The different server monitoring functions all did similar work and
combining them into one function makes the whole process of monitoring a
server simpler.
If a relay master server is found in the replication tree, it should not
get the master status. Previously all master servers were assigned the
master status regardless of their depth in the replication tree.
By comparing the depth value of each potential master, the monitor can
find the right master at the root of the replication tree.
The mysqlmon now supports proper detection of multi-master topologies by
building a directed graph out of the monitored server. If cycles are found from
this graph, they are assigned a master group ID. All servers with a positive
master group ID will receive the Master status unless they have `@@read_only`
enabled.
This new functionality can be enabled with the 'multimaster' boolean
parameter.
Mysqlmon now stores the values of read_only, slave_sql_running,
slave_io_running, the name and position of the masters binlog and the
replication configuration status of the slave.
This allows more detailed server information to be displayed with the
`show monitor <name>` diagnostic interface. In addition to this, the new
structure used to store them provides an easy way to store information
that is specific to a monitor and the servers it monitors.
These new status variables can be used to implement better multi-master
detection in mysqlmon by using the value of read_only to resolve
situations where multiple master candidates are available.
When a client executes commands which do not return results (for example
inserting BLOB data via the C API), readwritesplit expects a result for
each sent packet. This is a somewhat of a false assumption but it clears
itself out when the session is closed normally. If the session is closed
due to an error, the counter is not decremented.
Each sesssion should only increase the number of active operation on a
server by one operation. By checking that the session is not already
executing an operation before incrementing the active operation count the
runtime operation count will be correct.
If the installation directory is something else than /usr,
then the directories
<install-dir>/var/cache/maxscale
<install-dir>/var/log/maxscale
<install-dir>/var/run/maxscale
will be created at installation time.
Although claimed in the output of "--help", the long option
"--execdir" was not supported. Support for that now added.
The long options have now also been sorted in the same order
as the options are displayed by the help, to make it easy to
check that everything is there.
Further, the description column of the output of --help has
been aligned.
In the configuration section of services and monitors, the
password to be used can now be specified using 'password'
in addition to 'passwd'.
If both are provided, then the value of 'passwd' is used. That
way there cannot be any surprises, should someone for whatever
reason currently (in 1.4.3 an invalid parameter will not prevent
MaxScale from starting) have a 'password' entry in his config file.
In the next release 'passwd' can be deprecated and in the release
after that removed.
The service start retry mechanism mistakenly returned an error when a
service failed to start but a retry was queued. This caused MaxScale to
stop whenever a service failed to start.
dcb_count_by_usage did not iterate the list properly and would get stuck on the
first inactive DCB. Since this function is only called by maxinfo, it would be
the only one to get stuck.
In the case of a Unix domain socket, the required buffer size may
in principle be up to PATH_MAX, so better to explicitly ensure that
there's enough space.
It's now possible to use both a Unix domain socket and host/port
when connecting with MaxAdmin to MaxScale.
By default MaxAdmin will attempt to use the default Unix domain
socket, but if host and/or port has been specified, then an inet
socket will be used.
maxscaled will authenticate the connection attempt differently
depending on whether a Unix domain socket is used or not. If
a Unix domain socket is used, then the Linux user id will be
used for the authorization, otherwise the 1.4.3 username/password
handshake will be performed.
adminusers has now been extended so that there is one set of
functions for local users (connecting locally over a Unix socket)
and one set of functions for remote users (connecting locally
or remotely over an Inet socket).
The local users are stored in the new .../maxscale-users and the
remote users in .../passwd. That is, the old users of a 1.4
installation will work as such in 2.0.
One difference is that there will be *no* default remote user.
That is, remote users will always have to be added manually using
a local user.
The implementation is shared; the local and remote alternatives
use common functions to which the hashtable and filename to be
used are forwarded.
The commands "[add|remove] user" behave now exactly like they did
in 1.4.3, and also all existing users work out of the box.
In addition there is now the commands "[enable|disable] account"
using which Linux accounts can be enabled for MaxAdmin usage.
The change in readwritesplit routing priorities, where hints have the
highest priority, gives users more options to control how readwritesplit
acts.
For example, this allows read-only stored procedures to be routed to
slaves by adding a hint to the query:
CALL myproc(); -- maxscale route to slave
The readwritesplit documentation also warns the user not to use routing
hints unless they can be absolutely sure that no damage will be done.
The binlogrouter requires that users are not loaded at startup. This
allows it to inject the service user into the list of valid MySQL users so
that the binlogrouter can be controlled via the listeners.
The authenticator modules now load the user data when the new loadusers
entry point is called. This new entry point is optional.
At the moment the code that was in service.c was just moved into the
modules but the ground work for allowing different user loading mechanisms
is done.
Further improvements need to be made so that the authenticators behave
more like routers and filters. This work includes the creation of a
AUTHENTICATOR module object, addition of createInstance entry points for
authenticators and implementing it for all authenticators.
Local admins are the ones accessing MaxScale on the same host
over a Unix domain socket, and who are strongly identified), and
optional remote admins are the ones accessing MaxScale potentially
over a tcp socket (potentially over the network), and who are
weakly identified.
These are completely separate and a different set of functions
will be needed for managing them. This initial change merely
renames the functions.
With this change, if two master servers both have equal depths but
different weights, the one with the higher weight is used. If the depths
and weights are equal, the first master listed in the configuration is
used.
When a server goes into maintenance, the current state is set to
Maintenance and the previous state is left unmodified. The function which
checks for state changes uses the current and previous values and simply
compares them. Since servers in maintenance mode aren't monitored, the
function always returned true when servers were in maintenance mode.
When the state change to or from maintenance is ignored, the state change
function works. With this fix, users can safely put servers into
maintenance without having to worry about the scripts being executed. This
also allows the scripts themselves to put servers into maintenance.
The cache filter consists of two separate components; the cache
itself that evaluates whether a particular query is subject to
caching and the actual cache storage. The storage is loaded at
runtime by the cache filter. Currently using a custom mechanism;
once the new plugin loading macros/mechanism is in place, I'll see
if that can be used.
There are a few open questions/issues.
- Can a GWBUF delivered to the filter contain more MySQL packets
than one? If yes, then some queueing mechanism needs to be
introduced. Currently the code is written so that the packets
are processes in a loop, which will not work.
- Currently, the storage API is synchronous. That may work with a
storage built upon RocksDB, that writes asynchronously to disk,
but not with memcached that can be (and in MaxScale's case
would have to be) used asynchronously.
Reading may be problematic with RocksDB as values are returned
synchronously. So that will stall the thread being used. However,
as RocksDB uses in-memory caching and it is possible to arrange
so that e.g. selects targeting the same table are stored together,
it is not obvious what the impact would be.
So as not to block the MaxScale worker threads, there'd have to
be a separate thread-pool for RocksDB access and then arrange
the data to be moved across.
But initially, the inteface is synchronous.
- How is the cache configured? The original requirement mentions
all sorts of parameters - database name, table name, column name,
presence of WHERE clause, regexp, date/time of query, user -
but it's not alltogether clear exactly how they should be specified
and how they should interract. So initially all selects will
be subject to caching with a TTL.
The section name of a filter in the MaxScale configuration
file is unique for each filter. Hence, by providing that name
to the filter instance creation function, it is possible to
act differently depending on which particular instance is
being created.
Case in point.
There can be multiple cache filters defined in the MaxScale
configuration file, each with a different set of rules, ttl
and even backing store.
Each cache will be backed by a separate storage that e.g.
in the case of RocksDB will correspond to a particular path.
In other words, for each cache instance corresponding to a
particular cache definition in the MaxScale configuration file,
we need to be able to create a unique path.
If the filter section name (in the MaxScale configuration file)
that anyways needs to be unique, is provided to the filter, then
that name can be used when forming the unique path.
The alternative is to require the DBA to provide some unique
parameter for each cache definition, which adds configuration
overhead and is errorprone.
Furthermore, by providing the name to filters, also error
messages can be customized for a particular section when
appropriate.
Previously, if the same filter was used by multiple services,
the filter instance was created multiple times, yet only the
last created instance was used.
C++11 requires a space between literal and string macro.
Does not change the content or layout of GW_MYSQL_VERSION.
RocksDB must be compiled with C++11.
Currently, if the address/port information of a maxscaled protocol
listener is not updated to socket when MaxScale is upgraded to 2.0,
maxscaled would not start, with the effect of a user loosing maxadmin
after an upgrade.
After this change, if address/port information is detected, a warning
is logged and the default socket path is used. That way, maxadmin will
still be usable after an upgrade, even if the address/port information
is not updated.
