The parameter accepts both counts and percentages which requires special
handling in the router. This needs to be done when the configuration is
updated.
If a transaction is replayed, queued commands must not be processed. The
exception to this rule is when pending session commands are executed
before the first statement in the replayed transaction is executed.
If transaction replaying was enabled and a result was returned in more
than one call to clientReply, a NULL value would be added to the statement
which in turn would trigger a debug assertion.
Similarly any following statements in the transaction would be executed
regardless of whether the result was complete.
Renamed the statement execution function to better describe what it does.
Extended the basic functional test case to cover this.
Added a new router API entry point that allows configuration changes after
the instance has been created. This makes alterations to most service
parameters at runtime possible.
An option to reconfiguration would have been the creation of a new
service and the eventual destruction of the old one. This would be a more
complicated and costly method but from an architectural point of view it
is interesting.
The actual implementation of the configuration change is left to the
router. Currently, only readwritesplit performs reconfiguration as
implementing it with versioned configurations is very easy.
Versioned configurations can be considered an adequate first step but it
is not an optimal solution as it causes a bottleneck in the reference
counting of the shared configuration. Thread-specific configuration
definitions would make for a more efficient solution but the
implementation is more complex.
By using a shared pointer instead of a plain object, we can replace the
router configuration without it affecting existing sessions. This is a
change that is required to enable runtime reconfiguration of
readwritesplit.
The glib re-entrant random number generation functions crashe on CentOS 7
for no apparent reason. As the C++11 random number library provides a more
versatile, widely supported and simple method of acquiring random numbers,
it should be used instead.
In previously the status bits were assigned only for running servers. Due
to the changes done in the monitoring algorithm, the slave and master
status bits are assigned to servers that are down. This change broke a
number of tests and deviates from previous behavior.
To keep the old behavior and to fix the test, the status bits are not
assigned to servers that are down.
With the global configuration parameter 'query_classifier_cache'
the query classification cache can be turned on. At the moment it
does not matter what value it has; its presence simply enables the
caching.
Eventually you will be able to specify how much memory the cache
is allowed to consume.
Now takes a structure that, if present, enables the query
classification caching and specifies the properties of the
cache.
For the time being no actual properties are yet available.
The sql mode affects the result of the query classification.
Consequently, we cannot use the cached result if it was generated
when the sql mode was something else than what it currently is.
The mapping from a canonical statement to the query classification
result is maintained by the class QCInfoCache of which there exist
an instance per thread. That way no locking is needed but the
information will be cached multiple times (but that is a smaller
price to pay). Currently the information is stored in a regular
std::unordered_map, which means that the consumed amount of
memory will just keep on growing unless the number of canonical
statements used by clients happens to have an upper bound.
The LRU cache (that provides means for putting a bound on the
amount of memory used and number of items) used in the cache filter
will be generalized and be taken into use here as well.
The key is now the canonical statement itself, which means that
a fair amount of memory will be used. To preserve memory it might
make sense to use a hashed value instead, although that at least
in principle opens up the possibility for unintended collisions.
This feature will also be made configurable.
Only for qc_sqlite.
After a second look qc_mysqlembedded will not support dupping
the statement information. Without additional changes, simply stashing
an info object away, parsing another new GWBUF, deleting that and
then using the stashed away info object will not work; the THD object
will be corrupted. As qc_mysqlembedded is _only_ used for verifying the
sqlite-based parser this is not important anyway.
The query classifier stores information about the statement carried
by a GWBUF in the GWBUF itself. We need to be able to store that
object out side the lifetime of the GWBUF. So, we require that a
query classifier is capable of duplicating references to that object.
Minor cleanup:
- Unit variables places in anonymous namespace.
- Unit variables accessed via this_unit struct.
This is the first commit of many where the mapping from canonical
statement to query classification result is introduced.
The mapping is placed above the actual query classifier, so that all
query classifiers will benefit from it.
The mapping will be maintained by thread so that there will not be
any synchronization issues. Further, initially a simple map without
upper boundary will be used; if this is found to provide measurable
benefits, the map will then be replaced with an LRU mechanism so
that it becomes possible to specify just how much memory the mapping
may use.
The evq_length file held the returned number of descriptors from
the last epoll_wait() call. As such it is highly temporal and not
particularly meaningful.
That has now been removed and the instead the average number of
returned descriptors is maintained. That information changes slowly
and thus carries some meaning.
It is now possible to prevent the masking filter from rejecting
statements using functions in conjunction with fields to be
masked. So now it is possible to not use the blanket rejection
of the masking filter and replace it with more detailed firewall
rules.
The masking filter works only on the result-set. However, if
functions are used, the column names will not be available in
the result-set, and hence masking will not take place.
Now, the statement is checked and if functions are used in
conjunction with columns that should be masked, the statement
is rejected. Thus, functions can no longer be used for bypassing
the masking. That was possible earlier as well, but required
manually setting up the firewall filter.
Before the state of the backend servers is checked, MaxScale needs to be
stopped to prevent the automated failover from interfering in the start-up
process.
If a service has no active servers and users are injected, a warning would
be logged. This is a misleading warning if the service has no servers and
should only be logged if the failure to load any users is an unexpected
situation.
The log manager is the only one that uses the mlist_t versioned list. The
counter that keeps track of the version number was not modified using
atomic operations meaning that the compiler is free to optimize away parts
of the lock-free versioning mechanism that uses it.
To prevent this optimization, the variable is declared volatile. A rewrite
is direly needed but it cannot be done in 2.2.
Displaying the MaxScale version helps identify which package the
executable was bundled with. As the MaxCtrl source is a part of MaxScale,
there's no need for separate versioning.
