Use mule-module-requester https://github.com/mulesoft/mule-module-requester, together with the Poll Scheduler.
relevant posts: http://blogs.mulesoft.com/dev/mule-dev/introducing-the-mule-requester-module/
Another way is,
Set the FTP flow initialState="stopped", and let the poll scheduler start the flow. After the FTP processing, stop the flow again.
see sample code:
<ftp:connector name="FTP" pollingFrequency="1000"
validateConnections="true" moveToDirectory="/work/ftp/processed"
doc:name="FTP" />
<flow name="scheduleStartFTPFlow">
<poll doc:name="Poll">
<fixed-frequency-scheduler frequency="1"
timeUnit="MINUTES" />
<expression-component doc:name="START FTP FLOW"><![CDATA[if(app.registry.processFTPFlow.isStopped()){
app.registry.processFTPFlow.start();
}]]></expression-component>
</poll>
<logger message="Poll Logging: #[payload]" level="INFO"
doc:name="Logger" />
</flow>
<flow name="processFTPFlow" initialState="stopped">
<ftp:inbound-endpoint host="localhost" port="21"
path="/data/ftp" user="Sanjeet" password="sanjeet123" responseTimeout="10000"
doc:name="FTP" connector-ref="FTP" />
<logger message="Logging FTP #[payload]" level="INFO" doc:name="Logger" />
<expression-component doc:name="STOP FTP FLOW"><![CDATA[app.registry.processFTPFlow.stop();]]></expression-component>
</flow>