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.

Operation executions don’t trigger the reconnection strategy configured at the FTP Connector when failing with connectivity errors. In this example, the reconnection strategy applies only to the connection that ftp:listener needs to establish with the FTP server to query for new or updated files.

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:

An FTP configuration with reconnection strategy

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>