sc_need_room() now takes the required free space to receive more data as
parameter. All calls to this function are updated accordingly. For now, this
value is set but not used. When we are waiting for a buffer, 0 is used. So
we expect to be unblocked ASAP. However this must be reviewed because
SC_FL_NEED_BUF is probably enough in this case and this flag is already set
if the input buffer allocation fails.
The peers applet now use the applet API to send message instead of the
channel API. This way, it does not need to take care to request more room if
it fails to put data into the channel's buffer.
This puts an end to the occasional confusion between the "now" date
that is internal, monotonic and not synchronized with the system's
date, and "date" which is the system's date and not necessarily
monotonic. Variable "now" was removed and replaced with a 64-bit
integer "now_ns" which is a counter of nanoseconds. It wraps every
585 years, so if all goes well (i.e. if humanity does not need
haproxy anymore in 500 years), it will just never wrap. This implies
that now_ns is never nul and that the zero value can reliably be used
as "not set yet" for a timestamp if needed. This will also simplify
date checks where it becomes possible again to do "date1<date2".
All occurrences of "tv_to_ns(&now)" were simply replaced by "now_ns".
Due to the intricacies between now, global_now and now_offset, all 3
had to be turned to nanoseconds at once. It's not a problem since all
of them were solely used in 3 functions in clock.c, but they make the
patch look bigger than it really is.
The clock_update_local_date() and clock_update_global_date() functions
are now much simpler as there's no need anymore to perform conversions
nor to round the timeval up or down.
The wrapping continues to happen by presetting the internal offset in
the short future so that the 32-bit now_ms continues to wrap 20 seconds
after boot.
The start_time used to calculate uptime can still be turned to
nanoseconds now. One interrogation concerns global_now_ms which is used
only for the freq counters. It's unclear whether there's more value in
using two variables that need to be synchronized sequentially like today
or to just use global_now_ns divided by 1 million. Both approaches will
work equally well on modern systems, the difference might come from
smaller ones. Better not change anyhting for now.
One benefit of the new approach is that we now have an internal date
with a resolution of the nanosecond and the precision of the microsecond,
which can be useful to extend some measurements given that timestamps
also have this resolution.
Instead we're using ns_to_sec(tv_to_ns(&now)) which allows the tv_sec
part to disappear. At this point, "now" is only used as a timeval in
clock.c where it is updated.
Just like for other applets, we now use the SE descriptor instead of the
channel to report error and end-of-stream. We must just be sure to consume
request data when we are waiting the applet to be released.
It was done by hand by callers when a shutdown for read or write was
performed. It is now always handled by the functions performing the
shutdown. This way the callers don't take care of it. This will avoid some
bugs.
Since 2.6 with commit 34e4085f8 ("MEDIUM: peers: Balance applets across
threads") the initialization of a peers appctx may be postponed with a
wakeup, causing some partially initialized appctx to be visible. The
"show peers" command used to only care about peers without appctx, but
now it must also take care of those with no stconn, otherwise it can
occasionally crash while dumping them.
This fix must be backported to 2.6. Thanks to Patrick Hemmer for
reporting the problem.
CF_READ_NULL flag is not really useful and used. It is a transient event
used to wakeup the stream. As we will see, all read events on a channel may
be resumed to only one and are all used to wake up the stream.
In this patch, we introduce CF_READ_EVENT flag as a replacement to
CF_READ_NULL. There is no breaking change for now, it is just a
rename. Gradually, other read events will be merged with this one.
In process_peer_sync: a check was performed to know whether the peers section
handler should kill itself if the corresponding proxy was not started on the
current process.
This logic was initially implemented in early 1.6 development to prevent
some issues when peers where used in conjunction with nbproc > 1:
f83d3fe00a MEDIUM: init: stop any peers section not bound to the correct process
46dc1ca MEDIUM: peers: unregister peers that were never started
But later in 1.6 dev, a new commit has been introduced:
47c8c029db MEDIUM: init: completely deallocate unused peers
With the latter, the check implemented in 46dc1ca ("MEDIUM: peers: unregister
peers that were never started") will never succeed: it is dead code.
Since nbproc support has been dropped in 2.5, things have changed a bit:
f83d3fe00a logic was moved in mworker_cleanlisteners, but as in 46dc1ca :
peers task is safely destroyed before peers_fe is set to NULL.
Conversely, peers_fe is first set by init_peers_frontend() before peers task
is scheduled by peers_init_sync() in check_config_validity().
Again, it is safe to say that we will never reach !peers->peers_fe
in process_peer_sync(): this self-killing mechanism is not relevant anymore.
--
To cut a long story short: I stumbled on this while tracking down
current signal api usage.
This led me to a signal_unregister_handler() call performed in the
aforementionned dead code. To me this code was potentially unsafe because
signal_unregister_handler() is not thread safe and here it was used within a
task initialized via task_new_anywhere(). So I decided to check how bad this
could be (ie: conditions to be met for this code to run).. and here we are.
If shards are in use, we must fill the shard number on incoming updates,
otherwise some entries are assigned shard number zero, and may be broadcast
everywhere once updated, instead of being sent only to the peers having the
same shard number.
This fixes commit 36d156564 ("MINOR: peers: Support for peer shards"). No
backport is needed.
In peer_treat_updatemsg(), the lower layers of the stick-table code are
reimplemented, and the key length is never really known for an entry
being processed, it depends on the type being parsed and the moment
where it's done. This makes it quite difficult to stuff some shard
number calculation there.
This patch adds a keylen local variable that is always set to the length
of the current key depending on its type. It takes this opportunity for
reducing redudant expressions involving this length and always using the
new variable instead, limiting the risk of errors. Arguably that code
would have been way simpler by creating a dummy stktable_key and passing
it to stksess_new() as done anywhere else, but let's not change all that
a few days before the release.
In issue #1939, Ilya mentions that cppchecks warned about use of "%d" to
report the status state that's locally stored as an unsigned int. While
technically valid, this will never cause any trouble since in the end
what we store there are the applet's states (just a few enum values).
Better use %u anyway to silence this warning.
Since 0909f62266 ("BUG/MEDIUM: peers: messages about unkown tables not
correctly ignored"), the 'sc' variable is no longer used in
peer_treat_updatemsg() and peer_treat_definemsg() functions. So, we must
remove them to avoid compilation warning.
This patch must be backported with the commit above.
Table defintion's messages and update messages are not correctly
ignored if the table is not configured on the local peer.
It is a bug because, receiving those messages, the parser
returns an error and the upper layer considers that the state of the
peer's connection is modified (as it is done in the case of protocol
error) and switch immediatly the automate to process the new state.
But, even if message is silently ignored because the connection's
state doesn't change and we continue to process the next message, some
processing remains not performed: for instance the ALIVE flag is not set
on the peer's connection as it should be done after receiving any valid
messages. This results in a shutdown of the connection when timeout
is elapsed as if no message has been received during this delay.
This patch fix the behavior, those messages are now silently ignored
and the upper layer continue the processing as it is done for any valid
messages.
This bug appears with the code re-work of the peers on 2.0 so
it should be backported until this version.
We considered the resync process is finished if a full resync request
is ended receiving the "resync-finish" message. But in the case of
"shards" each node declared with a "shard" has only a partial view
of the table. And the resync process is ended whereas the original
peer tables content contains only a "shard" of the full content.
This patch allow to retrieve the entire tables requesting a resync
from all different "shards".
To do so we don't commit the end of a resync process receiving a
"resync-finish" if the node is part of "shard", we only flag this
peer and all peers using the same shard as "notup2date" as if we
received a "resync-partial" message, and we re-schedule a request
of a resync as it is done receiving a "resync-partial" message.
Doing this the peers flagged "notup2date" won't be addressed for the
next resync request round and the next resync request will be send to
a shard not yet requested.
Receving a "resync-finish" message we also check if all peers using
"shards" are flagged "notup2date". It meens that all peers have been
addressed and we can considered the resync process is now finished.
Note also that the "resync request" scheduler already handle a timeout
and if we are not able to retrieve a full resync after a delay. The
resync process is ended.
This patch should be backported in all versions handling "shard"
on peer lines.
Add "shards" new keyword for "peers" section to configure the number
of peer shards attached to such secions. This impact all the stick-tables
attached to the section.
Add "shard" new "server" parameter to configure the peers which participate to
all the stick-tables contents distribution. Each peer receive the stick-tables updates
only for keys with this shard value as distribution hash. The "shard" value
is stored in ->shard new server struct member.
cfg_parse_peers() which is the function which is called to parse all
the lines of a "peers" section is modified to parse the "shards" parameter
stored in ->nb_shards new peers struct member.
Add srv_parse_shard() new callback into server.c to pare the "shard"
parameter.
Implement stksess_getkey_hash() to compute the distribution hash for a
stick-table key as the 64-bits xxhash of the key concatenated to the stick-table
name. This function is called by stksess_setkey_shard(), itself
called by the already implemented function which create a new stick-table
key (stksess_new()).
Add ->idlen new stktable struct member to store the stick-table name length
to not have to compute it each time a stick-table key hash is computed.
Right now a spinlock is used, but most accesses are for reads, so let's
switch the lock to an rwlock and switch all accesses to exclusive locks
for now. There should be no visible difference at this point.
On a reload, if the previous resync was not finished, the freshly old worker
must not try to start a new resync. Otherwise, it will compete with the
older wokers, slowing down or blocking the resync. Only an up-to-date woker
must try to perform a local resync.
This patch must be backported as far as 2.0 (and maybe to 1.8 too).
When a worker is stopped, the resync timer is used to limit in time the
connection stage to the new worker to perform the local resync. However,
this timer must be stopped when the resync is in progress and it must be
re-armed if the resync is interrupted (for instance because another
reload). Otherwise, if the resync is a bit long, an old worker may be killed
too early.
This bug was introduce by the commit 160fff665 ("BUG/MEDIUM: peers: limit
reconnect attempts of the old process on reload"). It must be backported as
far as 2.0.
Only the client timeout was set. Nothing prevent a peer applet to stall
during a connect or waiting a message from a remote peer. To avoid any
issue, it is important to also set connection and server timeouts. The
connect timeout is set to 1s and the server timeout is set to 5s.
This patch must be backported to all supported versions.
As seen in GH issue #1770, peers synchronization do not cope well with
very large buffers because by default the only two reasons for stopping
the processing of updates is either that the end was reached or that
the buffer is full. This can cause high latencies, and even rightfully
trigger the watchdog when the operations are numerous and slowed down
by competition on the stick-table lock.
This patch introduces a limit to the number of messages one may send
at once, which now defaults to 200, regardless of the buffer size. This
means taking and releasing the lock up to 400 times in a row, which is
costly enough to let some other parts work.
After some observation this could be backported to 2.6. If so, however,
previous commits "BUG/MEDIUM: applet: fix incorrect check for abnormal
return condition from handler" and "BUG/MINOR: applet: make the call_rate
only count the no-progress calls" must be backported otherwise the call
rate might trigger the looping protection.
When a peer open a new connection to another peer, it is considered as
connected when the hello message is sent. To do so, the peer applet was
relying on CF_WRITE_PARTIAL channel flag. However it is not the right flag
to use. This one is a transient flag. Depending on the scheduling, this flag
may be removed by the stream before the peer has a chance to see
it. Instead, CF_WROTE_DATA flag must be checked.
This patch is related to the issue #1799. It must be backported as far as
2.0.
When peers are configured and HAProxy is reloaded or restarted, a
synchronization is performed between the old process and the new one. To do
so, the old process connects on the new one. If the synchronization fails,
it retries. However, there is no delay and reconnect attempts are not
bounded. Thus, it may loop for a while, consuming all the CPU. Of course, it
is unexpected, but it is possible. For instance, if the local peer is
misconfigured, an infinite loop can be observed if the connection succeeds
but not the synchronization. This prevents the old process to exit, except
if "hard-stop-after" option is set.
To fix the bug, the reconnect is delayed. The local peer already has a
expiration date to delay the reconnects. But it was not used on stopping
mode. So we use it not. Thanks to the previous fix, the reconnect timeout is
shorter in this case (500ms against 5s on running mode). In addition, we
also use the peers resync expiration date to not infinitely retries. It is
accurate because the new process, on its side, use this timeout to switch
from a local resync to a remote resync.
This patch depends on "MINOR: peers: Use a dedicated reconnect timeout when
stopping the local peer". It fixes the issue #1799. It should be backported
as far as 2.0.
When a process is stopped or reload, a dedicated reconnect timeout is now
used. For now, this timeout is not used because the current code retries
immediately to reconnect to perform the local synchronization with the new
local peer, if any.
This patch is required to fix the issue #1799. It should be backported as
far as 2.0 with next fixes.
At several places we need to figure the ID of the first thread allowed
to run a task. Till now this was performed using my_ffsl(t->thread_mask)
but since we now have the thread ID stored into the task, let's use it
instead. This is tagged major because it starts to assume that tid<0 is
strictly equivalent to atleast2(thread_mask), and that as such, among
the allowed threads are the current one.
By having the appctx in argument this function wouldn't have experienced
the previous bug. Better do that now to avoid proliferation of awkward
functions.
In the context of a CLI command, it's particularly not welcome to use
an "appctx" variable that is not the current one. In addition it was
created for use at exactly 6 places in 2 lines. Let's just remove it
and stick to peer->appctx which is used elsewhere in the function and
is unambiguous.
Commit d0a06d52f ("CLEANUP: applet: use applet_put*() everywhere possible")
replaced most accesses to the conn_stream with simpler accesses to the
appctx. Unfortunately, in all the CLI functions using an appctx, one
makes an exception where the appctx is not the caller's but the one being
inspected! When no peers connection is active, the early exit immediately
crashes.
No backport is needed.
There's no more reason for keepin the code and definitions in conn_stream,
let's move all that to stconn. The alphabetical ordering of include files
was adjusted.
This file contains all the stream-connector functions that are specific
to application layers of type stream. So let's name it accordingly so
that it's easier to figure what's located there.
The alphabetical ordering of include files was preserved.
An equivalent applet_need_more_data() was added as well since that function
is mostly used from applet code. It makes it much clearer that the applet
is waiting for data from the stream layer.
The new name mor eclearly indicates that a stream connector cannot make
any more progress because it needs room in the channel buffer, or that
it may be unblocked because the buffer now has more room available. The
testing function is sc_waiting_room(). This is mostly used by applets.
Note that the flags will change soon.
These functions return the app-layer associated with an stconn, which
is a check, a stream or a stream's task. They're used a lot to access
channels, flags and for waking up tasks. Let's just name them
appropriately for the stream connector.
We're starting to propagate the stream connector's new name through the
API. Most call places of these functions that retrieve the channel or its
buffer are in applets. The local variable names are not changed in order
to keep the changes small and reviewable. There were ~92 uses of cs_ic(),
~96 of cs_oc() (due to co_get*() being less factorizable than ci_put*),
and ~5 accesses to the buffer itself.
This applies the change so that the applet code stops using ci_putchk()
and friends everywhere possible, for the much saferapplet_put*() instead.
The change is mechanical but large. Two or three functions used to have no
appctx and a cs derived from the appctx instead, which was a reminiscence
of old times' stream_interface. These were simply changed to directly take
the appctx. No sensitive change was performed, and the old (more complex)
API is still usable when needed (e.g. the channel is already known).
The change touched roughly a hundred of locations, with no less than 124
lines removed.
It's worth noting that the stats applet, the oldest of the series, could
get a serious lifting, as it's still very channel-centric instead of
propagating the appctx along the chain. Given that this code doesn't
change often, there's no emergency to clean it up but it would look
better.
This renames the "struct conn_stream" to "struct stconn" and updates
the descriptions in all comments (and the rare help descriptions) to
"stream connector" or "connector". This touches a lot of files but
the change is minimal. The local variables were not even renamed, so
there's still a lot of "cs" everywhere.
When creating a new applet for peer outgoing connection, we check
the load on each thread. Threads with least applet count are
preferred.
With this solution we avoid a situation when many outgoing
connections run on the same thread causing significant load on
single CPU core.
