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https://issues.apache.org/jira/browse/CASSGO-92?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Hartig updated CASSGO-92:
-------------------------------
Description:
Right now there are several things that make writing an external
HostSelectionPolicy:
# No access to context in `ExecutableStatement`
# Cannot read statement metadata (via prepare)
# No access to the underlying Statement or Entries
# No access to the consistency
# No access to logging
# There's no executor on the session when `Init(session)` is called and trying
to query causes a panic
There are workarounds for some of these things:
# Assert `ExecutableStatement` matches `interface \{ Context() context.Context
}`.
# No workaround
# Typecast `Statement()` against `*Query` and `*Batch` but you lose support
for new/custom types.
# Same as #3
# Require setting logger separately
# No workaround
I'd like to start by exposing a `StatementMetadata` method on Session that
behaves much like `routingKeyInfo` but without a cache. I'll consolidate
`routingKeyInfo` to use the same code but keep the cache around for that
internal method. External calls should utilize their own cache if they want to
cache. We _could_ have `StatementMetadata` do caching but invalidation will be
hard so leaving it up to the caller means they can control when they want to
invalidate.
Also, we should fix session initialization to not initialize the
HostSelectionPolicy until after `executor` is set. But we should document that
when `Init(session)` is called, there might not be any ready pool and
`Init(session)` should not block.
was:
Right now there are several things that make writing an external
HostSelectionPolicy:
# No access to context in `ExecutableStatement`
# Cannot read statement metadata (via prepare)
# No access to the underlying Statement or Entries
# No access to the consistency
# No access to logging
# There's no executor on the session when `Init(session)` is called and trying
to query causes a panic
There are workarounds for some of these things:
# Assert `ExecutableStatement` matches `interface \{ Context() context.Context
}`.
# No workaround
# Typecast `Statement()` against `*Query` and `*Batch` but you lose support
for new/custom types.
# Same as #3
# No workaround
# No workaround
I'd like to start by exposing a `StatementMetadata` method on Session that
behaves much like `routingKeyInfo` but without a cache. I'll consolidate
`routingKeyInfo` to use the same code but keep the cache around for that
internal method. External calls should utilize their own cache if they want to
cache. We _could_ have `StatementMetadata` do caching but invalidation will be
hard so leaving it up to the caller means they can control when they want to
invalidate.
Also, we should fix session initialization to not initialize the
HostSelectionPolicy until after `executor` is set. But we should document that
when `Init(session)` is called, there might not be any ready pool and
`Init(session)` should not block.
> Improve usability for external HostSelectionPolicy
> --------------------------------------------------
>
> Key: CASSGO-92
> URL: https://issues.apache.org/jira/browse/CASSGO-92
> Project: Apache Cassandra Go driver
> Issue Type: Improvement
> Components: Core
> Reporter: James Hartig
> Assignee: James Hartig
> Priority: Normal
>
> Right now there are several things that make writing an external
> HostSelectionPolicy:
> # No access to context in `ExecutableStatement`
> # Cannot read statement metadata (via prepare)
> # No access to the underlying Statement or Entries
> # No access to the consistency
> # No access to logging
> # There's no executor on the session when `Init(session)` is called and
> trying to query causes a panic
>
> There are workarounds for some of these things:
> # Assert `ExecutableStatement` matches `interface \{ Context()
> context.Context }`.
> # No workaround
> # Typecast `Statement()` against `*Query` and `*Batch` but you lose support
> for new/custom types.
> # Same as #3
> # Require setting logger separately
> # No workaround
> I'd like to start by exposing a `StatementMetadata` method on Session that
> behaves much like `routingKeyInfo` but without a cache. I'll consolidate
> `routingKeyInfo` to use the same code but keep the cache around for that
> internal method. External calls should utilize their own cache if they want
> to cache. We _could_ have `StatementMetadata` do caching but invalidation
> will be hard so leaving it up to the caller means they can control when they
> want to invalidate.
> Also, we should fix session initialization to not initialize the
> HostSelectionPolicy until after `executor` is set. But we should document
> that when `Init(session)` is called, there might not be any ready pool and
> `Init(session)` should not block.
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