// In theory, if the migrator dies, you should be able to call this
// again (using the same configuration service!) to resume.
// XXX: Remember how far we got through a copy or cleanup pass.
public async Task MigrateAsync(TableRequestOptions requestOptions = null, OperationContext operationContext = null)
{
MTableConfiguration config;
base.configService.Subscribe(FixedSubscriber <MTableConfiguration> .Instance, out config).Dispose();
// XXX: Ideally we'd lock out other masters somehow.
StateSwitch:
switch (config.state)
{
case TableClientState.USE_OLD_HIDE_METADATA:
if (IsBugEnabled(MTableOptionalBug.MigrateSkipPreferOld))
{
goto case TableClientState.PREFER_OLD;
}
config = new MTableConfiguration(TableClientState.PREFER_OLD);
await configService.PushConfigurationAsync(config);
goto StateSwitch;
case TableClientState.PREFER_OLD:
if (IsBugEnabled(MTableOptionalBug.InsertBehindMigrator))
{
goto case TableClientState.PREFER_NEW;
}
config = new MTableConfiguration(TableClientState.PREFER_NEW);
await configService.PushConfigurationAsync(config);
goto StateSwitch;
case TableClientState.PREFER_NEW:
await CopyAsync(requestOptions, operationContext);
if (IsBugEnabled(MTableOptionalBug.MigrateSkipUseNewWithTombstones))
{
goto case TableClientState.USE_NEW_WITH_TOMBSTONES;
}
config = new MTableConfiguration(TableClientState.USE_NEW_WITH_TOMBSTONES);
await configService.PushConfigurationAsync(config);
goto StateSwitch;
case TableClientState.USE_NEW_WITH_TOMBSTONES:
config = new MTableConfiguration(TableClientState.USE_NEW_HIDE_METADATA);
await configService.PushConfigurationAsync(config);
goto StateSwitch;
case TableClientState.USE_NEW_HIDE_METADATA:
await CleanupAsync(requestOptions, operationContext);
break;
}
}
async Task ApplyConfigurationAsync(MTableConfiguration newConfig)
{
using (await LockAsyncBuggable())
{
PrimaryKey continuationKey = InternalGetContinuationPrimaryKey();
// ExecuteQueryStreamedAsync validated that mtableQuery has no select or top.
TableQuery <MTableEntity> newTableContinuationQuery =
(continuationKey == null) ? null : new TableQuery <MTableEntity>
{
// As in ExecuteQueryAtomicAsync, we have to retrieve all
// potential shadowing rows.
// XXX: This pays even a bigger penalty for not keeping
// conditions on the primary key. But if we were to simply
// keep all such conditions, there's a potential to add
// more and more continuation filter conditions due to
// layering of IChainTable2s, which would lead to some extra
// overhead and push us closer to the limit on number of
// comparisons. Either try to parse for this or change
// ExecuteQueryStreamedAsync to always take a continuation
// primary key?
FilterString =
outer.IsBugEnabled(MTableOptionalBug.QueryStreamedFilterShadowing)
? ChainTableUtils.CombineFilters(
ChainTableUtils.GenerateContinuationFilterCondition(continuationKey),
TableOperators.And,
mtableQuery.FilterString // Could be empty.
)
: ChainTableUtils.GenerateContinuationFilterCondition(continuationKey),
};
bool justStartedNewStream = false;
// Actually, if the query started in state
// USE_OLD_HIDE_METADATA, it is API-compliant to continue
// returning data from the old table until the migrator starts
// deleting it, at which point we switch to the new table. But
// some callers may benefit from fresher data, even if it is
// never guaranteed, so we go ahead and start the new stream.
// XXX: Is this the right decision?
if (newConfig.state > TableClientState.USE_OLD_HIDE_METADATA &&
currentConfig.state <= TableClientState.USE_OLD_HIDE_METADATA &&
newTableContinuationQuery != null)
{
newTableStream = await outer.newTable.ExecuteQueryStreamedAsync(newTableContinuationQuery, requestOptions, operationContext);
newTableNext = await newTableStream.ReadRowAsync();
justStartedNewStream = true;
}
if (newConfig.state >= TableClientState.USE_NEW_HIDE_METADATA &&
currentConfig.state < TableClientState.USE_NEW_HIDE_METADATA)
{
oldTableStream.Dispose();
oldTableStream = null;
oldTableNext = null; // Stop DetermineNextSide from trying to read the old stream.
if (!outer.IsBugEnabled(MTableOptionalBug.QueryStreamedBackUpNewStream) &&
newTableContinuationQuery != null && !justStartedNewStream)
{
// The new stream could have gotten ahead of the old
// stream if rows had not yet been migrated. This
// was OK as long as we still planned to read those
// rows from the old stream, but now we have to back
// up the new stream to where the old stream was.
newTableStream.Dispose();
newTableStream = await outer.newTable.ExecuteQueryStreamedAsync(newTableContinuationQuery, requestOptions, operationContext);
newTableNext = await newTableStream.ReadRowAsync();
}
}
if (!outer.IsBugEnabled(MTableOptionalBug.QueryStreamedSaveNewConfig))
{
currentConfig = newConfig;
}
}
}
async Task <IList <TableResult> > ExecuteBatchOnNewTableAsync(MTableConfiguration config,
TableBatchOperation batch, TableRequestOptions requestOptions, OperationContext operationContext)
{
string partitionKey = ChainTableUtils.GetBatchPartitionKey(batch);
await EnsurePartitionSwitchedAsync(partitionKey, requestOptions, operationContext);
if (config.state <= TableClientState.PREFER_NEW)
{
await EnsureAffectedRowsMigratedAsync(batch, requestOptions, operationContext);
}
Attempt:
// Batch on new table.
var query = GenerateQueryForAffectedRows(batch);
IList <MTableEntity> newRows = await newTable.ExecuteQueryAtomicAsync(query, requestOptions, operationContext);
Dictionary <string, MTableEntity> newDict = newRows.ToDictionary(ent => ent.RowKey);
// NOTE! At this point, the read has not yet been annotated. It is annotated below.
var newBatch = new TableBatchOperation();
var inputToNewTableIndexMapping = new List <int?>();
for (int i = 0; i < batch.Count; i++)
{
TableOperation op = batch[i];
ITableEntity passedEntity = op.GetEntity();
MTableEntity existingEntity = newDict.GetValueOrDefault(passedEntity.RowKey);
TableOperation newOp = null;
HttpStatusCode?errorCode = null;
TranslateOperationForNewTable(
op, existingEntity, config.state <= TableClientState.USE_NEW_WITH_TOMBSTONES,
ref newOp, ref errorCode);
if (errorCode != null)
{
Debug.Assert(newOp == null);
await monitor.AnnotateLastBackendCallAsync(wasLinearizationPoint : true);
throw ChainTableUtils.GenerateBatchException(errorCode.Value, i);
}
if (newOp != null)
{
inputToNewTableIndexMapping.Add(newBatch.Count);
newBatch.Add(newOp);
}
else
{
inputToNewTableIndexMapping.Add(null);
}
}
await monitor.AnnotateLastBackendCallAsync();
IList <TableResult> newResults;
try
{
newResults = await newTable.ExecuteBatchAsync(newBatch, requestOptions, operationContext);
}
catch (ChainTableBatchException)
{
// XXX: Try to distinguish expected concurrency exceptions from unexpected exceptions?
await monitor.AnnotateLastBackendCallAsync();
goto Attempt;
}
// We made it!
var results = new List <TableResult>();
for (int i = 0; i < batch.Count; i++)
{
ITableEntity passedEntity = batch[i].GetEntity();
int? newTableIndex = inputToNewTableIndexMapping[i];
string newETag =
(IsBugEnabled(MTableOptionalBug.TombstoneOutputETag)
? newTableIndex != null
: batch[i].GetOperationType() == TableOperationType.Delete)
? null : newResults[newTableIndex.Value].Etag;
if (newETag != null)
{
passedEntity.ETag = newETag;
}
results.Add(new TableResult
{
HttpStatusCode = (int)(
(batch[i].GetOperationType() == TableOperationType.Insert) ? HttpStatusCode.Created : HttpStatusCode.NoContent),
Etag = newETag,
Result = passedEntity,
});
}
await monitor.AnnotateLastBackendCallAsync(wasLinearizationPoint : true, successfulBatchResult : results);
return(results);
}
