Reconnection Strategies

When an operation in a Mule application fails to connect to an external server, the default behavior is for the operation to fail immediately and return a connectivity error.

For example, if an operation in Anypoint Connector for FTP (FTP Connector) fails to connect to an FTP server, the operation throws an FTP:CONNECTIVITY error. The error name reflects the namespace that is specific to the connector, such as FTP:CONNECTIVITY, or DB:CONNECTIVITY (for Anypoint Connector for Database (Database Connector).

You can modify this default behavior by configuring a reconnection strategy for the operation.

Configure an Operation Reconnection Strategy

You can configure a reconnection strategy for an operation either by modifying the operation properties or by modifying the configuration of the global element for the operation. For example, you can configure a reconnection strategy in an FTP Connector configuration:

The following are the available reconnection strategies and their behaviors:

None

Is the default behavior, which immediately returns a connectivity error if the attempt to connect is unsuccessful
Standard (reconnect)

Sets the number of reconnection attempts and the interval at which to execute them before returning a connectivity error
Forever (reconnect-forever)

Attempts to reconnect continually at a given interval

Example XML Reconnection Strategy Configurations

The following examples show different types of reconnection strategies and their configurations:

Standard reconnection strategy example

The following example illustrates a Standard reconnection strategy in an FTP connector configuration, setting the count of reconnection attempts before failing to 5 and setting failsDeployment to true, which causes the application deployment to fail if the connection test fails. Because a frequency is not specified, the retry interval is the default of every 2000 ms:

<ftp:config name="FTP_Config" doc:name="FTP Config" >
  <ftp:connection host="ftp.someftphost.com" port="21" username="myusername" password="mypassword" >
    <reconnection failsDeployment="true" >
      <reconnect count="5"/>
    </reconnection>
  </ftp:connection>
</ftp:config>
<flow name="reconnectionsFlow" >
  <ftp:listener doc:name="On New or Updated File" config-ref="FTP_Config">
    <scheduling-strategy >
      <fixed-frequency />
    </scheduling-strategy>
  </ftp:listener>
</flow>

Forever reconnection strategy example

The following example sets a Forever reconnection strategy in an FTP connector configuration by which the connector attempts to reconnect every 4000 ms for as long as the application runs:
```
<ftp:connection host="ftp.someftphost.com" port="21" username="myusername" password="mypassword" >
  <reconnection>
    <reconnect-forever frequency="4000"/>
  </reconnection>
</ftp:connection>
```

Reconnection Strategy Reference

Following are the different configuration attributes for each reconnection strategy you can configure by editing your Mule application’s XML configuration file:

Attributes of <reconnection>

Name Type Required Default Description

failsDeployment

boolean

no

false

If true, causes the deployment to fail when the test connection fails

Name	Type	Required	Default	Description
`failsDeployment`	boolean	no	false	If `true`, causes the deployment to fail when the test connection fails

Attributes of <reconnect>

Name Type Required Default Description

Name	Type	Required	Default	Description
`blocking`	boolean	no	true	If `false`, the reconnection strategy runs in a separate, nonblocking thread
`frequency`	long	no	2000	How often (in ms) to reconnect
`count`	integer	no	2	How many reconnection attempts to make

blocking

boolean

true

If false, the reconnection strategy runs in a separate, nonblocking thread

frequency

long

2000

How often (in ms) to reconnect

count

integer

How many reconnection attempts to make

Attributes of <reconnect-forever>