This PR is part of a series: see the prototype https://github.com/palantir/atlasdb/pull/7000 or the internal RFC for what all of the pieces together are expected to look like. I have tried to separate this feature into reasonably sized components as otherwise it'd probably have a 5k delta or so!
Before this PR: The immutable timestamp lock is tracked by SnapshotTransaction, among its myriad responsibilities.
After this PR:
==COMMIT_MSG==
The immutable timestamp lock and how to check it is no longer tracked by SnapshotTransaction itself; it is
==COMMIT_MSG==
Priority: High P2: nothing in particular but high priority workstream
Concerns / possible downsides (what feedback would you like?):
In ExpiredLocks, I opted not to include the actual tokens that expired and just the description of the error, because no calling code actually cares about which tokens failed outside of the error message.
// It seems perverse not to include the actual tokens that have expired, but these are not currently actually
// used by any caller; we can subsequently include them later if necessary. This API is only intended for
// internal usage.
I wasn't sure it made sense to extract an interface for the ImmutableTimestampLockManager, though happy to if we think it would be useful.
I don't like the whole SummarizedLockCheckResult business, but it is used for logging clarity in some code that handles the case where we got a KeyAlreadyExistsException when connecting to the database, and I didn't want to touch that for now at least.
Is documentation needed?: No
Compatibility
Does this PR create any API breaks (e.g. at the Java or HTTP layers) - if so, do we have compatibility?: YES: Removing a protected field from SnapshotTransaction is technically a breaking change. However, I was not able to find any users that extend SnapshotTransaction or SerializableTransaction using internal code search tooling.
Does this PR change the persisted format of any data - if so, do we have forward and backward compatibility?: No
The code in this PR may be part of a blue-green deploy. Can upgrades from previous versions safely coexist? (Consider restarts of blue or green nodes.): Yes
Does this PR rely on statements being true about other products at a deployment - if so, do we have correct product dependencies on these products (or other ways of verifying that these statements are true)?: No
Does this PR need a schema migration? No
Testing and Correctness
What, if any, assumptions are made about the current state of the world? If they change over time, how will we find out?: Nothing in particular
What was existing testing like? What have you done to improve it?: Added some tests.
If this PR contains complex concurrent or asynchronous code, is it correct? The onus is on the PR writer to demonstrate this.: N/A
If this PR involves acquiring locks or other shared resources, how do we ensure that these are always released?: N/A
Execution
How would I tell this PR works in production? (Metrics, logs, etc.): Nothing breaks.
Has the safety of all log arguments been decided correctly?: N/A
Will this change significantly affect our spending on metrics or logs?: No.
How would I tell that this PR does not work in production? (monitors, etc.): Things break.
If this PR does not work as expected, how do I fix that state? Would rollback be straightforward?: Rollback
If the above plan is more complex than “recall and rollback”, please tag the support PoC here (if it is the end of the week, tag both the current and next PoC): N/A
Scale
Would this PR be expected to pose a risk at scale? Think of the shopping product at our largest stack.:
Would this PR be expected to perform a large number of database calls, and/or expensive database calls (e.g., row range scans, concurrent CAS)?:
Would this PR ever, with time and scale, become the wrong thing to do - and if so, how would we know that we need to do something differently?:
Development Process
Where should we start reviewing?: ImmutableTimestampLockManager
If this PR is in excess of 500 lines excluding versions lock-files, why does it not make sense to split it?:
Please tag any other people who should be aware of this PR:
@jeremyk-91
@sverma30
@raiju
General
This PR is part of a series: see the prototype https://github.com/palantir/atlasdb/pull/7000 or the internal RFC for what all of the pieces together are expected to look like. I have tried to separate this feature into reasonably sized components as otherwise it'd probably have a 5k delta or so!
Before this PR: The immutable timestamp lock is tracked by
SnapshotTransaction, among its myriad responsibilities.After this PR:
==COMMIT_MSG== The immutable timestamp lock and how to check it is no longer tracked by
SnapshotTransactionitself; it is ==COMMIT_MSG==Priority: High P2: nothing in particular but high priority workstream
Concerns / possible downsides (what feedback would you like?):
ImmutableTimestampLockManager, though happy to if we think it would be useful.SummarizedLockCheckResultbusiness, but it is used for logging clarity in some code that handles the case where we got a KeyAlreadyExistsException when connecting to the database, and I didn't want to touch that for now at least.Is documentation needed?: No
Compatibility
Does this PR create any API breaks (e.g. at the Java or HTTP layers) - if so, do we have compatibility?: YES: Removing a
protectedfield fromSnapshotTransactionis technically a breaking change. However, I was not able to find any users that extendSnapshotTransactionorSerializableTransactionusing internal code search tooling.Does this PR change the persisted format of any data - if so, do we have forward and backward compatibility?: No
The code in this PR may be part of a blue-green deploy. Can upgrades from previous versions safely coexist? (Consider restarts of blue or green nodes.): Yes
Does this PR rely on statements being true about other products at a deployment - if so, do we have correct product dependencies on these products (or other ways of verifying that these statements are true)?: No
Does this PR need a schema migration? No
Testing and Correctness
What, if any, assumptions are made about the current state of the world? If they change over time, how will we find out?: Nothing in particular
What was existing testing like? What have you done to improve it?: Added some tests.
If this PR contains complex concurrent or asynchronous code, is it correct? The onus is on the PR writer to demonstrate this.: N/A
If this PR involves acquiring locks or other shared resources, how do we ensure that these are always released?: N/A
Execution
How would I tell this PR works in production? (Metrics, logs, etc.): Nothing breaks.
Has the safety of all log arguments been decided correctly?: N/A
Will this change significantly affect our spending on metrics or logs?: No.
How would I tell that this PR does not work in production? (monitors, etc.): Things break.
If this PR does not work as expected, how do I fix that state? Would rollback be straightforward?: Rollback
If the above plan is more complex than “recall and rollback”, please tag the support PoC here (if it is the end of the week, tag both the current and next PoC): N/A
Scale
Would this PR be expected to pose a risk at scale? Think of the shopping product at our largest stack.:
Would this PR be expected to perform a large number of database calls, and/or expensive database calls (e.g., row range scans, concurrent CAS)?:
Would this PR ever, with time and scale, become the wrong thing to do - and if so, how would we know that we need to do something differently?:
Development Process
Where should we start reviewing?:
ImmutableTimestampLockManagerIf this PR is in excess of 500 lines excluding versions lock-files, why does it not make sense to split it?:
Please tag any other people who should be aware of this PR: @jeremyk-91 @sverma30 @raiju