2c4228db47
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.
129 lines
3.8 KiB
C++
129 lines
3.8 KiB
C++
/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2022-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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// All log messages from this module are prefixed with this
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#define MXS_MODULE_NAME "examplecppfilter"
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/*
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* To use the filter in a configuration, add the following section to the config file:
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* [ExampleFilter]
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* type=filter
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* module=examplecppfilter
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* global_counts=true
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*
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* Then add the filter to a service:
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* [Read-Write-Service]
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* .
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* .
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* filters=ExampleFilter
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*/
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#include "examplefilter.hh"
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static const char CN_COUNT_GLOBALS[] = "global_counts";
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// This declares a module in MaxScale
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extern "C" MXS_MODULE* MXS_CREATE_MODULE()
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{
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static const char DESC[] = "An example filter that counts the number of queries and replies "
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"it has routed";
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static MXS_MODULE info =
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{
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MXS_MODULE_API_FILTER,
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MXS_MODULE_IN_DEVELOPMENT,
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MXS_FILTER_VERSION,
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DESC,
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"V1.0.0",
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RCAP_TYPE_STMT_INPUT, // See getCapabilities() below
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&ExampleFilter::s_object, // This is defined in the MaxScale filter template
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NULL, /* Process init. */
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NULL, /* Process finish. */
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NULL, /* Thread init. */
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NULL, /* Thread finish. */
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{
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{"an_example_parameter", MXS_MODULE_PARAM_STRING, "a-default-value"},
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{CN_COUNT_GLOBALS, MXS_MODULE_PARAM_BOOL, "true"},
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{MXS_END_MODULE_PARAMS}
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}
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};
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return &info;
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}
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ExampleFilter::ExampleFilter(const MXS_CONFIG_PARAMETER* pParams)
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{
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m_collect_global_counts = config_get_bool(pParams, CN_COUNT_GLOBALS);
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}
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ExampleFilter::~ExampleFilter()
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{
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}
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// static
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ExampleFilter* ExampleFilter::create(const char* zName, MXS_CONFIG_PARAMETER* pParams)
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{
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return new ExampleFilter(pParams);
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}
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ExampleFilterSession* ExampleFilter::newSession(MXS_SESSION* pSession)
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{
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return ExampleFilterSession::create(pSession, *this);
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}
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// static
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void ExampleFilter::diagnostics(DCB* pDcb) const
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{
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int queries = m_total_queries.load(std::memory_order_relaxed);
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int replies = m_total_replies.load(std::memory_order_relaxed);
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dcb_printf(pDcb, "\t\tTotal queries %i\n", queries);
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dcb_printf(pDcb, "\t\tTotal replies %i\n", replies);
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}
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// static
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json_t* ExampleFilter::diagnostics_json() const
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{
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json_t* rval = json_object();
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int queries = m_total_queries.load(std::memory_order_relaxed);
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int replies = m_total_replies.load(std::memory_order_relaxed);
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json_object_set_new(rval, "total_queries", json_integer(queries));
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json_object_set_new(rval, "total_replies", json_integer(replies));
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return rval;
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}
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// static
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uint64_t ExampleFilter::getCapabilities()
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{
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// Tells the protocol that the filter expects complete queries from client, that is, a query cannot be
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// sent in parts.
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return RCAP_TYPE_STMT_INPUT;
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// Try the following to also expect replies to be complete. This can cause problems if the server sends
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// a really big (e.g. 1 GB) resultset.
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// return RCAP_TYPE_STMT_INPUT | RCAP_TYPE_RESULTSET_OUTPUT;
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}
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void ExampleFilter::query_seen()
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{
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if (m_collect_global_counts)
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{
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m_total_queries.fetch_add(1, std::memory_order_relaxed);
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}
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}
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void ExampleFilter::reply_seen()
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{
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if (m_collect_global_counts)
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{
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m_total_replies.fetch_add(1, std::memory_order_relaxed);
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}
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} |