Tentative documentation.
With the 'switchover' config variable the switchover functionality
can be enabled. If enabled a REST API endpoint will appear, using
which that switchover can be initiated.
Switchover can only be performed when MaxScale is in active mode
and failover will be disabled for the duration of the switchover.
Only if the switchover succeeds, will failover be enabled again.
Might be easier to expose that REST API always and only change
the behaviour when calling it, instead of making it appear and
re-appear.
The `failover` and `failover_timeout` parameters are now declared as a
part of the mysqlmon module. Changed the implementation of the failover
function so that the dependencies on the monitor struct can be removed or
moved into parameters.
Split the state change processing and failover handling into two separate
functions and added a call to the failover function into mysqlmon. This
prevents unintended behavior when failover is enabled for non-mysqlmon
monitors. The parameter itself still needs to be moved into mysqlmon.
Moved the failover documentation to the mysqlmon documentation as it is
specific to this monitor.
The monitor performs simple monitoring of a group replication cluster. It
expects no extra parameters in addition to the common monitor parameters
and will only set master and slave status bits on the servers. It is a
part of the experimental package as it is a very experimental module.
Further improvements would be to add the usage of the synced state.
If MaxScale Binlog Server is detected by MySQL monitor, then Server
status is ‘Relay Master, Running’ without ‘Slave’: this way Binlog
Server cannot be used by any statement routing.
Additionally SELECT for replication lag is skipped as well.
It is now possible to specify the thread stack size to be used,
when a new thread is created. This will subsequently be used
for allowing the stack size to be specified for worker threads.
All monitors now persist the state of the server in a monitor journal
file.
Moved the removal of stale journals into the core and removed them from
the monitor journal interface.
Enabling the option hinders the use of maintenance mode with the root
master node in most use-cases.
This behavior occurs due to the fact that the maintenance mode causes a
server to be treted as if it was down. The Galera monitor waits for the
cluster to reorganize before assigning a new master node. This is correct
(but very unexpected) behavior for single instance use-cases.
The multimaster node detection uses stacks to sort the node groups. The
size of this stack was always assumed to be positive but it was possible
that it dropped down to -1 causing a crash when the stack was accessed
with the index number.
The multimaster node detection uses stacks to sort the node groups. The
size of this stack was always assumed to be positive but it was possible
that it dropped down to -1 causing a crash when the stack was accessed
with the index number.
The function should actually be in include/maxscale/protocol/mysql.h
and the implementation in MySQLCommon, but the monitors do not link
to that yet.
All MySQL related should be moved to MySQLCommon and the core
refactored so that no MySQL knowledge is needed there.
Whenever a server which is a slave of an external master is detected, it
will be assigned the slave status. This will allow the status to be used
the way it was intended to be used.
The MySQL monitor replication_heartbeat table now uses the default storage
engine of the database when creating the table. Most of the time the
default is InnoDB which makes the table crash-safe.
If a monitor is started and stopped before the external monitoring thread
has had time to start, a deadlock will occur.
The first thing that the monitoring threads do is read the monitor handle
from the monitor object. This handle is given as the return value of
startMonitor and it is stored in the monitor object. As this can still be
NULL when the monitor thread starts, the threads use locks to prevent
this.
The correct way to prevent this is to pass the handle as the thread
parameter so that no locks are required.
This number (defaults to 1) sets how many times mon_connect_to_db
will try to connect to a backend before returning an error. Every
connection attempt may take backend_connect_timeout seconds to
complete.
Also refactored code a bit. Renamed mon_connect_to_db to
mon_ping_or_connect_to_db, since it does not connect if the connection
is already alive.
When log messages are written with both address and port information, IPv6
addresses can cause confusion if the normal address:port formatting is
used. The RFC 3986 suggests that all IPv6 addresses are expressed as a
bracket enclosed address optionally followed by the port that is separate
from the address by a colon.
In practice, the "all interfaces" address and port number 3306 can be
written in IPv4 numbers-and-dots notation as 0.0.0.0:3306 and in IPv6
notation as [::]:3306. Using the latter format in log messages keeps the
output consistent with all types of addresses.
The details of the standard can be found at the following addresses:
https://www.ietf.org/rfc/rfc3986.txthttps://www.rfc-editor.org/std/std66.txt
The static capabilities declared in getCapabilities allows certain
capabilities to be queried before instances are created. The intended use
of this capability is to remove the need for the `is_internal_service`
function.
The server state information should be persisted even if a controlled
shutdown is done. This will allow the monitor to retain the server state
information across a restart.
The MySQL monitor stores the server states in a backup file which can be
used to restore the state of the servers even if MaxScale is stoppen in an
uncontrolled fashion.
When a standalone master server is detected, it should receive the stale
status to prevent it from losing the master status if another server is
started and allow_cluster_recovery is enabled.
When the real root master server went down, it still received the master
status bit due to how the replication tree was built. The bit should only
be set for servers that are running.
Also fixed a false state change event when the master status bit was
manually cleared from the downed root master server.
If all but one server in a cluster fail and `failover` is enabled for
mysqlmon, the last server would be used as if it were a master. With this
change, the restrictions on failover also require that the last server is
not configured as a slave.
This change will prevent unintended failovers from happening when network
connectivity is bad. It also allows external actors to clear the slave
configuration from the last remaining server to signal MaxScale that the
server can be used as a master.
