Hello!

On Tue, May 18, 2010 at 08:25:46PM +0400, Peter Leonov wrote:

> Hello devels,
>
> There is a module that requires a heavy testing in environment with
> low memory. Especialy it could be good to test how it goes if no
> more memory is available in the system.
>
> So the questions are: is there a way to test such a module without a
> virtual machines? and are there some tools which might be of help?

You may tune memory limit for a given process instead of using
virtual machine. Though this won't really help with testing nginx
modules as pool allocator will protect most of allocations from
seeing errors (while they still can happen with sligtly different
config).

Injecting random errors into allocation routines proven to be much
more usable. Just for completeness: attached trivial patch which
I used while searching for allocation error handling bugs in nginx
itself.

Maxim Dounin
diff --git a/src/core/ngx_palloc.c b/src/core/ngx_palloc.c
--- a/src/core/ngx_palloc.c
+++ b/src/core/ngx_palloc.c
@@ -117,6 +117,14 @@ ngx_palloc(ngx_pool_t *pool, size_t size
u_char *m;
ngx_pool_t *p;

+#if 1 /* XXX */
+ if (ngx_random() % 1000 == 1) {
+ ngx_log_error(NGX_LOG_EMERG, pool->log, 0,
+ "shit happens, failing allocation of %uz bytes", size);
+ return NULL;
+ }
+#endif
+
if (size <= pool->max) {

p = pool->current;
diff --git a/src/os/unix/ngx_alloc.c b/src/os/unix/ngx_alloc.c
--- a/src/os/unix/ngx_alloc.c
+++ b/src/os/unix/ngx_alloc.c
@@ -19,6 +19,14 @@ ngx_alloc(size_t size, ngx_log_t *log)
void *p;

p = malloc(size);
+
+#if 1 /* XXX */
+ if (p != NULL && ngx_random() % 100 == 1) {
+ free(p);
+ p = NULL;
+ }
+#endif
+
if (p == NULL) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_errno,
"malloc() %uz bytes failed", size);
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