pecl:mysqlnd_ms
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pecl:mysqlnd_ms [2012/04/16 12:23] – [Development steps (release planning)] uw | pecl:mysqlnd_ms [2017/09/22 13:28] (current) – external edit 127.0.0.1 | ||
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== Coding/ | == Coding/ | ||
- | * [open] Configurable | + | * [done] More fail over options |
- | * [open] Silent and automatic connection fail over if server returns configured error code | + | * [done] Automatic on-connect fail over, if activated, shall be done in a loop until a connection can be opened. Currently we stop after the first attempt. If automatic fail over is on, we try " |
- | * [open] Automatic on-connect fail over, if activated, shall be done in a loop until a connection can be opened. Currently we stop after the first attempt. If automatic fail over is on, we try " | + | * [done] Remember failed hosts for the duration of a web request (the plugins' |
+ | * [done] Refine QoS session consistency server selection policy | ||
+ | * [done] Support "wait for GTID". Currently we loop over all servers until we find a matching one. MySQL 5.6 allows SQL users either to fetch the latest GTID or SQL users can ask for a GTID and their request will block until the GTID has been replicated on the server. We should support the latter logic as well. | ||
+ | * [done] Improve load balancing | ||
+ | * [done] Allow users to set a ratio/ | ||
== QA == | == QA == | ||
- | + | * [done] 85-90% code coverage through tests | |
== Documentation, | == Documentation, | ||
+ | * [done] Update documentation | ||
+ | * [done] Assorted blog postings | ||
+ | === 1.5 - Tweaking based on user feedback | ||
- | === Open and delayed tasks === | + | Work has not started yet. |
== Coding/ | == Coding/ | ||
+ | |||
+ | * [open] More fail over options | ||
+ | * [open] Silent and automatic connection fail over if server returns configured error code | ||
+ | * NOTE: this may require refactoring of four filters. | ||
+ | * [open] Add failover timeout and failover (maximum) attempts limits/ | ||
+ | |||
+ | * [open] Support directing statements manually to a group of nodes for more efficient server cache usage | ||
+ | * [open] Remember the most current server and test this one first when searching for a GTID (a synchronous server). Use of cached information is possible for the duration of a read-only request sequence. The cache must be flushed and refreshed for every write. | ||
+ | |||
+ | * [open] Work with php.net Windows team to provide PECL/ | ||
+ | * Ensure the code builds | ||
+ | * Encourage Windows team to create builds | ||
- | * [incomplete - 1.2] make load balancer schemata aware | + | == QA == |
- | * for each statement detect database/ | + | |
- | * follow schemata based partitioning rules | + | |
- | * basic idea: http:// | + | |
- | * cancelled/ | + | |
- | * [cancelled] improve trx_stickiness using MYSQL*/ | + | |
- | * cancelled: http:// | + | |
- | * [open] bail on unknown config settings. For example, bail if someone uses round_robin instead of roundrobin | + | |
- | == QA == | + | * [open] 85-90% code coverage through tests |
+ | * [open] Cross-platform testing on all major MySQL build hosts | ||
- | * [open] >= 90% code coverage through tests | + | == Documentation, |
- | * [open] write report on parsing overhead, goal: <5% in worst case micro benchmarks | + | |
- | + | ||
- | == Documentation, | + | |
- | * [done] impact of connection limits such as allow_persistent, | + | * [open] Update documentation |
+ | * [open] Assorted blog postings | ||
Line 205: | Line 216: | ||
== Feature description == | == Feature description == | ||
- | === Eventual consistent: automatic chaining of PECL/ | + | === More fail over configuration options |
== Problem to solve / Idea == | == Problem to solve / Idea == | ||
- | MySQL replication is asnychronous. Slaves are //eventual consistent// | + | Whenever the plugin tries to connect to a node it may fail to do so. Connection attempts can be made when opening |
- | MySQL replication used for read scale-out requires applications to be able to cope with stale data. If stale data is acceptable, a replication system may replace a MySQL slave read access with an access to a local, eventually stale, cache. **The cache access | + | The fail over logic itself |
- | + | ||
- | For certain queries, PECL/ | + | |
- | + | ||
- | (MySQL semi-synchronous replication does not change the matter as it requires only one slave to have received but not yet applied the update.) | + | |
- | + | ||
- | **PECL/ | + | |
== Feature description == | == Feature description == | ||
- | Applications shall be able to define a " | ||
- | * [RW_]CONSISTENT | + | Automatic fail over is basic. We shall: |
- | * [RO_]EVENTUAL_CONSISTENT | + | |
- | With CONSISTENT every statement shall be run on the master | + | - make it configurable whether fail over node search tries one or all possible alternatives |
+ | - link fail over to certain error codes | ||
+ | - remember failed hosts to skip them for the rest of the web request | ||
- | PECL/ | + | Up to version |
- | However, PECL/ | + | Whether this shall become a new default or become configurable is to be decided. |
- | /* Force use of master - consistent read although no SQL hint is used */ | + | Furthermore, |
- | mysqlnd_ms_set_service_level($link, CONSISTENT); | + | |
- | $link-> | + | |
- | $link-> | + | |
- | + | ||
- | /* Use master or slaves for reads - allow read stale, non-consistent data is acceptable */ | + | |
- | mysqlnd_ms_set_service_level($link, | + | |
- | $link-> | + | |
- | + | ||
- | The service level EVENTUAL_CONSISTENT | + | |
- | If PECL/ | + | Upon request |
- | Use and integration | + | === Support directing statements manually to a group of nodes for more efficient server cache usage === |
- | |||
- | === Global Transaction ID === | ||
== Problem to solve / Idea == | == Problem to solve / Idea == | ||
- | In the scope of MySQL master - slave replication global transaction IDs can be understood as a measure | + | In large clusters users can improve performance by optimizing query distribution and server selection using criteria such as cache usage, distance or latency. Application developers shall be allowed |
- | The MySQL built-in replication does not feature global transaction IDs. MySQL replication uses transaction log files and log file positions | + | Server cache usage can be optimized by distributing queries |
- | If, for example, your setup is A -> B -> C (A is the master, B is a slave reading from A, C is a slave reading from B) and B fails you are faced with the challenge | + | Some nodes may be co-located |
- | + | ||
- | Today, it can become | + | |
- | + | ||
- | Fail-over and circular-replication is much easier | + | |
- | + | ||
- | The plugin | + | |
== Feature description == | == Feature description == | ||
- | Global transaction IDs can be used for multiple purposes: | + | For every node in the configuration users shall be able to set one or more group names. A SQL hint, for example, MS_GROUP=name can be used to hint the load balancer |
- | + | ||
- | * Simplify server fail-over (server-side, | + | |
- | + | ||
- | * Monitor slave replication status (client-side, | + | |
- | * Identify " | + | |
- | * Identify slaves which are " | + | |
- | * Let the load balancer skip slaves which have fallen to far behind to reduce their load | + | |
- | + | ||
- | The plugin shall support using a global transaction ID for: | + | |
- | + | ||
- | - server fail-over (e.g. promoting new master after master failure) | + | |
- | - selection of " | + | |
- | + | ||
- | Gobal transaction ID generation | + | |
- | + | ||
- | The SQL used for globals transaction ID generation can be different for the different purposes. It may be good enough | + | |
- | + | ||
- | Thus, the user shall be able to configure: | + | |
- | + | ||
- | * SQL used for ID generation | + | |
- | * SQL used to retrieve ID | + | |
- | + | ||
- | If no SQL is given to retrieve | + | |
- | + | ||
- | This is useful if, for example, an application does a write and needs to read the modified data " | + | |
- | /* write to master */ | ||
- | $link-> | ||
- | $write_trx_id = mysqlnd_ms_get_last_global_transaction_id(); | ||
- | | ||
- | /* Force use of master - consistent read although no SQL hint is used */ | ||
- | mysqlnd_ms_set_service_level($link, | ||
- | $link-> | ||
- | $link-> | ||
- | |||
- | /* Read from a slave which has replicated global transaction ID or, if no slave found, use master */ | ||
- | mysqlnd_ms_set_service_level($link, | ||
- | $link-> | ||
- | $link-> | ||
- | | ||
- | /* Use master or slaves for reads - allow read stale, non-consistent data is acceptable */ | ||
- | mysqlnd_ms_set_service_level($link, | ||
- | $link-> | ||
- | The global transaction ID feature of the plugin is turned off by default. The feature is seen as an experts topic. | + | === Refine QoS session consistency server selection policy === |
- | === mysqlnd_ms_change_user() === | ||
== Problem to solve / Idea == | == Problem to solve / Idea == | ||
- | Give users a way to overrule all automatic decisions, including | + | Users can request session consistency. Session consistency guarantees that a user will only be redirected |
== Feature description == | == Feature description == | ||
- | bool mysqlnd_ms_change_user(mixed $connection, | + | Two additional ways for finding candidates help lowering the overhead: |
- | + | ||
- | $where: MYSQLND_MS_ALL_CONNECTIONS, | + | |
- | + | ||
- | Consider: | + | |
- | | + | * Wait for GTID |
+ | | ||
- | === mysqlnd_ms_get_errors() === | + | There are two ways to check in MySQL 5.6 if a server has replicated a GTID. One can ask a node whether a GTID has been replicated and either get an immediate response (yes/no) or delay the reply until the node has replicated the GTID (wait for GTID). Currently only the first logic is used. We shall also support "wait for GTID". In that case we pick a candidate and wait until the candidate has replicated the GTID. This will lower the checking overhead as only one node is checked but not all configured nodes. |
- | == Problem | + | |
- | Not all MS errors | + | Furthermore we can persist GTID/ |
- | == Feature description == | ||
- | array mysqlnd_ms_get_errors([mixed $connection]) | ||
- | | ||
- | TDB. | ||
- | |
pecl/mysqlnd_ms.1334578993.txt.gz · Last modified: 2017/09/22 13:28 (external edit)