We need this all the time in traces, let's have it now. For the sake
of compact outputs, the strings are all 3-chars long. The "show fd"
output was improved to make use of this.
All functions of the h2 data path were updated to receive one or multiple
TRACE() calls, at least one pair of TRACE_ENTER()/TRACE_LEAVE(), and those
manipulating protocol elements have been improved to report frame types,
special state transitions or detected errors. Even with careful tests, no
performance impact was measured when traces are disabled.
They are not completely exploited yet, the callback function tries to
dump a lot about them, but still doesn't provide buffer dumps, nor does
it indicate the stream or connection error codes.
The first argument is always set to the connection when known. The second
argument is set to the h2s when known, sometimes a 3rd argument is set to
a buffer, generally the rxbuf or htx, and occasionally the 4th argument
points to an integer (number of bytes read/sent, error code).
Retrieving a 10kB object produces roughly 240 lines when at developer
level, 35 lines at data level, 27 at state level, and 10 at proto level
and 2 at user level.
For now the headers are not dumped, but the start line are emitted in
each direction at user level.
The patch is marked medium because it touches lots of places, though
it takes care not to change the execution path.
The new function h2_trace() is called when relevant by the trace subsystem
in order to provide extra information about the trace being produced. It
can for example display the connection pointer, the stream pointer, etc.
It is declared in the trace source as the default callback as we expect
it to be versatile enough to enrich most traces.
In addition, for requests and responses, if we have a buffer and we can
decode it as an HTX buffer, we can extract user-friendly information from
the start line.
For now the traces are not used. Supported events are categorized by
where the activity comes from (h2c, h2s, stream, etc), a direction
(send/recv/wake), and a list of possibilities for each of them (frame
types, errors, shut, ...). This results in ~50 different events that
try to cover a lot of possibilities when it's needed to filter on
something specific. Special events like protocol error are handled.
A few aggregate events like "rx_frame" or "tx_frame" are planed to
cover all frame types at once by being placed all the time with any
of the other ones.
We also state that the first argument is always the connection. This way
the trace subsystem will be able to safely retrieve some useful info, and
we'll still be able to get the h2c from there (conn->ctx) in a pretty
print function. The second argument will always be an h2s, and in order
to propose it for tracking, we add its description. We also define 4
verbosity levels, which seems more than enough.
The detail level initially based on syslog levels is not used, while
something related is missing, trace verbosity, to indicate whether or
not we want to call the decoding callback and what level of decoding
we want (raw captures etc). Let's change the field to "verbosity" for
this. A verbosity of zero means that the decoding callback is not
called, and all other levels are handled by this callback and are
source-specific. The source is now prompted to list the levels that
are proposed to the user. When the source doesn't define anything,
"quiet" and "default" are available.
It's very convenient to know the trace level in the output, at least to
grep/grep -v on it. The main usage is to filter/filter out the developer
traces at level DEVEL. For this we now add the numeric level (0 to 4) just
after the source name in the brackets. The output now looks like this :
[00|h2|4|mux_h2.c:3174] h2_send(): entering : h2c=0x27d75a0 st=2
-, -, | ------------, --------, -------------------> message
| | | | '-> function name
| | | '-> source file location
| | '-> trace level (4=dev)
| '-> trace source
'-> thread number
Working on adding traces to mux-h2 revealed that the function names are
manually copied a lot in developer traces. The reason is that they are
not preprocessor macros and as such cannot be concatenated. Let's
slightly adjust the trace() function call to take a function name just
after the file:line argument. This argument is only added for the
TRACE_DEVEL and 3 new TRACE_ENTER, TRACE_LEAVE, and TRACE_POINT macros
and left NULL for others. This way the function name is only reported
for traces aimed at the developers. The pretty-print callback was also
extended to benefit from this. This will also significantly shrink the
data segment as the "entering" and "leaving" strings will now be merged.
One technical point worth mentioning is that the function name is *not*
passed as an ist to the inline function because it's not considered as
a builtin constant by the compiler, and would lead to strlen() being
run on it from all call places before calling the inline function. Thus
instead we pass the const char * (that the compiler knows where to find)
and it's the __trace() function that converts it to an ist for internal
consumption and for the pretty-print callback. Doing this avoids losing
5-10% peak performance.
The "payload" trace level was ambigous because its initial purpose was
to be able to dump received data. But it doesn't make sense to force to
report data transfers just to be able to report state changes. For
example, all snd_buf()/rcv_buf() operations coming from the application
layer should be tagged at this level. So here we move this payload level
above the state transitions and rename it to avoid the ambiguity making
one think it's only about request/response payload. Now it clearly is
about any data transfer and is thus just below the developer level. The
help messages on the CLI and the doc were slightly reworded to help
remove this ambiguity.
In prompts on the CLI we now commonly need to propose a keyword name
and a description and it doesn't make sense to define a new struct for
each such pairs. Let's simply have a generic "name_desc" for this.
Save the authority TLV in a PROXYv2 header from the client connection,
if present, and make it available as fc_pp_authority.
The fetch can be used, for example, to set the SNI for a backend TLS
connection.
Previously the callback was almost mandatory so it made sense to have it
before the message. Now that it can default to the one declared in the
trace source, most TRACE() calls contain series of empty args and callbacks,
which make them suitable for being at the end and being totally omitted.
This patch thus reverses the TRACE arguments so that the message appears
first, then the mask, then arg1..arg4, then the callback. In practice
we'll mostly see 1 arg, or 2 args and nothing else, and it will not be
needed anymore to pass long series of commas in the middle of the
arguments. However if a source is enforced, the empty commas will still
be needed for all omitted arguments.
Traces were missing the thread number and the source name, which was
really annoying. Now the thread number is emitted on two digits inside
the square brackets, followed by the source name then the line location,
each delimited with a vertical bar, such as below :
[00|h2|mux_h2.c:2651] Notifying stream about SID change : h2c=0x7f3284581ae0 st=3 h2s=0x7f3284297f00 id=523 st=4
[00|h2|mux_h2.c:2708] receiving H2 HEADERS frame : h2c=0x7f3284581ae0 st=3 dsi=525 (st=0)
[02|h2|mux_h2.c:2194] Received H2 request : h2c=0x7f328d3d1ae0 st=2 : [525] H2 REQ: GET / HTTP/2.0
[02|h2|mux_h2.c:2561] Expecting H2 frame header : h2c=0x7f328d3d1ae0 st=2
It becomes apparent that most traces will use a single trace pretty
print callback, so let's allow the trace source to declare a default
one so that it can be omitted from trace calls, and will be used if
no other one is specified.
The principle is that when emitting a message, if some dropped events
were logged, we first attempt to report this counter before going
further. This is done under an exclusive lock while all logs are
produced under a shared lock. This ensures that the dropped line is
accurately reported and doesn't accidently arrive after a later
event.
The new "show events" CLI keyword lists supported event sinks. When
passed a buffer-type sink it completely dumps it.
no drops at all during attachment even at 8 millon evts/s.
still missing the attachment limit though.
This now provides sink_new_buf() which allocates a ring buffer. One such
ring ("buf0") of 1 MB is created already, and may be used by sink_write().
The sink's creation should probably be moved somewhere else later.
The three functions (attach, IO handler, and release) are meant to be
called by any CLI command which requires to dump the contents of a ring
buffer. We do not implement anything generic to dump any ring buffer on
the CLI since it's meant to be used by other functionalities above.
However these functions deal with locking and everything so it's trivial
to embed them in other code.
This function tries to write to the ring buffer, possibly removing enough
old messages to make room for the new one. It takes two arrays of fragments
on input to ease the insertion of prefixes by the caller. It atomically
writes the message, possibly truncating it if desired, and returns the
operation's status.
Our circular buffers are well suited for being used as ring buffers for
not-so-structured data. The machanism here consists in making room in a
buffer before inserting a new record which is prefixed by its size, and
looking up next record based on the previous one's offset and size. We
can have up to 255 consumers watching for data (dump in progress, tail)
which guarantee that entrees are not recycled while they're being dumped.
The complete representation is described in the header file. For now only
ring_new(), ring_resize() and ring_free() are created.
Let's not mess up with fd-specific code, locking nor message formating
here, and use the new generic function instead. This substantially
simplifies the sink_write() code and makes it more agnostic to the
output representation and storage.
Currently both logs and event sinks may use a file descriptor to
atomically emit some output contents. The two may use the same FD though
nothing is done to make sure they use the same lock. Also there is quite
some redundancy between the two. Better make a specific function to send
a fragmented message to a file descriptor which will take care of the
locking via the fd's lock. The function is also able to truncate a
message and to enforce addition of a trailing LF when building the
output message.
The new functions are :
__b_put_varint() : inserts a varint when it's known that it fits
b_put_varint() : tries to insert a varint at the tail
b_get_varint() : tries to get a varint from the head
b_peek_varint() : tries to peek a varint at a specific offset
Wrapping is supported so that they are expected to be safe to use to
manipulate varints with buffers anywhere.
It will sometimes be useful to encode varints to know the output size in
advance. Two versions are provided, one inline using a switch/case construct
which will be trivial for use with constants (and will be very fast albeit
huge) and one function iterating on the number which is 5 times smaller,
for use with variables.
The converter can be useful to look up a server queue from a dynamic value.
It takes an input value of type string, either a server name or
<backend>/<server> format and returns the number of queued sessions
on that server. Can be used in places where we want to look up
queued sessions from a dynamic name, like a cookie value (e.g.
req.cook(SRVID),srv_queue) and then make a decision to break
persistence or direct a request elsewhere.
Signed-off-by: Nenad Merdanovic <nmerdan@haproxy.com>
The url32 sample fetch does not take the path part of the URL into
account. This is because in smp_fetch_url32() we erroneously modify
path.len and path.ptr before testing their value and building the
path based part of the hash.
This fixes issue #235
This must be backported as far as 1.9, when HTX was introduced.
The delete_listener() function takes the listener's lock before taking
the proto_lock, which is contrary to what other functions do, possibly
causing an AB/BA deadlock. In practice the two only places where both
are taken are during protocol_enable_all() and delete_listener(), the
former being used during startup and the latter during stop. In practice
during reload floods, it is technically possible for a thread to be
initializing the listeners while another one is stopping. While this
is too hard to trigger on 2.0 and above due to the synchronization of
all threads during startup, it's reasonably easy to do in 1.9 by having
hundreds of listeners, starting 64 threads and flooding them with reloads
like this :
$ while usleep 50000; do killall -USR2 haproxy; done
Usually in less than a minute, all threads will be deadlocked. The fix
consists in always taking the proto_lock before the listener lock. It
seems to be the only place where these two locks were reversed. This
fix needs to be backported to 2.0, 1.9, and 1.8.
If haproxy is built with profiling enabled with -pg, it is possible to
see the master quit during a reload while it's re-executing itself with
error code 155 (signal 27) saying "Profile timer expired)". This happens
if the SIGPROF signal is delivered during the execve() call while the
handler was already unregistered. The issue itself is not directly inside
haproxy but it's easy to address. This patch disables this signal before
calling execvp() during a master reload. A simple test for this consists
in running this little script with haproxy started in master-worker mode :
$ while usleep 50000; do killall -USR2 haproxy; done
This fix should be backported to all versions using the master-worker
model.
If a receipt ends with the HTX buffer full and everything is completed except
appending the HTX EOM block, we end up detecting an error because the H1
parser did not switch to H1_MSG_DONE yet while all conditions for an end of
stream and end of buffer are met. This can be detected by retrieving 31532
or 31533 chunk-encoded bytes over H1 and seeing haproxy log "SD--" at the
end of a successful transfer.
Ideally the EOM part should be totally independent on the H1 message state
since the block was really parsed and finished. So we should switch to a
last state requiring to send only EOM. However this needs a few risky
changes. This patch aims for simplicity and backport safety, thus it only
adds a flag to the H1 stream indicating that an EOM is still needed, and
excludes this condition from the ones used to detect end of processing. A
cleaner approach needs to be studied, either by adding a state before DONE
or by setting DONE once the various blocks are parsed and before trying to
send EOM.
This fix must be backported to 2.0. The issue does not seem to affect 1.9
though it is not yet known why, probably that it is related to the different
encoding of trailers which always leaves a bit of room to let EOM be stored.
The H1 message parser calls the various message block parsers with an
offset indicating where in the buffer to start from, and only consumes
the data at the end of the parsing. The headers and trailers parsers
have a condition detecting if a headers or trailers block is too large
to fit into the buffer. This is detected by an incomplete block while
the buffer is full. Unfortunately it doesn't take into account the fact
that the block may be parsed after other blocks that are still present
in the buffer, resulting in aborting some transfers early as reported
in issue #231. This typically happens if a trailers block is incomplete
at the end of a buffer full of data, which typically happens with data
sizes multiple of the buffer size minus less than the trailers block
size. It also happens with the CRLF that follows the 0-sized chunk of
any transfer-encoded contents is itself on such a boundary since this
CRLF is technically part of the trailers block. This can be reproduced
by asking a server to retrieve exactly 31532 or 31533 bytes of static
data using chunked encoding with curl, which reports:
transfer closed with outstanding read data remaining
This issue was revealed in 2.0 and does not affect 1.9 because in 1.9
the trailers block was processed at once as part of the data block
processing, and would simply give up and wait for the rest of the data
to arrive.
It's interesting to note that the headers block parsing is also affected
by this issue but in practice it has a much more limited impact since a
headers block is normally only parsed at the beginning of a buffer. The
only case where it seems to matter is when dealing with a response buffer
full of 100-continue header blocks followed by a regular header block,
which will then be rejected for the same reason.
This fix must be backported to 2.0 and partially to 1.9 (the headers
block part).
I forgot to fix this one before pushing, despite my tests. lockon_ptr is
only used to compare pointers, it doesn't need to point to a writable
location. Without threads the atomic store is turned into an assignment
and rightfully complains.
At the moment the subsystem is still not complete and the various modules
do not yet produce traces (some dirty experimental code for H2 exists) but
this aims at easing a broad adoption.
Among the missing elements, we can enumerate the lack of configuration
of the sinks (e.g. it's still not possible to change their output format
nor enable/disable timestamps) and since timestamps are not availalbe in
the sinks, they are not collected nor passed by the traces.
Now we try to find frontend, listener, backend, server, connection,
session, stream, from the presented argument of type connection,
stream or session. Various combinations and bounces allow to
retrieve most of them almost all the time. The extraction is
performed early so that we'll be able to apply filters later.
The lock-on is set if it was not there while the trace is running and
a valid pointer is available. If it was already set and doesn't match,
no trace is produced.
When no criterion is provided, it carefully enumerates all available
ones, including those provided by the source itself. Otherwise it sets
the new criterion and resets the lockon pointer.
Given that we can pass typed arguments to the trace() function, let's
add provisions for tracking them. They are source-specific so we need
to let the source fill their name and description. Only those with a
non-null name will be proposed.
When we stop or pause a trace (either on a matching event or by hand),
we must also stop the lock-on feature so that we don't follow any
further activity on this pointer even if it is recycled. For now this
is not exploited.
With a few macros it's possible for a trace source to commit to only
using a certain type for a given argument (or set of). This will be
particularly useful to let the trace subsystem retrieve some precious
information such as a connection, session, listener, source address or
so, and enable/disable filtering and/or locking.
The new TRACE_<level>() macros take a mask, 4 args, a callback and a
static message. From this they also inherit the TRACE_SOURCE macro from
the caller, which contains the pointer to the trace source (so that it's
not required to paste it everywhere), and an ist string is also made by
the concatenation of the file name and the line number. This uses string
concatenation by the preprocessor, and turns it into an ist by the compiler
so that there is no operation at all to perform to adjust the data length
as the compiler knows where to cut during the optimization phase. Last,
the message is also automatically turned into an ist so that it's trivial
to put it into an iovec without having to run strlen() on it.
All arguments and the callback may be empty and will then automatically
be replaced with a NULL pointer. This makes the TRACE calls slightly
lighter especially since arguments are not always used. Several other
options were considered to use variadic macros but there's no outstanding
rule that justifies to place an argument before another one, and it still
looks convenient to have the message be the last one to encourage copy-
pasting of the trace statements.
A generic TRACE() macro takes TRACE_LEVEL in from the source file as the
trace level instead of taking it from its name. This may slightly simplify
the production of traces that always run at the same level (internal core
parts may probably only be called at developer level).
The trace() call will support an optional decoding callback and 4
arguments that this function is supposed to know how to use to provide
extra information. The output remains unchanged when the function is
NULL. Otherwise, the message is pre-filled into the thread-local
trace_buf, and the function is called with all arguments so that it
completes the buffer in a readable form depending on the expected
level of detail.
This new "level" argument will allow the trace sources to label the
traces for different purposes, and filter out some of them if they
are not relevant to the current target. Right now we have 5 different
levels:
- USER : the least verbose one, only a few functional information
- PAYLOAD: like user but also displays some payload-related information
- PROTO: focuses on the protocol's framing
- STATE: also indicate state internal transitions or non-transitions
- DEVELOPER: adds extra info about branches taken in the code (break
points, return points)
We now pass an extra argument "where" to the trace() call, which
is supposed to be an ist made of the concatenation of the filename
and the line number. We only keep the last 10 chars from this string
since the end of file names is most often easy to recognize. This
gives developers useful information at very low cost.
For now it remains quite basic. It performs a few state checks, calls
the source's sink if defined, and performs the transitions between
RUNNING, STOPPED and WAITING when the configured events match.
The new "show trace" CLI command lists available trace sources and
indicates their status, their sink, and number of dropped packets.
When "show trace <source>" is used, the list of known events is
also listed with their status per action (report/start/stop/pause).
The "level" keyword allows to indicate the expected level of verbosity
in the traces, among "user" (least verbose, just synthetic info) to
"developer" (very detailed, including function entry/leaving). It's only
displayed and set but not used yet.
For now it lists the sources if one is not provided, and checks
for the source's existence. It lists the events if not provided,
checks for their existence if provided, and adjusts reported
events/start/stop/pause events, and performs state transitions.
It lists sinks and adjusts them as well. Filters, lock, and
level are not implemented yet.
The principle of this subsystem will be to support taking live traces
at various places in the code with conditional triggers, filters, and
ability to lock on some elements. The traces will support typed events
and will be sent into sinks made of ring buffers, file descriptors or
remote servers.
