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Refactored SaveObservation implementation to be more succinct
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Nate Malubay committed Jan 25, 2022
1 parent 21b92df commit e16efcf
Showing 1 changed file with 53 additions and 73 deletions.
126 changes: 53 additions & 73 deletions src/lib/Microsoft.Health.Fhir.R4.Ingest/Service/R4FhirImportService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,90 +72,70 @@ public virtual async Task<string> SaveObservationAsync(ILookupTemplate<IFhirTemp
existingObservation = await GetObservationFromServerAsync(identifier).ConfigureAwait(false);
}

Model.Observation result = null;
ResourceOperation operationType = ResourceOperation.NoOperation;
var policyResult = await Policy<(Model.Observation observation, ResourceOperation operationType)>
.Handle<FhirOperationException>(ex => ex.Status == System.Net.HttpStatusCode.Conflict || ex.Status == System.Net.HttpStatusCode.PreconditionFailed)
.RetryAsync(2, async (polyRes, attempt) =>
{
// 409 Conflict or 412 Precondition Failed can occur if the Observation.meta.versionId does not match the update request.
// This can happen if 2 independent processes are updating the same Observation simultaneously.
// or
// The update operation failed because the Observation no longer exists.
// This can happen if a cached Observation was deleted from the FHIR Server.

_logger.LogTrace("A conflict or precondition caused an Observation update to fail. Getting the most recent Observation.");

// Attempt to get the most recent version of the Observation.
existingObservation = await GetObservationFromServerAsync(identifier).ConfigureAwait(false);

// If the Observation no longer exists on the FHIR Server, it was most likely deleted.
if (existingObservation == null)
{
_logger.LogTrace("A cached version of an Observation was deleted. Creating a new Observation.");

// Remove the Observation from the cache (this version no longer exists on the FHIR Server.
_observationCache.Remove(cacheKey);
}
})
.ExecuteAndCaptureAsync(async () =>
{
if (existingObservation == null)
{
var newObservation = GenerateObservation(config, observationGroup, identifier, ids);
return (await _client.CreateAsync(newObservation).ConfigureAwait(false), ResourceOperation.Created);
}

// Merge the new data with the existing Observation.
var mergedObservation = MergeObservation(config, existingObservation, observationGroup);

// Check to see if there are any changes after merging.
if (mergedObservation.IsExactly(existingObservation))
{
// There are no changes to the Observation - Do not update.
return (existingObservation, ResourceOperation.NoOperation);
}

// Update the Observation. Some failures will be handled in the RetryAsync block above.
return (await _client.UpdateAsync(mergedObservation, versionAware: true).ConfigureAwait(false), ResourceOperation.Updated);
}).ConfigureAwait(false);

if (existingObservation == null)
var exception = policyResult.FinalException;

if (exception != null)
{
var newObservation = GenerateObservation(config, observationGroup, identifier, ids);
result = await _client.CreateAsync(newObservation).ConfigureAwait(false);
operationType = ResourceOperation.Created;
throw exception;
}
else
{
var policyResult = await Policy<Model.Observation>
.Handle<FhirOperationException>(ex => ex.Status == System.Net.HttpStatusCode.Conflict || ex.Status == System.Net.HttpStatusCode.PreconditionFailed)
.RetryAsync(2, async (polyRes, attempt) =>
{
// 409 Conflict or 412 Precondition Failed can occur if the Observation.meta.versionId does not match the update request.
// This can happen if 2 independent processes are updating the same Observation simultaneously.
// or
// The update operation failed because the Observation no longer exists.
// This can happen if a cached Observation was deleted from the FHIR Server.

_logger.LogTrace("A conflict or precondition caused an Observation update to fail. Getting the most recent Observation.");

// Attempt to get the most recent version of the Observation.
existingObservation = await GetObservationFromServerAsync(identifier).ConfigureAwait(false);

// If the Observation no longer exists on the FHIR Server, it was most likely deleted.
if (existingObservation == null)
{
_logger.LogTrace("A cached version of an Observation was deleted. Creating a new Observation.");

// Remove the Observation from the cache (this version no longer exists on the FHIR Server.
_observationCache.Remove(cacheKey);

// Create a new Observation.
var newObservation = GenerateObservation(config, observationGroup, identifier, ids);
result = await _client.CreateAsync(newObservation).ConfigureAwait(false);
return;
}
})
.ExecuteAndCaptureAsync(async () =>
{
if (result != null)
{
// If result is not null, this means that a cached Observation was deleted from the FHIR Server.
// The RetryAsync has handled this condition, so no further action is required, return the result.
operationType = ResourceOperation.Created;
return result;
}

// Merge the new data with the existing Observation.
var mergedObservation = MergeObservation(config, existingObservation, observationGroup);

// Check to see if there are any changes after merging.
if (mergedObservation.IsExactly(existingObservation))
{
// There are no changes to the Observation - Do not update.
return existingObservation;
}

// Update the Observation. Some failures will be handled in the RetryAsync block above.
operationType = ResourceOperation.Updated;
return await _client.UpdateAsync(mergedObservation, versionAware: true).ConfigureAwait(false);
}).ConfigureAwait(false);

var exception = policyResult.FinalException;

if (exception != null)
{
throw exception;
}

result = policyResult.Result;
}
var observation = policyResult.Result.observation;

_logger.LogMetric(IomtMetrics.FhirResourceSaved(ResourceType.Observation, operationType), 1);
_logger.LogMetric(IomtMetrics.FhirResourceSaved(ResourceType.Observation, policyResult.Result.operationType), 1);

_observationCache.CreateEntry(cacheKey)
.SetAbsoluteExpiration(DateTimeOffset.UtcNow.AddHours(1))
.SetSize(1)
.SetValue(result)
.SetValue(observation)
.Dispose();

return result.Id;
return observation.Id;
}

public virtual Model.Observation GenerateObservation(ILookupTemplate<IFhirTemplate> config, IObservationGroup grp, Model.Identifier observationId, IDictionary<ResourceType, string> ids)
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