SFTP protocol over VFS transport in WSO2 ESB 5.0.0

The Virtual File System (VFS) transport is used by WSO2 ESB to process files in the specified source directory. After processing the files, it moves them to a specified location or deletes them.

Let's look at a sample scenario how we can use this functionality of WSO2 ESB.

Let's say you need to periodically check a file system location on a given remote server and if a file is available you need to send an email attaching that file and move that file to some other file system location. This can be achieved as follows.

1. Let's first configure your remote server so that ESB could securely communicate with it over SFTP.
First create a public-private key pair with ssh.

run ssh-keygen command.

eg:
manurip@manurip-ThinkPad-T540p:~/Documents/Work/Learning/blogstuff$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/manurip/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/manurip/.ssh/id_rsa.
Your public key has been saved in /home/manurip/.ssh/id_rsa.pub.
The key fingerprint is:
c3:57:b2:82:ee:d3:b3:74:55:bf:9c:93:b7:7a:2e:df manurip@manurip-ThinkPad-T540p
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|          . . .  |
|       o   + . . |
|      . S o .   .|
|     .   + .  . +|
|      ... .    *.|
|     ...o.   . .=|
|      ...o   .*+E|
+-----------------+

Now open your .ssh folder which is located at /home/user in linux and open the file id_rsa.pub which contains the public key.  Copy that and log in to your remote server and copy that and paste it in ~/.ssh/authorized_keys file.

2. Now, let's configure ESB.

First we need to enable VFS transport receiver so that we can monitor and receive the files from our remote server. To do that uncomment the following line in ESB-home/repository/conf/axis2/axis2.xml

<transportReceiver name="vfs" class="org.apache.synapse.transport.vfs.VFSTransportListener"/>

Also, we need to be able to send a mail. For that, uncomment the following line as well from the same file. Also fill in the configuration. In case you will be using a gmail address to send mail, the configuration would be as following.

<transportSender name="mailto" class="org.apache.axis2.transport.mail.MailTransportSender">
        <parameter name="mail.smtp.host">smtp.gmail.com</parameter>
        <parameter name="mail.smtp.port">587</parameter>
        <parameter name="mail.smtp.starttls.enable">true</parameter>
        <parameter name="mail.smtp.auth">true</parameter>
        <parameter name="mail.smtp.user">test@gmail.com</parameter>
        <parameter name="mail.smtp.password">password</parameter>
        <parameter name="mail.smtp.from">test@gmail.com</parameter>
    </transportSender>

3. Now, create the following proxy service and sequence and save them in ESB-home/repository/dpeloyment/server/synapse-configs/default/proxy-services and ESB-home/repository/dpeloyment/server/synapse-configs/default/sequences respectively.

Here is the proxy service

                             

Here, if your private key is in a different location(means its not at ~/.ssh/) or the name is different(i.e. name is not id_rsa) you will need to provide it as a parameter as follows.

<parameter name="transport.vfs.SFTPIdentities">/path/id_rsa_custom_name</parameter>

Here you can see that we have referred to sendMailSequence in our proxy service via the sequence mediator. The sendMailSequence will be as follows.

5. Now we are good to go! Go ahead and start WSO2 ESB. And log in to your remote server and create an xml file(say test.xml) in /home/user/test/source which the location we gave as the value for transport.vfs.FileURI property. Soon after doing that you will see that it gets moved to /home/user/dest which the location we gave as the value for transport.vfs.MoveAfterProcess property. Also an email with test.xml attached will be sent to the email address you specified in your sendMailSequence.xml.

Also if you added the log mediators I have put in the proxy service and sendMailSequence you should see the similar logs as follows in the wso2carbon.log.

[2016-12-13 22:04:28,510]  INFO - LogMediator log = ====VFS Proxy====
[2016-12-13 22:04:28,511]  INFO - LogMediator sequence = sendMailSequence

References
[1] https://docs.wso2.com/display/ESB500/VFS+Transport
[2] http://uthaiyashankar.blogspot.com/2013/07/wso2-esb-usecases-reading-file-from.html