89f6dedf48
Variable names are stored into a unified list that helps compare them
just based on a pointer instead of duplicating their name with every
variable. This is convenient for those declared in the configuration
but this started to cause issues with Lua when random names would be
created upon each access, eating lots of memory and CPU for lookups,
hence the work in 2.2 with commit 4e172c93f ("MEDIUM: lua: Add
`ifexist` parameter to `set_var`") to address this.
But there remains a corner case with get_var(), which also allocates
a new variables. After a bit of thinking and discussion, it never
makes sense to allocate a new variable name on get_var():
- if the name exists, it will be returned ;
- if it does not exist, then the only way for it to appear will
be that some code calls set_var() on it
- a call to get_var() after a careful set_var(ifexist) ruins the
effort on set_var().
For this reason, this patch addresses this issue by making sure that
get_var() will never cause a variable to be allocated. This is done
by modifying vars_get_by_name() to always call register_name() with
alloc=0, since vars_get_by_name() is exclusively used by Lua and the
new CLI's "get/set var" which also benefit from this protection.
It probably makes sense to backport this as far as 2.2 after some
observation period and feedback from users.
For more context and discussions about the issues this was causing,
see https://www.mail-archive.com/haproxy@formilux.org/msg40451.html
and in issue #664.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)