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.
The `failover_recovery` option allows failed servers to rejoin the
cluster. This should make using MaxScale with two node clusters easier.
One use case for this is when the replication-manager promotes the last
node in the cluster as the master. When this is done, the slave
configuration is cleared and the read-only mode is disabled. Since the
failover requires that the server is not configured as a slave and that it
is not in read-only mode, it is safe to use `failover_recovery` with
replication-manager.
Monitored nodes could be part of different cluster UUIDs: select only
the ones belonging to UUID with more joined nodes.
In case of different UUIDs if the joined numbers is less than (n_nodes
/ 2 ) + 1 don’t consider any node part of the cluster
Moved some typedefs to router.h and server.h, changed a few
constants to these enums. Renamed some types in config.h to
remove "Gateway".
There are still some functions in the public header which are
only used in core, but they seem to fit the theme of public functions
so were not moved.
The slave nodes par od the cluster are sorted by wsrep_local_index or
server priority.
The sorted list od nodes is then used in ‘wsrep_sst_donor’ variable.
Note: candidate master servers are always at the end of the list
Galeramon queries all slave nodes for SHOW VARIABLES LIKE
'wsrep_node_name'
The server list, currently not sorted, is used in SET GLOBAL
wsrep_sst_donor = “list”. The statement is sent to all slave nodes
All modules now declare a name for the module. This is name is added as a
prefix to all messages logged by a module. The prefix should help
determine which part of the system logs a message.
The header is divided into two parts, an external and an internal one. The
actual splitting is done in a later commit and this commit only prepares
the header for the split.
This removes parts of the nearly identical code from all monitors.
The removal of monitor type specific event checking is done based on the
assumption that only the monitor that is monitoring the server can be the
cause for a state change. This removes the need to actually check that the
state change is relevant for each monitor and allows the event handling to
be moved into the core.
- All (but the printing/debug functions) are now in snake_case.
- Functions made const correct.
- All function prototypes now have named arguments.
Documentation still to be moved, and file possibly split into
include/mascale/server.h and server/core/maxscale/server.h
The MXS_MODULDE object now contains optinal pointers for functions
to be called att process and thread startup and shutdown. Since the
functions were added to the end, strictly speaking, all structures
would not have needed to have been modified, but better to be
explicit. In a subsequent change, these will be called.
C++ does not support flexible arrays, so for the time being C++
modules are restricted to 10 parameters. Better approach is to
factor out the parameters to a separate array and then just store
a pointer to that array in MXS_MODULE.
All monitors now declare the parameters that they use. This allows the
core to check the validity of the parameters before they are passed to the
monitor. It also simplifies the processing of the parameters as they are
guaranteed to be valid.
The MODULE_INFO is now the main object which is used by modules to convey
information to the MaxScale core. The MXS_MODULE name is more apt as it
now contains the actual module definition.
The old MODULES structure was moved into load_utils.c as an internal
implementation and was renamed so that it is not confused with the new
MODULE structure.
The modules are now declared with a common macro. This allows future
additions to the module loading process while also making the loaded
symbol name a constant.
This allows modules to only expose one entry point with a consistent
signature. In the future, this could be used to implement declarations of
module parameters.
