If a master with a better rank and a slave with a worse rank were
available and master_accept_reads wasn't enabled, the slave would be
preferred over the master. The check for master_accept_reads was done
twice and also in the wrong place.
Although the default value is the maximum value of a signed 32-bit
integer, the value is stored as a 64-bit integer. The integer type
conversion functions return 64-bit values so storing it as one makes
sense.
Currently values higher than the default are allowed but the accepted
range of input should be restricted in the future.
Readwritesplit now respects server ranks. When servers are selected for
either routing or connection creation, the servers are partitioned by
their rank into sets of servers. These sets of servers are never mixed so
the end result is that only servers of the same rank are considered for
candidacy.
The master selection is slightly different: the server with the best rank
that is capable of acting as a master is chosen. This means that a session
can have a master with a lower rank and slaves with higher ranks than the
master. In most cases this actually is the preferred behavior as the rank
is used to prioritize usage but not outright prevent it.
The connection creation is now internal to RWSplitSession. This makes the
code more readable by removing the need to pass parameters and allowing
easier reuse of existing functions. The various conditions require to
create connections are now also checked in only one place.
Readwritesplit now picks the best available master if no open master
connection is available. This is required if the server rank is to be
taken into account when master selection is done.
Given the following query:
PREPARE ps FROM 'PREPARE ps2 FROM \'SELECT 1\'';
The debug assertion is hit even though this is valid, albeit unsupported,
SQL. An optimization would be to ignore the query if the prepared
statement type is another prepared statement.
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.
If a routing of a queued query caused it to be put back on the query
queue, the order in which the queue was reorganized was wrong. The first
query would get appended as the last query which caused the order to be
reversed.
Th discarding of connections in maintenance mode must be done after any
results have been written to them. This prevents closing of the connection
before the actual result is returned.
The candidate selection code used default values that would cause reads
past buffers. The code could also dereference the end iterator which
causes undefined behavior.
The `start services` and `stop services` command aliases now map to the
same command as `start maxscale` and `stop maxscale`. This should help
alleviate the confusion that the command naming caused.
The parameters are now written in the order they appear in the module
parameter definitions. Also enabled a previously disabled part in
server unit test.
This fixes some situations where MaxAdmin/MaxCtrl would block and wait
until a monitor operation or tick is complete. This also fixes a deadlock
caused by calling monitor diagnostics inside a monitor script.
Concurrency is enabled by adding one mutex per server object to protect
array-like fields from concurrent reading/writing.
Previously, runtime monitor modifications could directly alter monitor fields,
which could leave the text-form parameters and reality out-of-sync. Also,
the configure-function was not called for the entire monitor-object, only the
module-implementation.
Now, all modifications go through the overridden configure-function, which calls the
base-class function. As most configuration changes are given in text-form, this
removes the need for specific setters. The only exceptions are the server add/remove
operations, which must modify the text-form serverlist.
Was deprecated in 2.3. Similar features are in MariaDB-Monitor.
One system test was modified to use MariaDB-Monitor instead. Some parts
of the test are disabled for now to make it pass.
