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Module Nethttpd_plex

module Nethttpd_plex: sig .. end

Netplex support

The important function is nethttpd_factory, see below. The other functions are only needed for special effects.

An example is explained here: Example - A Simple Web Server

type config_log_error = Nethttpd_types.request_info -> string -> unit 
type config_log_access = Nethttpd_types.full_info -> unit 
type config_error_response = Nethttpd_types.error_response_params -> string 
Three type abbreviations for logging functions
val std_log_error : Netplex_types.container -> config_log_error
Returns a function that logs errors using the log_subch method of the passed container
val std_log_access : ?debug:bool -> Netplex_types.container -> config_log_access
Returns a function that logs accesses using the log_subch method of the passed container

If debug is set, additional debug log messages are printed that dump the whole access (incl. header and all available information)

val std_error_response : config_error_response
A sample error response function
val restrict_file_service_config : Netplex_types.config_file -> Netplex_types.address -> unit
Restricts the subsections and paremeters in the service configuration section of type "file" to the allowed ones.
val read_file_service_config : Netplex_types.config_file ->
Netplex_types.address -> string -> Nethttpd_services.file_service
read_file_service_config cfg addr uri_path: Reads the service configuration section of type "file" from config file cfg at address addr. uri_path is the default value put into the file_uri component of the returned record if no "uri" configuration parameter exists. (In other words, this is the path of the enclosing "uri" section, or "/" if there is only a "host" section.) All other parameters are only taken from the configuration section.

See below at nethttpd_factory how a file service needs to be configured.

val restrict_dynamic_service_config : Netplex_types.config_file -> Netplex_types.address -> unit
Restricts the subsections and paremeters in the service configuration section of type "dynamic" to the allowed ones.
val read_dynamic_service_config : (string *
(Netplex_types.config_file ->
Netplex_types.address ->
string -> (#Netcgi.cgi_activation as 'a) Nethttpd_services.dynamic_service))
list ->
Netplex_types.config_file ->
Netplex_types.address -> string -> 'a Nethttpd_services.dynamic_service
read_dynamic_service_config handlers cfg addr uri_path: Reads the service configuration section of type "dynamic" from config file cfg at address addr. The alist handlers defines the available handlers. Every handler h is called like h cfg addr uri_path. uri_path is like in read_file_service_config, i.e. the path of the enclosing "uri" section, or "/" by default.

The h function has to return the dynamic service to use, which is also returned by read_dynamic_service_config.

See below at nethttpd_factory how a dynamic service needs to be configured.

type encap = [ `Engine | `Reactor ] 
val nethttpd_processor : ?hooks:Netplex_types.processor_hooks ->
?encap:encap ->
(Netplex_types.container -> #Nethttpd_reactor.http_reactor_config) ->
'a Nethttpd_types.http_service -> Netplex_types.processor
netplex_processor mk_config http_service: Creates a Netplex processor for Nethttpd.

mk_config determines the nethttpd config for a container. This is especially useful for setting the logging functions.

The resulting processor must be turned into a full Netplex service by Netplex_sockserv.create_socket_service which can then be added by calling the controller's method add_service.

hooks: One can pass a Netplex hook object to set the hooks of the processor.

encap: Selects the encapsulation, `Reactor or `Engine. The default is `Reactor. Each encapsulation has specific strengths and weaknesses:

  • `Reactor is simpler code. Also, the request and response bodies need not to be buffered up, and are directly connected with the underlying socket (low memory requirement). The disadvantage is that a reactor processes TCP connections serially (important to know when there is only a single Unix process)
  • `Engine: The request body needs to be completely buffered up. If pipelining is enabled, the response bodies are also buffered (FIXME). The advantage of this encapsulation is that the engine can process multiple TCP connections simultaneously, even in a single process/thread.

type (#Netcgi.cgi_activation
, [ `Dynamic_service of
(#Netcgi.cgi_activation as 'a) Nethttpd_services.dynamic_service
| `File_service of Nethttpd_services.file_service ])
= (string * 'a Nethttpd_services.dynamic_service) list ->
Netplex_types.config_file ->
Netplex_types.address ->
string ->
[ `Dynamic_service of 'a Nethttpd_services.dynamic_service
| `File_service of Nethttpd_services.file_service ]
The service factory function is called when a service configuration section of a certain type needs to be read. The function has args handlers, cfg, addr, and uri_path. It needs to return the http_service.

Such a function is usually read_file_service_config, or read_dynamic_service_config, or a derivative, whose return value is turned into a http_service. This can be done with Nethttpd_services.file_service and Nethttpd_services.dynamic_service.

val default_services : (string *
(#Netcgi.cgi_activation as 'a,
[ `Dynamic_service of 'a Nethttpd_services.dynamic_service
| `File_service of Nethttpd_services.file_service ])
The default services
type httpd_factory = {
   httpd_factory : 'a.
(Netplex_types.container -> Nethttpd_reactor.http_reactor_config) ->
'a Nethttpd_types.http_service -> Netplex_types.processor
The type of the nethttpd_processor function
val nethttpd_factory : ?name:string ->
?hooks:Netplex_types.processor_hooks ->
?encap:encap ->
?config_cgi:Netcgi.config ->
?handlers:(string *
(#Netcgi.cgi_activation as 'a) Nethttpd_services.dynamic_service)
list ->
?services:(string *
[ `Dynamic_service of 'a Nethttpd_services.dynamic_service
| `File_service of Nethttpd_services.file_service ])
list ->
?log_error:(Netplex_types.container -> config_log_error) ->
?log_access:(?debug:bool ->
Netplex_types.container -> config_log_access) ->
?error_response:config_error_response ->
?processor_factory:httpd_factory ->
?tls:(module Netsys_crypto_types.TLS_PROVIDER) ->
unit -> Netplex_types.processor_factory
Factory for a web server component.

Configuration file. See below.

The services optional argument can be used to change the service types understood. If not passed, it defaults to default_services. The default includes "file" and "dynamic".


  • name: The processor name. Defaults to "nethttpd". This name can be referenced by the "type" parameters in the processor section of the config file.
  • hooks: One can pass a Netplex hook object to set the hooks of the processor. (This argument is ignored if a processor_factory is passed to this function.)
  • encap: See Nethttpd_plex.nethttpd_processor. (This argument is ignored if a processor_factory is passed to this function.)
  • config_cgi: The CGI configuration to use
  • handlers: a list of handler function. These functions can be referenced from a service section in the config file where type="dynamic" (see example above). Defaults to the empty list.
  • services: A list of service handlers that can be used by service sections in the config files. Defaults to Nethttpd_plex.default_services which defines "file" and "dynamic".
  • log_error: The error logger. Defaults to Nethttpd_plex.std_log_error.
  • log_access: The access logger. Defaults to Nethttpd_plex.std_log_access.
  • error_response: a handler which is invoked to generate error responses. Defaults to Nethttpd_plex.std_error_response.
  • processor_factory: the function creating the processor. Default is nethttpd_processor.
  • tls: the TLS provider to use. By default, Netsys_crypto.current_tls_opt is used.

Configuration files

The configuration file understood by nethttpd_factory looks like:

    processor {
      type = "nethttpd";          (* or what is passed as "name" arg *)
      timeout = 300.0;
      timeout_next_request = 15.0;
      access_log = "enabled";
      suppress_broken_pipe = true;
      host {
        pref_name = "myhost";     (* optional *)
        pref_port = 80;           (* optional *)
        names = "myhost:80 yourhost:81";  (* use *:0 for any name *)
        uri {
          path = "/the/path";
          method {
            allow = "GET POST";
            (* or: deny = "..." *)
            service {
              type = "...";
        uri {
      host {

The access_log parameter can be set to off, enabled, or debug. The default is off. Access messages go to the "access" subchannel of the component logger. If enabled, one line is printed with the most important data. If debug is set, all access data are printed.

If suppress_broken_pipe the error "Broken pipe" is not logged in the error log. This error occurs frequently, and may be regarded as a normal condition.

The sections host, uri and method can be nested to any depth. However, on every nesting level only one of these section types must be used. For example, if a host section already contains uri subsections, it is not allowed to add method subsections. Furthermore, the outermost section must be host.

The service section may be one of (at least if the services parameter is not overridden):

    service {
      type = "file";
      docroot = "/a/path/in/the/filesystem";
      uri = "/the/uri/prefix/corresponding/to/docroot";
      media_types_file = "/etc/mime.types";
      media_type {
        type = "application/foo";
        suffix = "foo"
      default_media_type = "text/plain";
      enable_gzip = true;   (* see doc in nethttpd_services.mli *)
      index_files = "index.html";
      enable_listings = true;
      hide_from_listings = "README";   (* list of PCRE regexps *)

Note that uri is taken from the surrounding uri section (or assumed to be "/" if there is none) if omitted.

    service {
      type = "dynamic";
      handler = "name_of_handler";

Binds the passed handler here.

Any of host, uri, and method sections may contain one or several access sections (which are AND-connected):

    access {
      type = "host";
      allow = "host1 host2 ...";
      (* or deny = "host1 host2 ..."; *)

Other access control methods are not yet available.

Configuring TLS

First of all, there needs to be a TLS provider. See Tls for more information how to get one.

If the TLS provider is initialized, you can have a tls subsection inside processor, like:

processor {
  tls {
    x509 {
      trust {
        crt_file = "ca.pem";
      key {
        crt_file = "server.crt";
        key_file = "server.key";

All of the files, ca.pem, server.crt and server.key need to be PEM-encoded. You can have several key sub-sections when you want to do name-based virtual hosting. Note, however, that this relies on the SNI extension of the TLS protocol, and not all clients support this extension.

Further parameters inside tls:

  • algorithms: This is a string describing the cipher suites and protocol options that are in effect. This string is provider-specific. (GnuTLS calls this string the "priority string".) Example:
    tls {
       algorithms = "SECURE-128 !ARCFOUR-128";
  • dh_params: This sub-section may set DH parameters. Example:
    tls {
      dh_params {
        pkcs3_file = "/path/to/pkcs3_file";
  • peer_auth: This string parameter may enable client certificates. Set it to "required" to enforce such a certificate.
    tls {
      peer_auth = "required";

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