HttpEchoModule

= Name =

ngx_echo - Brings "echo", "sleep", "time", "exec" and more shell-style goodies to Nginx config file.

This module is not distributed with the Nginx source. See the installation instructions.

= Status =

This module is production ready.

= Version =

This document describes ngx_echo v0.52 released on 20 March 2014.

= Synopsis =

location /hello { echo "hello, world!"; }

location /hello { echo -n "hello, "; echo "world!"; }

location /timed_hello { echo_reset_timer; echo hello world; echo "'hello world' takes about $echo_timer_elapsed sec."; echo hiya igor; echo "'hiya igor' takes about $echo_timer_elapsed sec."; }

location /echo_with_sleep { echo hello; echo_flush; # ensure the client can see previous output immediately echo_sleep  2.5;  # in sec echo world; }

# in the following example, accessing /echo yields #  hello #  world #  blah #  hiya #  igor location /echo { echo_before_body hello; echo_before_body world; proxy_pass $scheme://127.0.0.1:$server_port$request_uri/more; echo_after_body hiya; echo_after_body igor; } location /echo/more { echo blah; }

# the output of /main might be #   hello #  world #  took 0.000 sec for total. # and the whole request would take about 2 sec to complete. location /main { echo_reset_timer; # subrequests in parallel echo_location_async /sub1; echo_location_async /sub2; echo "took $echo_timer_elapsed sec for total."; } location /sub1 { echo_sleep 2; echo hello; } location /sub2 { echo_sleep 1; echo world; }

# the output of /main might be #   hello #  world #  took 3.003 sec for total. # and the whole request would take about 3 sec to complete. location /main { echo_reset_timer; # subrequests in series (chained by CPS) echo_location /sub1; echo_location /sub2; echo "took $echo_timer_elapsed sec for total."; } location /sub1 { echo_sleep 2; echo hello; } location /sub2 { echo_sleep 1; echo world; }

# Accessing /dup gives #  -- END -- location /dup { echo_duplicate 3 "--"; echo_duplicate 1 " END "; echo_duplicate 3 "--"; echo; }

# /bighello will generate 1000,000,000 hello's. location /bighello { echo_duplicate 1000_000_000 'hello'; }

# echo back the client request location /echoback { echo_duplicate 1 $echo_client_request_headers; echo "\r"; echo_read_request_body; echo_request_body; }

# GET /multi will yields #  querystring: foo=Foo #  method: POST #  body: hi  #   content length: 2 #  ///  #   querystring: bar=Bar #  method: PUT #  body: hello #  content length: 5 #  ///  location /multi { echo_subrequest_async POST '/sub' -q 'foo=Foo' -b 'hi'; echo_subrequest_async PUT '/sub' -q 'bar=Bar' -b 'hello'; } location /sub { echo "querystring: $query_string"; echo "method: $echo_request_method"; echo "body: $echo_request_body"; echo "content length: $http_content_length"; echo '///'; }

# GET /merge?/foo.js&/bar/blah.js&/yui/baz.js will merge the .js resources together location /merge { default_type 'text/javascript'; echo_foreach_split '&' $query_string; echo "/* JS File $echo_it */"; echo_location_async $echo_it; echo; echo_end; }

# accessing /if?val=abc yields the "hit" output # while /if?val=bcd yields "miss": location ^~ /if { set $res miss; if ($arg_val ~* '^a') { set $res hit; echo $res; }     echo $res; }

= Description =

This module wraps lots of Nginx internal APIs for streaming input and output, parallel/sequential subrequests, timers and sleeping, as well as various meta data accessing.

Basically it provides various utilities that help testing and debugging of other modules by trivially emulating different kinds of faked subrequest locations.

People will also find it useful in real-world applications that need to


 * 1) serve static contents directly from memory (loading from the Nginx config file).
 * 2) wrap the upstream response with custom header and footer (kinda like the addition module but with contents read directly from the config file and Nginx variables).
 * 3) merge contents of various "Nginx locations" (i.e., subrequests) together in a single main request (using echo_location and its friends).

This is a special dual-role module that can lazily serve as a content handler or register itself as an output filter only upon demand. By default, this module does not do anything at all.

Technially, this module has also demonstrated the following techniques that might be helpful for module writers:


 * 1) Issue parallel subreqeusts directly from content handler.
 * 2) Issue chained subrequests directly from content handler, by passing continuation along the subrequest chain.
 * 3) Issue subrequests with all HTTP 1.1 methods and even an optional faked HTTP request body.
 * 4) Interact with the Nginx event model directly from content handler using custom events and timers, and resume the content handler back if necessary.
 * 5) Dual-role module that can (lazily) serve as a content handler or an output filter or both.
 * 6) Nginx config file variable creation and interpolation.
 * 7) Streaming output control using output_chain, flush and its friends.
 * 8) Read client request body from the content handler, and returns back (asynchronously) to the content handler after completion.
 * 9) Use Perl-based declarative test suite to drive the development of Nginx C modules.

= Content Handler Directives =

Use of the following directives register this module to the current Nginx location as a content handler. If you want to use another module, like the standard proxy module, as the content handler, use the filter directives provided by this module.

All the content handler directives can be mixed together in a single Nginx location and they're supposed to run sequentially just as in the Bash scripting language.

Every content handler directive supports variable interpolation in its arguments (if any).

The MIME type set by the standard default_type directive is respected by this module, as in:

location /hello { default_type text/plain; echo hello; }

Then on the client side:

$ curl -I 'http://localhost/echo' HTTP/1.1 200 OK Server: nginx/0.8.20 Date: Sat, 17 Oct 2009 03:40:19 GMT Content-Type: text/plain Connection: keep-alive

Since the v0.22 release, all of the directives are allowed in the rewrite module's if directive block, for instance:

location ^~ /if { set $res miss; if ($arg_val ~* '^a') { set $res hit; echo $res; }       echo $res; }

echo
syntax: echo [options] ...

default: no

context: location, location if

phase: content

Sends arguments joined by spaces, along with a trailing newline, out to the client.

Note that the data might be buffered by Nginx's underlying buffer. To force the output data flushed immediately, use the echo_flush command just after, as in

echo hello world; echo_flush;

When no argument is specified, echo emits the trailing newline alone, just like the echo command in shell.

Variables may appear in the arguments. An example is

echo The current request uri is $request_uri;

where $request_uri is a variable exposed by the HttpCoreModule.

This command can be used multiple times in a single location configuration, as in

location /echo { echo hello; echo world; }

The output on the client side looks like this

$ curl 'http://localhost/echo' hello world

Special characters like newlines and tabs  can be escaped using C-style escaping sequences. But a notable exception is the dollar sign. As of Nginx 0.8.20, there's still no clean way to esacpe this characters. (A work-around might be to use a  variable that is always evaluated to the constant   character. This feature will possibly be introduced in a future version of this module.)

As of the echo v0.28 release, one can suppress the trailing newline character in the output by using the  option, as in

location /echo { echo -n "hello, "; echo "world"; }

Accessing  gives

$ curl 'http://localhost/echo' hello, world

Leading  in variable values won't take effect and will be emitted literally, as in

location /echo { set $opt -n; echo $opt "hello,"; echo "world"; }

This gives the following output

$ curl 'http://localhost/echo' -n hello, world

One can output leading  literals and other options using the special   option like this

location /echo { echo -- -n is an option; }

which yields

$ curl 'http://localhost/echo' -n is an option

echo_duplicate
syntax: echo_duplicate 

default: no

context: location, location if

phase: content

Outputs duplication of a string indicated by the second argument, using the times specified in the first argument.

For instance,

location /dup { echo_duplicate 3 "abc"; }

will lead to an output of.

Underscores are allowed in the count number, just like in Perl. For example, to emit 1000,000,000 instances of :

location /many_hellos { echo_duplicate 1000_000_000 "hello, world"; }

The  argument could be zero, but not negative. The second  argument could be an empty string ("") likewise.

Unlike the echo directive, no trailing newline is appended to the result. So it's possible to "abuse" this directive as a no-trailing-newline version of echo by using "count" 1, as in

location /echo_art { echo_duplicate 2 '---'; echo_duplicate 1 ' END '; # we don't want a trailing newline here echo_duplicate 2 '---'; echo; # we want a trailing newline here... }

You get

-- END --

This directive was first introduced in version 0.11.

echo_flush
syntax: echo_flush

default: no

context: location, location if

phase: content

Forces the data potentially buffered by underlying Nginx output filters to send immediately to the client side via socket.

Note that techically the command just emits a ngx_buf_t object with  slot set to 1, so certain weird third-party output filter module could still block it before it reaches Nginx's (last) write filter.

This directive does not take any argument.

Consider the following example:

location /flush { echo hello; echo_flush; echo_sleep 1; echo world; }

Then on the client side, using curl to access, you'll see the "hello" line immediately, but only after 1 second, the last "world" line. Without calling  in the example above, you'll most likely see no output until 1 second is elapsed due to the internal buffering of Nginx.

This directive will fail to flush the output buffer in case of subrequests get involved. Consider the following example:

location /main { echo_location_async /sub; echo hello; echo_flush; } location /sub { echo_sleep 1; }

Then the client won't see "hello" appear even if  has been executed before the subrequest to   has actually started executing. The outputs of  that are sent after echo_location_async will be postponed and buffered firmly.

This does not apply to outputs sent before the subrequest initiated. For a modified version of the example given above:

location /main { echo hello; echo_flush; echo_location_async /sub; } location /sub { echo_sleep 1; }

The client will immediately see "hello" before  enters sleeping.

See also echo, echo_sleep, and echo_location_async.

echo_sleep
syntax: echo_sleep 

default: no

context: location, location if

phase: content

Sleeps for the time period specified by the argument, which is in seconds.

This operation is non-blocking on server side, so unlike the echo_blocking_sleep directive, it won't block the whole Nginx worker process.

The period might takes three digits after the decimal point and must be greater than 0.001.

An example is

location /echo_after_sleep { echo_sleep 1.234; echo resumed!; }

Behind the scene, it sets up a per-request "sleep" ngx_event_t object, and adds a timer using that custom event to the Nginx event model and just waits for a timeout on that event. Because the "sleep" event is per-request, this directive can work in parallel subrequests.

echo_blocking_sleep
syntax: echo_blocking_sleep 

default: no

context: location, location if

phase: content

This is a blocking version of the echo_sleep directive.

See the documentation of echo_sleep for more detail.

Behind the curtain, it calls the ngx_msleep macro provided by the Nginx core which maps to usleep on POSIX-compliant systems.

Note that this directive will block the current Nginx worker process completely while being executed, so never use it in production environment.

echo_reset_timer
syntax: echo_reset_timer

default: no

context: location, location if

phase: content

Reset the timer begin time to now, i.e., the time when this command is executed during request.

The timer begin time is default to the starting time of the current request and can be overridden by this directive, potentially multiple times in a single location. For example:

location /timed_sleep { echo_sleep 0.03; echo "$echo_timer_elapsed sec elapsed."; echo_reset_timer; echo_sleep 0.02; echo "$echo_timer_elapsed sec elapsed."; }

The output on the client side might be

$ curl 'http://localhost/timed_sleep' 0.032 sec elapsed. 0.020 sec elapsed.

The actual figures you get on your side may vary a bit due to your system's current activities.

Invocation of this directive will force the underlying Nginx timer to get updated to the current system time (regardless the timer resolution specified elsewhere in the config file). Furthermore, references of the $echo_timer_elapsed variable will also trigger timer update forcibly.

See also echo_sleep and $echo_timer_elapsed.

echo_read_request_body
syntax: echo_read_request_body

default: no

context: location, location if

phase: content

Explicitly reads request body so that the $request_body variable will always have non-empty values (unless the body is so big that it has been saved by Nginx to a local temporary file).

Note that this might not be the original client request body because the current request might be a subrequest with a "artificial" body specified by its parent.

This directive does not generate any output itself, just like echo_sleep.

Here's an example for echo'ing back the original HTTP client request (both headers and body are included):

location /echoback { echo_duplicate 1 $echo_client_request_headers; echo "\r"; echo_read_request_body; echo $request_body; }

The content of  looks like this on my side (I was using Perl's LWP utility to access this location on the server):

$ (echo hello; echo world) | lwp-request -m POST 'http://localhost/echoback' POST /echoback HTTP/1.1 TE: deflate,gzip;q=0.3 Connection: TE, close Host: localhost User-Agent: lwp-request/5.818 libwww-perl/5.820 Content-Length: 12 Content-Type: application/x-www-form-urlencoded hello world

Because  is the main request, $request_body holds the original client request body.

Before Nginx 0.7.56, it makes no sense to use this directive because $request_body was first introduced in Nginx 0.7.58.

This directive itself was first introduced in the echo module's v0.14 release.

echo_location_async
syntax: echo_location_async []

default: no

context: location, location if

phase: content

Issue GET subrequest to the location specified (first argument) with optional url arguments specified in the second argument.

As of Nginx 0.8.20, the  argument does not support named location, due to a limitation in the   function. The same is true for its brother, the echo_location directive.

A very simple example is

location /main { echo_location_async /sub; echo world; }   location /sub { echo hello; }

Accessing  gets

hello world

Calling multiple locations in parallel is also possible:

location /main { echo_reset_timer; echo_location_async /sub1; echo_location_async /sub2; echo "took $echo_timer_elapsed sec for total."; }   location /sub1 { echo_sleep 2; # sleeps 2 sec echo hello; }   location /sub2 { echo_sleep 1; # sleeps 1 sec echo world; }

Accessing  yields

$ time curl 'http://localhost/main' hello world took 0.000 sec for total. real 0m2.006s user 0m0.000s sys  0m0.004s

You can see that the main handler  does not wait the subrequests   and   to complete and quickly goes on, hence the "0.000 sec" timing result. The whole request, however takes approximately 2 sec in total to complete because  and   run in parallel (or "concurrently" to be more accurate).

If you use echo_blocking_sleep in the previous example instead, then you'll get the same output, but with 3 sec total response time, because "blocking sleep" blocks the whole Nginx worker process.

Locations can also take an optional querystring argument, for instance

location /main { echo_location_async /sub 'foo=Foo&bar=Bar'; }   location /sub { echo $arg_foo $arg_bar; }

Accessing  yields

$ curl 'http://localhost/main' Foo Bar

Querystrings is not allowed to be concatenated onto the  argument with "?" directly, for example,  is an invalid location, and shouldn't be fed as the first argument to this directive.

Due to an unknown bug in Nginx (it still exists in Nginx 0.8.20), the standard SSI module is required to ensure that the contents of the subrequests issued by this directive are correctly merged into the output chains of the main one. Fortunately, the SSI module is enabled by default during Nginx's  process.

If calling this directive without SSI module enabled, you'll get truncated response without contents of any subrequests and get an alert message in your Nginx's, like this:

[alert] 24212#0: *1 the http output chain is empty, client: 127.0.0.1, ...

Technically speaking, this directive is an example that Nginx content handler issues one or more subrequests directly. AFAIK, the fancyindex module also does such kind of things ;)

Nginx named locations like  is not supported here.

This directive is logically equivalent to the GET version of echo_subrequest_async. For example,

echo_location_async /foo 'bar=Bar';

is logically equivalent to

echo_subrequest_async GET /foo -q 'bar=Bar';

But calling this directive is slightly faster than calling echo_subrequest_async using  because we don't have to parse the HTTP method names like   and options like.

This directive is first introduced in version 0.09 of this module and requires at least Nginx 0.7.46.

echo_location
syntax: echo_location []

default: no

context: location, location if

phase: content

Just like the echo_location_async directive, but  issues subrequests in series rather than in parallel. That is, the content handler directives following this directive won't be executed until the subrequest issued by this directive completes.

The final response body is almost always equivalent to the case when echo_location_async is used instead, only if timing variables is used in the outputs.

Consider the following example:

location /main { echo_reset_timer; echo_location /sub1; echo_location /sub2; echo "took $echo_timer_elapsed sec for total."; }   location /sub1 { echo_sleep 2; echo hello; }   location /sub2 { echo_sleep 1; echo world; }

The location  above will take for total 3 sec to complete (compared to 2 sec if echo_location_async is used instead here). Here's the result in action on my machine:

$ curl 'http://localhost/main' hello world took 3.003 sec for total. real 0m3.027s user 0m0.020s sys  0m0.004s

This directive is logically equivalent to the GET version of echo_subrequest. For example,

echo_location /foo 'bar=Bar';

is logically equivalent to

echo_subrequest GET /foo -q 'bar=Bar';

But calling this directive is slightly faster than calling echo_subrequest using  because we don't have to parse the HTTP method names like   and options like.

Behind the scene, it creates an  object as a continuation and passes it into the   function call. Nginx will later reopen this "continuation" in the subrequest's  function call. We resumes the execution of the parent-request's content handler and starts to run the next directive (command) if any.

Nginx named locations like  is not supported here.

This directive was first introduced in the release v0.12.

See also echo_location_async for more details about the meaning of the arguments.

echo_subrequest_async
syntax: echo_subrequest_async  [-q ] [-b ] [-f ]

default: no

context: location, location if

phase: content

Initiate an asynchronous subrequest using HTTP method, an optional url arguments (or querystring) and an optional request body which can be defined as a string or as a path to a file which contains the body.

This directive is very much like a generalized version of the echo_location_async directive.

Here's a small example demonstrating its usage:

location /multi { # body defined as string echo_subrequest_async POST '/sub' -q 'foo=Foo' -b 'hi'; # body defined as path to a file, relative to nginx prefix path if not absolute echo_subrequest_async PUT '/sub' -q 'bar=Bar' -f '/tmp/hello.txt'; }   location /sub { echo "querystring: $query_string"; echo "method: $echo_request_method"; echo "body: $echo_request_body"; echo "content length: $http_content_length"; echo '///'; }

Then on the client side:

$ echo -n hello > /tmp/hello.txt $ curl 'http://localhost/multi' querystring: foo=Foo method: POST body: hi content length: 2 /// querystring: bar=Bar method: PUT body: hello content length: 5 ///

Here's more funny example using the standard proxy module to handle the subrequest:

location /main { echo_subrequest_async POST /sub -b 'hello, world'; }   location /sub { proxy_pass $scheme://127.0.0.1:$server_port/proxied; }   location /proxied { echo "method: $echo_request_method."; # we need to read body explicitly here...or $echo_request_body #  will evaluate to empty ("") echo_read_request_body; echo "body: $echo_request_body."; }

Then on the client side, we can see that

$ curl 'http://localhost/main' method: POST. body: hello, world.

Nginx named locations like  is not supported here.

This directive takes several options:

-q        Specify the URL arguments (or URL querystring) for the subrequest.

-f           Specify the path for the file whose content will be serve as the subrequest's request body.

-b  option to define a file path for the body was introduced in the release v0.35.

See also the echo_subrequest and echo_location_async directives.

echo_subrequest
syntax: echo_subrequest  [-q ] [-b ] [-f ]

default: no

context: location, location if

phase: content

This is the synchronous version of the echo_subrequest_async directive. And just like echo_location, it does not block the Nginx worker process (while echo_blocking_sleep does), rather, it uses continuation to pass control along the subrequest chain.

See echo_subrequest_async for more details.

Nginx named locations like  is not supported here.

This directive was first introduced in the release v0.15.

echo_foreach_split
syntax: echo_foreach_split 

default: no

context: location, location if

phase: content

Split the second argument  using the delimiter specified in the first argument, and then iterate through the resulting items. For instance:

location /loop { echo_foreach_split ',' $arg_list; echo "item: $echo_it"; echo_end; }

Accessing /main yields

$ curl 'http://localhost/loop?list=cat,dog,mouse' item: cat item: dog item: mouse

As seen in the previous example, this directive should always be accompanied by an echo_end directive.

Parallel  loops are allowed, but nested ones are currently forbidden.

The  argument could contain multiple arbitrary characters, like

# this outputs "cat\ndog\nmouse\n" echo_foreach_split -- '-a-' 'cat-a-dog-a-mouse'; echo $echo_it; echo_end;

Logically speaking, this looping structure is just the  loop combined with a   function call in Perl (using the previous example):

foreach (split ',', $arg_list) { print "item $_\n"; }

People will also find it useful in merging multiple  or   resources into a whole. Here's an example:

location /merge { default_type 'text/javascript'; echo_foreach_split '&' $query_string; echo "/* JS File $echo_it */"; echo_location_async $echo_it; echo; echo_end; }

Then accessing /merge to merge the  resources specified in the query string:

$ curl 'http://localhost/merge?/foo/bar.js&/yui/blah.js&/baz.js'

One can also use third-party Nginx cache module to cache the merged response generated by the  location in the previous example.

This directive was first introduced in the release v0.17.

echo_end
syntax: echo_end

default: no

context: location, location if

phase: content

This directive is used to terminate the body of looping and conditional control structures like echo_foreach_split.

This directive was first introduced in the release v0.17.

echo_request_body
syntax: echo_request_body

default: no

context: location, location if

phase: content

Outputs the contents of the request body previous read.

Behind the scene, it's implemented roughly like this:

 if (r->request_body && r->request_body->bufs) { return ngx_http_output_filter(r, r->request_body->bufs); }

Unlike the $echo_request_body and $request_body variables, this directive will show the whole request body even if some parts or all parts of it are saved in temporary files on the disk.

It is a "no-op" if no request body has been read yet.

This directive was first introduced in the release v0.18.

See also echo_read_request_body and the chunkin module.

echo_exec
syntax: echo_exec []

syntax: echo_exec 

default: no

context: location, location if

phase: content

Does an internal redirect to the location specified. An optional query string can be specified for normal locations, as in

location /foo { echo_exec /bar weight=5; } location /bar { echo $arg_weight; }

Or equivalently

location /foo { echo_exec /bar?weight=5; } location /bar { echo $arg_weight; }

Named locations are also supported. Here's an example:

location /foo { echo_exec @bar; } location @bar { # you'll get /foo rather than @bar # due to a potential bug in nginx. echo $echo_request_uri; }

But query string (if any) will always be ignored for named location redirects due to a limitation in the  function.

Never try to echo things before the  directive or you won't see the proper response of the location you want to redirect to. Because any echoing will cause the original location handler to send HTTP headers before the redirection happens.

Technically speaking, this directive exposes the Nginx internal API functions  and.

This directive was first introduced in the v0.21 release.

echo_status
syntax: echo_status 

default: echo_status 200

context: location, location if

phase: content

Specify the default response status code. Default to. This directive is declarative and the relative order with other echo-like directives is not important.

Here is an example,

location = /bad { echo_status 404; echo "Something is missing..."; }

then we get a response like this:

HTTP/1.1 404 Not Found Server: nginx/1.2.1 Date: Sun, 24 Jun 2012 03:58:18 GMT Content-Type: text/plain Transfer-Encoding: chunked Connection: keep-alive

Something is missing...

This directive was first introduced in the  release.

= Filter Directives =

Use of the following directives trigger the filter registration of this module. By default, no filter will be registered by this module.

Every filter directive supports variable interpolation in its arguments (if any).

echo_before_body
syntax: echo_before_body [options] [argument]...

default: no

context: location, location if

phase: output filter

It's the filter version of the echo directive, and prepends its output to the beginning of the original outputs generated by the underlying content handler.

An example is

location /echo { echo_before_body hello; proxy_pass $scheme://127.0.0.1:$server_port$request_uri/more; }   location /echo/more { echo world }

Accessing  from the client side yields

hello world

In the previous sample, we borrow the standard proxy module to serve as the underlying content handler that generates the "main contents".

Multiple instances of this filter directive are also allowed, as in:

location /echo { echo_before_body hello; echo_before_body world; echo !; }

On the client side, the output is like

$ curl 'http://localhost/echo' hello world !

In this example, we also use the content handler directives provided by this module as the underlying content handler.

This directive also supports the  and   options like the echo directive.

This directive can be mixed with its brother directive echo_after_body.

echo_after_body
syntax: echo_after_body [argument]...

default: no

context: location, location if

phase: output filter

It's very much like the echo_before_body directive, but appends its output to the end of the original outputs generated by the underlying content handler.

Here's a simple example:

location /echo { echo_after_body hello; proxy_pass http://127.0.0.1:$server_port$request_uri/more; }   location /echo/more { echo world }

Accessing  from the client side yields

world hello

Multiple instances are allowed, as in:

location /echo { echo_after_body hello; echo_after_body world; echo i;       echo say; }

The output on the client side while accessing the  location looks like

i say hello world

This directive also supports the  and   options like the echo directive.

This directive can be mixed with its brother directive echo_before_body.

= Variables =

$echo_it
This is a "topic variable" used by echo_foreach_split, just like the  variable in Perl.

$echo_timer_elapsed
This variable holds the seconds elapsed since the start of the current request (might be a subrequest though) or the last invocation of the echo_reset_timer command.

The timing result takes three digits after the decimal point.

References of this variable will force the underlying Nginx timer to update to the current system time, regardless the timer resolution settings elsewhere in the config file, just like the echo_reset_timer directive.

$echo_request_body
Evaluates to the current (sub)request's request body previously read if no part of the body has been saved to a temporary file. To always show the request body even if it's very large, use the echo_request_body directive.

$echo_request_method
Evaluates to the HTTP request method of the current request (it can be a subrequest).

Behind the scene, it just takes the string data stored in.

Compare it to the $echo_client_request_method variable.

At least for Nginx 0.8.20 and older, the $request_method variable provided by the http core module is actually doing what our $echo_client_request_method is doing.

This variable was first introduced in our v0.15 release.

$echo_client_request_method
Always evaluates to the main request's HTTP method even if the current request is a subrequest.

Behind the scene, it just takes the string data stored in.

Compare it to the $echo_request_method variable.

This variable was first introduced in our v0.15 release.

$echo_client_request_headers
Evaluates to the original client request's headers.

Just as the name suggests, it will always take the main request (or the client request) even if it's currently executed in a subrequest.

A simple example is below:

location /echoback { echo "headers are:" echo $echo_client_request_headers; }

Accessing  yields

$ curl 'http://localhost/echoback' headers are GET /echoback HTTP/1.1 User-Agent: curl/7.18.2 (i486-pc-linux-gnu) libcurl/7.18.2 OpenSSL/0.9.8g Host: localhost:1984 Accept: */*

Behind the scene, it recovers  (or the large header buffers, if any) on the C level and does not construct the headers itself by traversing parsed results in the request object.

This variable was first introduced in version 0.15.

$echo_cacheable_request_uri
Evaluates to the parsed form of the URI (usually led by ) of the current (sub-)request. Unlike the $echo_request_uri variable, it is cacheable.

See $echo_request_uri for more details.

This variable was first introduced in version 0.17.

$echo_request_uri
Evaluates to the parsed form of the URI (usually led by ) of the current (sub-)request. Unlike the $echo_cacheable_request_uri variable, it is not cacheable.

This is quite different from the $request_uri variable exported by the HttpCoreModule, because  is the unparsed form of the current request's URI.

This variable was first introduced in version 0.17.

$echo_incr
It is a counter that always generate the current counting number, starting from 1. The counter is always associated with the main request even if it is accessed within a subrequest.

Consider the following example

 location /main { echo "main pre: $echo_incr"; echo_location_async /sub; echo_location_async /sub; echo "main post: $echo_incr"; }   location /sub { echo "sub: $echo_incr"; }

Accessing  yields

main pre: 1 sub: 3 sub: 4 main post: 2

This directive was first introduced in the v0.18 release.

$echo_response_status
Evaluates to the status code of the current (sub)request, null if not any.

Behind the scene, it's just the textual representation of.

This directive was first introduced in the v0.23 release.

= Installation =

You're recommended to install this module (as well as the Nginx core and many other goodies) via the ngx_openresty bundle. See the detailed instructions for downloading and installing ngx_openresty into your system. This is the easiest and most safe way to set things up.

Alternatively, you can install this module manually with the Nginx source:

Grab the nginx source code from nginx.org, for example, the version 1.5.11 (see nginx compatibility), and then build the source with this module:

$ wget 'http://nginx.org/download/nginx-1.5.11.tar.gz' $ tar -xzvf nginx-1.5.11.tar.gz   $ cd nginx-1.5.11/ # Here we assume you would install you nginx under /opt/nginx/. $ ./configure --prefix=/opt/nginx \ --add-module=/path/to/echo-nginx-module $ make -j2 $ make install

Download the latest version of the release tarball of this module from echo-nginx-module file list.

Also, this module is included and enabled by default in the ngx_openresty bundle.

= Compatibility =

The following versions of Nginx should work with this module:


 * 1.5.x                      (last tested: 1.5.11)
 * 1.4.x                      (last tested: 1.4.4)
 * 1.3.x                      (last tested: 1.3.7)
 * 1.2.x                      (last tested: 1.2.9)
 * 1.1.x                      (last tested: 1.1.5)
 * 1.0.x                      (last tested: 1.0.11)
 * 0.9.x                      (last tested: 0.9.4)
 * 0.8.x                      (last tested: 0.8.54)
 * 0.7.x >= 0.7.21            (last tested: 0.7.68)

In particular,


 * the directive echo_location_async and its brother echo_subrequest_async do not work with 0.7.x < 0.7.46.
 * the echo_after_body directive does not work at all with nginx < 0.8.7.
 * the echo_sleep directive cannot be used after echo_location or echo_subrequest for nginx < 0.8.11.

Earlier versions of Nginx like 0.6.x and 0.5.x will not work at all.

If you find that any particular version of Nginx above 0.7.21 does not work with this module, please consider reporting a bug.

= Modules that use this module for testing =

The following modules take advantage of this  module in their test suite:


 * The memc module that supports almost the whole memcached TCP protocol.
 * The chunkin module that adds HTTP 1.1 chunked input support to Nginx.
 * The headers_more module that allows you to add, set, and clear input and output headers under the conditions that you specify.
 * The  module itself.

Please mail me other modules that use  in any form and I'll add them to the list above :)

= Community =

English Mailing List
The openresty-en mailing list is for English speakers.

Chinese Mailing List
The openresty mailing list is for Chinese speakers.

= Report Bugs =

Although a lot of effort has been put into testing and code tuning, there must be some serious bugs lurking somewhere in this module. So whenever you are bitten by any quirks, please don't hesitate to


 * 1) create a ticket on the issue tracking interface provided by GitHub,
 * 2) or send a bug report, questions, or even patches to the OpenResty Community.

= Source Repository =

Available on github at agentzh/echo-nginx-module.

= Changes =

The changes of every release of this module can be obtained from the ngx_openresty bundle's change logs:

http://openresty.org/#Changes

= Test Suite =

This module comes with a Perl-driven test suite. The test cases are declarative too. Thanks to the Test::Nginx module in the Perl world.

To run it on your side:

$ PATH=/path/to/your/nginx-with-echo-module:$PATH prove -r t

You need to terminate any Nginx processes before running the test suite if you have changed the Nginx server binary.

Because a single nginx server (by default, ) is used across all the test scripts (  files), it's meaningless to run the test suite in parallel by specifying   when invoking the   utility.

Some parts of the test suite requires standard modules proxy, rewrite and SSI to be enabled as well when building Nginx.

= TODO =


 * Fix the echo_after_body directive in subrequests.
 * Add directives echo_read_client_request_body and echo_request_headers.
 * Add new directive echo_log to use Nginx's logging facility directly from the config file and specific loglevel can be specified, as in

echo_log debug "I am being called.";


 * Add support for options  and   to echo_subrequest_async and echo_subrequest. For example

echo_subrequest POST /sub -q 'foo=Foo&bar=Bar' -b 'hello' -t 'text/plan' -h 'X-My-Header: blah blah'


 * Add options to control whether a subrequest should inherit cached variables from its parent request (i.e. the current request that is calling the subrequest in question). Currently none of the subrequests issued by this module inherit the cached variables from the parent request.
 * Add new variable $echo_active_subrequests to show.
 * Add the echo_file and echo_cached_file directives.
 * Add new varaible $echo_request_headers to accompany the existing $echo_client_request_headers variable.
 * Add new directive echo_foreach, as in

echo_foreach 'cat' 'dog' 'mouse'; echo_location_async "/animals/$echo_it"; echo_end;


 * Add new directive echo_foreach_range, as in

echo_foreach_range '[1..100]' '[a-zA-z0-9]'; echo_location_async "/item/$echo_it"; echo_end;


 * Add new directive echo_repeat, as in

echo_repeat 10 $i { echo "Page $i"; echo_location "/path/to/page/$i"; }

This is just another way of saying

echo_foreach_range $i [1..10]; echo "Page $i"; echo_location "/path/to/page/$i"; echo_end;

Thanks Marcus Clyne for providing this idea.


 * Add new variable $echo_random which always returns a random non-negative integer with the lower/upper limit specified by the new directives  and  . For example,

echo_random_min 10 echo_random_max 200 echo "random number: $echo_random";

Thanks Marcus Clyne for providing this idea.

= Getting involved =

You'll be very welcomed to submit patches to the author or just ask for a commit bit to the source repository on GitHub.

= Author =

Yichun "agentzh" Zhang (章亦春) <agentzh@gmail.com>, CloudFlare Inc.

This wiki page is also maintained by the author himself, and everybody is encouraged to improve this page as well.

= Copyright & License =

Copyright (c) 2009-2014, Yichun "agentzh" Zhang (章亦春) <agentzh@gmail.com>, CloudFlare Inc.

This module is licensed under the terms of the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:


 * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

= See Also =


 * The original blog post about this module's initial development.
 * The standard addition filter module.
 * The standard proxy module.
 * The ngx_openresty bundle.