Remove prefill logic from resource pool

doc/releasenotes/15_0_0_summary.md

@@ -37,6 +37,12 @@ Information about which tables are used was being reported through the `Keyspace
 For multi-table queries, this output can be confusing, so we have added `TablesUsed`, that is a string array, listing all tables and which keyspace they are on.
 `Keyspace` and `Table` fields are deprecated and will be removed in the v16 release of Vitess.
 
+#### Connection Pool Prefill
+
+The connection pool with prefilled connections have been removed. The pool now does lazy connection creation.
+Following flags are deprecated: `queryserver-config-pool-prefill-parallelism`, `queryserver-config-stream-pool-prefill-parallelism`, `queryserver-config-transaction-prefill-parallelism`
+and will be removed in future version.
+
 ### Command-line syntax deprecations
 
 #### vttablet startup flag deletions

go/flags/endtoend/vtctld.txt

@@ -142,7 +142,7 @@ Usage of vtctld:
       --queryserver-config-max-result-size int                           query server max result size, maximum number of rows allowed to return from vttablet for non-streaming queries. (default 10000)
       --queryserver-config-message-postpone-cap int                      query server message postpone cap is the maximum number of messages that can be postponed at any given time. Set this number to substantially lower than transaction cap, so that the transaction pool isn't exhausted by the message subsystem. (default 4)
       --queryserver-config-passthrough-dmls                              query server pass through all dml statements without rewriting
-      --queryserver-config-pool-prefill-parallelism int                  query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-pool-prefill-parallelism int                  (DEPRECATED) query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-pool-size int                                 query server read pool size, connection pool is used by regular queries (non streaming, not in a transaction) (default 16)
       --queryserver-config-query-cache-lfu                               query server cache algorithm. when set to true, a new cache algorithm based on a TinyLFU admission policy will be used to improve cache behavior and prevent pollution from sparse queries (default true)
       --queryserver-config-query-cache-memory int                        query server query cache size in bytes, maximum amount of memory to be used for caching. vttablet analyzes every incoming query and generate a query plan, these plans are being cached in a lru cache. This config controls the capacity of the lru cache. (default 33554432)
@@ -154,14 +154,14 @@ Usage of vtctld:
       --queryserver-config-schema-change-signal-interval float           query server schema change signal interval defines at which interval the query server shall send schema updates to vtgate. (default 5)
       --queryserver-config-schema-reload-time float                      query server schema reload time, how often vttablet reloads schemas from underlying MySQL instance in seconds. vttablet keeps table schemas in its own memory and periodically refreshes it from MySQL. This config controls the reload time. (default 1800)
       --queryserver-config-stream-buffer-size int                        query server stream buffer size, the maximum number of bytes sent from vttablet for each stream call. It's recommended to keep this value in sync with vtgate's stream_buffer_size. (default 32768)
-      --queryserver-config-stream-pool-prefill-parallelism int           query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
+      --queryserver-config-stream-pool-prefill-parallelism int           (DEPRECATED) query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
       --queryserver-config-stream-pool-size int                          query server stream connection pool size, stream pool is used by stream queries: queries that return results to client in a streaming fashion (default 200)
       --queryserver-config-stream-pool-timeout float                     query server stream pool timeout (in seconds), it is how long vttablet waits for a connection from the stream pool. If set to 0 (default) then there is no timeout.
       --queryserver-config-stream-pool-waiter-cap int                    query server stream pool waiter limit, this is the maximum number of streaming queries that can be queued waiting to get a connection
       --queryserver-config-strict-table-acl                              only allow queries that pass table acl checks
       --queryserver-config-terse-errors                                  prevent bind vars from escaping in client error messages
       --queryserver-config-transaction-cap int                           query server transaction cap is the maximum number of transactions allowed to happen at any given point of a time for a single vttablet. E.g. by setting transaction cap to 100, there are at most 100 transactions will be processed by a vttablet and the 101th transaction will be blocked (and fail if it cannot get connection within specified timeout) (default 20)
-      --queryserver-config-transaction-prefill-parallelism int           query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-transaction-prefill-parallelism int           (DEPRECATED) query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-transaction-timeout float                     query server transaction timeout (in seconds), a transaction will be killed if it takes longer than this value (default 30)
       --queryserver-config-txpool-timeout float                          query server transaction pool timeout, it is how long vttablet waits if tx pool is full (default 1)
       --queryserver-config-txpool-waiter-cap int                         query server transaction pool waiter limit, this is the maximum number of transactions that can be queued waiting to get a connection (default 5000)

go/flags/endtoend/vtexplain.txt

@@ -172,7 +172,7 @@ Usage of vtexplain:
       --queryserver-config-max-result-size int                           query server max result size, maximum number of rows allowed to return from vttablet for non-streaming queries. (default 10000)
       --queryserver-config-message-postpone-cap int                      query server message postpone cap is the maximum number of messages that can be postponed at any given time. Set this number to substantially lower than transaction cap, so that the transaction pool isn't exhausted by the message subsystem. (default 4)
       --queryserver-config-passthrough-dmls                              query server pass through all dml statements without rewriting
-      --queryserver-config-pool-prefill-parallelism int                  query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-pool-prefill-parallelism int                  (DEPRECATED) query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-pool-size int                                 query server read pool size, connection pool is used by regular queries (non streaming, not in a transaction) (default 16)
       --queryserver-config-query-cache-lfu                               query server cache algorithm. when set to true, a new cache algorithm based on a TinyLFU admission policy will be used to improve cache behavior and prevent pollution from sparse queries (default true)
       --queryserver-config-query-cache-memory int                        query server query cache size in bytes, maximum amount of memory to be used for caching. vttablet analyzes every incoming query and generate a query plan, these plans are being cached in a lru cache. This config controls the capacity of the lru cache. (default 33554432)
@@ -184,14 +184,14 @@ Usage of vtexplain:
       --queryserver-config-schema-change-signal-interval float           query server schema change signal interval defines at which interval the query server shall send schema updates to vtgate. (default 5)
       --queryserver-config-schema-reload-time float                      query server schema reload time, how often vttablet reloads schemas from underlying MySQL instance in seconds. vttablet keeps table schemas in its own memory and periodically refreshes it from MySQL. This config controls the reload time. (default 1800)
       --queryserver-config-stream-buffer-size int                        query server stream buffer size, the maximum number of bytes sent from vttablet for each stream call. It's recommended to keep this value in sync with vtgate's stream_buffer_size. (default 32768)
-      --queryserver-config-stream-pool-prefill-parallelism int           query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
+      --queryserver-config-stream-pool-prefill-parallelism int           (DEPRECATED) query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
       --queryserver-config-stream-pool-size int                          query server stream connection pool size, stream pool is used by stream queries: queries that return results to client in a streaming fashion (default 200)
       --queryserver-config-stream-pool-timeout float                     query server stream pool timeout (in seconds), it is how long vttablet waits for a connection from the stream pool. If set to 0 (default) then there is no timeout.
       --queryserver-config-stream-pool-waiter-cap int                    query server stream pool waiter limit, this is the maximum number of streaming queries that can be queued waiting to get a connection
       --queryserver-config-strict-table-acl                              only allow queries that pass table acl checks
       --queryserver-config-terse-errors                                  prevent bind vars from escaping in client error messages
       --queryserver-config-transaction-cap int                           query server transaction cap is the maximum number of transactions allowed to happen at any given point of a time for a single vttablet. E.g. by setting transaction cap to 100, there are at most 100 transactions will be processed by a vttablet and the 101th transaction will be blocked (and fail if it cannot get connection within specified timeout) (default 20)
-      --queryserver-config-transaction-prefill-parallelism int           query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-transaction-prefill-parallelism int           (DEPRECATED) query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-transaction-timeout float                     query server transaction timeout (in seconds), a transaction will be killed if it takes longer than this value (default 30)
       --queryserver-config-txpool-timeout float                          query server transaction pool timeout, it is how long vttablet waits if tx pool is full (default 1)
       --queryserver-config-txpool-waiter-cap int                         query server transaction pool waiter limit, this is the maximum number of transactions that can be queued waiting to get a connection (default 5000)

go/flags/endtoend/vttablet.txt

@@ -318,7 +318,7 @@ Usage of vttablet:
       --queryserver-config-max-result-size int                           query server max result size, maximum number of rows allowed to return from vttablet for non-streaming queries. (default 10000)
       --queryserver-config-message-postpone-cap int                      query server message postpone cap is the maximum number of messages that can be postponed at any given time. Set this number to substantially lower than transaction cap, so that the transaction pool isn't exhausted by the message subsystem. (default 4)
       --queryserver-config-passthrough-dmls                              query server pass through all dml statements without rewriting
-      --queryserver-config-pool-prefill-parallelism int                  query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-pool-prefill-parallelism int                  (DEPRECATED) query server read pool prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-pool-size int                                 query server read pool size, connection pool is used by regular queries (non streaming, not in a transaction) (default 16)
       --queryserver-config-query-cache-lfu                               query server cache algorithm. when set to true, a new cache algorithm based on a TinyLFU admission policy will be used to improve cache behavior and prevent pollution from sparse queries (default true)
       --queryserver-config-query-cache-memory int                        query server query cache size in bytes, maximum amount of memory to be used for caching. vttablet analyzes every incoming query and generate a query plan, these plans are being cached in a lru cache. This config controls the capacity of the lru cache. (default 33554432)
@@ -330,14 +330,14 @@ Usage of vttablet:
       --queryserver-config-schema-change-signal-interval float           query server schema change signal interval defines at which interval the query server shall send schema updates to vtgate. (default 5)
       --queryserver-config-schema-reload-time float                      query server schema reload time, how often vttablet reloads schemas from underlying MySQL instance in seconds. vttablet keeps table schemas in its own memory and periodically refreshes it from MySQL. This config controls the reload time. (default 1800)
       --queryserver-config-stream-buffer-size int                        query server stream buffer size, the maximum number of bytes sent from vttablet for each stream call. It's recommended to keep this value in sync with vtgate's stream_buffer_size. (default 32768)
-      --queryserver-config-stream-pool-prefill-parallelism int           query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
+      --queryserver-config-stream-pool-prefill-parallelism int           (DEPRECATED) query server stream pool prefill parallelism, a non-zero value will prefill the pool using the specified parallelism
       --queryserver-config-stream-pool-size int                          query server stream connection pool size, stream pool is used by stream queries: queries that return results to client in a streaming fashion (default 200)
       --queryserver-config-stream-pool-timeout float                     query server stream pool timeout (in seconds), it is how long vttablet waits for a connection from the stream pool. If set to 0 (default) then there is no timeout.
       --queryserver-config-stream-pool-waiter-cap int                    query server stream pool waiter limit, this is the maximum number of streaming queries that can be queued waiting to get a connection
       --queryserver-config-strict-table-acl                              only allow queries that pass table acl checks
       --queryserver-config-terse-errors                                  prevent bind vars from escaping in client error messages
       --queryserver-config-transaction-cap int                           query server transaction cap is the maximum number of transactions allowed to happen at any given point of a time for a single vttablet. E.g. by setting transaction cap to 100, there are at most 100 transactions will be processed by a vttablet and the 101th transaction will be blocked (and fail if it cannot get connection within specified timeout) (default 20)
-      --queryserver-config-transaction-prefill-parallelism int           query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
+      --queryserver-config-transaction-prefill-parallelism int           (DEPRECATED) query server transaction prefill parallelism, a non-zero value will prefill the pool using the specified parallism.
       --queryserver-config-transaction-timeout float                     query server transaction timeout (in seconds), a transaction will be killed if it takes longer than this value (default 30)
       --queryserver-config-txpool-timeout float                          query server transaction pool timeout, it is how long vttablet waits if tx pool is full (default 1)
       --queryserver-config-txpool-waiter-cap int                         query server transaction pool waiter limit, this is the maximum number of transactions that can be queued waiting to get a connection (default 5000)