A GWBUF given to any gwbuf-function:
- Must not be NULL. Exceptions are gwbuf_free() and gwbuf_append(),
in analogy with free() and realloc() respectively.
- Must be the head of a chain.
- Must be owned by the calling thread.
Although not made unambiguously clear, it is *ONLY* allowed to
manipulate GWBUFs that are the first link of a GWBUF chain (that
may consist of just one link).
With this change, in debug mode the tail pointer of intermediate
links is invalidated so that an attempt to use an intermediate
link is likely to cause a crash.
When a single GWBUF was split into two with gwbuf_split, the new GWBUF
would point to the start of the shared data and the old one to the
end. Data-wise, this is fine but as the parsing info for queries is stored
in the shared buffer it causes problems when multiple packets get read in
one network payload. The end result would be that only the first query in
the lot would get parsed and the rest would get the same classification as
the first one.
To properly fix this without the need to deep clone the buffer would
require a reorganization of the buffer mechanism in MaxScale.
This commit alone doesn't fix the queued query routing problems in
readwritesplit. The commit from 2.2 which fixes the ordering problems with
queued queries is also required for a fully functional queued query
mechanism.
The callbacks iterated over all threads when only the local ones must be
iterated. This prevents a deadlock from occurring when multiple threads
start throttling at the same time.
Also fixed the gwbuf_append debug assertion.
As buffers are meant to be used only within a particular session, the
atomic operations are no longer necessary and can thus be removed. This
removes the extra overhead that the atomic operations add.
See script directory for method. The script to run in the top level
MaxScale directory is called maxscale-uncrustify.sh, which uses
another script, list-src, from the same directory (so you need to set
your PATH). The uncrustify version was 0.66.
When the query queue does not contain a complete packet
(i.e. modutil_get_next_MySQL_packet return NULL), an informative dump of
how many bytes and what is stored is logged.
By aborting the process if memory runs out when a buffer needs to be made
contiguous, we rule out other, more subtle, errors. Failing as soon as a
possible when memory allocation fails gives better error messages.
Single spot where an existing hint ptr was overwritten. Removed gwbuf_add_hint()
because it was adding hints at the opposite end compared to functions in hint.h.
Added hint_splice() to replace.
* MXS-199: Support Causal Read in Read Write Splitting
* move most causal read logic into rwsplit router and get server type from monitor
* misc fix: remove new line
* refactor, move config to right place, replace ltrim with gwbuf_consume
* refacter a little for previous commit
* fix code style
The GWBUF shared buffer and its data is now allocated in one
chunk so that the data directly follows the shared buffer.
That way, creating a GWBUF will involve 2 and not 3 calls to
malloc and freeing one will involve 2 and not 3 calls to free.
