broker. |
sasl_mechanisms
| string | The specific SASL mechanisms to use with the python client when authenticating to the broker. The value is a space separated list. |
reconnect
| boolean | Transparently reconnect if the connection is lost. |
reconnect_timeout
| integer | Total number of seconds to continue reconnection attempts before giving up and raising an exception. |
reconnect_limit
| integer | Maximum number of reconnection attempts before giving up and raising an exception. |
reconnect_interval_min
| integer representing time in seconds |
Minimum number of seconds between reconnection attempts. The first reconnection attempt is made immediately; if that fails, the first reconnection delay is set to the value of reconnect_interval_min; if that attempt fails, the reconnect interval increases exponentially until a reconnection attempt succeeds or reconnect_interval_max is reached.
|
reconnect_interval_max
| integer representing time in seconds | Maximum reconnect interval. |
reconnect_interval
| integer representing time in seconds |
Sets both reconnection_interval_min and reconnection_interval_max to the same value.
|
heartbeat
| integer representing time in seconds | Requests that heartbeats be sent every N seconds. If two successive heartbeats are missed the connection is considered to be lost. |
transport
| string | Sets the underlying transport protocol used. The default option is 'tcp'. To enable ssl, set to 'ssl'. The C++ client additionally supports 'rdma'. |
tcp-nodelay
| boolean | Set tcp no-delay, i.e. disable Nagle algorithm. [C++ only] |
protocol
| string | Sets the application protocol used. The default option is 'amqp0-10'. To enable AMQP 1.0, set to 'amqp1.0'. |
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