The macros MXS_SESSION_ROUTE_QUERY and MXS_SESSION_ROUTE_REPLY
are now defined in terms of functions that do the actual stuff.
Incidentally, the function session_route_reply() existed already
but was not used. Now slightly rewritten so that it does not simply
ignore misuse.
The earlier @maxscale.cache.enabled has now been replaced with
@maxscale.cache.populate and @maxscale.cache.use that provide
for more flexibility.
With the former it is possible to control in what circumstances
the cache is populated and with the latter one when it is used.
Together they can be used for having a completely client driven
caching.
With the changes in this commit it is possible to add and remove
MaxScale specific user variables. A MaxScale specific user variable
is a user variable that is interpreted by MaxScale and that
potentially changes the behaviour of MaxScale.
MaxScale specific user variables are of the format "@maxscale.x.y"
where "@maxscale" is a mandatory prefix, x a scope identifying the
component that handles the variable and y the component specific
variable. So, a variable might be called e.g. "@maxscale.cache.enabled".
The scope "core" is reserved (although not enforced yet) to MaxScale
itself.
The idea is that although MaxScale catches these, they are passed
through to the server. The benefit of this is that we do not need to
detect e.g. "SELECT @maxscale.cache.enabled", but can let the result
be returned from the server.
The interpretation of a provided value is handled by the component that
adds the variable. In a subsequent commit, it will be possible for a
component to reject a value, which will then cause an error to be
returned to the client.
There are 3 new functions:
- session_add_variable() using which a variable is added,
- session_remove_variable() using which a variable is removed, and
- session_set_variable_value().
The two former ones are to be called by components, the last one by
the protocol that catches the "set @maxscale..." statements.
By always starting the session shutdown process by stopping the client
DCB, the manipulation of the session state can be removed from the backend
protocol modules and replaced with a fake hangup event.
Delivering this event via the core allows the actual dcb_close call on the
client DCB to be done only when the client DCB is being handled by a
worker.
The backend DCBs didn't have a valid service pointer whereas the client
DCBs had one. The necessity of the pointer can be questioned as a similar
pointer is located in the session.
The internal header directory conflicted with in-source builds causing a
build failure. This is fixed by renaming the internal header directory to
something other than maxscale.
The renaming pointed out a few problems in a couple of source files that
appeared to include internal headers when the headers were in fact public
headers.
Fixed maxctrl in-source builds by making the copying of the sources
optional.
KILL commands are now sent to the backends in an asynchronous manner. As
the LocalClient class is used to connect to the servers, this will cause
an extra connection to be created on top of the original connections
created by the session.
If the user does not have the permissions to execute the KILL, the error
message is currently lost. This could be solved by adding a "result
handler" into the LocalClient class which is called with the result.
Now it is also possible to ensure that a DCB stays alive while
a task referring to it is posted from one worker to another.
That will be implemented in a subsequent commit.
The template class wraps a HashMap such that only a few operations
are allowed. Usage requires specializing a RegistryTraits class
template for each entry type.
The server internal session id may be larger than 4 bytes (MariaDB uses 8)
but only 4 are sent in the handshake. The full value can be queried
from the server, but this query is not supported by MaxScale yet. In any
case, both the protocol and MXS_SESSION now have 64 bit counters. Only the
low 32 bits are sent in the handshake, similar to server.
The top level resource self links pointed to the collection instead of the
resource itself. The individual resoures now also have a links field that
contains the self link to the resource. This should make navigation of the
API easier as all objects have valid links in them.
The JSON objects that are created from the various core MaxScale objects
share a lot of common code. Moving this into a separate files removes the
redundant code.
The sessions resource now follows the JSON API specification:
http://jsonapi.org/
This makes the API relatively easier to use as the specification and the
client libraries to consume this data exist.
Various small changes to part2, as suggested by comments and otherwise.
Mostly renaming, working logic should not change.
Exception: session id changed to 64bit in the container and associated
functions. Another commit will change it to 64bit in the session itself.
MySQL sessions are added to a hasmap when created, removed when closed.
MYSQL_COM_PROCESS_KILL is now detected, the thread_id is read and the kill
command sent to all worker threads to find the correct session. If found, a
fake hangup even is created for the client dcb.
As is, this function is of little use since the client could just disconnect
itself instead. Later on, additional commands of this nature will be added.
The /sessions/ resource was not implemented due to changes in the core
polling mechanics. With the new worker thread messaging system, sessions
can be listed in a safe manner.
The JSON API (http://jsonapi.org/) specifies a way to express relations in
a somewhat generic way. By moving towards a more generic schema for the
resources, it will be easier to handle the modification of the relations
between these resources.
When a resource has a relation to another resource, it should be expressed
as a working link to the resource. By passing the hostname of the server
to the functions, we are able to generate working relation links.
The modules that implement a diagnostics entry point now return a JSON
type object. This removes the need to format data inside the modules.
The module implementations of these are not yet complete which means that
MaxScale will fail to compile.
The resources now properly process parts of the uri. This allows, for
example, certain sessions to be inspected. The current functionality is
only intended for testing and provides no useful functionality.
The actions taken by the resource manager are not done via the
inter-thread messaging system. When the implementation of the messages and
the JSON representation of the resources is done, the REST API resource
can actually be used.
Preparation for adding KILL syntax support.
Session id changed to uint32 everywhere. Added atomic op.
Session id can be acquired before session_alloc().
Added session_alloc_with_id(), which is given a session id number.
Worker object has a session_id->SESSION* mapping, not used yet.
This is just a first step in a trial that will allow the addition
of any file descriptor to the general poll mechanism and hence
allow any i/o to be handled by the worker threads.
There is a structure
typedef struct mxs_poll_data
{
void (*handler)(struct mxs_poll_data *data, int wid, uint32_t events);
struct
{
int id;
} thread;
} MXS_POLL_DATA;
that any other structure (e.g. a DCB) encapsulating a file descriptor must
have as its first member (a C++ struct could basically derive from it).
That structure contains two members; 'handler' and 'thread.id'. Handler is a
pointer to a function taking a pointer to a struct mxs_poll_data, a worker thread
if and an epoll event mask as argument.
So, DCB is modified to have MXS_POLL_DATA as its first member and 'handler'
is initialized with a function that *knows* the passed MXS_POLL_DATA can
be downcast to a DCB.
process_pollq no longer exists, but is now called process_pollq_dcb. The
general stuff related to statistics etc. will be moved to poll_waitevents
itself after which the whole function is moved to dcb.c. At that point,
the handler pointer will be set in dcb_alloc().
Effectively poll.[h|c] will provide a generic mechanism for listening on
whatever descriptors and the dcb stuff will be part of dcb.[h|c].
