docs: documented the max concurrent subrequest count limitation and max error log line size limit.

Author: agentzh

README

@@ -1040,6 +1040,14 @@ Nginx API for Lua
     while Lua booleans result in literal "true" or "false" strings. And the
     "ngx.null" constant will yield the "null" string output.
 
+    There is a hard-coded length limitation on the error messages in the
+    Nginx core. It is 2048 bytes at most, including the trailing newlines
+    and the leading timestamps. You can manually modify this limit by
+    modifying the "NGX_MAX_ERROR_STR" macro definition in the
+    "src/core/ngx_log.h" file in the Nginx source tree. If the message size
+    exceeds this limit, the Nginx core will truncate the message text
+    automatically.
+
   ngx.ctx
     context: *set_by_lua*, rewrite_by_lua*, access_by_lua*, content_by_lua*,
     header_filter_by_lua**
@@ -1393,6 +1401,17 @@ Nginx API for Lua
     headers should be ignored by setting proxy_pass_request_headers to "off"
     in subrequest locations.
 
+    There is a hard-coded upper limit on the number of concurrent
+    subrequests every main request. In older versions of Nginx, the limit is
+    50, which is then increased to 200 in recent Nginx "1.1.x" releases. You
+    can manually edit this limit by modifying the definition of the
+    "NGX_HTTP_MAX_SUBREQUESTS" macro in the
+    "nginx/src/http/ngx_http_request.h" file in the Nginx source tree. When
+    you are exceeding this limit, you will get the following error message
+    in your "error.log" file:
+
+        [error] 13983#0: *1 subrequests cycle while processing "/uri"
+
     Please also refer to restrictions on capturing locations that include
     Echo Module directives.
 
@@ -2314,6 +2333,14 @@ Nginx API for Lua
     The "log_level" argument can take constants like "ngx.ERR" and
     "ngx.WARN". Check out Nginx log level constants for details.
 
+    There is a hard-coded length limitation on the error messages in the
+    Nginx core. It is 2048 bytes at most, including the trailing newlines
+    and the leading timestamps. You can manually modify this limit by
+    modifying the "NGX_MAX_ERROR_STR" macro definition in the
+    "src/core/ngx_log.h" file in the Nginx source tree. If the message size
+    exceeds this limit, the Nginx core will truncate the message text
+    automatically.
+
   ngx.flush
     syntax: *ngx.flush(wait?)*
 

README.markdown

@@ -982,6 +982,8 @@ It is equivalent to
 
 Lua `nil` arguments are accepted and result in literal `"nil"` strings while Lua booleans result in literal `"true"` or `"false"` strings. And the `ngx.null` constant will yield the `"null"` string output.
 
+There is a hard-coded length limitation on the error messages in the Nginx core. It is `2048` bytes at most, including the trailing newlines and the leading timestamps. You can manually modify this limit by modifying the `NGX_MAX_ERROR_STR` macro definition in the `src/core/ngx_log.h` file in the Nginx source tree. If the message size exceeds this limit, the Nginx core will truncate the message text automatically.
+
 ngx.ctx
 -------
 **context:** *set_by_lua*, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**
@@ -1335,6 +1337,12 @@ subrequests, an "Accept-Encoding: gzip" header in the main request may result
 in gzipped responses that cannot be handled properly in Lua code. Original request headers should be ignored by setting 
 [proxy_pass_request_headers](http://wiki.nginx.org/HttpProxyModule#proxy_pass_request_headers) to `off` in subrequest locations.
 
+There is a hard-coded upper limit on the number of concurrent subrequests every main request. In older versions of Nginx, the limit is `50`, which is then increased to `200` in recent Nginx `1.1.x` releases. You can manually edit this limit by modifying the definition of the `NGX_HTTP_MAX_SUBREQUESTS` macro in the `nginx/src/http/ngx_http_request.h` file in the Nginx source tree. When you are exceeding this limit, you will get the following error message in your `error.log` file:
+
+
+    [error] 13983#0: *1 subrequests cycle while processing "/uri"
+
+
 Please also refer to restrictions on [capturing locations that include Echo Module directives](http://wiki.nginx.org/HttpLuaModule#Locations_With_HttpEchoModule_Directives).
 
 ngx.location.capture_multi
@@ -2233,6 +2241,8 @@ Lua `nil` arguments are accepted and result in literal `"nil"` string while Lua
 
 The `log_level` argument can take constants like `ngx.ERR` and `ngx.WARN`. Check out [Nginx log level constants](http://wiki.nginx.org/HttpLuaModule#Nginx_log_level_constants) for details.
 
+There is a hard-coded length limitation on the error messages in the Nginx core. It is `2048` bytes at most, including the trailing newlines and the leading timestamps. You can manually modify this limit by modifying the `NGX_MAX_ERROR_STR` macro definition in the `src/core/ngx_log.h` file in the Nginx source tree. If the message size exceeds this limit, the Nginx core will truncate the message text automatically.
+
 ngx.flush
 ---------
 **syntax:** *ngx.flush(wait?)*

doc/HttpLuaModule.wiki

@@ -944,6 +944,8 @@ It is equivalent to
 
 Lua <code>nil</code> arguments are accepted and result in literal <code>"nil"</code> strings while Lua booleans result in literal <code>"true"</code> or <code>"false"</code> strings. And the <code>ngx.null</code> constant will yield the <code>"null"</code> string output.
 
+There is a hard-coded length limitation on the error messages in the Nginx core. It is <code>2048</code> bytes at most, including the trailing newlines and the leading timestamps. You can manually modify this limit by modifying the <code>NGX_MAX_ERROR_STR</code> macro definition in the <code>src/core/ngx_log.h</code> file in the Nginx source tree. If the message size exceeds this limit, the Nginx core will truncate the message text automatically.
+
 == ngx.ctx ==
 '''context:''' ''set_by_lua*, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*''
 
@@ -1295,6 +1297,12 @@ subrequests, an "Accept-Encoding: gzip" header in the main request may result
 in gzipped responses that cannot be handled properly in Lua code. Original request headers should be ignored by setting 
 [[HttpProxyModule#proxy_pass_request_headers|proxy_pass_request_headers]] to <code>off</code> in subrequest locations.
 
+There is a hard-coded upper limit on the number of concurrent subrequests every main request. In older versions of Nginx, the limit is <code>50</code>, which is then increased to <code>200</code> in recent Nginx <code>1.1.x</code> releases. You can manually edit this limit by modifying the definition of the <code>NGX_HTTP_MAX_SUBREQUESTS</code> macro in the <code>nginx/src/http/ngx_http_request.h</code> file in the Nginx source tree. When you are exceeding this limit, you will get the following error message in your <code>error.log</code> file:
+
+<geshi lang="text">
+    [error] 13983#0: *1 subrequests cycle while processing "/uri"
+</geshi>
+
 Please also refer to restrictions on [[#Locations_With_HttpEchoModule_Directives|capturing locations that include Echo Module directives]].
 
 == ngx.location.capture_multi ==
@@ -2169,6 +2177,8 @@ Lua <code>nil</code> arguments are accepted and result in literal <code>"nil"</c
 
 The <code>log_level</code> argument can take constants like <code>ngx.ERR</code> and <code>ngx.WARN</code>. Check out [[#Nginx log level constants|Nginx log level constants]] for details.
 
+There is a hard-coded length limitation on the error messages in the Nginx core. It is <code>2048</code> bytes at most, including the trailing newlines and the leading timestamps. You can manually modify this limit by modifying the <code>NGX_MAX_ERROR_STR</code> macro definition in the <code>src/core/ngx_log.h</code> file in the Nginx source tree. If the message size exceeds this limit, the Nginx core will truncate the message text automatically.
+
 == ngx.flush ==
 '''syntax:''' ''ngx.flush(wait?)''