With post_action or subrequests, it is possible that the timer set for
wev->delayed will expire while the active subrequest write event handler
is not ready to handle this. This results in request hangs as observed
with limit_rate / sendfile_max_chunk and post_action (ticket #776) or
subrequests (ticket #1228).
Moving the handling to the connection event handler fixes the hangs observed,
and also slightly simplifies the code.
Since limit_req uses connection's write event to delay request processing,
it can conflict with timers in other subrequests. In particular, even
if applied to an active subrequest, it can break things if wev->delayed
is already set (due to limit_rate or sendfile_max_chunk), since after
limit_req finishes the wev->delayed flag will be set and no timer will be
active.
Fix is to use the wev->delayed flag in limit_req as well. This ensures that
wev->delayed won't be set after limit_req finishes, and also ensures that
limit_req's timers will be properly handled by other subrequests if the one
delayed by limit_req is not active.
All streams in connection must be finalized before the connection
itself can be finalized and all related memory is freed. That's
not always possible on the current event loop iteration.
Thus when the last stream is finalized, it sets the special read
event handler ngx_http_v2_handle_connection_handler() and posts
the event.
Previously, this handler didn't check the connection state and
could call the regular event handler on a connection that was
already in finalization stage. In the worst case that could
lead to a segmentation fault, since some data structures aren't
supposed to be used during connection finalization. Particularly,
the waiting queue can contain already freed streams, so the
WINDOW_UPDATE frame received by that moment could trigger
accessing to these freed streams.
Now, the connection error flag is explicitly checked in
ngx_http_v2_handle_connection_handler().
In order to finalize stream the error flag is set on fake connection and
either "write" or "read" event handler is called. The read events of fake
connections are always ready, but it's not the case with the write events.
When the ready flag isn't set, the error flag can be not checked in some
cases and as a result stream isn't finalized. Now the ready flag is
explicilty set on write events for proper finalization in all cases.
Previously, flow control didn't account for padding in DATA frames,
which meant that its view of the world could drift from peer's view
by up to 256 bytes per received padded DATA frame, which could lead
to a deadlock.
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Previously, its value accounted for payloads of HEADERS, CONTINUATION
and DATA frames, as well as frame headers of HEADERS and DATA frames,
but it didn't account for frame headers of CONTINUATION frames.
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Previously, connection write handler was called, resulting in wake up
of the active subrequest. This change makes it possible to read data
in non-active subrequests as well. For example, this allows SSI to
process instructions in non-active subrequests earlier and start
additional subrequests if needed, reducing overall response time.
If the subrequest is already finalized, the handler set with aio_write
may still be used by sendfile in threads when using range requests
(see also e4c1f5b32868, and the original note in 9fd738b85fad). Calling
already finalized subrequest's r->write_event_handler in practice
results in request hang in some cases.
Fix is to trigger connection event handler if the subrequest was already
finalized.
The ngx_linux_sendfile() function is now used for both normal sendfile()
and sendfile in threads. The ngx_linux_sendfile_thread() function was
modified to use the same interface as ngx_linux_sendfile(), and is simply
called from ngx_linux_sendfile() when threads are enabled.
Special return code NGX_DONE is used to indicate that a thread task was
posted and no further actions are needed.
If number of bytes sent is less that what we were sending, we now always
retry sending. This is needed for sendfile() in threads as the number
of bytes we are sending might have been changed since the thread task
was posted. And this is also needed for Linux 4.3+, as sendfile() might
be interrupted at any time and provides no indication if it was interrupted
or not (ticket #1174).
If of.err is 0, it means that there was a memory allocation error
and no further logging and/or processing is needed. The of.failed
string can be only accessed if of.err is not 0.
Some combinations of options might cause the builds with the
--with-stream option to break due to invalid value of the
STREAM_INCS make variable, e.g.
auto/configure \
--with-stream \
--with-http_perl_module=dynamic \
--without-http_memcached_module \
--without-http_empty_gif_module \
--without-http_browser_module \
--without-http_upstream_hash_module \
--without-http_upstream_ip_hash_module \
--without-http_upstream_least_conn_module \
--without-http_upstream_keepalive_module \
--without-http_upstream_zone_module \
Explicit initialization of ngx_module_libs and ngx_module_link
matches what we already do when processing mail modules, and
is also required after the next change.
The directive configures a timeout to be used when gracefully shutting down
worker processes. When the timer expires, nginx will try to close all
the connections currently open to facilitate shutdown.
There is no need to cancel timers early if there are other timers blocking
shutdown anyway. Preserving such timers allows nginx to continue some
periodic work till the shutdown is actually possible.
With the new approach, timers with ev->cancelable are simply ignored when
checking if there are any timers left during shutdown.
The ev->timedout flag is set on first timer expiration, and never reset
after it. Due to this the code to stop the timer when the timer was
canceled never worked (except in a very specific time frame immediately
after start), and the timer was always armed again. This essentially
resulted in a buffer flush at the end of an event loop iteration.
This behaviour actually seems to be better than just stopping the flush
timer for the whole shutdown, so it is preserved as is instead of fixing
the code to actually remove the timer. It will be further improved by
upcoming changes to preserve cancelable timers if there are other timers
blocking shutdown.
Most notably, this fixes possible buffer overflows if number of large
client header buffers in a virtual server is different from the one in
the default server.
Reported by Daniil Bondarev.
Cloned subrequests should inherit r->content_handler. This way they will
be able to use the same location configuration as the original request
if there are "if" directives in the configuration.
Without r->content_handler inherited, the following configuration tries
to access a static file in the update request:
location / {
set $true 1;
if ($true) {
# nothing
}
proxy_pass http://backend;
proxy_cache one;
proxy_cache_use_stale updating;
proxy_cache_background_update on;
}
See http://mailman.nginx.org/pipermail/nginx/2017-February/053019.html for
initial report.
Dates in ISO 8601 format are in line with what is used in nginx.org news,
and are generally less ambiguous and easier to work with.
The changes.xml was converted using sed:
$ sed 's/date="\(..\)\.\(..\)\.\(....\)"/date="\3-\2-\1"/g' changes.xml
Appropriate changes to changes.xsls were introduced.
