|
| 1 | +.. _connpool_module: |
| 2 | + |
| 3 | +Module experimental.connpool |
| 4 | +============================ |
| 5 | + |
| 6 | +**Since:** :doc:`3.1.0 </release/3.1.0>` |
| 7 | + |
| 8 | +.. important:: |
| 9 | + |
| 10 | + ``experimental.connpool`` is an experimental module and is subject to changes. |
| 11 | + |
| 12 | +An ``experimental.connpool`` module provides a set of features for connecting to remote cluster instances and for executing remote procedure calls on an instance that satisfies the specified criteria. |
| 13 | + |
| 14 | + |
| 15 | +.. _connpool_module_load: |
| 16 | + |
| 17 | +Loading a module |
| 18 | +---------------- |
| 19 | + |
| 20 | +To load the ``experimental.connpool`` module, use the ``require()`` directive: |
| 21 | + |
| 22 | +.. code-block:: lua |
| 23 | +
|
| 24 | + connpool = require('experimental.connpool') |
| 25 | +
|
| 26 | +
|
| 27 | +.. _connpool_module_api_reference: |
| 28 | + |
| 29 | +API Reference |
| 30 | +------------- |
| 31 | + |
| 32 | +.. container:: table |
| 33 | + |
| 34 | + .. rst-class:: left-align-column-1 |
| 35 | + .. rst-class:: left-align-column-2 |
| 36 | + |
| 37 | + .. list-table:: |
| 38 | + :widths: 35 65 |
| 39 | + |
| 40 | + * - **Functions** |
| 41 | + - |
| 42 | + |
| 43 | + * - :ref:`connpool.call() <connpool_module_call>` |
| 44 | + - Execute the specified function on a remote instance |
| 45 | + |
| 46 | + * - :ref:`connpool.connect() <connpool_module_connect>` |
| 47 | + - Create a connection to the specified instance |
| 48 | + |
| 49 | + * - :ref:`connpool.filter() <connpool_module_filter>` |
| 50 | + - Get names of instances that match the specified conditions |
| 51 | + |
| 52 | + |
| 53 | + |
| 54 | + |
| 55 | + |
| 56 | +.. module:: connpool |
| 57 | + |
| 58 | +.. _connpool_module_api_reference_functions: |
| 59 | + |
| 60 | +Functions |
| 61 | +~~~~~~~~~ |
| 62 | + |
| 63 | +.. _connpool_module_call: |
| 64 | + |
| 65 | +.. function:: call(func_name, args, opts) |
| 66 | + |
| 67 | + Execute the specified function on a remote instance. |
| 68 | + |
| 69 | + .. NOTE:: |
| 70 | + |
| 71 | + You need to grant the ``execute`` :ref:`permission <configuration_credentials_managing_users_roles_granting_privileges>` for the specified function to a user used for replication to execute this function on a remote instance. |
| 72 | + |
| 73 | + :param string func_name: a name of the function to execute. |
| 74 | + :param table/nil args: function arguments. |
| 75 | + :param table/nil opts: options used to select candidates on which the function should be executed: |
| 76 | + |
| 77 | + * ``labels`` -- the :ref:`labels <configuration_reference_labels>` an instance has. |
| 78 | + * ``roles`` -- the :ref:`roles <configuration_application_roles>` of an instance. |
| 79 | + * ``prefer_local`` -- if ``true``, ``call()`` tries to execute the specified function on a local instance. If ``false``, ``call()`` tries to connect to a random candidate until a connection is established. |
| 80 | + * ``mode`` -- a mode that allows filtering candidates based on their read-only status. This option accepts the following values: |
| 81 | + |
| 82 | + * ``nil`` -- don't check the read-only status of instances. |
| 83 | + * ``ro`` -- consider only read-only instances. |
| 84 | + * ``rw`` -- consider only read-write instances. |
| 85 | + * ``prefer_ro`` -- consider read-only instances, then read-write instances. |
| 86 | + * ``prefer_rw`` -- consider read-write instances, then read-only instances. |
| 87 | + |
| 88 | + * ``instances`` -- the names of instances to consider as candidates. |
| 89 | + * ``replicasets`` -- the names of replica sets whose instances are considered as candidates. |
| 90 | + * ``groups`` -- the names of groups whose instances are considered as candidates. |
| 91 | + * ``timeout`` -- a connection timeout (in seconds). |
| 92 | + * ``buffer`` -- a :ref:`buffer <buffer-module>` used to read a returned value. |
| 93 | + * ``on_push`` -- a function to execute when the client receives an out-of-band message. Learn more from :ref:`box_session-push`. |
| 94 | + * ``on_push_ctx`` -- an argument of the function executed when the client receives an out-of-band message. Learn more from :ref:`box_session-push`. |
| 95 | + * ``is_async`` -- whether to wait for the result of the call. |
| 96 | + |
| 97 | + :return: a function's return value. |
| 98 | + |
| 99 | + **Example** |
| 100 | + |
| 101 | + In the example below, the following conditions are specified to choose an instance to execute the :ref:`vshard.storage.buckets_count <storage_api-buckets_count>` function: |
| 102 | + |
| 103 | + * An instance has the ``roles.crud-storage`` role. |
| 104 | + * An instance has the ``dc`` label set to ``east``. |
| 105 | + * An instance is read-only. |
| 106 | + |
| 107 | + .. code-block:: lua |
| 108 | +
|
| 109 | + local buckets_count = connpool.call('vshard.storage.buckets_count', |
| 110 | + nil, |
| 111 | + { roles = { 'roles.crud-storage' }, |
| 112 | + labels = { dc = 'east' }, |
| 113 | + mode = 'ro' } |
| 114 | + ) |
| 115 | +
|
| 116 | +
|
| 117 | +.. _connpool_module_connect: |
| 118 | + |
| 119 | +.. function:: connect(instance_name, opts) |
| 120 | + |
| 121 | + Create a connection to the specified instance. |
| 122 | + |
| 123 | + :param string instance_name: an instance name. |
| 124 | + :param table/nil opts: none, any, or all of the following parameters: |
| 125 | + |
| 126 | + * ``connect_timeout`` -- a connection timeout (in seconds). |
| 127 | + * ``wait_connected`` -- if ``true``, the connection is blocked until it is established. If ``false``, the connection is returned immediately. |
| 128 | + * ``fetch_schema`` -- whether to fetch schema changes from a remote instance. |
| 129 | + |
| 130 | + :return: a :ref:`net.box <net_box-module>` connection. |
| 131 | + |
| 132 | + **Example** |
| 133 | + |
| 134 | + In the example below, ``connect()`` is used to create the active connection to ``storage-b-002``: |
| 135 | + |
| 136 | + .. code-block:: lua |
| 137 | +
|
| 138 | + local conn = connpool.connect("storage-b-002", { fetch_schema = true }) |
| 139 | +
|
| 140 | + Once you have a connection, you can execute requests on a remote instance, for example, select data from a space using :ref:`conn.space.\<space-name\>:select() <conn-select>`. |
| 141 | + |
| 142 | + |
| 143 | +.. _connpool_module_filter: |
| 144 | + |
| 145 | +.. function:: filter(opts) |
| 146 | + |
| 147 | + Get names of instances that match the specified conditions. |
| 148 | + |
| 149 | + :param table/nil opts: none, any, or all of the following parameters: |
| 150 | + |
| 151 | + * ``labels`` -- the :ref:`labels <configuration_reference_labels>` an instance has. |
| 152 | + * ``roles`` -- the :ref:`roles <configuration_application_roles>` of an instance. |
| 153 | + * ``mode`` -- a mode that allows filtering candidates based on their read-only status. This option accepts the following values: |
| 154 | + |
| 155 | + * ``nil`` -- don't check the read-only status of instances. |
| 156 | + * ``ro`` -- consider only read-only instances. |
| 157 | + * ``rw`` -- consider only read-write instances. |
| 158 | + |
| 159 | + * ``instances`` -- the names of instances to consider as candidates. |
| 160 | + * ``replicasets`` -- the names of replica sets whose instances are considered as candidates. |
| 161 | + * ``groups`` -- the names of groups whose instances are considered as candidates. |
| 162 | + |
| 163 | + :return: an array of instance names. |
| 164 | + |
| 165 | + **Example** |
| 166 | + |
| 167 | + In the example below, ``filter()`` should return a list of instances with the ``roles.crud-storage`` role and specified label value: |
| 168 | + |
| 169 | + .. code-block:: lua |
| 170 | +
|
| 171 | + local instance_names = connpool.filter({ roles = { 'roles.crud-storage' }, |
| 172 | + labels = { dc = 'east' } }) |
0 commit comments