This macro should be used to declare variables or struct members depending on
the USE_THREAD compile option. It avoids the encapsulation of such declarations
between #ifdef/#endif. It is used to declare all lock variables.
It was a leftover from the last cleaning session; this mask applies
to threads and calling it process_mask is a bit confusing. It's the
same in fd, task and applets.
There was a flaw in the way the threads was created. the main one was just used
to create all the others and just wait to exit. Now, it is used to run a poll
loop. So we only create nbthread-1 threads.
This also fixes a bug about the compression filter when there is only 1 thread
(nbthread == 1 or no threads support). The bug was in the way thread-local
resources was initialized. per-thread init/deinit callbacks were never called
for the main process. So, with nthread set to 1, some buffers remained
uninitialized.
Many changes have been made to do so. First, the fd_updt array, where all
pending FDs for polling are stored, is now a thread-local array. Then 3 locks
have been added to protect, respectively, the fdtab array, the fd_cache array
and poll information. In addition, a lock for each entry in the fdtab array has
been added to protect all accesses to a specific FD or its information.
For pollers, according to the poller, the way to manage the concurrency is
different. There is a poller loop on each thread. So the set of monitored FDs
may need to be protected. epoll and kqueue are thread-safe per-se, so there few
things to do to protect these pollers. This is not possible with select and
poll, so there is no sharing between the threads. The poller on each thread is
independant from others.
Finally, per-thread init/deinit functions are used for each pollers and for FD
part for manage thread-local ressources.
Now, you must be carefull when a FD is created during the HAProxy startup. All
update on the FD state must be made in the threads context and never before
their creation. This is mandatory because fd_updt array is thread-local and
initialized only for threads. Because there is no pollers for the main one, this
array remains uninitialized in this context. For this reason, listeners are now
enabled in run_thread_poll_loop function, just like the worker pipe.
When running with multiple process, if some proxies are just assigned
to some processes, the other processes will just close the file descriptors
for the listening sockets. However, we may still have to provide those
sockets when reloading, so instead we just try hard to pretend those proxies
are dead, while keeping the sockets opened.
A new global option, no-reused-socket", has been added, to restore the old
behavior of closing the sockets not bound to this process.
In C89, "void *" is automatically promoted to any pointer type. Casting
the result of malloc/calloc to the type of the LHS variable is therefore
unneeded.
Most of this patch was built using this Coccinelle patch:
@@
type T;
@@
- (T *)
(\(lua_touserdata\|malloc\|calloc\|SSL_get_app_data\|hlua_checkudata\|lua_newuserdata\)(...))
@@
type T;
T *x;
void *data;
@@
x =
- (T *)
data
@@
type T;
T *x;
T *data;
@@
x =
- (T *)
data
Unfortunately, either Coccinelle or I is too limited to detect situation
where a complex RHS expression is of type "void *" and therefore casting
is not needed. Those cases were manually examined and corrected.
In order for HTTP/2 not to eat too much memory, we'll have to support
on-the-fly buffer allocation, since most streams will have an empty
request buffer at some point. Supporting allocation on the fly means
being able to sleep inside I/O callbacks if a buffer is not available.
Till now, the I/O callbacks were called from two locations :
- when processing the cached events
- when processing the polled events from the poller
This change cleans up the design a bit further than what was started in
1.5. It now ensures that we never call any iocb from the poller itself
and that instead, events learned by the poller are put into the cache.
The benefit is important in terms of stability : we don't have to care
anymore about the risk that new events are added into the poller while
processing its events, and we're certain that updates are processed at
a single location.
To achieve this, we now modify all the fd_* functions so that instead of
creating updates, they add/remove the fd to/from the cache depending on
its state, and only create an update when the polling status reaches a
state where it will have to change. Since the pollers make use of these
functions to notify readiness (using fd_may_recv/fd_may_send), the cache
is always up to date with the poller.
Creating updates only when the polling status needs to change saves a
significant amount of work for the pollers : a benchmark showed that on
a typical TCP proxy test, the amount of updates per connection dropped
from 11 to 1 on average. This also means that the update list is smaller
and has more chances of not thrashing too many CPU cache lines. The first
observed benefit is a net 2% performance gain on the connection rate.
A second benefit is that when a connection is accepted, it's only when
we're processing the cache, and the recv event is automatically added
into the cache *after* the current one, resulting in this event to be
processed immediately during the same loop. Previously we used to have
a second run over the updates to detect if new events were added to
catch them before waking up tasks.
The next gain will be offered by the next steps on this subject consisting
in implementing an I/O queue containing all cached events ordered by priority
just like the run queue, and to be able to leave some events pending there
as long as needed. That will allow us *not* to perform some FD processing
if it's not the proper time for this (typically keep waiting for a buffer
to be allocated if none is available for an recv()). And by only processing
a small bunch of them, we'll allow priorities to take place even at the I/O
level.
As a result of this change, functions fd_alloc_or_release_cache_entry()
and fd_process_polled_events() have disappeared, and the code dedicated
to checking for new fd events after the callback during the poll() loop
was removed as well. Despite the patch looking large, it's mostly a
change of what function is falled upon fd_*() and almost nothing was
added.
When run in daemon mode (i.e. with at least one forked process) and using
the epoll poller, sending USR1 (graceful shutdown) to the worker processes
can cause some workers to start running at 100% CPU. Precondition is having
an established HTTP keep-alive connection when the signal is received.
The cloned (during fork) listening sockets do not get closed in the parent
process, thus they do not get removed from the epoll set automatically
(see man 7 epoll). This can lead to the process receiving epoll events
that it doesn't feel responsible for, resulting in an endless loop around
epoll_wait() delivering these events.
The solution is to explicitly remove these file descriptors from the epoll
set. To not degrade performance, care was taken to only do this when
neccessary, i.e. when the file descriptor was cloned during fork.
Signed-off-by: Conrad Hoffmann <conrad@soundcloud.com>
[wt: a backport to 1.4 could be studied though chances to catch the bug are low]
Currently, each poll loop handles the polled events the same way,
resulting in a lot of duplicated, complex code. Additionally, epoll
was the only one to handle newly created FDs immediately.
So instead, let's move that code to fd.c in a new function dedicated
to this task : fd_process_polled_events(). All pollers now use this
function.
This commit heavily changes the polling system in order to definitely
fix the frequent breakage of SSL which needs to remember the last
EAGAIN before deciding whether to poll or not. Now we have a state per
direction for each FD, as opposed to a previous and current state
previously. An FD can have up to 8 different states for each direction,
each of which being the result of a 3-bit combination. These 3 bits
indicate a wish to access the FD, the readiness of the FD and the
subscription of the FD to the polling system.
This means that it will now be possible to remember the state of a
file descriptor across disable/enable sequences that generally happen
during forwarding, where enabling reading on a previously disabled FD
would result in forgetting the EAGAIN flag it met last time.
Several new state manipulation functions have been introduced or
adapted :
- fd_want_{recv,send} : enable receiving/sending on the FD regardless
of its state (sets the ACTIVE flag) ;
- fd_stop_{recv,send} : stop receiving/sending on the FD regardless
of its state (clears the ACTIVE flag) ;
- fd_cant_{recv,send} : report a failure to receive/send on the FD
corresponding to EAGAIN (clears the READY flag) ;
- fd_may_{recv,send} : report the ability to receive/send on the FD
as reported by poll() (sets the READY flag) ;
Some functions are used to report the current FD status :
- fd_{recv,send}_active
- fd_{recv,send}_ready
- fd_{recv,send}_polled
Some functions were removed :
- fd_ev_clr(), fd_ev_set(), fd_ev_rem(), fd_ev_wai()
The POLLHUP/POLLERR flags are now reported as ready so that the I/O layers
knows it can try to access the file descriptor to get this information.
In order to simplify the conditions to add/remove cache entries, a new
function fd_alloc_or_release_cache_entry() was created to be used from
pollers while scanning for updates.
The following pollers have been updated :
ev_select() : done, built, tested on Linux 3.10
ev_poll() : done, built, tested on Linux 3.10
ev_epoll() : done, built, tested on Linux 3.10 & 3.13
ev_kqueue() : done, built, tested on OpenBSD 5.2
We're completely changing the way FDs will be polled. First, let's fix
a few field names which become confusing. "spec_e" was used to store a
speculative I/O event state. Now we'll store the whole R/W states for
the FD there.
Some rare unexplained busy loops were observed on versions up to 1.5-dev19.
It happens that if a file descriptor happens to be disabled for both read and
write while it was speculatively enabled for both and this without creating a
new update entry, there will be no way to remove it from the speculative I/O
list until some other changes occur. It is suspected that a double sequence
such as enable_both/disable_both could have led to this situation where an
update cancels itself and does not clear the spec list in the poll loop.
While it is unclear what I/O sequence may cause this situation to arise, it
is safer to always add the FD to the update list if nothing could be done on
it so that the next poll round will automatically take care of it.
This is 1.5-specific, no backport is needed.
Right now we see many places doing their own setsockopt(SO_LINGER).
Better only do it just before the close() in fd_delete(). For this
we add a new flag on the file descriptor, indicating if it's safe or
not to linger. If not (eg: after a connect()), then the setsockopt()
call is automatically performed before a close().
The flag automatically turns to safe when receiving a read0.
Commit 09f245 came with a bug : if we don't process events from the
spec list that are also being polled, we can end up with some stuck
events that nobody processes.
We must process all events from the spec list even if they're being
polled in parallel.
ev_sepoll already provides everything needed to manage FD events
by only manipulating the speculative I/O list. Nothing there is
sepoll-specific so move all this to fd.
At the moment sepoll is not 100% event-driven, because a call to fd_set()
on an event which is already being polled will not change its state.
This causes issues with OpenSSL because if some I/O processing is interrupted
after clearing the I/O event (eg: read all data from a socket, can't put it
all into the buffer), then there is no way to call the SSL_read() again once
the buffer releases some space.
The only real solution is to go 100% event-driven. The principle is to use
the spec list as an event cache and that each time an I/O event is reported
by epoll_wait(), this event is automatically scheduled for addition to the
spec list for future calls until the consumer explicitly asks for polling
or stopping.
Doing this is a bit tricky because sepoll used to provide a substantial
number of optimizations such as event merging. These optimizations have
been maintained : a dedicated update list is affected when events change,
but not the event list, so that updates may cancel themselves without any
side effect such as displacing events. A specific case was considered for
handling newly created FDs as soon as they are detected from within the
poll loop. This ensures that their read or write operation will always be
attempted as soon as possible, thus reducing the number of poll loops and
process_session wakeups. This is especially true for newly accepted fds
which immediately perform their first recv() call.
Two new flags were added to the fdtab[] struct to tag the fact that a file
descriptor already exists in the update list. One flag indicates that a
file descriptor is new and has just been created (fdtab[].new) and the other
one indicates that a file descriptor is already referenced by the update list
(fdtab[].updated). Even if the FD state changes during operations or if the
fd is closed and replaced, it's not an issue because the update flag remains
and is easily spotted during list walks. The flag must absolutely reflect the
presence of the fd in the update list in order to avoid overflowing the update
list with more events than there are distinct fds.
Note that this change also recovers the small performance loss introduced
by its connection counter-part and goes even beyond.
These functions have a more explicity meaning and will offer provisions
for explicit polling.
EV_FD_ISSET() has been left for now as it is still in use in checks.
In an attempt to get rid of fdtab[].state, and to move the relevant
parts to the connection struct, we remove the FD_STCLOSE state which
can easily be deduced from the <owner> pointer as there is a 1:1 match.
When running with -vv or -V -d, the list of usable polling systems
is reported. The final selection did not take into account the
possible failures during the tests, which is misleading and could
make one think that a non-working poller will be used, while it is
not the case. Fix that to really report the correct ones.
(cherry picked from commit 6d0e354e0171f08b7b3868ad2882c3663bd068a7)
Some rarely information are stored in fdtab, making it larger for no
reason (source port ranges, remote address, ...). Such information
lie there because the checks can't find them anywhere else. The goal
will be to move these information to the stream interface once the
checks make use of it.
For now, we move them to an fdinfo array. This simple change might
have improved the cache hit ratio a little bit because a 0.5% of
performance increase has measured.
Some users are already hitting the 64k source port limit when
connecting to servers. The system usually maintains a list of
unused source ports, regardless of the source IP they're bound
to. So in order to go beyond the 64k concurrent connections, we
have to manage the source ip:port lists ourselves.
The solution consists in assigning a source port range to each
server and use a free port in that range when connecting to that
server, either for a proxied connection or for a health check.
The port must then be put back into the server's range when the
connection is closed.
This mechanism is used only when a port range is specified on
a server. It makes it possible to reach 64k connections per
server, possibly all from the same IP address. Right now it
should be more than enough even for huge deployments.
The global tuning options right now only concern the polling mechanisms,
and they are not in the global struct itself. It's not very practical to
add other options so let's move them to the global struct and remove
types/polling.h which was not used for anything else.
Using pipe pools makes pipe management a lot easier. It also allows to
remove quite a bunch of #ifdefs in areas which depended on the presence
or not of support for kernel splicing.
The buffer now holds a pointer to a pipe structure which is always NULL
except if there are still data in the pipe. When it needs to use that
pipe, it dynamically allocates it from the pipe pool. When the data is
consumed, the pipe is immediately released.
That way, there is no need anymore to care about pipe closure upon
session termination, nor about pipe creation when trying to use
splice().
Another immediate advantage of this method is that it considerably
reduces the number of pipes needed to use splice(). Tests have shown
that even with 0.2 pipe per connection, almost all sessions can use
splice(), because the same pipe may be used by several consecutive
calls to splice().
It should be stated as a rule that a C file should never
include types/xxx.h when proto/xxx.h exists, as it gives
less exposure to declaration conflicts (one of which was
caught and fixed here) and it complicates the file headers
for nothing.
Only types/global.h, types/capture.h and types/polling.h
have been found to be valid includes from C files.
New functions implemented:
- deinit_pollers: called at the end of deinit())
- prune_acl: called via list_for_each_entry_safe
Add missing pool_destroy2 calls:
- p->hdr_idx_pool
- pool2_tree64
Implement all task stopping:
- health-check: needs new "struct task" in the struct server
- queue processing: queue_mgt
- appsess_refresh: appsession_refresh
before (idle system):
==6079== LEAK SUMMARY:
==6079== definitely lost: 1,112 bytes in 75 blocks.
==6079== indirectly lost: 53,356 bytes in 2,090 blocks.
==6079== possibly lost: 52 bytes in 1 blocks.
==6079== still reachable: 150,996 bytes in 504 blocks.
==6079== suppressed: 0 bytes in 0 blocks.
after (idle system):
==6945== LEAK SUMMARY:
==6945== definitely lost: 7,644 bytes in 137 blocks.
==6945== indirectly lost: 9,913 bytes in 587 blocks.
==6945== possibly lost: 0 bytes in 0 blocks.
==6945== still reachable: 0 bytes in 0 blocks.
==6945== suppressed: 0 bytes in 0 blocks.
before (running system for ~2m):
==9343== LEAK SUMMARY:
==9343== definitely lost: 1,112 bytes in 75 blocks.
==9343== indirectly lost: 54,199 bytes in 2,122 blocks.
==9343== possibly lost: 52 bytes in 1 blocks.
==9343== still reachable: 151,128 bytes in 509 blocks.
==9343== suppressed: 0 bytes in 0 blocks.
after (running system for ~2m):
==11616== LEAK SUMMARY:
==11616== definitely lost: 7,644 bytes in 137 blocks.
==11616== indirectly lost: 9,981 bytes in 591 blocks.
==11616== possibly lost: 0 bytes in 0 blocks.
==11616== still reachable: 4 bytes in 1 blocks.
==11616== suppressed: 0 bytes in 0 blocks.
Still not perfect but significant improvement.
Gcc provides __attribute__((constructor)) which is very convenient
to execute functions at startup right before main(). All the pollers
have been converted to have their register() function declared like
this, so that it is not necessary anymore to call them from a centralized
file.
Some pollers such as kqueue lose their FD across fork(), meaning that
the registered file descriptors are lost too. Now when the proxies are
started by start_proxies(), the file descriptors are not registered yet,
leaving enough time for the fork() to take place and to get a new pollfd.
It will be the first call to maintain_proxies that will register them.
select, poll and epoll now have their dedicated functions and have
been split into distinct files. Several FD manipulation primitives
have been provided with each poller.
The rest of the code needs to be cleaned to remove traces of
StaticReadEvent/StaticWriteEvent. A trick involving a macro has
temporarily been used right now. Some work needs to be done to
factorize tests and sets everywhere.
The timeouts, expiration timers and results are now stored in the buffers.
The timers will have to change a bit to become more flexible, and when the
I/O completion functions will be written, the connect_complete() will have
to be extracted from the write() function.
The files are now stored under :
- include/haproxy for the generic includes
- include/types.h for the structures needed within prototypes
- include/proto.h for function prototypes and inline functions
- src/*.c for the C files
Most include files are now covered by LGPL. A last move still needs
to be done to put inline functions under GPL and not LGPL.
Version has been set to 1.3.0 in the code but some control still
needs to be done before releasing.
