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MXS-2400 Extend examplefilter

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Added more comments. Also the filter now demonstrates how to
1) read configuration parameters
2) react to queries and replies
3) handle shared filter data
4) print diagnostics output
5) add log entries

As the filter is already built and moved to the library directory,
it is immediately usable. This should be helpful with assignments.
This commit is contained in:
Esa Korhonen
2019-03-20 17:18:45 +02:00
parent 65b4ac7c1b
commit 2c4228db47
4 changed files with 170 additions and 25 deletions
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69
examples/examplefilter.cc
View File

@ -12,28 +12,47 @@
*/
// All log messages from this module are prefixed with this
#define MXS_MODULE_NAME "examplefilter"
#define MXS_MODULE_NAME "examplecppfilter"
/*
* To use the filter in a configuration, add the following section to the config file:
* [ExampleFilter]
* type=filter
* module=examplecppfilter
* global_counts=true
*
* Then add the filter to a service:
* [Read-Write-Service]
* .
* .
* filters=ExampleFilter
*/
#include "examplefilter.hh"
static const char CN_COUNT_GLOBALS[] = "global_counts";
// This declares a module in MaxScale
extern "C" MXS_MODULE* MXS_CREATE_MODULE()
{
static const char DESC[] = "An example filter that counts the number of queries and replies "
"it has routed";
static MXS_MODULE info =
{
MXS_MODULE_API_FILTER,
MXS_MODULE_IN_DEVELOPMENT,
MXS_FILTER_VERSION,
"An example filter that does nothing",
DESC,
"V1.0.0",
RCAP_TYPE_NONE,
RCAP_TYPE_STMT_INPUT, // See getCapabilities() below
&ExampleFilter::s_object, // This is defined in the MaxScale filter template
NULL, /* Process init. */
NULL, /* Process finish. */
NULL, /* Thread init. */
NULL, /* Thread finish. */
{
{"an_example_parameter", MXS_MODULE_PARAM_STRING,"a-default-value"},
{"an_example_parameter", MXS_MODULE_PARAM_STRING, "a-default-value"},
{CN_COUNT_GLOBALS, MXS_MODULE_PARAM_BOOL, "true"},
{MXS_END_MODULE_PARAMS}
}
};
@ -41,8 +60,9 @@ extern "C" MXS_MODULE* MXS_CREATE_MODULE()
return &info;
}
ExampleFilter::ExampleFilter()
ExampleFilter::ExampleFilter(const MXS_CONFIG_PARAMETER* pParams)
{
m_collect_global_counts = config_get_bool(pParams, CN_COUNT_GLOBALS);
}
ExampleFilter::~ExampleFilter()
@ -52,27 +72,58 @@ ExampleFilter::~ExampleFilter()
// static
ExampleFilter* ExampleFilter::create(const char* zName, MXS_CONFIG_PARAMETER* pParams)
{
return new ExampleFilter();
return new ExampleFilter(pParams);
}
ExampleFilterSession* ExampleFilter::newSession(MXS_SESSION* pSession)
{
return ExampleFilterSession::create(pSession, this);
return ExampleFilterSession::create(pSession, *this);
}
// static
void ExampleFilter::diagnostics(DCB* pDcb) const
{
int queries = m_total_queries.load(std::memory_order_relaxed);
int replies = m_total_replies.load(std::memory_order_relaxed);
dcb_printf(pDcb, "\t\tTotal queries %i\n", queries);
dcb_printf(pDcb, "\t\tTotal replies %i\n", replies);
}
// static
json_t* ExampleFilter::diagnostics_json() const
{
return NULL;
json_t* rval = json_object();
int queries = m_total_queries.load(std::memory_order_relaxed);
int replies = m_total_replies.load(std::memory_order_relaxed);
json_object_set_new(rval, "total_queries", json_integer(queries));
json_object_set_new(rval, "total_replies", json_integer(replies));
return rval;
}
// static
uint64_t ExampleFilter::getCapabilities()
{
return RCAP_TYPE_NONE;
// Tells the protocol that the filter expects complete queries from client, that is, a query cannot be
// sent in parts.
return RCAP_TYPE_STMT_INPUT;
// Try the following to also expect replies to be complete. This can cause problems if the server sends
// a really big (e.g. 1 GB) resultset.
// return RCAP_TYPE_STMT_INPUT | RCAP_TYPE_RESULTSET_OUTPUT;
}
void ExampleFilter::query_seen()
{
if (m_collect_global_counts)
{
m_total_queries.fetch_add(1, std::memory_order_relaxed);
}
}
void ExampleFilter::reply_seen()
{
if (m_collect_global_counts)
{
m_total_replies.fetch_add(1, std::memory_order_relaxed);
}
}