/// <summary>
/// Arguments used to create a point mapping.
/// </summary>
/// <param name="point">Point value being mapped.</param>
/// <param name="shard">Shard used as the mapping target.</param>
/// <param name="status">Status of the mapping.</param>
public PointMappingCreationInfo(TKey point, Shard shard, MappingStatus status)
{
ExceptionUtils.DisallowNullArgument(shard, "shard");
this.Value = point;
this.Shard = shard;
this.Status = status;
this.Key = new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), point);
}
/// <summary>
/// Looks up the key value and returns the corresponding mapping.
/// </summary>
/// <typeparam name="TMapping">Mapping type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="key">Input key value.</param>
/// <param name="useCache">Whether to use cache for lookups.</param>
/// <param name="constructMapping">Delegate to construct a mapping object.</param>
/// <param name="errorCategory">Category under which errors must be thrown.</param>
/// <returns>Mapping that contains the key value.</returns>
protected TMapping Lookup <TMapping, TKey>(
TKey key,
bool useCache,
Func <ShardMapManager, ShardMap, IStoreMapping, TMapping> constructMapping,
ShardManagementErrorCategory errorCategory)
where TMapping : class, IShardProvider
{
ShardKey sk = new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), key);
if (useCache)
{
ICacheStoreMapping cachedMapping = this.Manager.Cache.LookupMappingByKey(this.ShardMap.StoreShardMap, sk);
if (cachedMapping != null)
{
return(constructMapping(this.Manager, this.ShardMap, cachedMapping.Mapping));
}
}
// Cache-miss, find mapping for given key in GSM.
TMapping m = null;
IStoreResults gsmResult;
Stopwatch stopwatch = Stopwatch.StartNew();
using (IStoreOperationGlobal op = this.Manager.StoreOperationFactory.CreateFindMappingByKeyGlobalOperation(
this.Manager,
"Lookup",
this.ShardMap.StoreShardMap,
sk,
CacheStoreMappingUpdatePolicy.OverwriteExisting,
errorCategory,
true,
false))
{
gsmResult = op.Do();
}
stopwatch.Stop();
Tracer.TraceVerbose(
TraceSourceConstants.ComponentNames.BaseShardMapper,
"Lookup",
"Lookup key from GSM complete; Key type : {0}; Result: {1}; Duration: {2}",
typeof(TKey),
gsmResult.Result,
stopwatch.Elapsed);
// If we could not locate the mapping, we return null and do nothing here.
if (gsmResult.Result != StoreResult.MappingNotFoundForKey)
{
return(gsmResult.StoreMappings.Select(sm => constructMapping(this.Manager, this.ShardMap, sm)).Single());
}
return(m);
}
/// <summary>
/// Constructs range based on its low boundary value. The low boundary value is
/// set to the one specified in <paramref name="low"/> while the
/// high boundary value is set to maximum possible value i.e. +infinity.
/// </summary>
/// <param name="low">Low boundary value (inclusive).</param>
public Range(TKey low)
{
ShardKeyType k = ShardKey.ShardKeyTypeFromType(typeof(TKey));
_r = new ShardRange(
new ShardKey(k, low),
new ShardKey(k, null));
this.Low = low;
this.HighIsMax = true;
}
/// <summary>
/// Constructs range based on its low and high boundary values.
/// </summary>
/// <param name="low">Low boundary value (inclusive).</param>
/// <param name="high">High boundary value (exclusive).</param>
public Range(TKey low, TKey high)
{
ShardKeyType k = ShardKey.ShardKeyTypeFromType(typeof(TKey));
_r = new ShardRange(
new ShardKey(k, low),
new ShardKey(k, high));
this.Low = low;
this.High = high;
}
public RangeMappingCreationInfo(Range <TKey> value, Shard shard, MappingStatus status)
{
ExceptionUtils.DisallowNullArgument(value, "value");
ExceptionUtils.DisallowNullArgument(shard, "shard");
this.Value = value;
this.Shard = shard;
this.Status = status;
this.Range = new ShardRange(
new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), value.Low),
new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), value.HighIsMax ? null : (object)value.High));
}
/// <summary>
/// Gets all the mappings that exist within given range.
/// </summary>
/// <param name="range">Optional range value, if null, we cover everything.</param>
/// <param name="shard">Optional shard parameter, if null, we cover all shards.</param>
/// <param name="constructMapping">Delegate to construct a mapping object.</param>
/// <param name="errorCategory">Category under which errors will be posted.</param>
/// <param name="mappingType">Name of mapping type.</param>
/// <returns>Read-only collection of mappings that overlap with given range.</returns>
protected IReadOnlyList <TMapping> GetMappingsForRange <TMapping, TKey>(
Range <TKey> range,
Shard shard,
Func <ShardMapManager, ShardMap, IStoreMapping, TMapping> constructMapping,
ShardManagementErrorCategory errorCategory,
string mappingType)
where TMapping : class
{
ShardRange sr = null;
if (shard != null)
{
ExceptionUtils.EnsureShardBelongsToShardMap(
this.Manager,
this.ShardMap,
shard,
"GetMappings",
mappingType);
}
if (range != null)
{
sr = new ShardRange(
new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), range.Low),
new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), range.HighIsMax ? null : (object)range.High));
}
IStoreResults result;
using (IStoreOperationGlobal op = this.Manager.StoreOperationFactory.CreateGetMappingsByRangeGlobalOperation(
this.Manager,
"GetMappingsForRange",
this.ShardMap.StoreShardMap,
shard != null ? shard.StoreShard : null,
sr,
errorCategory,
true, // Always cache.
false))
{
result = op.Do();
}
return(result.StoreMappings
.Select(sm => constructMapping(this.Manager, this.ShardMap, sm))
.ToList()
.AsReadOnly());
}
/// <summary>
/// Internal constructor used for deserialization from store representation of
/// the mapping object.
/// </summary>
/// <param name="manager">Owning ShardMapManager.</param>
/// <param name="shardMap">Owning shard map.</param>
/// <param name="mapping">Storage representation of the mapping.</param>
internal PointMapping(
ShardMapManager manager,
ShardMap shardMap,
IStoreMapping mapping)
{
Debug.Assert(manager != null);
this.Manager = manager;
Debug.Assert(mapping != null);
Debug.Assert(mapping.ShardMapId != default(Guid));
Debug.Assert(mapping.StoreShard.ShardMapId != default(Guid));
this.StoreMapping = mapping;
_shard = new Shard(this.Manager, shardMap, mapping.StoreShard);
this.Key = ShardKey.FromRawValue(ShardKey.ShardKeyTypeFromType(typeof(TKey)), mapping.MinValue);
this.Value = (TKey)this.Key.Value;
}
/// <summary>
/// Creates a list based <see cref="ListShardMap{TKey}"/>.
/// </summary>
/// <typeparam name="TKey">Type of keys.</typeparam>
/// <param name="shardMapName">Name of shard map.</param>
/// <returns>List shard map with the specified name.</returns>
public ListShardMap <TKey> CreateListShardMap <TKey>(string shardMapName)
{
ShardMapManager.ValidateShardMapName(shardMapName);
using (ActivityIdScope activityIdScope = new ActivityIdScope(Guid.NewGuid()))
{
DefaultStoreShardMap dssm = new DefaultStoreShardMap(
Guid.NewGuid(),
shardMapName,
ShardMapType.List,
ShardKey.ShardKeyTypeFromType(typeof(TKey)));
ListShardMap <TKey> listShardMap = new ListShardMap <TKey>(this, dssm);
Tracer.TraceInfo(
TraceSourceConstants.ComponentNames.ShardMapManager,
"CreateListShardMap",
"Start; ShardMap: {0}",
shardMapName);
Stopwatch stopwatch = Stopwatch.StartNew();
this.AddShardMapToStore("CreateListShardMap", dssm);
stopwatch.Stop();
Tracer.TraceInfo(
TraceSourceConstants.ComponentNames.ShardMapManager,
"CreateListShardMap",
"Added ShardMap to Store; ShardMap: {0} Duration: {1}",
shardMapName,
stopwatch.Elapsed);
Tracer.TraceInfo(
TraceSourceConstants.ComponentNames.ShardMapManager,
"CreateListShardMap",
"Complete; ShardMap: {0} Duration: {1}",
shardMapName,
stopwatch.Elapsed);
return(listShardMap);
}
}
/// <summary>
/// Internal constructor used for deserialization from store representation of
/// the mapping object.
/// </summary>
/// <param name="manager">Owning ShardMapManager.</param>
/// <param name="shardMap">Owning shard map.</param>
/// <param name="mapping">Storage representation of the mapping.</param>
internal RangeMapping(
ShardMapManager manager,
ShardMap shardMap,
IStoreMapping mapping)
{
Debug.Assert(manager != null);
this.Manager = manager;
Debug.Assert(mapping != null);
Debug.Assert(mapping.ShardMapId != default(Guid));
Debug.Assert(mapping.StoreShard.ShardMapId != default(Guid));
this.StoreMapping = mapping;
_shard = new Shard(this.Manager, shardMap, mapping.StoreShard);
this.Range = new ShardRange(
ShardKey.FromRawValue(ShardKey.ShardKeyTypeFromType(typeof(TKey)), mapping.MinValue),
ShardKey.FromRawValue(ShardKey.ShardKeyTypeFromType(typeof(TKey)), mapping.MaxValue));
this.Value = this.Range.High.IsMax ?
new Range <TKey>(this.Range.Low.GetValue <TKey>()) :
new Range <TKey>(this.Range.Low.GetValue <TKey>(), this.Range.High.GetValue <TKey>());
}
/// <summary>
/// Splits the given mapping into 2 at the given key. The new mappings point to the same shard
/// as the existing mapping.
/// </summary>
/// <param name="existingMapping">Given existing mapping.</param>
/// <param name="splitAt">Split point.</param>
/// <param name="lockOwnerId">Lock owner id of this mapping</param>
/// <returns>Read-only collection of 2 new mappings thus created.</returns>
internal IReadOnlyList <RangeMapping <TKey> > Split(RangeMapping <TKey> existingMapping, TKey splitAt, Guid lockOwnerId)
{
this.EnsureMappingBelongsToShardMap <RangeMapping <TKey> >(
existingMapping,
"Split",
"existingMapping");
ShardKey shardKey = new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), splitAt);
if (!existingMapping.Range.Contains(shardKey) ||
existingMapping.Range.Low == shardKey ||
existingMapping.Range.High == shardKey)
{
throw new ArgumentOutOfRangeException(
"splitAt",
Errors._ShardMapping_SplitPointOutOfRange);
}
IStoreShard newShard = new DefaultStoreShard(
existingMapping.Shard.StoreShard.Id,
Guid.NewGuid(),
existingMapping.ShardMapId,
existingMapping.Shard.StoreShard.Location,
existingMapping.Shard.StoreShard.Status);
IStoreMapping mappingToRemove = new DefaultStoreMapping(
existingMapping.StoreMapping.Id,
existingMapping.StoreMapping.ShardMapId,
newShard,
existingMapping.StoreMapping.MinValue,
existingMapping.StoreMapping.MaxValue,
existingMapping.StoreMapping.Status,
existingMapping.StoreMapping.LockOwnerId);
IStoreMapping[] mappingsToAdd = new IStoreMapping[2]
{
new DefaultStoreMapping(
Guid.NewGuid(),
newShard.ShardMapId,
newShard,
existingMapping.Range.Low.RawValue,
shardKey.RawValue,
(int)existingMapping.Status,
lockOwnerId),
new DefaultStoreMapping(
Guid.NewGuid(),
newShard.ShardMapId,
newShard,
shardKey.RawValue,
existingMapping.Range.High.RawValue,
(int)existingMapping.Status,
lockOwnerId)
};
using (IStoreOperation op = this.Manager.StoreOperationFactory.CreateReplaceMappingsOperation(
this.Manager,
StoreOperationCode.SplitMapping,
this.ShardMap.StoreShardMap,
new[] { new Tuple <IStoreMapping, Guid>(mappingToRemove, lockOwnerId) },
mappingsToAdd.Select(mappingToAdd => new Tuple <IStoreMapping, Guid>(mappingToAdd, lockOwnerId)).ToArray()))
{
op.Do();
}
return(mappingsToAdd
.Select(m => new RangeMapping <TKey>(this.Manager, this.ShardMap, m))
.ToList()
.AsReadOnly());
}
/// <summary>
/// Given a key value, asynchronously obtains a SqlConnection to the shard in the mapping
/// that contains the key value.
/// </summary>
/// <typeparam name="TMapping">Mapping type.</typeparam>
/// <typeparam name="TKey">Key type.</typeparam>
/// <param name="key">Input key value.</param>
/// <param name="constructMapping">Delegate to construct a mapping object.</param>
/// <param name="errorCategory">Error category.</param>
/// <param name="connectionString">
/// Connection string with credential information, the DataSource and Database are
/// obtained from the results of the lookup operation for key.
/// </param>
/// <param name="options">Options for validation operations to perform on opened connection.</param>
/// <returns>A task encapsulating an opened SqlConnection as the result.</returns>
protected async Task <SqlConnection> OpenConnectionForKeyAsync <TMapping, TKey>(
TKey key,
Func <ShardMapManager, ShardMap, IStoreMapping, TMapping> constructMapping,
ShardManagementErrorCategory errorCategory,
string connectionString,
ConnectionOptions options = ConnectionOptions.Validate) where TMapping : class, IShardProvider
{
ShardKey sk = new ShardKey(ShardKey.ShardKeyTypeFromType(typeof(TKey)), key);
// Try to find the mapping within the cache.
ICacheStoreMapping csm = this.Manager.Cache.LookupMappingByKey(this.ShardMap.StoreShardMap, sk);
IStoreMapping sm;
if (csm != null)
{
sm = csm.Mapping;
}
else
{
sm = await this.LookupMappingForOpenConnectionForKeyAsync(
sk,
CacheStoreMappingUpdatePolicy.OverwriteExisting,
errorCategory).ConfigureAwait(false);
}
SqlConnection result;
bool lookupMappingOnEx = false;
CacheStoreMappingUpdatePolicy cacheUpdatePolicyOnEx = CacheStoreMappingUpdatePolicy.OverwriteExisting;
try
{
// Initially attempt to connect based on lookup results from either cache or GSM.
result = await this.ShardMap.OpenConnectionAsync(
constructMapping(this.Manager, this.ShardMap, sm),
connectionString,
options).ConfigureAwait(false);
csm.ResetTimeToLiveIfNecessary();
return(result);
}
catch (ShardManagementException smme)
{
// If we hit a validation failure due to stale version of mapping, we will perform one more attempt.
if (((options & ConnectionOptions.Validate) == ConnectionOptions.Validate) &&
smme.ErrorCategory == ShardManagementErrorCategory.Validation &&
smme.ErrorCode == ShardManagementErrorCode.MappingDoesNotExist)
{
// Assumption here is that this time the attempt should succeed since the cache entry
// has already been either evicted, or updated based on latest data from the server.
lookupMappingOnEx = true;
cacheUpdatePolicyOnEx = CacheStoreMappingUpdatePolicy.OverwriteExisting;
}
else
{
// The error was not due to validation but something else e.g.
// 1) Shard map does not exist
// 2) Mapping could not be found.
throw;
}
}
catch (SqlException)
{
// We failed to connect. If we were trying to connect from an entry in cache and mapping expired in cache.
if (csm != null && csm.HasTimeToLiveExpired())
{
using (IdLock _idLock = new IdLock(csm.Mapping.StoreShard.Id))
{
// Similar to DCL pattern, we need to refresh the mapping again to see if we still need to go to the store
// to lookup the mapping after acquiring the shard lock. It might be the case that a fresh version has already
// been obtained by some other thread.
csm = this.Manager.Cache.LookupMappingByKey(this.ShardMap.StoreShardMap, sk);
// Only go to store if the mapping is stale even after refresh.
if (csm == null || csm.HasTimeToLiveExpired())
{
// Refresh the mapping in cache. And try to open the connection after refresh.
lookupMappingOnEx = true;
cacheUpdatePolicyOnEx = CacheStoreMappingUpdatePolicy.UpdateTimeToLive;
}
else
{
sm = csm.Mapping;
}
}
}
else
{
// Either:
// 1) The mapping is still within the TTL. No refresh.
// 2) Mapping was not in cache, we originally did a lookup for mapping in GSM and even then could not connect.
throw;
}
}
if (lookupMappingOnEx)
{
sm = await this.LookupMappingForOpenConnectionForKeyAsync(
sk,
cacheUpdatePolicyOnEx,
errorCategory).ConfigureAwait(false);
}
// One last attempt to open the connection after a cache refresh
result = await this.ShardMap.OpenConnectionAsync(
constructMapping(this.Manager, this.ShardMap, sm),
connectionString,
options).ConfigureAwait(false);
// Reset TTL on successful connection.
csm.ResetTimeToLiveIfNecessary();
return(result);
}
