Add SessionPoolOptions to SpannerConfig

[manitgupta]

Add support for configuring SessionPoolOptions in SpannerAccessor.

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R: @robertwb for label java. R: @damondouglas for label io. R: @nielm for label spanner.

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[nielm]

Can you explain why you believe this is necessary to add?

The default session pool options in Java are:

• MinSessions =100
• MaxSessions = 400
• WriteSessionsFraction = 0.2

These will apply to each worker indivudually.

@olavloite for comment.

[manitgupta]

This is my primary motivation - https://github.com/googleapis/java-spanner/blob/main/session-and-channel-pool-configuration.md#automatically-clean-inactive-transactions

Currently, there is no way to set setWarnAndCloseIfInactiveTransactions(). SpannerAccessor is used in Dataflow templates like DatastreamToSpanner, which customers use as a black box, therefore, having this enabled by default makes sense.

[nielm]

In theory there should never be an inactive transaction left open by SpannerIO. If there is, then it is a bug in SpannerIO.

Writes use blind writes by calling DatabaseClient.writeAtLeastOnce, which internally uses the single_use_transaction feature of the Commit API so that a transaction is automatically started and closed by the Spanner server.

Reads use a single read transaction, which is shared across all workers. By their nature these are long-running transactions.

SpannerIO is intended to isolate users from needing to worry about transactions, and to just pass their data in and let the connecter deal with it.

If you are experiencing issues with session pool exhaustion, and believe that there may be a bug, then please raise an issue.

[manitgupta]

SpannerAccessor is not only consumed by SpannerIO, it is directly used by Flex templates such as DatastreamToSpanner here. Therefore a pipeline may leverage the accessor from beam directly and have a session leak in the application code they write using the accessor.

[github-actions[bot]]

Reminder, please take a look at this pr: @robertwb @damondouglas @nielm

[manitgupta]

Bump! @nielm @olavloite

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Assigning new set of reviewers because Pr has gone too long without review. If you would like to opt out of this review, comment assign to next reviewer:

R: @kennknowles for label java. R: @ahmedabu98 for label io. R: @nielm for label spanner.

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[nielm]

Result of out-of-band discussion between @manitgupta and @olavloite - Change the PR such that SpannerAccessor always sets

SessionPoolOptions.setFailIfPoolExhausted()

to avoid expanding the SpannerIO public API surface while also catching potential session leak bugs.

[nielm]

LGTM

Precommit fails for unrelated reason in org.apache.beam.sdk.io.gcp.spanner.changestreams.it.SpannerChangeStreamOrderedWithinKeyIT > restOrderedWithinKey

[github-actions[bot]]

Reminder, please take a look at this pr: @kennknowles @ahmedabu98 @nielm

[nielm]

reverted in #32694