=encoding utf-8


=head1 Name


stream_processing - How nginx processes a TCP/UDP session


=head1



A TCPE<sol>UDP session from a client is processed
in successive steps called B<phases>:


=over



=item 
C<Post-accept>





The first phase after accepting a client connection.
The L<ngx_stream_realip_module|ngx_stream_realip_module>
module is invoked at this phase.



=item 
C<Pre-access>





Preliminary check for access.
The
L<ngx_stream_limit_conn_module|ngx_stream_limit_conn_module>
and
L<ngx_stream_set_module|ngx_stream_set_module>
modules are invoked at this phase.



=item 
C<Access>





Client access limitation before actual data processing.
At this phase,
the L<ngx_stream_access_module|ngx_stream_access_module>
module is invoked,
for L<njs|index>,
the L<ngx_stream_js_module> directive
is invoked.



=item 
C<SSL>





TLSE<sol>SSL termination.
The L<ngx_stream_ssl_module|ngx_stream_ssl_module>
module is invoked at this phase.



=item 
C<Preread>





Reading initial bytes of data into the
L<preread buffer|ngx_stream_core_module>
to allow modules such as
L<ngx_stream_ssl_preread_module|ngx_stream_ssl_preread_module>
analyze the data before its processing.
For L<njs|index>,
the L<ngx_stream_js_module> directive
is invoked at this phase.



=item 
C<Content>





Mandatory phase where data is actually processed, usually
L<proxied|ngx_stream_proxy_module> to
L<upstream|ngx_stream_upstream_module> servers,
or a specified value
is L<returned|ngx_stream_return_module> to a client.
For L<njs|index>,
the L<ngx_stream_js_module> directive
is invoked at this phase.



=item 
C<Log>





The final phase
where the result of a client session processing is recorded.
The L<ngx_stream_log_module|ngx_stream_log_module>
module is invoked at this phase.



=back