Commit Graph

2879 Commits

Author SHA1 Message Date
Kyriakos Tharrouniatis
5ba8477733
CORDA-3491 - Do not keep flow state in memory after a flow has finished (#6573)
Do not retain in database `checkpoint.flowState` for flows that have completed 
or failed and have started with a client id, after their lifetime.
2020-08-06 09:46:04 +01:00
Kyriakos Tharrouniatis
5192a9a2dd
CORDA-3612 - Delete flow results/ exceptions once received by rpc client (#6566)
Enhance rpc acknowledgement method (`removeClientId`) to remove checkpoint 
from all checkpoint database tables.

Optimize `CheckpointStorage.removeCheckpoint` to not delete from all checkpoint
tables if not needed. This includes excluding the results (`DBFlowResult`) and 
exceptions (`DBFlowException`) tables.
2020-08-05 12:40:35 +01:00
Kyriakos Tharrouniatis
5d42b8847c
CORDA-3681 - Store serialised exception in database for failed and hospitalized flows (#6539)
Integrate `DBFlowException` with the rest of the checkpoint schema, so now 
we are saving the flow's exception result in the database.

Making statemachine not remove `FAILED` flows' checkpoints from the 
database if they are started with a clientId.

Retrieve the DBFlowException from the database to construct a 
`FlowStateMachineHandle` future and complete exceptionally the flow's result 
future for requests (`startFlowDynamicWithClientId`) that pick FAILED flows , 
started with client id, of status Removed.

On killing a flow the client id mapping of the flow gets removed.

The storage serialiser is used for serialising exceptions. Note, that if an
exception cannot be serialised, it will not fail and will instead be stored
as a `CordaRuntimeException`. This could be improved in future
changes.
2020-08-04 16:33:44 +01:00
Kyriakos Tharrouniatis
f2bcc85f30 Fix compilation error 2020-07-30 10:54:24 +01:00
Kyriakos Tharrouniatis
8a37108a58 Merge branch 'release/os/4.6' into os_4.6-feature_pass_in_client_id_when_starting_a_flow-merge 2020-07-30 10:34:03 +01:00
Kyriakos Tharrouniatis
ad61d7b3f4
CORDA-3692 - Store result information in checkpoint results table (#6473)
Making statemachine not remove COMPLETED flows' checkpoints from the database 
if they are started with a clientId, instead they are getting persisted and retained within 
the database along with their result (`DBFlowResult`).

On flow start with a client id (`startFlowDynamicWithClientId`), if the client id maps to
a flow that was previously started with the same client id and the flow is now finished, 
then fetch the `DBFlowResult` from the database to construct a 
`FlowStateMachineHandle` done future and return it back to the client.

Object stored as results must abide by the storage serializer rules. If they fail to do so
the result will not be stored and an exception is thrown to the client to indicate this.
2020-07-29 15:57:00 +01:00
Yiftach Kaplan
0bedbd8c75
INFRA-530: Start notary node in process (#6521) 2020-07-29 15:47:45 +01:00
Dan Newton
c2fd8253ea
CORDA-3777 Reload after every checkpoint (#6494)
Enable reloading of a flow after every checkpoint is saved. This
includes reloading the checkpoint from the database and recreating the
fiber.

When a flow and its `StateMachineState` is created it checks the node's
config to see if the `reloadCheckpointAfterSuspend` is set to true. If it is
it initialises `StateMachineState.reloadCheckpointAfterSuspendCount`
with the value 0. Otherwise, it remains `null`.

This count represents how many times the flow has reloaded from its
checkpoint (not the same as retrying). It is incremented every time the
flow is reloaded.

When a flow suspends, it processes the suspend event like usual, but
it will now also check if `reloadCheckpointAfterSuspendCount` is not
`null` (that it is activated) and process a 
`ReloadFlowFromCheckpointAfterSuspend`event, if and only if 
`reloadCheckpointAfterSuspendCount` is greater than
`CheckpointState.numberOfSuspends`.

This means idempotent flows can reload from the start and not reload
again until reaching a new suspension point.

Flows that skip checkpoints can reload from a previously saved
checkpoint (or from the initial checkpoint) and will continue reloading
on reaching the next new suspension point (not the suspension point that
it skipped saving).

If the flow fails to deserialize the checkpoint from the database upon
reloading a `ReloadFlowFromCheckpointException` is throw. This causes
the flow to be kept for observation.
2020-07-28 16:27:51 +01:00
Stefan Iliev
52cbe04b8c
EG-2375 - batching notary open sourcing. (#6507) 2020-07-28 15:50:19 +01:00
Dimitris Gounaris
1e6be340eb
CORDA-3844: bulk node infos request (#6411)
* CORDA-3844: Add new functions to network map client

* CORDA-3844: Apply new fetch logic to nm updater

* CORDA-3844: Fix base url and warnings

* CORDA-3844: Change response object and response validation

In order to make sure that the returned node infos are not maliciously modified, either a signed list response
or a signed reference object would need to be provided. As providing a signed list requires a lot of effort from NM and Signer services,
the signed network map is provided instead, allowing nodes to validate that the list provided conforms to the entries of the signed network map.

* CORDA-3844: Add clarifications and comments

* CORDA-3844: Add error handling for bulk request

* CORDA-3844: Enhance testing

* CORDA-3844: Fix detekt issues

* EG-3844: Apply pr suggestions
2020-07-28 15:02:53 +01:00
Dimos Raptis
f2336f397d
CORDA-3506 - Add test for session close API (#6512) 2020-07-28 10:20:24 +01:00
Ryan Fowler
2ca10464b7
CORDA-3845: Update BC, log4j, slf4j (#6464)
* CORDA-3845: Update BC to 1.64

* CORDA-3845: Upgraded log4j to 2.13.3

* We can remove the use of Manifests from the logging package so that when _it_ logs it doesn't error on the fact the stream was already closed by the default Java logger.

* Some more tidy up

* Remove the logging package as a plugin

* latest BC version

* Remove old test

* fix up

* Fix some rebased changes to log file handling

* Fix some rebased changes to log file handling

* Update slf4j too

Co-authored-by: Adel El-Beik <adel.el-beik@r3.com>
2020-07-23 16:37:29 +01:00
Yiftach Kaplan
4acf41ea3d
INFRA-477: Start nodes in parallel when possible (#6460)
Co-authored-by: Ross Nicoll <ross.nicoll@r3.com>
2020-07-23 16:35:34 +01:00
Joseph Zuniga-Daly
c33720c73d
CORDA-3717: Apply custom serializers to checkpoints (#6392)
* CORDA-3717: Apply custom serializers to checkpoints

* Remove try/catch to fix TooGenericExceptionCaught detekt rule

* Rename exception

* Extract method

* Put calls to the userSerializer on their own lines to improve readability

* Remove unused constructors from exception

* Remove unused proxyType field

* Give field a descriptive name

* Explain why we are looking for two type parameters when we only use one

* Tidy up the fetching of types

* Use 0 seconds when forcing a flow checkpoint inside test

* Add test to check references are restored correctly

* Add CheckpointCustomSerializer interface

* Wire up the new CheckpointCustomSerializer interface

* Use kryo default for abstract classes

* Remove unused imports

* Remove need for external library in tests

* Make file match original to remove from diff

* Remove maySkipCheckpoint from calls to sleep

* Add newline to end of file

* Test custom serializers mapped to interfaces

* Test serializer configured with abstract class

* Move test into its own package

* Rename test

* Move flows and serializers into their own source file

* Move broken map into its own source file

* Delete comment now source file is simpler

* Rename class to have a shorter name

* Add tests that run the checkpoint serializer directly

* Check serialization of final classes

* Register as default unless the target class is final

* Test PublicKey serializer has not been overridden

* Add a broken serializer for EdDSAPublicKey to make test more robust

* Split serializer registration into default and non-default registrations. Run registrations at the right time to preserve Cordas own custom serializers.

* Check for duplicate custom checkpoint serializers

* Add doc comments

* Add doc comments to CustomSerializerCheckpointAdaptor

* Add test to check duplicate serializers are logged

* Do not log the duplicate serializer warning when the duplicate is the same class

* Update doc comment for CheckpointCustomSerializer

* Sort serializers by classname so we are not registering in an unknown or random order

* Add test to serialize a class that references itself

* Store custom serializer type in the Kryo stream so we can spot when a different serializer is being used to deserialize

* Testing has shown that registering custom serializers as default is more robust when adding new cordapps

* Remove new line character

* Remove unused imports

* Add interface net.corda.core.serialization.CheckpointCustomSerializer to api-current.txt

* Remove comment

* Update comment on exception

* Make CustomSerializerCheckpointAdaptor internal

* Revert "Add interface net.corda.core.serialization.CheckpointCustomSerializer to api-current.txt"

This reverts commit b835de79bd.

* Restore "Add interface net.corda.core.serialization.CheckpointCustomSerializer to api-current.txt""

This reverts commit 718873a4e9.

* Pass the class loader instead of the context

* Do less work in test setup

* Make the serialization context unique for CustomCheckpointSerializerTest so we get a new Kryo pool for the test

* Rebuild the Kryo pool for the given context when we change custom serializers

* Rebuild all Kryo pools on serializer change to keep serializer list consistent

* Move the custom serializer list into CheckpointSerializationContext to reduce scope from global to a serialization context

* Remove unused imports

* Make the new checkpointCustomSerializers property default to the empty list

* Delegate implementation using kotlin language feature
2020-07-22 17:31:59 +01:00
Dan Newton
a41152edf6
CORDA-3899 Refactor flow's transient fields (#6441)
Refactor `FlowStateMachineImpl.transientValues` and
`FlowStateMachineImpl.transientState` to stop the fields from exposing
the fact that they are nullable.

This is done by having private backing fields `transientValuesReference`
and `transientStateReference` that can be null. The nullability is still
needed due to serialisation and deserialisation of flow fibers. The
fields are transient and therefore will be null when reloaded from the
database.

Getters and setters hide the private field, allowing a non-null field to
returned.

There is no point other than in `FlowCreator` where the transient fields
can be null. Therefore the non null checks that are being made are
valid.

Add custom kryo serialisation and deserialisation to `TransientValues`
and `StateMachineState` to ensure that neither of the objects are ever
touched by kryo.
2020-07-22 16:19:20 +01:00
Yiftach Kaplan
a03fb8c6fd
INFRA-438: Close session factory before closing the locator (#6477) 2020-07-21 18:10:09 +01:00
Dimos Raptis
7261fa690f
CORDA-3506 - Implement session close operations (#6357) 2020-07-21 13:26:11 +01:00
Viktor Kolomeyko
234ac2c246 Merge remote-tracking branch 'origin/release/os/4.5' into vkolomeyko/os-4.5-os-4.6-merge 2020-07-21 10:29:07 +01:00
Viktor Kolomeyko
1c48418904
NOTICK: Remove relaxedThoroughness variable (#6483)
It is:
a. No longer works in Jenkins
b. May result spawning 100s of process that kill Windows build. Evidence: https://ci02.dev.r3.com/blue/organizations/jenkins/Corda-Enterprise%2FCorda-ENT-MS-Win-Compatibility%2Fenterprise/detail/PR-3553/25/pipeline/
2020-07-21 09:58:29 +01:00
Kyriakos Tharrouniatis
5fef0726a2
Add missing 'Suspendable' annotations to suspending methods (#6480) 2020-07-20 15:09:26 +01:00
Ryan Fowler
d4444e520a
ENT-5140: Tighten network parameters checks (#6390)
* ENT-5140: Tighten network parameters checks
2020-07-20 11:26:27 +01:00
jakubbielawa
3721b7c701
Decrease the ring buffer size (#6470) 2020-07-20 11:14:23 +01:00
Dimos Raptis
e5a8351dc3
ENT-5437 - Add test for sendAll with multiple sessions from the same party (#6476) 2020-07-20 11:13:49 +01:00
Oliver Knowles
a500084d38
CORDA-3201 - Enforce separate key for notary identity (#6308) 2020-07-20 10:59:08 +01:00
Yiftach Kaplan
e6d5842a23
INFRA-482: Correct exception caught testing for node death (#6471) 2020-07-17 13:57:40 +01:00
Ross Nicoll
5d7060ec3a
CORDA-3901 Eliminate random reconnect test (#6446)
Remove a legacy test for RPC reconnection, which takes 5 minutes to run a random set of tests. This is expensive and low value.
2020-07-17 12:26:51 +01:00
Kyriakos Tharrouniatis
22d92d5ef0
CORDA-3809 Expose client side unique RPC ID for flow starts (#6307)
Introducing a new flow start method (`startFlowDynamicWithClientId`) passing in a `clientId`.

Once `startFlowDynamicWithClientId` gets called, the `clientId` gets injected into `InvocationContext` and also pushed to the logging context.

If a new flow starts with this method, then a < `clientId` to flow > pair is kept on node side, even after the flow's lifetime. If `startFlowDynamicWithClientId` is called again with the same `clientId` then the node identifies that this `clientId` refers to an existing < `clientId` to flow > pair and returns back to the rpc client a `FlowStateMachineHandle` future, created out of that pair.

`FlowStateMachineHandle` interface was introduced as a thinner `FlowStateMachine`. All `FlowStateMachine` properties used by call sites are moved into this new interface along with `clientId` and then `FlowStateMachine` extends it.

Introducing an acknowledgement method (`removeClientId`). Calling this method removes the < `clientId` to flow > pair on the node side and frees resources.
2020-07-16 10:52:08 +01:00
Adel El-Beik
2fa6b5a208
CORDA-3769: Switched attachments class loader cache to use caffeine (#6326)
* CORDA-3769: Switched attachments class loader cache to use caffeine with original implementation used by determinstic core.

* CORDA-3769: Removed default ctor arguments.

* CORDA-3769: Switched mapping function to Function type to avoid synthetic method being generated.

* CORDA-3769: Now using a cache created from NamedCacheFactory for the attachments class loader cache.

* CORDA-3769: Making detekt happy.

* CORDA-3769: The finality tests now check for UntrustedAttachmentsException which will actually happen in reality.

* CORDA-3769: Refactored after review comments.

* CORDA-3769: Removed the AttachmentsClassLoaderSimpleCacheImpl as DJVM does not need it. Also updated due to review comments.

* CORDA-3769: Removed the generic parameters from AttachmentsClassLoader.

* CORDA-3769: Removed unused imports.

* CORDA-3769: Updates from review comments.

* CORDA-3769: Updated following review comments. MigrationServicesForResolution now uses cache factory. Ctor updated for AttachmentsClassLoaderSimpleCacheImpl.

* CORDA-3769: Reduced max class loader cache size

* CORDA-3769: Fixed the attachments class loader cache size to a fixed default

* CORDA-3769: Switched attachments class loader size to be reduced by fixed value.
2020-07-16 09:58:36 +01:00
Dan Newton
ac4907a429
CORDA-3721 Finishing + retrying a flow cancels its future (#6454)
Cancel the future being run by a flow when finishing or retrying it. The
cancellation of the future no longer cares about what type of future it
is.

`StateMachineState` has the `future` field, which holds the 3
(currently) possible types of futures:
- sleep
- wait for ledger commit
- async operation / external operation

Move the starting of all futures triggered by actions into
`ActionFutureExecutor`.
2020-07-14 08:04:52 +01:00
Chris Rankin
e684cfd1e6
NOTICK: Avoid configuring more tasks in the deterministic modules. (#6452) 2020-07-13 10:33:23 +01:00
Dan Newton
52240dc3d1
Merge pull request #6451 from corda/dan/os-4.5-to-4.6-merge-2020-07-08
NOTICK OS 4.5 to 4.6 merge 2020-07-08
2020-07-09 14:02:22 +01:00
LankyDan
8b231dc936 NOTICK Suppress detekt warning on StaffedFlowHospital 2020-07-08 16:18:16 +01:00
LankyDan
b6d649634f ENT-5196 handle errors during flow initialisation (#6378)
Update flow error handling tests after merging from earlier releases
2020-07-08 16:02:17 +01:00
LankyDan
b05c0f0cc1 ENT-5196 handle errors during flow initialisation (#6378)
Changes to `StaffedFlowHospital` after merging from earlier releases.
2020-07-08 14:43:24 +01:00
LankyDan
2204f44332 ENT-5196 handle errors during flow initialisation (#6378)
Changes to `TopLevelTransition` after merging from earlier releases.

When a flow is kept for observation and its checkpoint is saved as
HOSPITALIZED in the database, we must acknowledge the session init and
flow start events so that they are not replayed on node startup.

Otherwise the same flow will be ran twice when the node is restarted,
one from the checkpoint and one from artemis.
2020-07-08 14:41:29 +01:00
Chris Rankin
72938fdf38
CORDA-3892: Upgrade to Gradle 5.6.4 again, with build fixes. (#6448) 2020-07-08 11:34:25 +01:00
LankyDan
fdae04fc28 Merge branch 'release/os/4.5' into dan/os-4.5-to-4.6-merge-2020-07-08 2020-07-08 10:44:47 +01:00
Chris Rankin
16eb9dfc08
NOTICK: Fix some Gradle technical debt. (#6430) 2020-07-07 09:08:58 +01:00
Kyriakos Tharrouniatis
b619356bff
Reduce exception_message and stack_trace lengths in table node_flow_exceptions (#6432)
Reduce exception_message and stack_trace lengths in table node_flow_exceptions from 4000 to 2000 to fix Oracle failing with: 'ORA-00910: specified length too long for its datatype'
2020-07-07 09:07:01 +01:00
Dan Newton
9a8ae0fd32
CORDA-3841 Update session init flow error handling tests (#6431)
These tests were removed after doing a merge from 4.4. They needed
updating after the changes from 4.4 anyway. These have been included in
this change.

Also fix kill flow tests and send initial tests.
2020-07-07 08:47:09 +01:00
Dan Newton
a1e1bf4e6d
CORDA-3848 Uncaught exception hospitalises flow (#6377)
When an uncaught exception propagates all the way to the flow exception
handler, the flow will be forced into observation/hospitalised.

The updating of the checkpoints status is done on a separate thread as
the fiber cannot be relied on anymore. The new thread is needed to allow
database transaction to be created and committed. Failures to the status
update will be rescheduled to ensure that this information is eventually
reflected in the database.
2020-07-06 22:43:48 +01:00
Ryan Fowler
0d5bed5243
ENT-5131: Avoid NPE by throwing a catchable exception when openAttachment fails. (#6408) 2020-07-06 11:42:36 +01:00
Ross Nicoll
6aa19723e6
INFRA-417 Improve driver DSL test stability (#6415)
* Move log messages that are not useful in typical usage from info to debug level to reduce log spam.
* Add node startup check before attempting to connect.
2020-07-03 20:42:29 +01:00
Dan Newton
6bc2c79e23
NOTICK NodeBasedTest take in cordapps (#6424)
In enterprise, `AuthDBTests` picked up a schema from a unit test and
included it in the cordapp it builds. This schema does not have a
migration and therefore fails the integration tests.

`NodeBasedTest` now lets cordapps to be defined and passed in to avoid
this issue. It defaults to making a cordapp from the tests base
directory if none are provided.
2020-07-02 16:14:51 +01:00
Denis Rekalov
adc0879e8e
CORDA-3867: Add tests for AMQ_VALIDATED_USER (#6418)
* CORDA-3867: Add tests for AMQ_VALIDATED_USER

* CORDA-3867: detekt
2020-07-02 09:20:23 +01:00
Ross Nicoll
9f12e6bbc5
INFRA-433 Rebuild node config parsing tests (#6423)
Replace node configuration parsing tests with lighter weight equivalents which just parse the configuration rather than starting a full node.
2020-07-01 22:47:09 +01:00
LankyDan
c06830d851 Merge branch 'release/os/4.4' into dan/os-4.4-to-4.5-merge-2020-07-01
# Conflicts:
#	core/src/main/kotlin/net/corda/core/node/ServiceHub.kt
#	node/src/integration-test-slow/kotlin/net/corda/node/services/statemachine/StatemachineGeneralErrorHandlingTest.kt
#	node/src/integration-test-slow/kotlin/net/corda/node/services/statemachine/StatemachineKillFlowErrorHandlingTest.kt
#	node/src/integration-test/kotlin/net/corda/node/flows/FlowEntityManagerTest.kt
#	node/src/main/kotlin/net/corda/node/internal/AbstractNode.kt
#	node/src/main/kotlin/net/corda/node/services/statemachine/TransitionExecutorImpl.kt
#	node/src/main/kotlin/net/corda/node/services/statemachine/interceptors/HospitalisingInterceptor.kt
2020-07-01 17:32:36 +01:00
Kyriakos Tharrouniatis
5499e2c050
ENT-5384 Rename MAX_SQL_IN_CLAUSE_SET (#6414)
Rename constant to `DEFAULT_SOFT_LOCKING_SQL_IN_CLAUSE_SIZE`
2020-07-01 09:31:12 +01:00
Dan Newton
efd633c7b9 CORDA-3722 withEntityManager can rollback its session (#6187)
* CORDA-3722 withEntityManager can rollback its session

Improve the handling of database transactions when using
`withEntityManager` inside a flow.

Extra changes have been included to improve the safety and
correctness of Corda around handling database transactions.

This focuses on allowing flows to catch errors that occur inside an
entity manager and handle them accordingly.

Errors can be caught in two places:

- Inside `withEntityManager`
- Outside `withEntityManager`

Further changes have been included to ensure that transactions are
rolled back correctly.

Errors caught inside `withEntityManager` require the flow to manually
`flush` the current session (the entity manager's individual session).
By manually flushing the session, a `try-catch` block can be placed
around the `flush` call, allowing possible exceptions to be caught.

Once an error is thrown from a call to `flush`, it is no longer possible
to use the same entity manager to trigger any database operations. The
only possible option is to rollback the changes from that session.
The flow can continue executing updates within the same session but they
will never be committed. What happens in this situation should be handled
by the flow. Explicitly restricting the scenario requires a lot of effort
and code. Instead, we should rely on the developer to control complex
workflows.

To continue updating the database after an error like this occurs, a new
`withEntityManager` block should be used (after catching the previous
error).

Exceptions can be caught around `withEntityManager` blocks. This allows
errors to be handled in the same way as stated above, except the need to
manually `flush` the session is removed. `withEntityManager` will
automatically `flush` a session if it has not been marked for rollback
due to an earlier error.

A `try-catch` can then be placed around the whole of the
`withEntityManager` block, allowing the error to be caught while not
committing any changes to the underlying database transaction.

To make `withEntityManager` blocks work like mini database transactions,
save points have been utilised. A new savepoint is created when opening
a `withEntityManager` block (along with a new session). It is then used
as a reference point to rollback to if the session errors and needs to
roll back. The savepoint is then released (independently from
completing successfully or failing).

Using save points means, that either all the statements inside the
entity manager are executed, or none of them are.

- A new session is created every time an entity manager is requested,
but this does not replace the flow's main underlying database session.
- `CordaPersistence.transaction` can now determine whether it needs
to execute its extra error handling code. This is needed to allow errors
escape `withEntityManager` blocks while allowing some of our exception
handling around subscribers (in `NodeVaultService`) to continue to work.
2020-06-30 11:54:16 +01:00
Dan Newton
f6b5737277
ENT-5196 handle errors during flow initialisation (#6378)
## Summary

This change deals with multiple issues:

* Errors that occur during flow initialisation.

* Errors that occur when handling the outcome of an existing flow error.

* Failures to rollback and close a database transaction when an error
occurs in `TransitionExecutorImpl`.

* Removal of create and commit transaction actions around retrying a flow.

## Errors that occur during flow initialisation

Flow initialisation has been moved into the try/catch that exists inside
`FlowStateMachineImpl.run`. This means if an error is thrown all the way
out of `initialiseFlow` (which should rarely happen) it will be caught 
and move into a flow's standard error handling path. The flow should 
then properly terminate.

`Event.Error` was changed to make the choice to rollback be optional. 
Errors during flow initialisation cause the flow to not have a open 
database transaction. Therefore there is no need to rollback.

## Errors that occur when handling the outcome of an existing flow error

When an error occurs a flow goes to the flow hospital and is given an 
outcome event to address the original error. If the transition that was 
processing the error outcome event (`StartErrorPropagation` and
`RetryFlowFromSafePoint`) has an error then the flow aborts and
nothing happens. This means that the flow is left in a runnable state.

To resolve this, we now retry the original error outcome event whenever 
another error occurs doing so.

This is done by adding a new staff member that looks for 
`ErrorStateTransitionException` thrown in the error code path of 
`TransitionExecutorImpl`. It then takes the last outcome for that flow 
and schedules it to run again. This scheduling runs with a backoff.

This means that a flow will continually retry the original error outcome
event until it completes it successfully.

## Failures to rollback and close a database transaction when an error occurs in `TransitionExecutorImpl`
   
Rolling back and closing the database transaction inside of 
`TransitionExecutorImpl` is now done inside individual try/catch blocks
as this should not prevent the flow from continuing.

## Removal of create and commit transaction actions around retrying a flow

The database commit that occurs after retrying a flow can fail which 
required some custom code just for that event to prevent inconsistent 
behaviour. The transaction was only needed for reading checkpoints from 
the database, therefore the transaction was moved into 
`retryFlowFromSafePoint` instead and the commit removed.

If we need to commit data inside of `retryFlowFromSafePoint` in the 
future, a commit should be added directly to `retryFlowFromSafePoint`. 
The commit should occur before the flow is started on a new fiber.
2020-06-30 11:50:42 +01:00