Avoid using conn_xprt_want_send/recv, and totally nuke cs_want_send/recv,
from the upper layers. The polling is now directly handled by the connection
layer, it is activated on subscribe(), and unactivated once we got the event
and we woke the related task.
When subscribing, we don't need to provide a list element, only the h2 mux
needs it. So instead, Add a list element to struct h2s, and use it when a
list is needed.
This forces us to use the unsubscribe method, since we can't just unsubscribe
by using LIST_DEL anymore.
This patch is larger than it should be because it includes some renaming.
Instead of using si_cs_io_cb() in process_stream() use si_cs_send/si_cs_recv
instead, as si_cs_io_cb() may lead to process_stream being woken up when it
shouldn't be, and thus timeout would never get triggered.
Instead of waiting for the connection layer to let us know we can read,
attempt to receive as soon as process_stream() is called, and subscribe
to receive events if we can't receive yet.
Now, except for idle connections, the recv(), send() and wake() methods are
no more, all the lower layers do is waking tasklet for anybody waiting
for I/O events.
Remove the recv() method from mux and conn_stream.
The goal is to always receive from the upper layers, instead of waiting
for the connection later. For now, recv() is still called from the wake()
method, but that should change soon.
For struct connection, struct conn_stream, and for the h2 mux, add 2 new
lists, one that handles waiters for recv, and one that handles waiters for
recv and send. That way we can ask to subscribe for either recv or send.
Call si_cs_send() at the beginning of si_cs_wake_cb(), instead of from
stream_int_notify-), so that if we get a connection error while trying to
send, the stream_interface will get SI_FL_ERR, the associated task will
be woken up, and the connection will be properly destroyed.
No backport needed.
If we subscribed to send, and the callback is called, call the wake callback
after, so that process_stream() may be woken up if needed.
This is 1.9-specific, no backport is needed.
It is possible that the conn_stream gets detached from the stream_interface,
and as it subscribed to the wait list, si_cs_io_cb() gets called anyway,
so make sure we have a conn_stream before attempting to send more data.
This is 1.9-specific, no backport is needed.
Instead of just using the conn_stream wait_list, give the stream_interface
its own. When the conn_stream will have its own buffers, the stream_interface
may have to wait on it.
Instead of using si_cs_send() as a task handler, define a new function,
si_cs_io_cb(), and give si_cs_send() its original prototype. Right now
si_cs_io_cb() just handles send, but later it'll handle recv() too.
It is mandatory to be sure to process data blocked in the RX buffer of the
conn_stream while the shutr/read0 was already processed. The stream interface
doesn't need to rely on this flags because it already tests CS_FL_EOS.
This function is generic and is able to automatically transfer data from a
buffer to the conn_stream's tx buffer. It does this automatically if the mux
doesn't define another snd_buf() function.
It cannot yet be used as-is with the conn_stream's txbuf without risking to
lose data on close since conn_streams need to be orphaned for this.
There is a long-time issue which affects some applets, at least the stats
applet. If a large stats page is read over a slow link, regularly the
channel's buffer contains too many response data to allow another round
of ci_putblk() to copy a new message. In this case the applet calls
si_applet_cant_put() to mention that it failed to emit data into the
channel's buffer, and wants to be called only once some room is made.
The problem is that stream_int_update(), which is called from
process_stream(), will clear this flag whenever it sees there's some
spare room in the channel's buffer. It causes the applet to be woken
again immediately. This is very visible when reading a large stats
page over a slow link, because in this case haproxy will run at 100%
CPU and strace shows mostly epoll_wait(0). It is very likely that some
other applets like CLI, Lua, peers or SPOE have also been affected but
that the effect were less noticeable because it was mixed with traffic.
Ideally stream_int_update() should not touch these flags, but changing
this would require a very careful auditing of all users. Instead here
what we do is that we respect the flag if the channel still has output
data. This way the flag will automatically disappear once the buffer is
empty, and the applet function will be called only when input data
remains, if at all.
This patch alone is not enough to observe the behaviour change on the
stats page because another bug takes over, addressed by next patch
(BUG/MEDIUM: stats: don't ask for more data as long as we're responding).
When both are applied, dumping stats for 5k backends over a 10 Mbps link
take 1% CPU instead of 100%, with 1.5k epoll_wait() calls instead of 80k.
This fix should be backported at least as far as 1.5.
If the cs has data pending or shutdown and the input channel is still
waiting for reads, let's simply call the recv() function from the wake()
callback. This will allow the lower layers to simply wake the upper one
up without having to consider the recv() nor anything else.
This function is generic and is able to automatically transfer data
from a conn_stream's rx buffer to the destination buffer. It does this
automatically if the mux doesn't define another rcv_buf() function.
This new function wl_set_waitcb() prepopulates a wait_list with a tasklet
and a context and returns it so that it can be passed to ->subscribe() to
be added to a connection or conn_stream's wait_list. The caller doesn't
need to know all the insiders details anymore this way.
Totally nuke the "send" method, instead, the upper layer decides when it's
time to send data, and if it's not possible, uses the new subscribe() method
to be called when it can send data again.
Now all the code used to manipulate chunks uses a struct buffer instead.
The functions are still called "chunk*", and some of them will progressively
move to the generic buffer handling code as they are cleaned up.
Chunks are only a subset of a buffer (a non-wrapping version with no head
offset). Despite this we still carry a lot of duplicated code between
buffers and chunks. Replacing chunks with buffers would significantly
reduce the maintenance efforts. This first patch renames the chunk's
fields to match the name and types used by struct buffers, with the goal
of isolating the code changes from the declaration changes.
Most of the changes were made with spatch using this coccinelle script :
@rule_d1@
typedef chunk;
struct chunk chunk;
@@
- chunk.str
+ chunk.area
@rule_d2@
typedef chunk;
struct chunk chunk;
@@
- chunk.len
+ chunk.data
@rule_i1@
typedef chunk;
struct chunk *chunk;
@@
- chunk->str
+ chunk->area
@rule_i2@
typedef chunk;
struct chunk *chunk;
@@
- chunk->len
+ chunk->data
Some minor updates to 3 http functions had to be performed to take size_t
ints instead of ints in order to match the unsigned length here.
Now the buffers only contain the header and a pointer to the storage
area which can be anywhere. This will significantly simplify buffer
swapping and will make it possible to map chunks on buffers as well.
The buf_empty variable was removed, as now it's enough to have size==0
and area==NULL to designate the empty buffer (thus a non-allocated head
is the empty buffer by default). buf_wanted for now is indicated by
size==0 and area==(void *)1.
The channels and the checks now embed the buffer's head, and the only
pointer is to the storage area. This slightly increases the unallocated
buffer size (3 extra ints for the empty buffer) but considerably
simplifies dynamic buffer management. It will also later permit to
detach unused checks.
The way the struct buffer is arranged has proven quite efficient on a
number of tests, which makes sense given that size is always accessed
and often first, followed by the othe ones.
A few locations still accessing ->i and ->o directly were changed to
use ci_data() and co_data() respectively. A call to b_del() was replaced
with co_set_data() in si_cs_send() so that ->o will is automatically be
decremented after the migration.
With this flag we introduce the notion of "dry" vs "wet" buffers : some
demultiplexers like the H2 mux require as much room as possible for some
operations that are not retryable like decoding a headers frame. For this
they need to know if the buffer is congested with data scheduled for
leaving soon or not. Since the new API will not provide this information
in the buffer itself, the caller must indicate it. We never need to know
the amount of such data, just the fact that the buffer is not in its
optimal condition to be used for receipt. This "CO_RFL_BUF_WET" flag is
used to mention that such outgoing data are still pending in the buffer
and that a sensitive receiver should better let it "dry" before using it.
The mux and transport rcv_buf() now takes a "flags" argument, just like
the snd_buf() one or like the equivalent syscall lower part. The upper
layers will use this to pass some information such as indicating whether
the buffer is free from outgoing data or if the lower layer may allocate
the buffer itself.
This way the mux doesn't need to modify the buffer's metadata anymore
nor to know the output's size. The mux->snd_buf() function now takes a
const buffer and it's up to the caller to update the buffer's state.
The return type was updated to return a size_t to comply with the count
argument.
These ones manipulate the output data count which will be specific to
the channel soon, so prepare the call points to use the channel only.
The b_* functions are now unused and were removed.
Instead of looking for CO_FL_EARLY_DATA to know if we have to try to wake
up a stream, because it is waiting for a SSL handshake, instead add a new
conn_stream flag, CS_FL_WAIT_FOR_HS. This way we don't have to rely on
CO_FL_EARLY_DATA, and we will only wake streams that are actually waiting.
When an end of stream has been reported, we should not try to receive again
as the mux layer might not be prepared to this and could report unexpected
errors.
This is more of a strengthening measure that follows the introduction of
conn_stream that came in 1.8. It's desired to backport this into 1.8 though
it's uncertain at this time whether it may have caused real issues.
When a stream interface tries to read data from a mux using rcv_buf(),
sometimes it sees 0 as the return value and concludes that there's no
more data while there are, resulting in the connection being polled for
more data and no new attempt being made at reading these pending data.
Now it will automatically check for flag CS_FL_RCV_MORE to know if the
mux really did not have anything available or was not able to provide
these data by lack of room in the destination buffer, and will set
SI_FL_WAIT_ROOM accordingly. This will ensure that once current data
lying in the buffer are forwarded to the other side, reading chk_rcv()
will be called to re-enable reading.
It's important to note that in practice it will rely on the mux's
update_poll() function to re-enable reading and that where the calls
are placed in the stream interface, it's not possible to perform a
new synchronous rcv_buf() call. Thus a corner case remains where the
mux cannot receive due to a full buffer or any similar condition, but
needs to be able to wake itself up to deliver pending data. This is a
limitation of the current connection/conn_stream API which will likely
need a new event subscription to at least call ->wake() asynchronously
(eg: mux->{kick,restart,touch,update} ?).
For now the affected mux (h2 only) will have to take care of the extra
logic to carefully enable polling to restart processing incoming data.
This patch relies on previous one (MINOR: conn_stream: add new flag
CS_FL_RCV_MORE to indicate pending data) and both must be backported to
1.8.
In case any stream was waiting for the handshake after receiving early data,
we have to wake all of them. Do so by making the mux responsible for
removing the CO_FL_EARLY_DATA flag after all of them are woken up, instead
of doing it in si_cs_wake_cb(), which would then only work for the first one.
This makes wait_for_handshake work with HTTP/2.
Commit 9aaf778 ("MAJOR: connection : Split struct connection into struct
connection and struct conn_stream.") had to change the way the stream
interface deals with incoming data to accomodate the mux. A break
statement got lost during a change, leading to the receive call being
performed twice even when CF_READ_DONTWAIT is set. The most noticeable
effect is that it made the bug described in commit 33982cb ("BUG/MAJOR:
stream: ensure analysers are always called upon close") much easier to
reproduce as it would appear even with an HTTP frontend.
Let's just restore the stream-interface flag and the break here, as in
the previous code.
No backport is needed as this was introduced during 1.8-dev.
When a write activity is reported on a channel, it is important to keep this
information for the stream because it take part on the analyzers' triggering.
When some data are written, the flag CF_WRITE_PARTIAL is set. It participates to
the task's timeout updates and to the stream's waking. It is also used in
CF_MASK_ANALYSER mask to trigger channels anaylzers. In the past, it was cleared
by process_stream. Because of a bug (fixed in commit 95fad5ba4 ["BUG/MAJOR:
stream-int: don't re-arm recv if send fails"]), It is now cleared before each
send and in stream_int_notify. So it is possible to loss this information when
process_stream is called, preventing analyzers to be called, and possibly
leading to a stalled stream.
Today, this happens in HTTP2 when you call the stat page or when you use the
cache filter. In fact, this happens when the response is sent by an applet. In
HTTP1, everything seems to work as expected.
To fix the problem, we need to make the difference between the write activity
reported to lower layers and the one reported to the stream. So the flag
CF_WRITE_EVENT has been added to notify the stream of the write activity on a
channel. It is set when a send succedded and reset by process_stream. It is also
used in CF_MASK_ANALYSER. finally, it is checked in stream_int_notify to wake up
a stream and in channel_check_timeouts.
This bug is probably present in 1.7 but it seems to have no effect. So for now,
no needs to backport it.
Commit 4ac4928 ("BUG/MINOR: stream-int: don't set MSG_MORE on SHUTW_NOW
without AUTO_CLOSE") was incomplete. H2 reveals another situation where
the input stream is marked closed with the request and we set MSG_MORE,
causing a delay before the request leaves.
Better avoid setting the flag on the request path for close cases in
general.
At all call places where a conn_stream is in use, we can now use
cs_close() to get rid of a conn_stream and of its underlying connection
if the mux estimates it makes sense. This is what is currently being
done for the pass-through mux.
Instead of having to manually handle lingering outside, let's make
conn_sock_shutw() check for it before calling shutdown(). We simply
don't want to emit the FIN if we're going to reset the connection
due to lingering. It's particularly important for silent-drop where
it's absolutely mandatory that no packet leaves the machine.
In a 1:1 connection:stream there's no problem relying on the connection
flags alone to check for errors. But in a mux, it will be possible to mark
certain streams in error without having to mark all of them. An example is
an H2 client sending RST_STREAM frames to abort a long download, or a parse
error requiring to abort only this specific stream.
This commit ensures that stream-interface and checks properly check for
CS_FL_ERROR in cs->flags wherever CO_FL_ERROR was in use. Most likely over
the long term, any check for CO_FL_ERROR will have to disappear.
All the references to connections in the data path from streams and
stream_interfaces were changed to use conn_streams. Most functions named
"something_conn" were renamed to "something_cs" for this. Sometimes the
connection still is what matters (eg during a connection establishment)
and were not always renamed. The change is significant and minimal at the
same time, and was quite thoroughly tested now. As of this patch, all
accesses to the connection from upper layers go through the pass-through
mux.
Add a new sample fetch, "ssl_fc_has_early", a boolean that will be true
if early data were sent, and a new action, "wait-for-handshake", if used,
the request won't be forwarded until the SSL handshake is done.
We've been keep this test for a connection being established since 1.5-dev14
when the stream-interface was still accessing the FD directly. The test on
CO_FL_HANDSHAKE and L{4,6}_CONN is totally useless here, and can even be
counter-productive on pure TCP where it could prevent a request from being
sent on a connection still attempting to complete its establishment. And it
creates an abnormal dependency between the layers that will complicate the
implementation of the mux, so let's get rid of it now.
