optimize: now we recycle the special flush buf and chain link for ngx.flush() to prevent request-scoped memory leaks when emitting long data streams to the downstream.

Author: agentzh

src/ngx_http_lua_common.h

@@ -153,6 +153,7 @@ typedef struct {
     ngx_chain_t             *free_bufs;
     ngx_chain_t             *busy_bufs;
     ngx_chain_t             *free_recv_bufs;
+    ngx_chain_t             *flush_buf;
 
     ngx_http_cleanup_pt     *cleanup;
 
@@ -215,6 +216,7 @@ typedef struct {
     unsigned         socket_ready:1;
 
     unsigned         aborted:1;
+    unsigned         buffering:1;
 
 } ngx_http_lua_ctx_t;
 

src/ngx_http_lua_output.c

@@ -464,20 +464,36 @@ ngx_http_lua_ngx_flush(lua_State *L)
         return luaL_error(L, "already seen eof");
     }
 
-    buf = ngx_calloc_buf(r->pool);
-    if (buf == NULL) {
-        return luaL_error(L, "memory allocation error");
+    if (ctx->buffering) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                       "lua http 1.0 buffering makes ngx.flush() a no-op");
+
+        return 0;
     }
 
-    buf->flush = 1;
+    if (ctx->flush_buf) {
+        cl = ctx->flush_buf;
 
-    cl = ngx_alloc_chain_link(r->pool);
-    if (cl == NULL) {
-        return luaL_error(L, "out of memory");
-    }
+    } else {
+        dd("allocating new flush buf");
+        buf = ngx_calloc_buf(r->pool);
+        if (buf == NULL) {
+            return luaL_error(L, "memory allocation error");
+        }
 
-    cl->next = NULL;
-    cl->buf = buf;
+        buf->flush = 1;
+
+        dd("allocating new flush chain");
+        cl = ngx_alloc_chain_link(r->pool);
+        if (cl == NULL) {
+            return luaL_error(L, "out of memory");
+        }
+
+        cl->next = NULL;
+        cl->buf = buf;
+
+        ctx->flush_buf = cl;
+    }
 
     rc = ngx_http_lua_send_chain_link(r, ctx, cl);
 

src/ngx_http_lua_util.c

@@ -373,19 +373,24 @@ ngx_http_lua_send_chain_link(ngx_http_request_t *r, ngx_http_lua_ctx_t *ctx,
         return rc;
     }
 
+    if (!ctx->buffering && !ctx->headers_sent
+        && r->http_version < NGX_HTTP_VERSION_11)
+    {
+        ctx->buffering = 1;
+    }
+
     if (r->header_only) {
         ctx->eof = 1;
 
-        if (!ctx->headers_sent && r->http_version < NGX_HTTP_VERSION_11)
-        {
+        if (ctx->buffering) {
             return ngx_http_lua_send_http10_headers(r, ctx);
         }
 
         return rc;
     }
 
     if (in == NULL) {
-        if (!ctx->headers_sent && r->http_version < NGX_HTTP_VERSION_11) {
+        if (ctx->buffering) {
             rc = ngx_http_lua_send_http10_headers(r, ctx);
             if (rc == NGX_ERROR || rc >= NGX_HTTP_SPECIAL_RESPONSE) {
                 return rc;
@@ -427,7 +432,7 @@ ngx_http_lua_send_chain_link(ngx_http_request_t *r, ngx_http_lua_ctx_t *ctx,
 
     /* in != NULL */
 
-    if (r->http_version < NGX_HTTP_VERSION_11 && !ctx->headers_sent) {
+    if (ctx->buffering) {
         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                 "lua buffering output bufs for the HTTP 1.0 request");
 

t/056-flush.t

@@ -14,7 +14,7 @@ use Test::Nginx::Socket;
 
 repeat_each(2);
 
-plan tests => repeat_each() * (blocks() * 2 + 1);
+plan tests => repeat_each() * (blocks() * 2 + 5);
 
 #no_diff();
 #no_long_string();
@@ -95,25 +95,55 @@ hiya
 
 
 
-=== TEST 5: http 1.0
+=== TEST 5: http 1.0 (sync)
 --- config
     location /test {
         content_by_lua '
             ngx.say("hello, world")
             ngx.flush(true)
             ngx.say("hiya")
+            ngx.flush(true)
+            ngx.say("blah")
         ';
     }
 --- request
 GET /test HTTP/1.0
 --- response_body
 hello, world
 hiya
+blah
+--- timeout: 5
+--- error_log
+lua buffering output bufs for the HTTP 1.0 request
+lua http 1.0 buffering makes ngx.flush() a no-op
+
+
+
+=== TEST 6: http 1.0 (async)
+--- config
+    location /test {
+        content_by_lua '
+            ngx.say("hello, world")
+            ngx.flush(false)
+            ngx.say("hiya")
+            ngx.flush(false)
+            ngx.say("blah")
+        ';
+    }
+--- request
+GET /test HTTP/1.0
+--- response_body
+hello, world
+hiya
+blah
+--- error_log
+lua buffering output bufs for the HTTP 1.0 request
+lua http 1.0 buffering makes ngx.flush() a no-op
 --- timeout: 5
 
 
 
-=== TEST 6: flush wait - big data
+=== TEST 7: flush wait - big data
 --- config
     location /test {
         content_by_lua '
@@ -131,7 +161,7 @@ hiya
 
 
 
-=== TEST 7: flush wait - content
+=== TEST 8: flush wait - content
 --- config
     location /test {
         content_by_lua '

util/build2.sh

@@ -19,6 +19,7 @@ force=$2
 
 time ngx-build $force $version \
             --with-cc-opt=$'-I/opt/pcre821jit/include' \
+            --with-http_realip_module \
         --with-http_ssl_module \
             --add-module=$root/../ndk-nginx-module \
             --add-module=$root/../set-misc-nginx-module \