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Function comments were outdated, probably because they have not been
updated during the previous refactors.
Fixing comments to better reflect the current behavior.
This may be backported up to 2.2, or even 2.0 by slightly adapting the
patch (in 2.0, such functions are documented in proto/pattern.h)
Organize reference to pattern element of map (struct pat_ref_elt) into an ebtree:
- add an eb_root member to the map (pat_ref struct) and an ebpt_node to its
element (pat_ref_elt struct),
- modify the code to insert these nodes into their ebtrees each time they are
allocated. This is done in pat_ref_append().
Note that ->head member (struct list) of map (struct pat_ref) is not removed
could have been removed. This is not the case because still necessary to dump
the map contents from the CLI in the order the map elememnts have been inserted.
This patch also modifies http_action_set_map() which is the callback at least
used by "set-map" action. The pat_ref_elt element returned by pat_ref_find_elt()
is no more ignored, but reused if not NULL by pat_ref_set() as first element to
lookup from. This latter is also modified to use the ebtree attached to the map
in place of the ->head list attached to each map element (pat_ref_elt struct).
Also modify pat_ref_find_elt() to makes it use ->eb_root map ebtree added to the
map by this patch in place of inspecting all the elements with a strcmp() call.
This function was not used anymore after the atomic updates were
implemented in 2.3, and it must not be used given that it does not
yield and can easily make the process hang for tens of seconds on
large acls/maps. Let's remove it before someone uses it as an
example to implement something else!
Instead of being able to purge only values older than a specific value,
let's support arbitrary ranges and make pat_ref_purge_older() just be
one special case of this one.
Interestingly, all arrays used to declare patterns were read-write while
only hard-coded. Let's mark them const so that they move from data to
rodata and don't risk to experience false sharing.
Currently our atomic ops return a value but it's never known whether
the fetch is done before or after the operation, which causes some
confusion each time the value is desired. Let's create an explicit
variant of these operations suffixed with _FETCH to explicitly mention
that the fetch occurs after the operation, and make use of it at the
few call places.
It's about the third time I get confused by these functions, half of
which manipulate the reference as a whole and those manipulating only
an entry. For me "pat_ref_commit" means committing the pattern reference,
not just an element, so let's rename it. A number of other ones should
really be renamed before 2.4 gets released :-/
This function will be usable to purge at most a specified number of old
entries from a reference. Entries are declared old if their generation
number is in the past compared to the one passed in argument. This will
ease removal of early entries when new ones have been appended.
We also call malloc_trim() when available, at the end of the series,
because this is one place where there is a lot of memory to save. Reloads
of 1M IP addresses used in an ACL made the process grow up to 1.7 GB RSS
after 10 reloads and roughly stabilize there without this call, versus
only 260 MB when the call is present. Sadly there is no direct equivalent
for jemalloc, which stabilizes around 800MB-1GB.
pat_ref_load() basically combines pat_ref_append() and pat_ref_commit().
It's very similar to pat_ref_add() except that it also allows to set the
generation ID and the line number. pat_ref_add() was modified to directly
rely on it to avoid code duplication. Note that a previous declaration
of pat_ref_load() was removed as it was just a leftover of an earlier
incarnation of something possibly similar, so no existing functionality
was changed here.
This function will be used after a successful pat_ref_append() to propagate
the pattern to all use places (including parsing and indexing). On failure,
it will entirely roll back all insertions and free the pattern itself. It
also preserves the generation number so that it is convenient for use in
association with pat_ref_append(). pat_ref_add() was modified to rely on
it instead of open-coding the insertion and roll-back.
Till now the only way to remove a known reference was via
pat_ref_delete_by_id() which scans the whole list to find a matching pointer.
Let's add pat_ref_delete_by_ptr() which takes a valid pointer. It can be
called by the function above after the pointer is found, and can also be
used to roll back a failed insertion much more efficiently.
These ones are not used anymore, so let's remove them to remove a bit
of the complexity. The ACL keyword's delete() function could be removed
as well, though most keyword declarations are positional and we have a
high risk of introducing a mistake here, so let's not touch the ACL part.
pat_del_tree_gen() was already chained onto pat_del_list_gen() to deal
with remaining cases, so let's complete the merge and have a generic
pattern deletion function acting on the reference and taking care of
reliably removing all elements.
This is the next step in speeding up entry removal. Now we don't scan
the whole lists or trees for elements pointing to the target reference,
instead we start from the reference and delete all linked patterns.
This simplifies some delete functions since we don't need anymore to
delete multiple times from an expression since all nodes appear after
the reference element. We can now have one generic list and one generic
tree deletion function.
This required the replacement of pattern_delete() with an open-coded
version since we now need to lock all expressions first before proceeding.
This means there is a high risk of lock inversion here but given that the
expressions are always scanned in the same order from the same head, this
must not happen.
Now deleting first entries is instantaneous, and it's still slow to
delete the last ones when looking up their ID since it still requires
to look them up by a full scan, but it's already way faster than
previously. Typically removing the last 10 IP from a 20M entries ACL
with a full-scan each took less than 2 seconds.
It would be technically possible to make use of indexed entries to
speed up most lookups for removal by value (e.g. IP addresses) but
that's for later.
Now we have a single prune() function to act on an expression, and one
delete function for the lists and one for the trees. The presence of a
pointer in the lists is enough to warrant a free, and we rely on the
PAT_SF_REGFREE flag to decide whether to free using free() or regfree().
It's more convenient to return the element than to return just 0 or 1,
as the next thing we'll want to do is to act on this element! In addition
it was using variable arguments instead of consts, causing some reuse
constraints which were also addressed. This doesn't change its use as
a boolean, hence why call places were not modified.
As reported in issue #419, a "clear map" operation on a very large map
can take a lot of time and freeze the entire process for several seconds.
This patch makes sure that pat_ref_prune() can regularly yield after
clearing some entries so that the rest of the process continues to work.
The first part, the removal of the patterns, can take quite some time
by itself in one run but it's still relatively fast. It may block for
up to 100ms for 16M IP addresses in a tree typically. This change needed
to declare an I/O handler for the clear operation so that we can get
back to it after yielding.
The second part can be much slower because it deconstructs the elements
and its users, but it iterates progressively so we can yield less often
here.
The patch was tested with traffic in parallel sollicitating the map being
released and showed no problem. Some traffic will definitely notice an
incomplete map but the filling is already not atomic anyway thus this is
not different.
It may be backported to stable versions once sufficiently tested for side
effects, at least as far as 2.0 in order to avoid the watchdog triggering
when the process is frozen there. For a better behaviour, all these
prune_* functions should support yielding so that the callers have a
chance to continue also yield in turn.
The struct sample_data is used by pattern, map and vars, and currently
requires to include sample-t which comes with many other dependencies.
Let's move sample_data into its own file to shorten the dependency tree.
This revealed a number of issues in adjacent files which were hidden by
the fact that sample-t.h brought everything that was missing.
It was moved as-is, except for extern declaration of pattern_reference.
A few C files used to include it but didn't need it anymore after having
been split apart so this was cleaned.
