I think I found a fix for the memory leak issue on gRPC module
Roman Arutyunyan
arut at nginx.com
Mon May 27 10:06:58 UTC 2024
Hi,
Following an internal discussion with Sergey, here's an updated version of
the patch.
On Thu, May 23, 2024 at 01:42:24PM +0400, Roman Arutyunyan wrote:
> Hi,
>
> On Wed, May 22, 2024 at 06:14:26PM +0400, Roman Arutyunyan wrote:
> > Hi,
> >
> > Indeed there's a problem there. We have similar problems in other places as
> > well. Attached is a patch that fixes all I could find.
> >
> > I did some testing for the sub_filter with the following config. Small buffers
> > exaggerate the problem.
> >
> > http {
> > server {
> > listen 8000;
> >
> > location / {
> > root html;
> >
> > output_buffers 2 128;
> >
> > sub_filter 1 2;
> > sub_filter_types *;
> > sub_filter_once off;
> > }
> > }
> > }
> >
> > Retrieving a 10m file resulted in 7304 (patched) vs 1317704 (unpatched) bytes
> > allocated from the request pool. With the default output_buffers (2 32768),
> > it's 79880 vs 84040.
>
> I tested ssi with the following config.
>
> server {
> listen 8000;
>
> location / {
> root html;
>
> output_buffers 2 128;
>
> ssi on;
> ssi_types *;
> }
> }
>
> The result is similar:
>
> 6224 vs 1316912 with small buffers
> 38864 vs 43952 with the default buffers
>
> > On Thu, May 02, 2024 at 07:59:44AM +0000, Pavel Pautov via nginx-devel wrote:
> > > Hi Sangmin,
> > >
> > > Your analysis looks correct. Client streaming RPCs can lead to unbound accumulation of ngx_chain_t objects (although, at very slow rate). Gzip module had a similar issue (https://trac.nginx.org/nginx/ticket/1046).
> > > Attaching somewhat simplified patch based on yours. I was able to reproduce the issue locally and the patch fixes it.
> > >
> > > From: nginx-devel <nginx-devel-bounces at nginx.org> On Behalf Of Sangmin Lee
> > > Sent: Thursday, April 4, 2024 19:29
> > > To: nginx-devel at nginx.org
> > > Subject: I think I found a fix for the memory leak issue on gRPC module
> > >
> > > CAUTION: This email has been sent from an external source. Do not click links, open attachments, or provide sensitive business information unless you can verify the sender's legitimacy.
> > >
> > > I am sending this mail again because I did a mistake while I was writing a mail. I didn't know, in gmail, "Ctrl - Enter" would send a mail immediately even without a title!
> > > I am sorry for that, so I am sending again.
> > >
> > > Hello,
> > >
> > > I think I found the main cause of the memory leak issue when using gRPC stream so I made a patch for it.
> > > Please find the test scenario and details here -- This is what I wrote.:
> > > https://trac.nginx.org/nginx/ticket/2614
> > > After I changed the memory pool totally on nginx and tested our workload -- long-lived gRPC streams with many connections -- using Valgrind and massif, I was able to find what brought up the memory leak issue.
> > > like the picture below.
> > >
> > > [cid:image001.png at 01DA9C29.C792CD90]
> > > ( I am not sure whether this picture will be sent properly )
> > >
> > > After I patched one part, it seems okay now I have tested it for 1 week with out workload.
> > >
> > > [cid:image002.png at 01DA9C29.C792CD90]
> > > ( I am not sure whether this picture will be sent properly )
> > >
> > > But because I am not familiar with Mercurial, I couldn't find a way to create PR like on github. I guess this mailing list is for this patch.
> > > From my point of view, it is more like a workaround and I think the way of using ngx_chain_add_copy() or itself needs to be changed because it allocates a ngx_chain_t structure using ngx_alloc_chain_link() but inside of that, it just copies pointer, like cl->buf = in->buf;
> > > so this ngx_chain_t instance should be dealt with differently unlike other ngx_chain_t instances.
> > > But I am quite new to nginx codes so my view might be wrong.
> > > Anyhow, please go over this patch and I would like to further talk here.
> > >
> > > --------------------------------------------------------------------------------------------------------------------------------------------
> > >
> > > diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
> > > index dfe49c586..1db67bd0a 100644
> > > --- a/src/http/modules/ngx_http_grpc_module.c
> > > +++ b/src/http/modules/ngx_http_grpc_module.c
> > > @@ -1462,6 +1462,12 @@ ngx_http_grpc_body_output_filter(void *data, ngx_chain_t *in)
> > > in = in->next;
> > > }
> > >
> > > + ngx_chain_t *nl;
> > > + for (ngx_chain_t *dl = ctx->in; dl != in; dl = nl ) {
> > > + nl = dl->next;
> > > + ngx_free_chain(r->pool, dl);
> > > + }
> > > +
> > > ctx->in = in;
> > >
> > > if (last) {
> > >
> > > --------------------------------------------------------------------------------------------------------------------------------------------
> > >
> > > Best regards,
> > > Sangmin
> >
> >
> >
> >
> >
> > > _______________________________________________
> > > nginx-devel mailing list
> > > nginx-devel at nginx.org
> > > https://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> >
> > --
> > Roman Arutyunyan
>
> > # HG changeset patch
> > # User Roman Arutyunyan <arut at nginx.com>
> > # Date 1716386385 -14400
> > # Wed May 22 17:59:45 2024 +0400
> > # Node ID 95af5fe4921294b48e634defc03b6b0f0201d6f7
> > # Parent e60377bdee3d0f8dbd237b5ae8a5deab2af785ef
> > Optimized chain link usage (ticket #2614).
> >
> > Previously chain links could sometimes be dropped instead of being reused,
> > which could result in increased memory consumption during long requests.
> >
> > A similar chain link issue in ngx_http_gzip_filter_module was fixed in
> > da46bfc484ef (1.11.10).
> >
> > Based on a patch by Sangmin Lee.
> >
> > diff --git a/src/core/ngx_output_chain.c b/src/core/ngx_output_chain.c
> > --- a/src/core/ngx_output_chain.c
> > +++ b/src/core/ngx_output_chain.c
> > @@ -117,7 +117,10 @@ ngx_output_chain(ngx_output_chain_ctx_t
> >
> > ngx_debug_point();
> >
> > - ctx->in = ctx->in->next;
> > + cl = ctx->in;
> > + ctx->in = cl->next;
> > +
> > + ngx_free_chain(ctx->pool, cl);
> >
> > continue;
> > }
> > @@ -203,7 +206,10 @@ ngx_output_chain(ngx_output_chain_ctx_t
> > /* delete the completed buf from the ctx->in chain */
> >
> > if (ngx_buf_size(ctx->in->buf) == 0) {
> > - ctx->in = ctx->in->next;
> > + cl = ctx->in;
> > + ctx->in = cl->next;
> > +
> > + ngx_free_chain(ctx->pool, cl);
> > }
> >
> > cl = ngx_alloc_chain_link(ctx->pool);
> > diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
> > --- a/src/http/modules/ngx_http_grpc_module.c
> > +++ b/src/http/modules/ngx_http_grpc_module.c
> > @@ -1459,7 +1459,10 @@ ngx_http_grpc_body_output_filter(void *d
> > last = 1;
> > }
> >
> > + cl = in;
> > in = in->next;
> > +
> > + ngx_free_chain(r->pool, cl);
> > }
> >
> > ctx->in = in;
> > diff --git a/src/http/modules/ngx_http_gunzip_filter_module.c b/src/http/modules/ngx_http_gunzip_filter_module.c
> > --- a/src/http/modules/ngx_http_gunzip_filter_module.c
> > +++ b/src/http/modules/ngx_http_gunzip_filter_module.c
> > @@ -333,6 +333,8 @@ static ngx_int_t
> > ngx_http_gunzip_filter_add_data(ngx_http_request_t *r,
> > ngx_http_gunzip_ctx_t *ctx)
> > {
> > + ngx_chain_t *cl;
> > +
> > if (ctx->zstream.avail_in || ctx->flush != Z_NO_FLUSH || ctx->redo) {
> > return NGX_OK;
> > }
> > @@ -344,8 +346,11 @@ ngx_http_gunzip_filter_add_data(ngx_http
> > return NGX_DECLINED;
> > }
> >
> > - ctx->in_buf = ctx->in->buf;
> > - ctx->in = ctx->in->next;
> > + cl = ctx->in;
> > + ctx->in_buf = cl->buf;
> > + ctx->in = cl->next;
> > +
> > + ngx_free_chain(r->pool, cl);
> >
> > ctx->zstream.next_in = ctx->in_buf->pos;
> > ctx->zstream.avail_in = ctx->in_buf->last - ctx->in_buf->pos;
> > @@ -383,8 +388,12 @@ ngx_http_gunzip_filter_get_buf(ngx_http_
> > conf = ngx_http_get_module_loc_conf(r, ngx_http_gunzip_filter_module);
> >
> > if (ctx->free) {
> > - ctx->out_buf = ctx->free->buf;
> > - ctx->free = ctx->free->next;
> > +
> > + cl = ctx->free;
> > + ctx->out_buf = cl->buf;
> > + ctx->free = cl->next;
> > +
> > + ngx_free_chain(r->pool, cl);
> >
> > ctx->out_buf->flush = 0;
> >
> > diff --git a/src/http/modules/ngx_http_gzip_filter_module.c b/src/http/modules/ngx_http_gzip_filter_module.c
> > --- a/src/http/modules/ngx_http_gzip_filter_module.c
> > +++ b/src/http/modules/ngx_http_gzip_filter_module.c
> > @@ -985,10 +985,12 @@ static void
> > ngx_http_gzip_filter_free_copy_buf(ngx_http_request_t *r,
> > ngx_http_gzip_ctx_t *ctx)
> > {
> > - ngx_chain_t *cl;
> > + ngx_chain_t *cl, *next;
> >
> > - for (cl = ctx->copied; cl; cl = cl->next) {
> > + for (cl = ctx->copied; cl; cl = next) {
> > ngx_pfree(r->pool, cl->buf->start);
> > + next = cl->next;
> > + ngx_free_chain(r->pool, cl);
> > }
> >
> > ctx->copied = NULL;
> > diff --git a/src/http/modules/ngx_http_ssi_filter_module.c b/src/http/modules/ngx_http_ssi_filter_module.c
> > --- a/src/http/modules/ngx_http_ssi_filter_module.c
> > +++ b/src/http/modules/ngx_http_ssi_filter_module.c
> > @@ -482,9 +482,13 @@ ngx_http_ssi_body_filter(ngx_http_reques
> > while (ctx->in || ctx->buf) {
> >
> > if (ctx->buf == NULL) {
> > - ctx->buf = ctx->in->buf;
> > - ctx->in = ctx->in->next;
> > +
> > + cl = ctx->in;
> > + ctx->buf = cl->buf;
> > + ctx->in = cl->next;
> > ctx->pos = ctx->buf->pos;
> > +
> > + ngx_free_chain(r->pool, cl);
> > }
> >
> > if (ctx->state == ssi_start_state) {
> > diff --git a/src/http/modules/ngx_http_sub_filter_module.c b/src/http/modules/ngx_http_sub_filter_module.c
> > --- a/src/http/modules/ngx_http_sub_filter_module.c
> > +++ b/src/http/modules/ngx_http_sub_filter_module.c
> > @@ -335,9 +335,13 @@ ngx_http_sub_body_filter(ngx_http_reques
> > while (ctx->in || ctx->buf) {
> >
> > if (ctx->buf == NULL) {
> > - ctx->buf = ctx->in->buf;
> > - ctx->in = ctx->in->next;
> > +
> > + cl = ctx->in;
> > + ctx->buf = cl->buf;
> > + ctx->in = cl->next;
> > ctx->pos = ctx->buf->pos;
> > +
> > + ngx_free_chain(r->pool, cl);
> > }
> >
> > if (ctx->buf->flush || ctx->buf->recycled) {
>
> > _______________________________________________
> > nginx-devel mailing list
> > nginx-devel at nginx.org
> > https://mailman.nginx.org/mailman/listinfo/nginx-devel
>
> --
> Roman Arutyunyan
> _______________________________________________
> nginx-devel mailing list
> nginx-devel at nginx.org
> https://mailman.nginx.org/mailman/listinfo/nginx-devel
--
Roman Arutyunyan
-------------- next part --------------
# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1716477338 -14400
# Thu May 23 19:15:38 2024 +0400
# Node ID f7d53c7f70140b1cd1eaf51ce4346a873692f879
# Parent f58b6f6362387eeace46043a6fc0bceb56a6786a
Optimized chain link usage (ticket #2614).
Previously chain links could sometimes be dropped instead of being reused,
which could result in increased memory consumption during long requests.
A similar chain link issue in ngx_http_gzip_filter_module was fixed in
da46bfc484ef (1.11.10).
Based on a patch by Sangmin Lee.
diff --git a/src/core/ngx_output_chain.c b/src/core/ngx_output_chain.c
--- a/src/core/ngx_output_chain.c
+++ b/src/core/ngx_output_chain.c
@@ -117,7 +117,10 @@ ngx_output_chain(ngx_output_chain_ctx_t
ngx_debug_point();
- ctx->in = ctx->in->next;
+ cl = ctx->in;
+ ctx->in = cl->next;
+
+ ngx_free_chain(ctx->pool, cl);
continue;
}
@@ -203,7 +206,10 @@ ngx_output_chain(ngx_output_chain_ctx_t
/* delete the completed buf from the ctx->in chain */
if (ngx_buf_size(ctx->in->buf) == 0) {
- ctx->in = ctx->in->next;
+ cl = ctx->in;
+ ctx->in = cl->next;
+
+ ngx_free_chain(ctx->pool, cl);
}
cl = ngx_alloc_chain_link(ctx->pool);
diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -1231,7 +1231,7 @@ ngx_http_grpc_body_output_filter(void *d
ngx_buf_t *b;
ngx_int_t rc;
ngx_uint_t next, last;
- ngx_chain_t *cl, *out, **ll;
+ ngx_chain_t *cl, *out, *ln, **ll;
ngx_http_upstream_t *u;
ngx_http_grpc_ctx_t *ctx;
ngx_http_grpc_frame_t *f;
@@ -1459,7 +1459,10 @@ ngx_http_grpc_body_output_filter(void *d
last = 1;
}
+ ln = in;
in = in->next;
+
+ ngx_free_chain(r->pool, ln);
}
ctx->in = in;
diff --git a/src/http/modules/ngx_http_gunzip_filter_module.c b/src/http/modules/ngx_http_gunzip_filter_module.c
--- a/src/http/modules/ngx_http_gunzip_filter_module.c
+++ b/src/http/modules/ngx_http_gunzip_filter_module.c
@@ -333,6 +333,8 @@ static ngx_int_t
ngx_http_gunzip_filter_add_data(ngx_http_request_t *r,
ngx_http_gunzip_ctx_t *ctx)
{
+ ngx_chain_t *cl;
+
if (ctx->zstream.avail_in || ctx->flush != Z_NO_FLUSH || ctx->redo) {
return NGX_OK;
}
@@ -344,8 +346,11 @@ ngx_http_gunzip_filter_add_data(ngx_http
return NGX_DECLINED;
}
- ctx->in_buf = ctx->in->buf;
- ctx->in = ctx->in->next;
+ cl = ctx->in;
+ ctx->in_buf = cl->buf;
+ ctx->in = cl->next;
+
+ ngx_free_chain(r->pool, cl);
ctx->zstream.next_in = ctx->in_buf->pos;
ctx->zstream.avail_in = ctx->in_buf->last - ctx->in_buf->pos;
@@ -374,6 +379,7 @@ static ngx_int_t
ngx_http_gunzip_filter_get_buf(ngx_http_request_t *r,
ngx_http_gunzip_ctx_t *ctx)
{
+ ngx_chain_t *cl;
ngx_http_gunzip_conf_t *conf;
if (ctx->zstream.avail_out) {
@@ -383,8 +389,12 @@ ngx_http_gunzip_filter_get_buf(ngx_http_
conf = ngx_http_get_module_loc_conf(r, ngx_http_gunzip_filter_module);
if (ctx->free) {
- ctx->out_buf = ctx->free->buf;
- ctx->free = ctx->free->next;
+
+ cl = ctx->free;
+ ctx->out_buf = cl->buf;
+ ctx->free = cl->next;
+
+ ngx_free_chain(r->pool, cl);
ctx->out_buf->flush = 0;
diff --git a/src/http/modules/ngx_http_gzip_filter_module.c b/src/http/modules/ngx_http_gzip_filter_module.c
--- a/src/http/modules/ngx_http_gzip_filter_module.c
+++ b/src/http/modules/ngx_http_gzip_filter_module.c
@@ -985,10 +985,14 @@ static void
ngx_http_gzip_filter_free_copy_buf(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx)
{
- ngx_chain_t *cl;
+ ngx_chain_t *cl, *ln;
- for (cl = ctx->copied; cl; cl = cl->next) {
- ngx_pfree(r->pool, cl->buf->start);
+ for (cl = ctx->copied; cl; /* void */) {
+ ln = cl;
+ cl = cl->next;
+
+ ngx_pfree(r->pool, ln->buf->start);
+ ngx_free_chain(r->pool, ln);
}
ctx->copied = NULL;
diff --git a/src/http/modules/ngx_http_ssi_filter_module.c b/src/http/modules/ngx_http_ssi_filter_module.c
--- a/src/http/modules/ngx_http_ssi_filter_module.c
+++ b/src/http/modules/ngx_http_ssi_filter_module.c
@@ -482,9 +482,13 @@ ngx_http_ssi_body_filter(ngx_http_reques
while (ctx->in || ctx->buf) {
if (ctx->buf == NULL) {
- ctx->buf = ctx->in->buf;
- ctx->in = ctx->in->next;
+
+ cl = ctx->in;
+ ctx->buf = cl->buf;
+ ctx->in = cl->next;
ctx->pos = ctx->buf->pos;
+
+ ngx_free_chain(r->pool, cl);
}
if (ctx->state == ssi_start_state) {
diff --git a/src/http/modules/ngx_http_sub_filter_module.c b/src/http/modules/ngx_http_sub_filter_module.c
--- a/src/http/modules/ngx_http_sub_filter_module.c
+++ b/src/http/modules/ngx_http_sub_filter_module.c
@@ -335,9 +335,13 @@ ngx_http_sub_body_filter(ngx_http_reques
while (ctx->in || ctx->buf) {
if (ctx->buf == NULL) {
- ctx->buf = ctx->in->buf;
- ctx->in = ctx->in->next;
+
+ cl = ctx->in;
+ ctx->buf = cl->buf;
+ ctx->in = cl->next;
ctx->pos = ctx->buf->pos;
+
+ ngx_free_chain(r->pool, cl);
}
if (ctx->buf->flush || ctx->buf->recycled) {
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