Class used to manage connections to Spanner.

**You don't need to use this class directly, connections will be handled for you.**

{EventEmitter}

Inheritance

Constructs a new instance of theSessionPool class

Total number of available sessions. {number}

Total number of borrowed sessions. {number}

Current fraction of write-prepared sessions in the pool. {number}

Flag to determine if Pool is full. {boolean}

Current number of waiters for a read-only session. {number}

Current number of waiters for a read/write session. {number}

Number of sessions currently being prepared for a read/write transaction before being released into the pool. This number does not include the number of sessions being prepared for a read/write transaction that have already been checked out of the pool. {number}

Total number of read sessions. {number}

Total size of pool. {number}

Number of sessions being created or prepared for a read/write transaction. {number}

Sum of read and write waiters. {number}

Total number of write sessions. {number}

Attempts to borrow a session from the pool.

Moves a session into the borrowed group.

Borrows the first session from specific group. This method may only be called if the inventory actually contains a session of the desired type.

Grabs the next available session.

Attempts to create a single session of a certain type.

Batch creates sessions and prepares any necessary transactions.

Attempts to delete a session, optionally creating a new one of the same type if the pool is still open and we're under the configured min value.

SessoinPool#error

Deletes idle sessions that exceed the maxIdle configuration.

Fills the pool with the minimum number of sessions.

{Promise}

Retrieves a list of all the idle sessions.

Returns stack traces for sessions that have not been released.

{string[]}

Attempts to get a session of a specific type. If the type is unavailable it may try to use a different type.

Returns true if the pool has a session that is usable for the specified type, i.e. if a read-only session is requested, it returns true if the pool has a read-only or a read/write session. If a read/write session is requested, the method only returns true if the pool has a read/write session available.

Checks to see whether or not session is expired.

Pings an individual session.

Makes a keep alive request to all the idle sessions.

Creates a transaction for a session.

Releases a session back into the pool.

SessionPool#available SessionPool#readonly-available SessionPool#readwrite-available

Starts housekeeping (pinging/evicting) of idle sessions.

Stops housekeeping.

Closes and the pool.

SessionPool#close

Formats stack trace objects into Node-like stack trace.

Retrieve a read session.

Retrieve a read/write session.

Opens the pool, filling it to the configured number of read and write sessions.

SessionPool#open {Promise}

Releases session back into the pool. If the session is a write session it will also prepare a new transaction before releasing it.