Ubuntu Manpage: /etc/yaws/yaws.conf - Configuration file for the Yaws web server

Provided by: yaws_2.0.4+dfsg-2ubuntu0.1_all

NAME

       /etc/yaws/yaws.conf - Configuration file for the Yaws web server

DESCRIPTION

       Yaws  is  fast  lightweight  web server. It reads a configuration file called yaws.conf to
       control its operations. The configuration contains two distinct parts: a global part which
       affects  all  the  virtual  hosts and a server part where options for each virtual host is
       supplied.

GLOBAL PART

logdir = [+]Directory
All Yaws logs will be written to files in this directory. If specified with +, Yaws
will attempt to create the directory if it does not exist. There are several
different log files written by Yaws:

report.log - this is a text file that contains all error logger printouts from
Yaws.

<Host>.access - for each virtual host served by Yaws, a file <Host>.access will be
written that contains an access log in NCSA combined/XLF/ELF log format. (See
http://www.w3.org/TR/WD-logfile.html for more details on Extended Log File Format.)

<Host>.auth - for each virtual host served by Yaws, a file <Host>.auth will be
written which contains all http auth related messages.

trace_<YYYYMMDD_hhmmss> - Trace files are written in this subdirectory, suffixed by
the creation date.

trace.<Pid>.http - this file contains the HTTP trace if that is enabled, where
<Pid> is the process id handling the TCP connection.

trace.<Pid>.traffic - this file contains the traffic trace if that is enabled,
where <Pid> is the process id handling the TCP connection.

Note that <Host>.access and <Host>.auth files will be used only if the directive
logger_mod is not set or set to yaws_log. The default value for logdir is "."

ebin_dir = Directory
This directive adds Directory to the Erlang search path. It is possible to have
several of these commands in the configuration file. The default value is
"yaws_dir"/examples/ebin

src_dir = Directory
This directive defines a Directory as a source directory. Yaws will compile all
erlang modules found in this directory and all its subdirectories. The compilation
occurs when the configuration is loaded or reloaded. The include_dir directives are
used to search for includes files. Multiple src_dir directives may be used. There
is no such directory configured by default.

id = String
It is possible to run multiple Yaws servers on the same machine. We use the id of a
Yaws server to control it using the different control commands such as:

# /usr/local/bin/yaws --id foobar --stop

To stop the Yaws server with id "foobar". Each Yaws server will write its internal
data into a file called $HOME/.yaws/yaws/ID where ID is the identity of the server.
Yaws also creates a file called $HOME/.yaws/yaws/ID/CTL which contains the port
number where the server is listening for control commands. The default id is
"default".

server_signature = String
This directive sets the "Server: " output header to the custom value. The default
value is "yaws/%VSN%, Yet Another Web Server".

include_dir = Directory
This directive adds Directory to the path of directories where the Erlang compiler
searches for include files. We need to use this if we want to include .hrl files in
our Yaws Erlang code. It is possible to have several of these commands in the
configuration file. The default value is "yaws_dir"/examples/include.

max_num_cached_files = Integer
Yaws will cache small files such as commonly accessed GIF images in RAM. This
directive sets a maximum number on the number of cached files. The default value
is 400.

max_num_cached_bytes = Integer
This directive controls the total amount of RAM which can maximally be used for
cached RAM files. The default value is 1000000, 1 megabyte.

max_size_cached_file = Integer
This directive sets a maximum size on the files that are RAM cached by Yaws. The
default value is 8000, 8 kBytes.

cache_refresh_secs = Integer
The RAM cache is used to serve pages that sit in the cache. An entry sits in cache
at most cache_refresh_secs number of seconds. The default is 30. This means that
when the content is updated under the docroot, that change doesn't show until 30
seconds have passed. While developing a Yaws site, it may be convenient to set this
value to 0. If the debug flag (-d) is passed to the Yaws start script, this value
is automatically set to 0.

trace = false | traffic | http
This enables traffic or http tracing. Tracing is also possible to enable with a
command line flag to Yaws. Default is false.

auth_log = true | false
Deprecated and ignored. Now, this target must be set in server part.

max_connections = nolimit | Integer
Set this value to control the maximum number of connections from HTTP clients into
the server. This is implemented by closing the last socket if the limit threshold
is reached.

keepalive_maxuses = nolimit | Integer
Normally, Yaws does not restrict the number of times a connection is kept alive
using keepalive. Setting this parameter to an integer X will ensure that
connections are closed once they have been used X times. This can be a useful to
guard against long running connections collecting too much garbage in the Erlang
VM.

process_options = undefined | Proplist
Set process spawn options for client acceptor processes. Options must be specified
as a quoted string of either the atom undefined or as a proplist of valid process
options. The supported options are fullsweep_after, min_heap_size, and
min_bin_vheap_size, each taking an associated integer value. Other process options
are ignored. The proplist may also be empty. See erlang:spawn_opt/4 for details on
these options.

large_file_chunk_size = Integer
Set the chunk size used by Yaws to send large files when sendfile is not supported
or disabled. The default value is 10240.

large_file_sendfile = erlang | yaws | disable
Set the version of sendfile method to use to send large files (if supported):

erlang - use file:sendfile/5, if supported.

yaws - use Yaws sendfile linked-in driver, if supported.

disable - do not use any sendfile method, but gen_tcp:send/2.

The default value is yaws.

acceptor_pool_size = Integer
Set the size of the pool of cached acceptor processes. The specified value must be
greater than or equal to 0. The default value is 8. Specifying a value of 0
effectively disables the process pool.

log_wrap_size = Integer
The logs written by Yaws are all wrap logs, the default value at the size where
they wrap around and the original gets renamed to File.old is 1000000, 1 megabyte.
This value can be changed.
If we set the value to 0 the logs will never wrap. If we want to use Yaws in
combination with a more traditional log wrapper such as logrotate, set the size to
0 and Yaws will reopen the logfiles once they have be renamed/removed.

log_resolve_hostname = true | false
By default the client host IP is not resolved in the access logs.

fail_on_bind_err = true | false
Fail completely or not if Yaws fails to bind a listen socket Default is true.

enable_soap = true | false
If true, a soap server will be started at startup of Yaws. Default is false.

soap_srv_mods = ListOfModuleSetting
If enable_soap is true, a startup Yaws will invoke yaws_soap_srv:setup() to setup
modules set here. ModuleSetting is either a triad like <Mod, HandlerFunc, WsdlFile>
or a quadruple form like <Mod, HandlerFunc, WsdlFile, Prefix> which specifies the
prefix. A prefix will be used as argument of yaws_soap_lib:initModel() and then be
used as a XML namespace prefix. Note, the WsdlFile here should be an absolute-path
file in local file systems.

For example, we can specify

soap_srv_mods=<Mod1, Handler, Wsdl1> <Mod2, Handler, Wsdl2, Prefix> ...

php_exe_path = Path
this target is deprecated and useless. use 'php_handler' target in server part
instead.
The name of (and possibly path to) the php executable used to interpret php scripts
(if allowed). Default is php_exe_path = php-cgi.

copy_error_log = true | false
Enable or disable copying of the error log. When we run in embedded mode, there may
very well be some other systems process that is responsible for writing the
errorlog to a file whereas when we run in normal standalone mode, we typically want
the Erlang errorlog written to a report.log file. Default value is true.

ysession_mod = Module
Allows to specify a different Yaws session storage mechanism instead of an ETS
table. One of the drawbacks of the default yaws_session_server implementation is
that server side cookies are lost when the server restarts. Specifying a different
module here will pass all write/read operations to this module (it must implement
appropriate callbacks).

ysession_idle_timeout = Integer
Controls Yaws session idle cleanup. If a server has been idle for
ysession_idle_timeout milliseconds, check all Yaws sessions and remove any that
have timed out. The default ysession_idle_timeout value is 2*60*1000 (2 minutes).

ysession_long_timeout = Integer
Controls Yaws session periodic cleanup. Every ysession_long_timeout milliseconds,
check all Yaws sessions and remove any that have timed out. The default
ysession_long_timeout value is 60*60*1000 (1 hour).

runmod = ModuleName
At startup Yaws will invoke ModuleName:start() in a separate process. It is
possible to have several runmods. This is useful if we want to reuse the Yaws
startup shell script for our own application.

pick_first_virthost_on_nomatch = true | false
When Yaws gets a request, it extracts the Host header from the client request to
choose a virtual server amongst all servers with the same IP/Port pair. This
configuration parameter decides whether Yaws should pick the first server (as
defined in the yaws.conf file) if no name match or not. If this is false and no
Host header is present in the request, Yaws returns a 400 Bad Request as required
by the HTTP standard. In real live hosting scenarios we typically want this to be
false, whereas in testing/development scenarios it may be convenient to set it to
true. Default is true.

keepalive_timeout = TimeInMilliseconds | infinity
If the HTTP session will be kept alive (i.e., not immediately closed) it will close
after keepalive_timeout milliseconds unless a new request is received in that time.
The default value is 30000. The value infinity is legal but not recommended.

subconfig = File
Load specified config file. Absolute paths or relative ones to the configuration
location are allowed. Unix-style wildcard strings can be used to include several
files at once. See filelib:wildcard/1 for details. Hidden files, starting by a dot,
will be ignored. For example:

subconfig = /etc/yaws/global.conf
subconfig = /etc/yaws/vhosts/*.conf

Or, relatively to the configuration location:

subconfig = global.conf
subconfig = vhosts/*.conf

subconfigdir = Directory
Load all config files found in the specified directory. The given Directory can be
an absolute path or relative to the configuration location. Hidden files, starting
by a dot, will be ignored.

x_forwarded_for_log_proxy_whitelist = ListOfUpstreamProxyServerIps
this target is deprecated and will be ignored.

default_type = MimeType
Defines the default MIME type to be used where Yaws cannot determine it by its MIME
types mappings. Default is text/plain.

default_charset = Charset
Defines the default charset to be added when a response content-type is text/*. By
default, no charset is added.

mime_types_file = File
Overrides the default mime.types file included with Yaws. This file must use the
following format:

# Lines beginning with a '#' or a whitespace are ignored
# blank lines are also ignored
<MIME type> <space separated file extensions>

The default file is located at ${PREFIX}/lib/yaws/priv/mime.types. You should not
edit this file because it may be replaced when you upgrade your server.

add_types = ListOfTypes
Specifies one or more mappings between MIME types and file extensions. More than
one extension can be assigned to a MIME type. ListOfTypes is defined as follows:

add_types = <MimeType1, Ext> <MimeType2, Ext1 Ext2 ...> ...

The mappings defined using this directive will overload all other definitions. If a
file extension is defined several times, only the last one is kept. Multiple
add_types directives may be used.

add_charsets = ListOfCharsets
Specifies one or more mappings between charsets and file extensions. More than one
extension can be assigned to a charset. ListOfCharsets is defined as follows:

add_charsets = <Charset1, Ext> <Charset2, Ext1 Ext2 ...> ...

The mappings defined using this directive will overload all other definitions. If a
file extension is defined several times, only the last one is kept. Multiple
add_charsets directives may be used.

sni = disable | enable | strict
Enables or disables the TLS SNI (Server Name Indication) support.

When disabled (or not supported), all virtual servers in the same group (same
IP/Port) must share the same SSL configuration, especially the same SSL
certificate. Only the HTTP Host header will be considered to find the right virtual
server.

When enabled, SSL configuration can be different from a virtual server to another,
each one can have its own SSL certificate. In this case, if a client provides a SNI
hostname, it will be used to find the right virtual server. To accept the SNI
information from the client, The first virtual server (the default one, see
pick_first_virthost_on_nomatch) must include TLS as a permitted protocol.

If sni directive is set to enable, non SNI clients are allowed. For such clients,
virtual servers are selected as if Yaws did not have SNI support. If it is set to
strict, SNI hostname is mandatary to access a SSL virtual server. But, in all
cases, when SNI support is enabled, if a client provides a SNI hostname, it must
match the HTTP Host header (which is mandatory too). Note that the first virtual
server (the default one) will be used for any request where the provided SNI
hostname doesn't match any of virtual server names. So, it is important that the
first virtual server have the most restrictive access control, otherwise clients
can access restricted resources by sending a request for any unknown hostname.
(This isn't actually any different from using virtual servers without SNI support.)

The sni directive is a global one, so if you set it to strict, non SNI clients will
be refused for all SSL groups. See require_sni directive from the server part to
mitigate this requirement.

Default is disable.

WARNING: The SNI support was introduced in the SSL application in Erlang/OTP 18.0,
so Yaws ignores it for previous releases.

SERVER PART

Yaws can virthost several web servers on the same IP address as well as several web
servers on different IP addresses. This includes SSL servers.

Each virtual host is defined within a matching pair of <server ServerName> and </server>.
The ServerName will be the name of the webserver.

The following directives are allowed inside a server definition.

port = Port
This makes the server listen on Port. Default is 8000.

listen = IpAddress
This makes the server listen on IpAddress. When virthosting several servers on the
same ip/port address, if the browser doesn't send a Host: field, Yaws will pick the
first server specified in the config file. If the specified IP address is 0.0.0.0
Yaws will listen on all local IP addresses on the specified port. Default is
127.0.0.1. Multiple listen directives may be used to specify several addresses to
listen on.

listen_backlog = Integer
This sets the TCP listen backlog for the server to define the maximum length the
queue of pending connections may grow to. The default is 1024.

<listen_opts> ... </listen_opts>
Defines extra options to be set on the listen socket and, by inheritance, on
accepted sockets. See inet:setopts/2 for details. Supported options are:

buffer = Integer (default: same as inet:setopts/2)

delay_send = true | false (default: same as inet:setopts/2)

linger = Integer | false (default: same as inet:setopts/2)

nodelay = true | false (default: same as inet:setopts/2)

priority = Integer (default: same as inet:setopts/2)

sndbuf = Integer (default: same as inet:setopts/2)

recbuf = Integer (default: same as inet:setopts/2)

send_timeout = Integer | infinity (default: same as inet:setopts/2)

send_timeout_close = true | false (default: same as inet:setopts/2)

server_signature = String
This directive sets the "Server: " output header to the custom value and overloads
the global one for this virtual server.

subconfig = File
Same as subconfig directive of the global part, but here files should only contain
directives allowed in the server part.

subconfigdir = Directory
Same as subconfigdir directive of the global part, but here files should only
contain directives allowed in server part.

rhost = Host[:Port]
This forces all local redirects issued by the server to go to Host. This is useful
when Yaws listens to a port which is different from the port that the user connects
to. For example, running Yaws as a non-privileged user makes it impossible to
listen to port 80, since that port can only be opened by a privileged user. Instead
Yaws listens to a high port number port, 8000, and iptables are used to redirect
traffic to port 80 to port 8000 (most NAT:ing firewalls will also do this for you).

rmethod = http | https
This forces all local redirects issued by the server to use this method. This is
useful when an SSL off-loader, or stunnel, is used in front of Yaws.

auth_log = true | false
Enable or disable the auth log for this virtual server. Default is true.

access_log = true | false
Setting this directive to false turns off traffic logging for this virtual server.
The default value is true.

logger_mod = Module
It is possible to set a special module that handles access and auth logging. The
default is to log all web server traffic to <Host>.access and <Host>.auth files in
the configured or default logdir.
This module must implement the behaviour yaws_logger. Default value is yaws_log.

The following functions should be exported:

Module:open_log(ServerName, Type, LogDir)
When Yaws is started, this function is called for this virtual server. If the
initialization is successful, the function must return {true,State} and if an
error occurred, it must return false.

Module:close_log(ServerName, Type, State)
This function is called for this virtual server when Yaws is stopped.

Module:wrap_log(ServerName, Type, State, LogWrapSize)
This function is used to rotate log files. It is regularly called by Yaws and
must return the possibly updated internal NewState.

Module:write_log(ServerName, Type, State, Infos)
When it needs to log a message, Yaws will call this function. The parameter
Infos is {Ip,Req,InHdrs,OutHdrs,Time} for an access log and {Ip,Path,Item} for
an auth log, where:

Ip - IP address of the accessing client (as a tuple).

Req - the HTTP method, URI path, and HTTP version of the request (as a
#http_request{} record).

InHdrs - the HTTP headers which were received from the WWW client (as a
#headers{} record).

OutHdrs - the HTTP headers sent to the WWW client (as a #outh{} record)

Path - the URI path of the request (as a string).

Item - the result of an authentication request. May be {ok,User}, 403 or
{401,Realm}.

Time - The time taken to serve the request, in microseconds.

For all of these callbacks, ServerName is the virtual server's name, Type is the
atom access or auth and State is the internal state of the logger.

shaper = Module
Defines a module to control access to this virtual server. Access can be controlled
based on the IP address of the client. It is also possible to throttle HTTP
requests based on the client's download rate. This module must implement the
behaviour yaws_shaper.

There is no such module configured by default.

dir_listings = true | true_nozip | false
Setting this directive to false disallows the automatic dir listing feature of
Yaws. A status code 403 Forbidden will be sent. Set to true_nozip to avoid the
auto-generated all.zip entries. Default is false.

extra_cgi_vars = .....
Add additional CGI or FastCGI variables. For example:

<extra_cgi_vars dir='/path/to/some/scripts'>
var = val
...
</extra_cgi_vars>

statistics = true | false
Turns on/off statistics gathering for a virtual server. Default is false.

fcgi_app_server = Host:Port
The hostname and TCP port number of a FastCGI application server. To specify an
IPv6 address, put it inside square brackets (ex: "[::1]:9000"). The TCP port number
is not optional. There is no default value.

fcgi_trace_protocol = true | false
Enable or disable tracing of FastCGI protocol messages as info log messages.
Disabled by default.

fcgi_log_app_error = true | false
Enable or disable logging of application error messages (output to stderr and non-
zero exit value). Disabled by default.

deflate = true | false
Turns on or off deflate compression for a server. Default is false.

<deflate> ... </deflate>
This begins and ends the deflate compression configuration for this server. The
following items are allowed within a matching pair of <deflate> and </deflate>
delimiters.

min_compress_size = nolimit | Integer
Defines the smallest response size that will be compressed. If nolimit is not
used, the specified value must be strictly positive. The default value is
nolimit.

compression_level = none | default | best_compression | best_speed | 0..9
Defines the compression level to be used. 0 (none), gives no compression at
all, 1 (best_speed) gives best speed and 9 (best_compression) gives best
compression. The default value is default.

window_size = 9..15
Specifies the zlib compression window size. It should be in the range 9
through 15. Larger values of this parameter result in better compression at
the expense of memory usage. The default value is 15.

mem_level = 1..9
Specifies how much memory should be allocated for the internal compression
state. mem_level=1 uses minimum memory but is slow and reduces compression
ratio; mem_level=9 uses maximum memory for optimal speed. The default value is
8.

strategy = default | filtered | huffman_only
This parameter is used to tune the compression algorithm. See zlib(3erl) for
more details on the strategy parameter. The default value is default.

use_gzip_static = true | false
If true, Yaws will try to serve precompressed versions of static files. It
will look for precompressed files in the same location as original files that
end in ".gz". Only files that do not fit in the cache are concerned. The
default value is false.

mime_types = ListOfTypes | defaults | all
Restricts the deflate compression to particular MIME types. The special value
all enable it for all types (It is a synonym of `*/*'). MIME types into
ListOfTypes must have the form `type/subtype' or `type/*' (indicating all
subtypes of that type). Here is an example:

mime_types = default image/*
mime_types = application/xml application/xhtml+xml application/rss+xml

By default, the following MIME types are compressed (if deflate is set to
true): text/*, application/rtf, application/msword, application/pdf,
application/x-dvi, application/javascript, application/x-javascript. Multiple
mime_types directive can be used.

docroot = Directory ...
This makes the server serve all its content from Directory.
It is possible to pass a space-separated list of directories as docroot. If this is
the case, the various directories will be searched in order for the requested file.
This also works with the ssi and yssi constructs where the full list of directories
will be searched for files to ssi/yssi include. Multiple docroot directives can be
used. You need at least one valid docroot, invalid docroots are skipped with their
associated auth structures.

auth_skip_docroot = true | false
If true, the docroot will not be searched for .yaws_auth files. This is useful when
the docroot is quite large and the time to search it is prohibitive when Yaws
starts up. Defaults to false.

partial_post_size = Integer | nolimit
When a Yaws file receives large POSTs, the amount of data received in each chunk is
determined by this parameter. The default value is 10240. Setting it to nolimit is
potentially dangerous.

dav = true | false
Turns on the DAV protocol for this server. The dav support in Yaws is highly
limited. If dav is turned on, .yaws processing of .yaws pages is turned off.
Default is false. The socket read timeout is supplied by the keepalive_timeout
setting. If the read is not done within the timeout, the POST will fail.

tilde_expand = true|false
If this value is set to false Yaws will never do tilde expansion. The default is
false. tilde_expansion is the mechanism whereby a URL on the form
http://www.foo.com/~username is changed into a request where the docroot for that
particular request is set to the directory ~username/public_html/.

allowed_scripts = ListOfSuffixes
The allowed script types for this server. Recognized are `yaws', `cgi', `fcgi',
`php'. Default is allowed_scripts = yaws php cgi fcgi.

Note: for fcgi scripts, the FastCGI application server is only called if a local
file with the .fcgi extension exists. However, the contents of the local .fcgi file
are ignored.

tilde_allowed_scripts = ListOfSuffixes
The allowed script types for this server when executing files in a users
public_html folder Recognized are `yaws', `cgi', `fcgi', `php'. Default is
tilde_allowed_scripts = i.e. empty

index_files = ListOfResources
This directive sets the list of resources to look for, when a directory is
requested by the client. If the last entry begins with a `/', and none of the
earlier resources are found, Yaws will perform a redirect to this uri. Default is
index_files = index.yaws index.html index.php.

appmods = ListOfModuleNames
If any of the names in ListOfModuleNames appear as components in the path for a
request, the path request parsing will terminate and that module will be called.
There is also an alternate syntax for specifying the appmods if we don't want our
internal erlang module names to be exposed in the URL paths. We can specify

appmods = <Path1, Module1> <Path2, Modules2> ...

Assume for example that we have the URL
http://www.hyber.org/myapp/foo/bar/baz?user=joe while we have the module foo
defined as an appmod, the function foo:out(Arg) will be invoked instead of
searching the filesystems below the point foo.
The Arg argument will have the missing path part supplied in its appmoddata field.

It is also possible to exclude certain directories from appmod processing. This is
particulaly interesting for '/' appmods. Here is an example:

appmods = </, myapp exclude_paths icons js top/static>

The above configuration will invoke the 'myapp' erlang module on everything except
any file found in directories 'icons', 'js' and 'top/static' relative to the
docroot.

dispatchmod = DispatchModule
Set DispatchModule as a server-specific request dispatching module. Yaws expects
DispatchModule to export a dispatch/1 function. When it receives a request, Yaws
passes an #arg{} record to the dispatch module's dispatch/1 function, which returns
one of the following atom results:

done - this indicates the dispatch module handled the request itself and
already sent the response, and Yaws should resume watching for new requests on
the connection

closed - same as done but the DispatchModule also closed the connection

continue - the dispatch module has decided not to handle the request, and
instead wants Yaws to perform its regular request dispatching

Note that when DispatchModule handles a request itself, Yaws does not support
tracing, increment statistics counters or allow traffic shaping for that request.
It does however still keep track of maximum keepalive uses on the connection.

errormod_404 = Module
It is possible to set a special module that handles 404 Not Found messages. The
function Module:out404(Arg, GC, SC) will be invoked. The arguments are

Arg - a #arg{} record

GC - a #gconf{} record (defined in yaws.hrl)

SC - a #sconf{} record (defined in yaws.hrl)

The function can and must do the same things that a normal out/1 does.

errormod_401 = Module
It is possible to set a special module that handles 401 Unauthorized messages. This
can for example be used to display a login page instead. The function
Module:out401(Arg, Auth, Realm) will be invoked. The arguments are

Arg - a #arg{} record

Auth - a #auth{} record

Realm - a string

The function can and must do the same things that a normal out/1 does.

errormod_crash = Module
It is possible to set a special module that handles the HTML generation of server
crash messages. The default is to display the entire formatted crash message in the
browser. This is good for debugging but not in production.
The function Module:crashmsg(Arg, SC, Str) will be called. The Str is the real
crash message formatted as a string.
The function must return, {content,MimeType,Cont} or {html, Str} or {ehtml, Term}.
That data will be shipped to the client.

expires = ListOfExpires
Controls the setting of the Expires HTTP header and the max-age directive of the
Cache-Control HTTP header in server responses for specific MIME types. The
expiration date can be set as relative to either the time the source file was last
modified; as the time of the client access; or as always in order to empty the
cache altogether. ListOfExpires is defined as follows:

expires = <MimeType1, access+Seconds> <MimeType2, modify+Seconds> <MimeType3, always> ...

A MimeType can also have a wildcard as subtype or both as subtype and type, like
type/* or */*.

These HTTP headers are an instruction to the client about the document's validity
and persistence. If cached, the document may be fetched from the cache rather than
from the source until this time has passed. After that, the cache copy is
considered "expired" and invalid, and a new copy must be obtained from the source.
Here is an example:

expires = <image/gif, access+2592000> <image/png, access+2592000>
expires = <image/jpeg, access+2592000> <text/css, access+2592000>
expires = <text/*, always>

and here is another:

expires = <*/*, always>

arg_rewrite_mod = Module
It is possible to install a module that rewrites all the Arg #arg{} records at an
early stage in the Yaws server. This can be used to do various things such as
checking a cookie, rewriting paths etc. An arg_rewrite_mod must export an
arg_rewrite/1 function taking and returning an #arg{} record. If the function wants
to return a response, it must set the #arg.state field of its return value to an
instance of the #rewrite_response{} record.

The module yaws_vdir can be used in case you want to serve static content that is
not located in your docroot. See the example at the bottom of this man page for how
to use the opaque + vdir elements to instruct the yaws_vdir module what paths to
rewrite.

start_mod = Module
Defines a user provided callback module. At startup of the server, Module:start/1
will be called. The #sconf{} record (defined in yaws.hrl) will be used as the
input argument. This makes it possible for a user application to synchronize the
startup with the Yaws server as well as getting hold of user specific configuration
data, see the explanation for the <opaque> context.

revproxy = Prefix Url [intercept_mod Module]
Make Yaws a reverse proxy. Prefix is a path inside our own docroot and Url argument
is a URL pointing to a website we want to "mount" under the Prefix path. This
example:

revproxy = /tmp/foo http://yaws.hyber.org

makes the hyber website appear under /tmp/foo.

It is possible to have multiple reverse proxies inside the same server.

You can optionally configure an interception module for each reverse proxy,
allowing your application to examine and modify requests and HTTP headers as they
pass through the proxy from client to backend server and also examine and modify
responses and HTTP headers as they return from the backend server through the proxy
to the client.

You specify an interception module by including the optional intercept_mod keyword
followed by Module, which should be the name of your interception module.

An interception module is expected to export two functions: rewrite_request/2 and
rewrite_response/2. The two arguments passed to rewrite_request/2 function are a
#http_request{} record and a #headers{} record, whereas rewrite_response/2 function
takes a #http_response{} record and also a #headers{} record. You can find
definitions for these record types in the yaws_api.hrl header file. Each function
can examine each record instance and can either return each original instance or
can return a modified copy of each instance in its response. The rewrite_request/2
function should return a tuple of the following form:

{ok, #http_request{}, #headers{}}

and the rewrite_response/2 function should similarly return a tuple of the
following form:

{ok, #http_response{}, #headers{}}

A #headers{} record can easily be manipulated in an interceptor using the functions
listed below:

yaws_api:set_header/2, yaws_api:set_header/3
yaws_api:get_header/2, yaws_api:get_header/3
yaws_api:delete_header/2

Any failures in your interception module's functions will result in HTTP status
code 500, indicating an internal server error.

fwdproxy = true|false
Make Yaws a forward proxy. By enabling this option you can use Yaws as a proxy for
outgoing web traffic, typically by configuring the proxy settings in a web-browser
to explicitly target Yaws as its proxy server.

servername = Name
If we're virthosting several servers and want to force a server to match specific
Host: headers we can do this with the "servername" directive. This name doesn't
necessarily have to be the same as the the name inside <server Name> in certain NAT
scenarios. Rarely used feature.

serveralias = ListOfNames

This directive sets the alternate names for a virtual host. A server alias may
contain wildcards:
'*' matches any sequence of zero or more characters
'?' matches one character unless that character is a period ('.')

Multiple serveralias directives may be used. Here is an example:

<server server.domain.com>
serveralias = server server2.domain.com server2
serveralias = *.server.domain.com *.server?.domain.com
...
</server>

php_handler = <Type, Spec>
Set handler to interpret .php files. It can be one of the following definitions:

php_handler = <cgi, Filename> - The name of (and possibly path to) the php
executable used to interpret php scripts (if allowed).

php_handler = <fcgi, Host:Port> - Use the specified fastcgi server to interpret
.php files (if allowed).

Yaws does not start the PHP interpreter in fastcgi mode for you. To run PHP in
fastcgi mode, call it with the -b option. For example:

php5-cgi -b '127.0.0.1:54321'

This starts a php5 in fastcgi mode listening on the local network interface.
To make use of this PHP server from Yaws, specify:

php_handler = <fcgi, 127.0.0.1:54321>

If you need to specify an IPv6 address, use square brackets:

php_handler = <fcgi, [::1]:54321>

The PHP interpreter needs read access to the files it is to serve. Thus, if
you run it in a different security context than Yaws itself, make sure it has
access to the .php files.
Please note that anyone who is able to connect to the php fastcgi server
directly can use it to read any file to which it has read access. You should
consider this when setting up a system with several mutually untrusted
instances of php.

php_handler = <extern, Module:Function | Node:Module:Function> - Use an external
handler, possibly on another node, to interpret .php files (if allowed).

To interpret a .php file, the function Module:Function(Arg) will be invoked
(Evaluated inside a rpc call if a Node is specified), where Arg is an #arg{}
record.
The function must do the same things that a normal out/1 does.

Default value is <cgi, "/usr/bin/php-cgi">.

phpfcgi = Host:Port
this target is deprecated. use 'php_handler' target in server part instead.
Using this directive is the same as: php_handler = <fcgi, Host:Port>.

default_type = MimeType
Overloads the global default_type value for this virtual server.

default_charset = Charset
Overloads the global default_charset value for this virtual server.

mime_types_file = File
Overloads the global mime_type_file value for this virtual server. Mappings defined
in File will not overload those defined by add_types directives in the global part.

add_types = ListOfTypes
Overloads the global add_types values for this virtual server. If a mapping is
defined in the global part and redefined in a server part using this directive,
then it is replaced. Else it is kept.

add_charsets = ListOfCharsets
Overloads the global add_charsets values for this virtual server. If a mapping is
defined in the global part and redefined in a server part using this directive,
then it is replaced. Else it is kept.

nslookup_pref = [inet | inet6]
For fcgi servers and revproxy URLs, define the name resolution preference. For
example, to perform only IPv4 name resolution, use [inet]. To do both IPv4 and IPv6
but try IPv6 first, use [inet6, inet]. Default value is [inet].

This begins and ends an SSL configuration for this server. It's possible to
virthost several SSL servers on the same IP/Port. If SNI support is disabled or not
supported, they must share the same certificate configuration. In this situation,
it is complicated to virthost several SSL servers on the same IP/Port since the
certificate is typically bound to a domainname in the common name part of the
certificate. One solution to this problem is to have a certificate with multiple
subjectAltNames. If SNI support is enabled, SSL servers on the same IP/Port can
have their own SSL configuration with a different SSL certificate for each one. See
the global sni directive.

The SNI support was introduced in the SSL application in Erlang/OTP 18.0. It is an
extension to the TLS protocol (RFC 4366), which allows the client to include the
requested hostname in the first message of its SSL handshake.

See also http://wiki.cacert.org/VhostTaskForce#Interoperability_Test for browser
compatibility.

keyfile = File
Specifies which file contains the private key for the certificate. If not
specified then the certificate file will be used.

certfile = File
Specifies which file contains the certificate for the server.

cacertfile = File
A file containing trusted certificates to use during client authentication and
to use when attempting to build the server certificate chain. The list is
also used in the list of acceptable client CAs passed to the client when a
certificate is requested.

dhfile = File
A file containing PEM-encoded Diffie-Hellman parameters to be used by the
server if a cipher suite using Diffie-Hellman key exchange is negotiated. If
not specified, default parameters are used.

verify = verify_none | verify_peer
Specifies the level of verification the server does on client certs. Setting
verify_none means that the x509 validation will be skipped (no certificate
request is sent to the client), verify_peer means that a certificate request
is sent to the client (x509 validation is performed.

You might want to use fail_if_no_peer_cert in combination with verify_peer.

fail_if_no_peer_cert = true | false
If verify is set to verify_peer and set to true the connection will fail if
the client does not send a certificate (i.e. an empty certificate). If set to
false the server will fail only if an invalid certificate is supplied (an
empty certificate is considered valid).

depth = Int
Specifies the depth of certificate chains the server is prepared to follow
when verifying client certs. For the OTP new SSL implementation it is also
used to specify how far the server, i.e. we, shall follow the SSL certificates
we present to the clients. Hence, using self-signed certs, we typically need
to set this to 0.

password = String
If the private key is encrypted on disc, this password is the 3DES key to
decrypt it.

ciphers = String
This string specifies the SSL cipher string. The syntax of the SSL cipher
string is an erlang term compliant with the output of ssl:cipher_suites().

ciphers = "[{dhe_rsa,aes_256_cbc,sha}, \
{dhe_dss,aes_256_cbc,sha}]"

secure_renegotiate = true | false
Specifies whether to reject renegotiation attempt that does not live up to RFC
5746. By default secure_renegotiate is set to false i.e. secure renegotiation
will be used if possible but it will fallback to unsecure renegotiation if the
peer does not support RFC 5746.

client_renegotiation = true | false
Enables or disables the Erlang/OTP SSL application client renegotiation
option. Defaults to true. See the ssl manual page at
http://www.erlang.org/doc/man/ssl.html for more details.

WARNING: This option was introduced in the SSL application in Erlang/OTP 18.0,
so Yaws ignores it for previous releases.

honor_cipher_order = true | false
If true (the default), use the server's preference for cipher selection. If
false, use the client's preference.

WARNING: This option was introduced in the SSL application in Erlang/OTP 17.0,
so Yaws ignores it for previous releases.

protocol_version = ProtocolList
Specifies the list of SSL protocols that will be supported. If not set,
defaults to all protocols supported by the erlang ssl application. For
example, to support only TLS versions 1.2, 1.1, and 1:

protocol_version = tlsv1.2, tlsv1.1, tlsv1

require_sni = true | false
If true,the server will reject non SNI clients and clients providing an
unknown SNI hostname (this last remark is only relevant for the first virtual
server of a SSL group). This directive is ignored if SNI support is disabled
(or not supported).

Default is false.

<redirect> ... </redirect>
Defines a redirect mapping. The following items are allowed within a matching pair
of <redirect> and </redirect> delimiters.

We can have a series of redirect rules in one of the formats below:

Path = URL
Path = code
Path = code URL

Path must be an url-decoded path beginning with a slash. URL may be either a
relative URL (a path beginning with a slash), or an absolute URL. In the first
case, the scheme:hostname:port of the current server will be added. All accesses to
Path will be redirected to URL/Path (or scheme:hostname:port/URL/Path if URL is
relative). URL must be url-encoded. Note that the original path is appended to the
redirected URL.

For example, assume we have the following redirect configuration:

<redirect>
/foo = http://www.mysite.org/zapp
/bar = /tomato.html
</redirect>

Assuming this config resides on a site called http://abc.com, we have the following
redirects:

http://abc.com/foo -> http://www.mysite.org/zapp/foo
http://abc.com/foo/test -> http://www.mysite.org/zapp/foo/test
http://abc.com/bar -> http://abc.com/tomato.html/bar
http://abc.com/bar/x/y/z -> http://abc.com/tomato.html/bar/x/y/z

By default, Yaws will perform a 302 redirect. The HTTP status code can be changed
using the code parameter. Note that the status code must be known by Yaws.

• For 3xx status codes, the URL parameter must be present and will be used to
build the new location.

• For other status codes (1xx, 2xx, 4xx and 5xx), it can be omitted. In the
absence of URL, Yaws will return a generic response with the specified status
code.

• Otherwise, the URL parameter must be a relative URL and will be used to
customize the response.

Sometimes we do not want to have the original path appended to the redirected path.
To get that behaviour we specify the config with '==' instead of '='.

<redirect>
/foo == http://www.mysite.org/zapp
/bar = /tomato.html
</redirect>

Now a request for http://abc.com/foo/x/y/z simply gets redirected to
http://www.mysite.org/zapp. This is typically used when we simply want a static
redirect at some place in the docroot.

When we specify a relative URL as the target for the redirect, the redirect will be
to the current http(s) server.

<auth> ... </auth>
Defines an auth structure. The following items are allowed within a matching pair
of <auth> and </auth> delimiters.

docroot = Docroot
If a docroot is defined, this auth structure will be tested only for requests
in the specified docroot. No docroot configured means all docroots. If two
auth structures are defined, one with a docroot and one with no docroot, the
first of both overrides the second one for requests in the configured docroot.

dir = Dir
Makes Dir to be controlled by WWW-authenticate headers. In order for a user to
have access to WWW-Authenticate controlled directory, the user must supply a
password. The Dir must be specified relative to the docroot. Multiple dir can
be used. If no dir is set, the default value, "/", will be used.

realm = Realm
In the directory defined here, the WWW-Authenticate Realm is set to this
value.

authmod = AuthMod
If an auth module is defined then AuthMod:auth(Arg, Auth) will be called for
all access to the directory. The auth/2 function should return one of: true,
false, {false, Realm}, {appmod, Mod}. If {appmod, Mod} is returned then a
call to Mod:out401(Arg, Auth, Realm) will be used to deliver the content. If
errormod_401 is defined, the call to Mod will be ignored. (Mod:out(Arg) is
deprecated).

This can, for example, be used to implement cookie authentication. The auth()
callback would check if a valid cookie header is present, if not it would
return {appmod, ?MODULE} and the out401/1 function in the same module would
return {redirect_local, "/login.html"}.

user = User:Password | "User:{Algo}Hash" | "User:{Algo}$Salt$Hash"
Inside this directory, the user User has access if the user supplies the
password Password in the popup dialogue presented by the browser. It is also
possible to provide a hashed password, encoded in base64. In that case, the
algorithm used to hash the password must be set. Algo must be a one of the
following algorithms:

md5 | ripemd160 | sha | sha224 | sha256 | sha384 | sha512

It is possible to use salted hashes. If so, the Salt must be provided, encoded
in base64. We can obviously have several of these value inside a single <auth>
</auth> pair.

pam service = pam-service
If the item pam is part of the auth structure, Yaws will also try to
authenticate the user using "pam" using the pam service indicated. Usual
services are typically found under /etc/pam.d. Usual values are "system-auth"
etc.

pam authentication is performed by an Erlang port program which is typically
installed as suid root by the Yaws install script.

allow = all | ListOfHost
The allow directive affects which hosts can access an area of the server.
Access can be controlled by IP address or IP address range. If all is
specified, then all hosts are allowed access, subject to the configuration of
the deny and order directives. To allow only particular hosts or groups of
hosts to access the server, the host can be specified in any of the following
formats:

A full IP address
allow = 10.1.2.3
allow = 192.168.1.104, 192.168.1.205

A network/netmask pair
allow = 10.1.0.0/255.255.0.0

A network/nnn CIDR specification
allow = 10.1.0.0/16

deny = all | ListOfHost
This directive allows access to the server to be restricted based on IP
address. The arguments for the deny directive are identical to the arguments
for the allow directive.

order = Ordering
The order directive, along with allow and deny directives, controls a three-
pass access control system. The first pass processes either all allow or all
deny directives, as specified by the order directive. The second pass parses
the rest of the directives (deny or allow). The third pass applies to all
requests which do not match either of the first two.

Ordering is one of (Default value is deny,allow):

allow,deny
First, all allow directives are evaluated; at least one must match, or
the request is rejected. Next, deny directives are evaluated. If any
matches, the request is rejected. Last, any requests which do not match
an allow or a deny directive are denied by default.

deny,allow
First, all deny directives are evaluated; if any matched, the request
is denied unless it also matches an allow directive. Any requests which
do not match any allow or deny directives are permitted.

<opaque> ... </opaque>
This begins and ends an opaque configuration context for this server, where 'Key =
Value' directives can be specified. These directives are ignored by Yaws (hence the
name opaque), but can be accessed as a list of tuples {Key,Value} stored in the
#sconf.opaque record entry. See also the description of the start_mod directive.

This mechanism can be used to pass data from a surrounding application into the
individual .yaws pages.

EXAMPLES

       The following example defines a single server on port 80.

           logdir = /var/log/yaws
           <server www.mydomain.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www
           </server>

       And this example shows a similar setup but two web servers on the same IP address.

           logdir = /var/log/yaws
           <server www.mydomain.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www
           </server>

           <server www.funky.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www_funky_org
           </server>

       An example with www-authenticate and no access logging at all.

           logdir = /var/log/yaws
           <server www.mydomain.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www
               access_log = false
               <auth>
                   dir = secret/dir1
                   realm = foobar
                   user = jonny:verysecretpwd
                   user = benny:thequestion
                   user = ronny:havinganamethatendswithy
              </auth>
           </server>

       An example specifying a user defined module to be called at startup, as well as some  user
       specific configuration.

           <server www.funky.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www_funky_org
               start_mod = btt
               <opaque>
                       mydbdir = /tmp
                       mylogdir = /tmp/log
               </opaque>
           </server>

       An   example   specifying  the  GSSAPI/SPNEGO  module  (authmod_gssapi)  to  be  used  for
       authentication. This module requires  egssapi  version  0.1~pre2  or  later  available  at
       http://www.hem.za.org/egssapi/.

       The  Kerberos5  keytab  is  specified  as 'keytab = File' directive in opaque. This keytab
       should contain the keys of  the  HTTP  service  principal,  'HTTP/www.funky.org'  in  this
       example.

           <server www.funky.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www_funky_org
               start_mod = authmod_gssapi
               <auth>
                       authmod = authmod_gssapi
                       dir = secret/dir1
               </auth>
               <opaque>
                       keytab = /etc/yaws/http.keytab
               </opaque>
           </server>

       And  finally  a slightly more complex example with two servers on the same IP, and one SSL
       server on a different IP.

       When there are more than one server on the same IP, and  they  have  different  names  the
       server  must be able to choose one of them if the client doesn't send a Host: header. Yaws
       will choose the first one defined in the conf file.

           logdir = /var/log/yaws
           max_num_cached_files = 8000
           max_num_cached_bytes = 6000000

           <server www.mydomain.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www
           </server>

           <server www.funky.org>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www_funky_org
           </server>

           <server www.funky.org>
               port = 443
               listen = 192.168.128.32
               docroot = /var/yaws/www_funky_org
               <ssl>
                  keyfile = /etc/funky.key
                  certfile = /etc/funky.cert
                  password = gazonk
               </ssl>
           </server>

       Finally an example with virtual directories, vdirs.

           <server server.domain>
               port = 80
               listen = 192.168.128.31
               docroot = /var/yaws/www
               arg_rewrite_mod = yaws_vdir
               <opaque>
                   vdir = "/virtual1/ /usr/local/somewhere/notrelated/to/main/docroot"
                   vdir = "/myapp/ /some/other/path can include/spaces"
                   vdir = "/icons/  /usr/local/www/yaws/icons"
               </opaque>
           </server>

       The first defined vdir can then be accessed at or under http://server.domain/virtual1/  or
       http://server.domain/virtual1

AUTHOR