Given that the original list-based version was using a list head as the
root of the variables, while the tree is using a single pointer, it made
sense to reuse that space to place multiple roots, indexed on the lower
bits of the name hash. Two roots slightly increase the performance level,
but the best gain is obtained with 4 roots. The performance is now always
above that of the list, even with small counts, and with 100 vars, it's
21% higher than before, or 67% higher than with the list.
We keep the same lock (it could have made sense to use one lock per head),
because most of the variables in large configs are attached to a stream
or a session, hence are not shared between threads. Thus there's no point
in sharding the pointer.
Configs involving many variables can start to eat a lot of CPU in name
lookups. The reason is that the names themselves are dynamic in that
they are relative to dynamic objects (sessions, streams, etc), so
there's no fixed index for example. The current implementation relies
on a standard linked list, and in order to speed up lookups and avoid
comparing strings, only a 64-bit hash of the variable's name is stored
and compared everywhere.
But with just 100 variables and 1000 accesses in a config, it's clearly
visible that variable name lookup can reach 56% CPU with a config
generated this way:
for i in {0..100}; do
printf "\thttp-request set-var(txn.var%04d) int(%d)" $i $i;
for j in {1..10}; do [ $i -lt $j ] || printf ",add(txn.var%04d)" $((i-j)); done;
echo;
done
The performance and a 4-core skylake 4.4 GHz reaches 85k RPS with a perf
profile showing:
Samples: 170K of event 'cycles', Event count (approx.): 142378815419
Overhead Shared Object Symbol
56.39% haproxy [.] var_to_smp
6.65% haproxy [.] var_set.part.0
5.76% haproxy [.] sample_process_cnv
3.23% haproxy [.] sample_conv_var2smp
2.88% haproxy [.] sample_conv_arith_add
2.33% haproxy [.] __pool_alloc
2.19% haproxy [.] action_store
2.13% haproxy [.] vars_get_by_desc
1.87% haproxy [.] smp_dup
[above, var_to_smp() calls var_get() under the read lock].
By switching to a binary tree, the cost is significantly lower, the
performance reaches 117k RPS (+37%) with this profile:
Samples: 170K of event 'cycles', Event count (approx.): 142323631229
Overhead Shared Object Symbol
40.22% haproxy [.] cebu64_lookup
7.12% haproxy [.] sample_process_cnv
6.15% haproxy [.] var_to_smp
4.75% haproxy [.] cebu64_insert
3.79% haproxy [.] sample_conv_var2smp
3.40% haproxy [.] cebu64_delete
3.10% haproxy [.] sample_conv_arith_add
2.36% haproxy [.] action_store
2.32% haproxy [.] __pool_alloc
2.08% haproxy [.] vars_get_by_desc
1.96% haproxy [.] smp_dup
1.75% haproxy [.] var_set.part.0
1.74% haproxy [.] cebu64_first
1.07% [kernel] [k] aq_hw_read_reg
1.03% haproxy [.] pool_put_to_cache
1.00% haproxy [.] sample_process
The performance lowers a bit earlier than with the list however. What
can be seen is that the performance maintains a plateau till 25 vars,
starts degrading a little bit for the tree while it remains stable till
28 vars for the list. Then both cross at 42 vars and the list continues
to degrade doing a hyperbole while the tree resists better. The biggest
loss is at around 32 variables where the list stays 10% higher.
Regardless, given the extremely narrow band where the list is better, it
looks relevant to switch to this in order to preserve the almost linear
performance of large setups. For example at 1000 variables and 10k
lookups, the tree is 18 times faster than the list.
In addition this reduces the size of the struct vars by 8 bytes since
there's a single pointer, though it could make sense to re-invest them
into a secondary head for example.
All callers of vars_prune_* currently check the list for emptiness.
Let's leave that to vars_prune() itself, it will ease some changes in
the code. Thanks to the previous inlining of the vars_prune() function,
there's no performance loss, and even a very tiny 0.1% gain.
vars_prune() and vars_prune_all() take the variable lock while purging
all variables from a head. However this is not needed:
- proc scope variables are only purged during deinit, hence no lock
is needed ;
- all other scopes are attached to entities bound to a single thread
so no lock is needed either.
Removing the lock saves about 0.5% CPU on variables-intensive setups,
but above all simplify the code, so let's do it.
It is now possible to retrieved the value of a variable using the parent
stream or the parent session instead of the current one. It remains
forbidden to set or unset this value. The sample fetch used to store the
result is a local copy. So it may be safely altered by a converter without
changing the value of the original variable.
Note that for now, the parent of a stream is never set. So this part is not
really used. This will change with the SPOE.
Now a variable description is retrieved when a variable is parsed, we can
use it to get the variable value. It is mandatory to be able to know the
parent stream, if any, must be used, instead of the current one.
Add session/stream scopes related to the parent. To do so, "psess", "ptxn",
"preq" or "pres" must be used instead of tranditionnal scopes (without the
first "p"). the "proc" scope is not concerned by this change because it is
not linked to a stream. When such scopes are used, a specific flags is added
on the variable description during the variable parsing.
For now, theses scopes are parsed and the variable description is updated
accordingly. But at the end, any operation on the variable value fails.
Now a variable description is retrieved when a variable is parsed, we can
use it to set or unset the variable value. It is mandatory to be able to
know the parent stream, if any, must be used, instead of the current one.
A variable description is now used to parse a variable and extract its name
and its scope. It is mandatory to be able to add some flags on the variable
when it is evaluated (set or get). Among other things, this will be used to
know the parent stream, if any, must be used, instead of the current one.
This patch tries to address a design flaw with how logformat expressions
are parsed from config. Indeed, some parse_logformat_string() calls are
performed during config parsing when the proxy mode is not yet known.
Here's a config example that illustrates the issue:
defaults
mode tcp
listen test
bind :8888
http-response set-header custom-hdr "%trl" # needs http
mode http
The above config should work, because the effective proxy mode is http,
yet haproxy fails with this error:
[ALERT] (99051) : config : parsing [repro.conf:6] : error detected in proxy 'test' while parsing 'http-response set-header' rule : format tag 'trl' is reserved for HTTP mode.
To fix the issue once and for all, let's implement smart postparsing for
logformat expressions encountered during config parsing:
- split parse_logformat_string() (and subfonctions) in order to create a
new lf_expr_postcheck() function that must be called to finish
preparing and checking the logformat expression once the proxy type is
known.
- save some config hints info during parse_logformat_string() to
generate more precise error messages during lf_expr_postcheck(), if
needed, we rely on curpx->conf.args.{file,line} hints for that because
parse_logformat_string() doesn't know about current file and line
number.
- lf_expr_postcheck() uses PR_FL_CHECKED proxy flag to know if the
function may try to make the proxy compatible with the expression, or
if it should simply fail as soon as an incompatibility is detected.
- if parse_logformat_string() is called from an unchecked proxy, then
schedule the expression for postparsing, else (ie: during runtime),
run the postcheck right away.
This change will also allow for some logformat expression error handling
simplifications in the future.
log format expressions are broadly used within the code: once they are
parsed from input string, they are converted to a linked list of
logformat nodes.
We're starting to face some limitations because we're simply storing the
converted expression as a generic logformat_node list.
The first issue we're facing is that storing logformat expressions that
way doesn't allow us to add metadata alongside the list, which is part
of the prerequites for implementing log-profiles.
Another issue with storing logformat expressions as generic lists of
logformat_node elements is that it's starting to become really hard to
tell when we rely on logformat expressions or not in the code given that
there isn't always a comment near the list declaration or manipulation
to indicate that it's relying on logformat expressions under the hood,
so this adds some complexity for code maintenance.
This patch looks quite impressive due to changes in a lot of header and
source files (since logformat expressions are broadly used), but it does
a simple thing: it defines the lf_expr structure which itself holds a
generic list of logformat nodes, and then declares some helpers to
manipulate lf_expr elements and fixes the code so that we now exclusively
manipulate logformat_node lists as lf_expr elements outside of log.c.
For now, lf_expr struct only contains the list of logformat nodes (no
additional metadata), but now that we have dedicated type and helpers,
doing so in the future won't be problematic at all and won't require
extensive code changes.
"get var" on the CLI was also missing an LF, and the vtest as well, so
that fixing only the code breaks the vtest. This must be backported to
2.4 as the issue was brought with commit c35eb38f1d ("MINOR: vars/cli:
add a "get var" CLI command to retrieve global variables").
In several places in the source, there was the same block of code that was
used to deinitialize the log buffer. There were even two functions that
did this, but they were called only from the code that is in the same
source file (free_tcpcheck_fmt() in src/tcpcheck.c and free_logformat_list()
in src/proxy.c - they were both static functions).
The function free_logformat_list() was moved from the file src/proxy.c to
src/log.c, and a check of the list before freeing the memory was added to
that function.
There's no point keeping the vars_init_head() call in init() when we
already have a vars_init() registered at the right time to do that,
and it complexifies the boot sequence, so let's move it there.
Compiling vars.c with gcc 4.2 shows that we're initializing some local
structs field members in a not really portable way:
src/vars.c: In function 'vars_parse_cli_set_var':
src/vars.c:1195: warning: initialized field overwritten
src/vars.c:1195: warning: (near initialization for 'px.conf.args')
src/vars.c:1195: warning: initialized field overwritten
src/vars.c:1195: warning: (near initialization for 'px.conf')
src/vars.c:1201: warning: initialized field overwritten
src/vars.c:1201: warning: (near initialization for 'rule.conf')
It's totally harmless anyway, but better clean this up.
This patch adds the possibility to add a set of conditions to a set-var
call, be it a converter or an action (http-request or http-response
action for instance). The conditions must all be true for the given
set-var call for the variable to actually be set. If any of the
conditions is false, the variable is left untouched.
The managed conditions are the following : "ifexists", "ifnotexists",
"ifempty", "ifnotempty", "ifset", "ifnotset", "ifgt", "iflt". It is
possible to combine multiple conditions in a single set-var call since
some of them apply to the variable itself, and some others to the input.
This patch does not change the fact that variables of scope proc are
still created during configuration parsing, regardless of the conditions
that might be added to the set-var calls in which they are mentioned.
For instance, such a line :
http-request set-var(proc.foo,ifexists) int(5)
would not prevent the creation of the variable during init, and when
actually reaching this line during runtime, the proc.foo variable would
already exist. This is specific to the proc scope.
These new conditions mean that a set-var could "fail" for other reasons
than memory allocation failures but without clearing the contents of the
variable.
This patch adds the parsing of the optional condition parameters that
can be passed to the set-var and set-var-fmt actions (http as well as
tcp). Those conditions will not be taken into account yet in the var_set
function so conditions passed as parameters will not have any effect.
Since actions do not benefit from the parameter preparsing that
converters have, parsing conditions needed to be done by hand.
This patch adds the parsing of the optional condition parameters that
can be passed to the set-var converter. Those conditions will not be
taken into account yet in the var_set function so conditions passed as
parameters will not have any effect. This is true for any condition
apart from the "ifexists" one that is also used to replace the
VF_UPDATEONLY flag that was used to prevent proc scope variable creation
from a LUA module.
When calling var_set on a variable of type string (SMP_T_STR, SMP_T_BIN
or SMP_T_METH), the contents of the variable were freed directly. When
adding conditions to set-var calls we might have cases in which the
contents of an existing variable should be kept unchanged so the freeing
of the internal buffers is delayed in the var_set function (so that we
can bypass it later).
The type of a newly created variable was not initialized. This patch
sets it to SMP_T_ANY by default. This will be required when conditions
can be added to a set-var call because we might end up creating a
variable without setting it yet.
The vars_set_by_name_ifexist function was created to avoid creating too
many variables from a LUA module. This was made thanks to the
VF_UPDATEONLY flags which prevented variable creation in the var_set
function. Since commit 3a4bedccc ("MEDIUM: vars: replace the global name
index with a hash") this limitation was restricted to 'proc' scope
variables only.
This patch simply moves the scope test to the vars_set_by_name_ifexist
function instead of the var_set function.
In commit 3a4bedccc6 the variable logic was changed. Instead of
accessing variables by their name during runtime, the variable tables
are now indexed by a hash of the name. But the set-var and unset-var
converters try to access the correct variable by calculating a hash on
the sample instead of the already calculated variable hash.
It should be backported to 2.5.
Session struct is already allocated when "tcp-request connection" rules
are evaluated so session-scoped variables turned out easy to support.
This resolves github issue #1408.
A long-standing issue was reported in issue #1215.
In short, var() was initially internally declared as returning a string
because it was not possible by then to return "any type". As such, users
regularly get trapped thinking that when they're storing an integer there,
then the integer matching method automatically applies. Except that this
is not possible since this is related to the config parser and is decided
at boot time where the variable's type is not known yet.
As such, what is done is that the output being declared as type string,
the string match will automatically apply, and any value will first be
converted to a string. This results in several issues like:
http-request set-var(txn.foo) int(-1)
http-request deny if { var(txn.foo) lt 0 }
not working. This is because the string match on the second line will in
fact compare the string representation of the variable against strings
"lt" and "0", none of which matches.
The doc says that the matching method is mandatory, though that's not
the case in the code due to that default string type being permissive.
There's not even a warning when no explicit match is placed, because
this happens very deep in the expression evaluator and making a special
case just for "var" can reveal very complicated.
The set-var() converter already mandates a matching method, as the
following will be rejected:
... if { int(12),set-var(txn.truc) 12 }
while this one will work:
... if { int(12),set-var(txn.truc) -m int 12 }
As such, this patch this modifies var() to match the doc, returning the
type "any", and mandating the matching method, implying that this bogus
config which does not work:
http-request set-var(txn.foo) int(-1)
http-request deny if { var(txn.foo) lt 0 }
will need to be written like this:
http-request set-var(txn.foo) int(-1)
http-request deny if { var(txn.foo) -m int lt 0 }
This *will* break some configs (and even 3 of our regtests relied on
this), but except those which already match string exclusively, all
other ones are already broken and silently fail (and one of the 3
regtests, the one on FIX, was bogus regarding this).
In order to fix existing configs, one can simply append "-m str"
after a "var()" in an ACL or "if" expression:
http-request deny unless { var(txn.jwt_alg) "ES" }
must become:
http-request deny unless { var(txn.jwt_alg) -m str "ES" }
Most commonly, patterns such as "le", "lt", "ge", "gt", "eq", "ne" in
front of a number indicate that the intent was to match an integer,
and in this case "-m int" would be desired:
tcp-response content reject if ! { var(res.size) gt 3800 }
ought to become:
tcp-response content reject if ! { var(res.size) -m int gt 3800 }
This must not be backported, but if a solution is found to at least
detect this exact condition in the generic expression parser and
emit a warning, this could probably help spot configuration bugs.
Link: https://www.mail-archive.com/haproxy@formilux.org/msg41341.html
Cc: Christopher Faulet <cfaulet@haproxy.com>
Cc: Tim Düsterhus <tim@bastelstu.be>
When the sample validity flags are computed to check if a sample is used in
a valid scope, the flags depending on the proxy capabilities must be
cumulated. Historically, for a sample on the request, only the frontend
capability was used to set the sample validity flags while for a sample on
the response only the backend was used. But it is a problem for listen or
defaults proxies. For those proxies, all frontend and backend samples should
be valid. However, at many place, only frontend ones are possible.
For instance, it is impossible to set the backend name (be_name) into a
variable from a listen proxy.
This bug exists on all stable versions. Thus this patch should probably be
backported. But with some caution because the code has probably changed
serveral times. Note that nobody has ever noticed this issue. So the need to
backport this patch must be evaluated for each branch.
With the commit eaba25dd9 ("BUG/MINOR: tcpcheck: Don't use arg list for
default proxies during parsing"), we restricted the use of sample fetch in
tcpcheck rules defined in a defaults section to those depending on explicit
arguments only. This means a tcpcheck rules defined in a defaults section
cannot rely on argument unresolved during the configuration parsing.
Thanks to recent changes, it is now possible again.
This patch is mandatory to support TCP/HTTP rules in defaults sections.
These ones are passed on rule creation for the sole purpose of being
reported in "show sess", which is not done yet. For now the entries
are allocated upon rule creation and freed in free_act_rules().
During tcp/http check rules parsing, when a sample fetch or a log-format
string is parsed, the proxy's argument list used to track unresolved
argument is no longer passed for default proxies. It means it is no longer
possible to rely on sample fetches depending on the execution context (for
instance 'nbsrv').
It is important to avoid HAProxy crashes because these arguments are
resolved during the configuration validity check. But, default proxies are
not evaluated during this stage. Thus, these arguments remain unresolved.
It will probably be possible to relax this rule. But to ease backports, it
is forbidden for now.
This patch must be backported as far as 2.2. It depends on the commit
"MINOR: arg: Be able to forbid unresolved args when building an argument
list". It must be adapted for the 2.3 because PR_CAP_DEF capability was
introduced in the 2.4. A solution may be to test The proxy's id agains NULL.
The sole purpose of the variable's usage accounting is to enforce
limits at the session or process level, but very commonly these are not
set, yet the bookkeeping (especially at the process level) is extremely
expensive.
Let's simply disable it when the limits are not set. This further
increases the performance of 12 variables on 16-thread from 1.06M
to 1.24M req/s.
Right now we have a per-process max variable size and a per-scope one,
with the proc scope covering all others. As such, the per-process global
one is always exactly equal to the per-proc-scope one. And bookkeeping
on these process-wide variables is extremely expensive (up to 38% CPU
seen in var_accounting_diff() just for them).
Let's kill vars_global_size and only rely on the proc one. Doing this
increased the request rate from 770k to 1.06M in a config having only
12 variables on a 16-thread machine.
The global table of known variables names can only grow and was designed
for static names that are registered at boot. Nowadays it's possible to
set dynamic variable names from Lua or from the CLI, which causes a real
problem that was partially addressed in 2.2 with commit 4e172c93f
("MEDIUM: lua: Add `ifexist` parameter to `set_var`"). Please see github
issue #624 for more context.
This patch simplifies all this by removing the need for a central
registry of known names, and storing 64-bit hashes instead. This is
highly sufficient given the low number of variables in each context.
The hash is calculated using XXH64() which is bijective over the 64-bit
space thus is guaranteed collision-free for 1..8 chars. Above that the
risk remains around 1/2^64 per extra 8 chars so in practice this is
highly sufficient for our usage. A random seed is used at boot to seed
the hash so that it's not attackable from Lua for example.
There's one particular nit though. The "ifexist" hack mentioned above
is now limited to variables of scope "proc" only, and will only match
variables that were already created or declared, but will now verify
the scope as well. This may affect some bogus Lua scripts and SPOE
agents which used to accidentally work because a similarly named
variable used to exist in a different scope. These ones may need to be
fixed to comply with the doc.
Now we can sum up the situation as this one:
- ephemeral variables (scopes sess, txn, req, res) will always be
usable, regardless of any prior declaration. This effectively
addresses the most problematic change from the commit above that
in order to work well could have required some script auditing ;
- process-wide variables (scope proc) that are mentioned in the
configuration, referenced in a "register-var-names" SPOE directive,
or created via "set-var" in the global section or the CLI, are
permanent and will always accept to be set, with or without the
"ifexist" restriction (SPOE uses this internally as well).
- process-wide variables (scope proc) that are only created via a
set-var() tcp/http action, via Lua's set_var() calls, or via an
SPOE with the "force-set-var" directive), will not be permanent
but will always accept to be replaced once they are created, even
if "ifexist" is present
- process-wide variables (scope proc) that do not exist will only
support being created via the set-var() tcp/http action, Lua's
set_var() calls without "ifexist", or an SPOE declared with
"force-set-var".
This means that non-proc variables do not care about "ifexist" nor
prior declaration, and that using "ifexist" should most often be
reliable in Lua and that SPOE should most often work without any
prior declaration. It may be doable to turn "ifexist" to 1 by default
in Lua to further ease the transition. Note: regtests were adjusted.
Cc: Tim Düsterhus <tim@bastelstu.be>
Variables names will be hashed, but for this we need a random seed.
The XXH3() algorithms is bijective over the whole 64-bit space, which
is great as it guarantees no collision for 1..8 byte names. But above
that even if the risk is extremely faint, it theoretically exists and
since variables may be set from Lua we'd rather do our best to limit
the risk of controlled collision, hence the random seed.
All variables whose names are parsed by the config parser, the
command-line parser or the SPOE's register-var-names parser are
now preset as permanent. This will guarantee that these variables
will exist through out all the process' life, and that it will be
possible to implement the "ifexist" feature by looking them up.
This was marked medium because pre-setting a variable with an empty
value may always have side effects, even though none was spotted at
this stage.
We certainly do not want that a permanent variable (one that is listed
in the configuration) be erased by accident by an "unset-var" action.
Let's make sure these ones are only reset to an empty sample, like at
the moment of their initial registration. One trick is that the same
function is used to purge the memory at the end and to delete, so we
need to add an extra "force" argument to make the choice.
In order to continue to honor the ifexist Lua option and prevent rogue
SPOA agents from creating too many variables, we'll need to keep the
ability to mark certain proc.* variables as permanent when they're
known from the config file.
Let's add a flag there for this. It's added to the variable when the
variable is created with this flag set by the caller.
Another approach could have been to use a distinct list or distinct
scope but that sounds complicated and bug-prone.
Storing an unset sample (SMP_T_ANY == 0) will be used to only reserve
the variable's space but associate no value. We need to slightly adjust
var_to_smp() for this so that it considers a value-less variable as non
existent and falls back to the default value.
Passing this flag to var_set() will result in the variable to only be
created if it did not exist, otherwise nothing is done (it's not even
updated). This will be used for pre-registering names.
When setting variables, there are currently two variants, one which will
always create the variable, and another one, "ifexist", which will only
create or update a variable if a similarly named variable in any scope
already existed before.
The goal was to limit the risk of injecting random names in the proc
scope, but it was achieved by making use of the somewhat limited name
indexing model, which explains the scope-agnostic restriction.
With this change, we're moving the check downwards in the chain, at the
variable level, and only variables under the scope "proc" will be subject
to the restriction. A new set of VF_* flags was added to adjust how
variables are set, and VF_UPDATEONLY is used to mention this restriction.
In this exact state of affairs, this is not completely exact, as if a
similar name was not known in any scope, the variable will continue to
be rejected like before, but this will change soon.
The names for these two functions are totally misleading, they have
nothing to do with samples, they're purely dedicated to variables. The
former is only used by the second one and makes no sense by itself, so
it cannot even get a meaningful name. Let's remerge them into a single
one called "var_set()" which, as its name tries to imply, sets a variable
to a given value.
This name was quite misleading, as it has nothing to do with samples nor
streams. This function's sole purpose is to unset a variable, so let's
call it "var_unset()" and document it a little bit.
The vars_init() name is particularly confusing as it does not initialize
the variables code but the head of a list of variables passed in
arguments. And we'll soon need to have proper initialization code, so
let's rename it now.
