Error parsing afsocket, inner-dest plugin disk-buffer not found...?

I'm modifying syslog-ng.conf with the following changes.

destination d_tls{
    syslog("IP"
            port(514)
            transport("tls")
            tls(
                    ca-dir(CertPath)
                    cert_file(NodeCredentialCert)
                    key_file(NodeCredentialKey)
                    peer_verify(requared-trusted)
            )
            disk-buffer(
                    mem-buf-size(524288)
                    disk-buf-size(1048576)
                    reliable(yes)
                    dir(SYSLOG_BUFFER_DIR)
            )
    );

};

Now I'm getting following error.

Error parsing afsocket, inner-dest plugin disk-buffer not found in /etc/syslog-ng.conf at line 350, column 3:

    disk-buffer(
    ^^^^^^^^^^^

Can anyone tell me the issue here? What should I change?

I'm using following syslog-ng version.

syslog-ng 3.3.6
Installer-Version: 3.3.6
Revision: ssh+git://[email protected]//var/scm/git/syslog-ng/syslog-ng-ose--mainline- 
-3.3#master#d32b5c63e09a4c3897cbc2239c07967cea393de9
Compile-Date: Apr  9 2020 09:58:41
Default-Modules: affile,afprog,afsocket,afuser,basicfuncs,csvparser,dbparser,syslogformat
Error opening plugin module; module='afsocket-notls', error='/usr/lib64/syslog- 
ng/libafsocket- 
notls.so: undefined symbol: tls_context_setup_session'
Available-Modules: 
affile,afprog,convertfuncs,tfjson,dummy,syslogformat,csvparser,dbparser,afsocket- 
tls,afuser,confgen,afmongodb,afsocket,basicfuncs
Enable-Debug: off
Enable-GProf: off
Enable-Memtrace: off
Enable-IPv6: on
Enable-Spoof-Source: off
Enable-TCP-Wrapper: on
Enable-Linux-Caps: off
Enable-Pcre: off

Solution

The disk-buffer() module is not available in such an old syslog-ng version. Please upgrade to at least v3.8.1. The current version (v3.28.1) contains quite a few bug fixes.