It is possible that the routing fails even if master_reconnection is
enabled and a second master is available. This is the case when a
transaction is open or autocommit is disabled which is what the
mxs359_master_switch test tests.
The old hkheartbeat variable was changed to the mxs_clock() function that
simply wraps an atomic load of the variable. This allows it to be
correctly read by MaxScale as well as opening up the possibility of
converting the value load to a relaxed memory order read.
Renamed the header and associated macros. Removed inclusion of the
heartbeat header from the housekeeper header and added it to the files
that were missing it.
This is a proof-of-concept that validates the query retrying method. The
actual implementation of the query retrying mechanism needs more thought
as using the housekeeper is not very efficient.
The MASTER_GTID_WAIT "prefix" should only be added if it fits into one
packet. This is not a complete solution as it prevents queries larger than
16MB from benefiting from the consistent reads.
Most of the funtionality is now a member function of either the RWSplit or
RWSplitSession class. This removes the need to pass the router and session
parameters to all functions.
The warning that tells the user that the session command history has been
exceeded is now only logged once. This is to prevent the message from
being repeatedly logged when the default value is not large enough.
Also fixed the session_limits test to use distinct session commands. This
way the session command history compaction is not in effect and the test
again tests the correct thing.
It is possible, and perfectly OK, for the new master to be in use at the
same time the old master is. This is the case if one of the slaves is
promoted as the master.
The code that logs the master failure error was not working correctly
after the changes done for MXS-359 and MXS-1503. Updated the logic and
converted impossible cases into debug assertions.
The master_failure_mode=error_on_write mode was broken due to a faulty
assumption that all successfully routed queries would produce a
target. This is not the case when a write in error_on_write mode is
received.
Moved the RWBackend class implementation into its own file. Made some of
the command type functions a part of the <maxscale/protocol/mysql.h>
header to make it reusable.
When a non-connected target is chosed as the target server and the session
command history is not empty, the query needs to be placed into the query
queue and routed only after the session commands have been executed.
The session command history is now compacted to contain only the first and
last execution of a session command. This should still allow most of the
more eccentric use-cases of user variables while keeping the session
command history smaller.
Added some convenience functions into the SessionCommand class to make the
pruning process easier.
The slave selection now again respects max_slave_connections. This means
that the amount of slave connections each session has will never grow
beyond the configured value.
The slave connections can now be recovered after a failure as long as the
session command history is enabled. In comparison to the old
functionality, the server now replaces the connection when a query is
received instead of reconnecting when the slave fails.
As a negative side effect of this change, the max_slave_connections is no
longer enforced after the connection is created. To fix this broken
functionality, the connected slaves need to be preferred over unconnected
ones. This will be added in a follow-up commit.
The `master_reconnection` parameter now controls both the reconnection of
the master server as well as the migration of the master server to another
server. Although these two cases appear to be different, the end result
from readwritesplit's point of view is the same and are thus controlled
with the same parameter.
The RWBackend class now resets its internal state when it is closed. This
allows readwritesplit to handle the case when a result was expected from
the master but the master died before the result was returned. The same
code should also handle slave connection failures mid-result, allowing
Backend reuse.
Added a test case that verifies the new functionality when combined with
`master_failure_mode=error_on_write`.
Moved session command execution into the Backend class itself as the
session commands are defined as a related part of it. This allows all
connections to execute session commands if some are available.
Removed explicit SERVER_REF usage in the readwritesplit connection
creation code and replaced it with SRWBackend. This allows the removal of
the get_root_master_backend function which duplicated the functionality in
get_root_master.
Provides a clearer separation between what deals with query
classification and what deals with query routing.
Functions have only been moved. No other cleanup has been
done.
When the master changes mid-session, the temporary tables are inevitably
lost. This could be avoided by routing temporary table creation to all
servers.
With the `allow_master_change` parameter enabled, sessions can start using
a different master node if one is available. This will not prevent
sessions from closing if a write query is received while no master
replacement is available.
After a temporary table is created, readwritesplit will check whether a
query drops or targets that temporary table. The check for query type was
missing from the table dropping part of the code. The temporary table read
part was checking that the query is a text form query.
Added a debug assertion to the query parsing function in qc_sqlite to
catch this type of interface misuse.
The debug assertion wasn't well placed as it is perfectly possible that a
master connnection exists but it is not in use. This can be further
checked by asserting that the master is indeed closed and not in use.
Moved the original debug assertion into a separate branch that should
catch any errors in the routing logic.
* MXS-199: Support Causal Read in Read Write Splitting
* move most causal read logic into rwsplit router and get server type from monitor
* misc fix: remove new line
* refactor, move config to right place, replace ltrim with gwbuf_consume
* refacter a little for previous commit
* fix code style
