/// <summary>
/// Attempt to get a lock for updating a persiston. Fails if another user has it locked already.
/// Succeeds efficiently if this user already had it locked.
/// </summary>
/// <returns>success flag and error reason code</returns>
public (bool, string) RequestLock(DatonKey datonKey, string version, string sessionKey)
{
//check if already locked by this server
if (Locks.TryGetValue(datonKey, out LockInfo linfo))
{
bool isLockedByMe = linfo.SessionKey == sessionKey;
if (!isLockedByMe)
{
return(false, Constants.ERRCODE_LOCK); //someone else on this server has it locked
}
return(true, null); //this session already has it locked
}
//attempt lock on database
using (var lockdb = GetLockConnection())
{
if (RetroLock.Lock(lockdb, datonKey, version, sessionKey))
{
//success
Locks[datonKey] = new LockInfo {
SessionKey = sessionKey, DatonKey = datonKey, OldVersion = version
};
return(true, null);
}
//failed, so determine why
(string verifiedVersion, _) = RetroLock.GetVersion(lockdb, datonKey);
if (verifiedVersion != version)
{
return(false, Constants.ERRCODE_VERSION); //the most recent version is newer than the version known by the caller
}
return(false, Constants.ERRCODE_LOCK); //someone else on another server has it locked
}
}
/// <summary>
/// Attempt to release a lock
/// </summary>
/// <returns>success flag and new version number (new version only provided if persiston was actually written)</returns>
public (bool, string) ReleaseLock(DatonKey datonKey, string sessionKey)
{
//check if it is possible to unlock
if (Locks.TryGetValue(datonKey, out LockInfo linfo))
{
bool isLockedByMe = linfo.SessionKey == sessionKey;
if (!isLockedByMe)
{
return(false, null); //can't unlock because someone else on this server has it locked
}
}
else
{
return(false, null); //can't unlock because it is not locked by anyone on this server
}
//attempt unlock on database
using (var lockdb = GetLockConnection())
{
(bool unlockOK, string newVersion) = RetroLock.Unlock(lockdb, datonKey, sessionKey, linfo.WasWritten, ServerLifeNumber);
Locks.TryRemove(datonKey, out _); //we forget in memory even if there was a database problem (should not happen)
//propogate change (this is hooked up to code that pushes the change to subscribed sessions)
if (linfo.WasWritten)
{
ChangePropogator?.Invoke(datonKey, newVersion);
}
return(unlockOK, newVersion);
}
}
/// <summary>
/// Get the version of the persiston. This ALWAYS goes to the database so don't call this too much.
/// The result is guaranteed and will assign a version if there was none recorded.
/// </summary>
public string GetVersion(DatonKey datonKey)
{
using (var lockdb = GetLockConnection())
{
(string version, _) = RetroLock.GetVersion(lockdb, datonKey);
return(version);
}
}
/// <summary>
/// Get the state of a daton lock. This only checks the local server, so the daton could be locked even if it returns
/// a value indicating not locked.
/// </summary>
/// <returns>3 values: is locked at all; is locked by the given session; version number when locked</returns>
public (bool, bool, string) GetLockState(DatonKey datonKey, string sessionKey)
{
if (Locks.TryGetValue(datonKey, out LockInfo linfo))
{
bool isLockedByMe = linfo.SessionKey == sessionKey;
return(true, isLockedByMe, linfo.OldVersion);
}
return(false, false, null);
}
/// <summary>
/// Notify the lock system that a daton was written to the database. This does not unlock it, but it changes the behavior when unlocked.
/// </summary>
/// <returns>true if successful</returns>
public bool NotifyDatonWritten(DatonKey datonKey)
{
if (Locks.TryGetValue(datonKey, out LockInfo linfo))
{
linfo.WasWritten = true;
return(true);
}
return(false);
}
/// <summary>
/// Update the touched column for the daton, only if locked by the given session.
/// </summary>
public static void Touch(DbConnection db, DatonKey key, string sessionKey)
{
using (var cmd = db.CreateCommand())
{
cmd.CommandText = "update RetroLock set Touched=@t where DatonKey=@k and LockedBy=@s";
Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
Utils.AddParameterWithValue(cmd, "k", key.ToString());
Utils.AddParameterWithValue(cmd, "s", sessionKey);
cmd.ExecuteNonQuery();
}
}
/// <summary>
/// Get where clause for main table, or null if none
/// </summary>
protected SqlSelectBuilder.Where MainTableWhereClause(TableDef tabledef, DatonKey key)
{
if (key is PersistonKey pkey)
{
return(MainTableWhereClause(tabledef, pkey));
}
if (key is ViewonKey vkey)
{
return(MainTableWhereClause(tabledef, vkey));
}
return(null);
}
public Daton Get(DatonKey key)
{
if (Cache.TryGetValue(key, out Item i))
{
if (key is PersistonKey) //don't keep viewons in cache very long
{
i.LastAccessedUtc = DateTime.UtcNow;
}
return(i.Daton);
}
return(null);
}
/// <summary>
/// Attempt to obtain a lock
/// </summary>
/// <param name="version">the version which was known</param>
/// <param name="sessionKey"></param>
/// <returns>true if successful</returns>
public static bool Lock(DbConnection db, DatonKey key, string version, string sessionKey)
{
//assuming first there is a record, attempt to get the lock by updating it
using (var cmd = db.CreateCommand())
{
cmd.CommandText = "update RetroLock set Touched=@t, LockedBy=@s where DatonKey=@k and DatonVersion=@v and (LockedBy is null or Touched<@old)";
Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
Utils.AddParameterWithValue(cmd, "s", sessionKey);
Utils.AddParameterWithValue(cmd, "k", key.ToString());
Utils.AddParameterWithValue(cmd, "v", version);
Utils.AddParameterWithValue(cmd, "old", DateTime.UtcNow.AddSeconds(-120));
int nrows = cmd.ExecuteNonQuery();
if (nrows == 1)
{
return(true);
}
}
//update touched date: this tells us if the record exists, and ensures it won't be cleaned up during the lock process;
//also unlock it if the lock is too old
//bool recordExists;
//using (var cmd = db.CreateCommand())
//{
// cmd.CommandText = "update RetroLock set LockedBy=(case when Touched<@old then null else LockedBy end), Touched=@t where DatonKey=@k";
// Utils.AddParameterWithValue(cmd, "old", DateTime.UtcNow.AddSeconds(-120));
// Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
// Utils.AddParameterWithValue(cmd, "k", key.ToString());
// int nrows = cmd.ExecuteNonQuery();
// recordExists = nrows == 1;
//}
//reached here, so there was no record; create one with lock
//(this won't occur if everything is working, since reading the version should happen before attempting to lock)
using (var cmd = db.CreateCommand())
{
cmd.CommandText = "insert into RetroLock (DatonKey,DatonVersion,Touched,LockedBy) values(@k,@v,@t,@s)";
Utils.AddParameterWithValue(cmd, "k", key.ToString());
Utils.AddParameterWithValue(cmd, "v", version);
Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
Utils.AddParameterWithValue(cmd, "s", sessionKey);
try
{
cmd.ExecuteNonQuery();
return(true);
}
catch
{
return(false); //another user created the lock record since we queried it above
}
}
}
/// <summary>
/// Determine if any subscription from any client is out of date; that is, if there is a client
/// whose latest version is not the new version provided for the daton key provided.
/// </summary>
public bool IsAnyOutOfDate(DatonKey key, string newVersion)
{
foreach (var cli in Sessions.Values)
{
if (!cli.Subscriptions.TryGetValue(key, out string clientsVersion))
{
continue;
}
if (clientsVersion != newVersion)
{
return(true);
}
}
return(false);
}
/// <summary>
/// Given parsed untyped JSON in full compatible format, construct it into a typed daton
/// </summary>
public static Daton FromCompatibleWireFull(DataDictionary dbdef, JObject jroot)
{
var datonKey = DatonKey.Parse(jroot.Value <string>("key"));
var datondef = dbdef.FindDef(datonKey);
var daton = Utils.ConstructDaton(datondef.Type, datondef);
daton.Key = datonKey;
daton.Version = jroot.Value <string>("version");
if (daton is Viewon viewon && jroot.Value <bool>("isComplete") == false)
{
viewon.IsCompleteLoad = false;
}
var mainRowsNode = jroot[CamelCasify(datondef.MainTableDef.Name)];
if (mainRowsNode == null)
{
return(daton);
}
if (!(mainRowsNode is JArray mainRowsArray))
{
throw new Exception($"{datondef.MainTableDef.Name} node must be an array");
}
if (datondef.MultipleMainRows)
{
var targetListInfo = datondef.Type.GetField(datondef.MainTableDef.Name);
if (targetListInfo == null)
{
throw new Exception($"Expected {datondef.MainTableDef.Name} to be a member of {datondef.Type.Name}");
}
var targetList = Utils.CreateOrGetFieldValue <IList>(daton, targetListInfo) as IList;
ReadCompatibleJsonRowArray(mainRowsArray, datondef.MainTableDef, (IList)targetList);
}
else
{
if (mainRowsArray.Count != 1)
{
throw new Exception($"{datondef.MainTableDef.Name} node must have one element for this daton type");
}
ReadCompatibleJsonRow(mainRowsArray[0] as JObject, datondef.MainTableDef, daton);
}
daton.Recompute(datondef);
return(daton);
}
/// <summary>
/// Get the daton version code and session key holding the lock if any; if the lock row was missing, create it and assign
/// the version
/// </summary>
/// <returns>(version,lockedBy) where lockedBy might be null</returns>
public static (string, string) GetVersion(DbConnection db, DatonKey key)
{
retry:
//read existing row
using (var cmd = db.CreateCommand())
{
cmd.CommandText = "select DatonVersion,LockedBy from RetroLock where DatonKey=@k";
var p = cmd.CreateParameter();
p.ParameterName = "k";
p.Value = key.ToString();
cmd.Parameters.Add(p);
using (var rdr = cmd.ExecuteReader())
{
if (rdr.Read())
{
return(Utils.Read <string>(rdr, 0), Utils.Read <string>(rdr, 1));
}
}
}
//not found, so create it
string version = Guid.NewGuid().ToString();
using (var cmd = db.CreateCommand())
{
try
{
cmd.CommandText = "insert into RetroLock (DatonKey,DatonVersion,Touched) values(@k,@v,@t)";
Utils.AddParameterWithValue(cmd, "k", key.ToString());
Utils.AddParameterWithValue(cmd, "v", version);
Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
cmd.ExecuteNonQuery();
return(version, null);
}
catch
{
//rare failure: another user created the row between when we queried and attempted the insert
Thread.Sleep(1);
goto retry;
}
}
}
/// <summary>
/// Change the subscription state of a daton for a client
/// </summary>
public void ManageSubscribe(string sessionKey, DatonKey datonKey, string version, bool subscribe)
{
if (datonKey.IsNew)
{
throw new Exception("Cannot subscribe to an unsaved persiston");
}
if (!Sessions.TryGetValue(sessionKey, out var ses))
{
return;
}
if (subscribe)
{
ses.Subscriptions[datonKey] = version;
}
else
{
ses.Subscriptions.TryRemove(datonKey, out _);
}
}
/// <summary>
/// Get the list of daton keys with version numbers that were updated by other servers since the given time
/// </summary>
/// <param name="serverLifeNumber">the number for this server; updates from this server are excluded from the query</param>
public static List <(DatonKey, string)> GetRecentUpdatesByOtherServers(DbConnection db, DateTime sinceUtc, int serverLifeNumber)
{
var ret = new List <(DatonKey, string)>();
using (var cmd = db.CreateCommand())
{
cmd.CommandText = $"select DatonKey,DatonVersion from RetroLock where Touched>@t and UpdatedByServer<>@u";
Utils.AddParameterWithValue(cmd, "t", sinceUtc);
Utils.AddParameterWithValue(cmd, "u", serverLifeNumber);
using (var rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
var key = DatonKey.Parse(Utils.Read <string>(rdr, 0));
string version = Utils.Read <string>(rdr, 1);
ret.Add((key, version));
}
}
}
return(ret);
}
/// <summary>
/// Unlock a daton and optionally assign new version; only has an effect if it was locked by the given session
/// </summary>
/// <param name="datonWasWritten">pass true if this unlock is following a write, or false if it is an abandoned lock</param>
/// <returns>success flag and the new version (version only returned if datonWasWritten)</returns>
public static (bool, string) Unlock(DbConnection db, DatonKey key, string sessionKey, bool datonWasWritten, int serverLifeNumber)
{
string version = datonWasWritten ? Guid.NewGuid().ToString() : null;
using (var cmd = db.CreateCommand())
{
string versionsql = datonWasWritten ? ",DatonVersion=@v,UpdatedByServer=@u" : "";
cmd.CommandText = $"update RetroLock set LockedBy=null,Touched=@t{versionsql} where DatonKey=@k and LockedBy=@s";
Utils.AddParameterWithValue(cmd, "t", DateTime.UtcNow);
Utils.AddParameterWithValue(cmd, "k", key.ToString());
Utils.AddParameterWithValue(cmd, "s", sessionKey);
if (datonWasWritten)
{
Utils.AddParameterWithValue(cmd, "v", version);
Utils.AddParameterWithValue(cmd, "u", serverLifeNumber);
}
int nrows = cmd.ExecuteNonQuery();
bool success = nrows == 1;
return(success, version);
}
}
/// <summary>
/// Given parsed untyped JSON in diff format, construct a PersistonDiff
/// </summary>
public static PersistonDiff FromDiff(DataDictionary dbdef, JObject jroot)
{
var datonKey = DatonKey.Parse(jroot.Value <string>("key"));
var datondef = dbdef.FindDef(datonKey);
var diff = new PersistonDiff(datondef, datonKey, jroot.Value <string>("version"));
ReadJsonDiffRowArray(jroot, datondef.MainTableDef, diff.MainTable);
//existing single-main-row diffs might not include the primary key in the main row, so add it here
if (!datondef.MultipleMainRows)
{
var mainDiffRow = diff.MainTable.First();
if (!mainDiffRow.Columns.ContainsKey(datondef.MainTableDef.PrimaryKeyColName))
{
var pkColdef = datondef.MainTableDef.FindCol(datondef.MainTableDef.PrimaryKeyColName);
var pk = Utils.ChangeType(((PersistonKey)datonKey).PrimaryKey, pkColdef.CSType);
mainDiffRow.Columns[datondef.MainTableDef.PrimaryKeyColName] = pk;
}
}
return(diff);
}
/// <summary>
/// Get a daton, from cache or load from database. The reutrn value is a shared instance so the caller may not modify it.
/// For new unsaved persistons with -1 as the key, this will create the instance with default values.
/// </summary>
/// <param name="user">if null, the return value is a shared guaranteed complete daton; if user is provided,
/// the return value may be a clone with some rows removed or columns set to null</param>
/// <param name="forceCheckLatest">if true then checks database to ensure latest version even if it was cached</param>
/// <returns>object with daton, or readable errors</returns>
public async Task <RetroSql.LoadResult> GetDaton(DatonKey key, IUser user, bool forceCheckLatest = false)
{
//new persiston: return now
if (key.IsNew)
{
var datondef2 = DataDictionary.FindDef(key);
Daton newDaton = Utils.Construct(datondef2.Type) as Daton;
Utils.FixTopLevelDefaultsInNewPersiston(datondef2, newDaton);
newDaton.Key = key;
if (datondef2.Initializer != null)
{
await datondef2.Initializer(newDaton);
}
return(new RetroSql.LoadResult {
Daton = newDaton
});
}
//get from cache if possible, and optionally ignore cached version if it is not the latest
string verifiedVersion = null;
Daton daton = DatonCache.Get(key);
if (forceCheckLatest && daton != null)
{
//viewons: always ignore cache; persistons: use cached only if known to be latest
if (daton is Persiston)
{
verifiedVersion = LockManager.GetVersion(key);
if (verifiedVersion != daton.Version)
{
daton = null;
}
}
else
{
daton = null;
}
}
//get from database if needed (and cache it), or abort
var datondef = DataDictionary.FindDef(key);
if (typeof(Persiston).IsAssignableFrom(datondef.Type) && (key is ViewonKey))
{
throw new Exception("Persiston requested but key format is for viewon");
}
if (typeof(Viewon).IsAssignableFrom(datondef.Type) && (key is PersistonKey))
{
throw new Exception("Viewon requested but key format is for persiston");
}
if (daton == null)
{
var sql = GetSqlInstance(key);
RetroSql.LoadResult loadResult;
using (var db = GetDbConnection(datondef.DatabaseNumber))
loadResult = await sql.Load(db, DataDictionary, user, key, ViewonPageSize);
if (loadResult.Daton == null)
{
return(loadResult);
}
daton = loadResult.Daton;
if (verifiedVersion == null && daton is Persiston)
{
verifiedVersion = LockManager.GetVersion(key);
}
daton.Version = verifiedVersion;
DatonCache.Put(daton);
Diagnostics.IncrementLoadCount();
}
//enforce permissions on the user
if (user != null)
{
daton = daton.Clone(datondef);
var guard = new SecurityGuard(DataDictionary, user);
guard.HidePrivateParts(daton);
}
return(new RetroSql.LoadResult {
Daton = daton
});
}
private async Task HandleHttpMain(MainRequest req, IUser user, MainResponse resp)
{
//initialize
if (req.Initialze != null)
{
resp.DataDictionary = Retrovert.DataDictionaryToWire(DataDictionary, user, LanguageMessages);
}
//load datons
if (req.GetDatons != null)
{
var getResponses = new List <GetDatonResponse>();
foreach (var drequest in req.GetDatons)
{
var loadResult = await GetDaton(DatonKey.Parse(drequest.Key), user, forceCheckLatest : drequest.ForceLoad);
var getResponse = new GetDatonResponse
{
Errors = loadResult.Errors
};
if (loadResult.Daton != null) //null means it was not found by key, usually
{
bool doReturnToCaller = loadResult.Daton.Version == null || drequest.KnownVersion != loadResult.Daton.Version; //omit if client already has the current version
if (doReturnToCaller)
{
getResponse.CondensedDaton = new CondensedDatonResponse
{
CondensedDatonJson = Retrovert.ToWire(DataDictionary, loadResult.Daton, false)
};
}
if (drequest.DoSubscribe && loadResult.Daton is Persiston)
{
ClientPlex.ManageSubscribe(req.SessionKey, loadResult.Daton.Key, loadResult.Daton.Version, true);
}
}
else
{
getResponse.Key = drequest.Key; //only needed if daton is not returned to client
}
getResponses.Add(getResponse);
}
resp.GetDatons = getResponses.ToArray();
}
//save datons
if (req.SaveDatons != null)
{
var diffs = new List <PersistonDiff>();
foreach (var saveRequest in req.SaveDatons)
{
var diff = Retrovert.FromDiff(DataDictionary, saveRequest);
diffs.Add(diff);
}
(bool success, var results) = await SaveDatons(req.SessionKey, user, diffs.ToArray());
var saveResponses = new List <SavePersistonResponse>();
foreach (var result in results)
{
saveResponses.Add(new SavePersistonResponse
{
IsDeleted = result.IsDeleted,
IsSuccess = result.IsSuccess,
OldKey = result.OldKey.ToString(),
NewKey = result.NewKey?.ToString(),
Errors = result.Errors
});
}
resp.SavedPersistons = saveResponses.ToArray();
resp.SavePersistonsSuccess = success;
}
//change datons state
if (req.ManageDatons != null)
{
var manageResponses = new List <ManageDatonResponse>(req.ManageDatons.Length);
foreach (var mrequest in req.ManageDatons)
{
//what does the caller wants to change?
var datonKey = DatonKey.Parse(mrequest.Key);
bool wantsLock = mrequest.SubscribeState == 2;
bool wantsSubscribe = mrequest.SubscribeState >= 1;
//handle change in subscription
//(Performance note: unsubscribe should happen before unlock so that the unlock-propogation can short circuit reloading. Ultimately
//if only one client is dealing with a daton and that client releases the lock and subscription, this server can forget about it
//immediately.)
bool isSubscribed = false;
if (datonKey is PersistonKey)
{
ClientPlex.ManageSubscribe(req.SessionKey, datonKey, mrequest.Version, wantsSubscribe);
isSubscribed = wantsSubscribe;
}
//handle change in lock
string lockErrorCode = "";
bool hasLock = false;
if (wantsLock)
{
if (string.IsNullOrEmpty(mrequest.Version))
{
throw new Exception("Version required to lock daton");
}
(hasLock, lockErrorCode) = LockManager.RequestLock(datonKey, mrequest.Version, req.SessionKey);
}
else
{
LockManager.ReleaseLock(datonKey, req.SessionKey);
}
manageResponses.Add(new ManageDatonResponse
{
ErrorCode = lockErrorCode,
Key = mrequest.Key,
SubscribeState = hasLock ? 2 : (isSubscribed ? 1 : 0)
});
}
resp.ManageDatons = manageResponses.ToArray();
}
//quit - free up locks and memory
if (req.DoQuit)
{
ClientPlex.DeleteSession(req.SessionKey);
LockManager.ReleaseLocksForSession(req.SessionKey);
}
}
/// <summary>
/// Load daton from database. Caller is responsible for setting the version (this does not deal with locks or versions)
/// </summary>
/// <param name="pageSize">only inspected for viewons main table</param>
/// <returns>null if not found</returns>
public virtual async Task <LoadResult> Load(IDbConnection db, DataDictionary dbdef, IUser user, DatonKey key, int pageSize)
{
var datondef = dbdef.FindDef(key);
//viewon validation
if (key is ViewonKey vkey2)
{
var validator = new Validator(user);
await validator.ValidateCriteria(datondef, vkey2);
if (validator.Errors.Any())
{
return new LoadResult {
Errors = validator.Errors.ToArray()
}
}
;
}
//handle viewon paging and ordering
string sortColName = datondef.MainTableDef.DefaulSortColName;
int pageNo = 0;
if (key is ViewonKey vkey)
{
pageNo = vkey.PageNumber;
if (vkey.SortColumnName != null)
{
sortColName = vkey.SortColumnName;
}
}
else
{
pageSize = 0; //prohibit paging in persistons
}
//load main table
var whereClause = MainTableWhereClause(datondef.MainTableDef, key);
var loadResult = await LoadTable(db, dbdef, datondef.MainTableDef, whereClause, sortColName, pageSize, pageNo);
loadResult.RowsByParentKey.TryGetValue("", out var rowsForParent);
//single-main-row datons cannot have zero main rows
if (!datondef.MultipleMainRows && (rowsForParent == null || rowsForParent.Count == 0))
{
return(null); //was throw new Exception("Single-main-row not found using: " + whereClause.ToString());
}
Daton daton = Utils.Construct(datondef.Type) as Daton;
if (datondef.MultipleMainRows)
{
if (daton is Viewon viewon)
{
viewon.IsCompleteLoad = loadResult.IsComplete;
}
//copy rowsDict into daton's main table IList
var listField = datondef.Type.GetField(datondef.MainTableDef.Name);
if (rowsForParent != null)
{
var list = Utils.CreateOrGetFieldValue <IList>(daton, listField);
foreach (var row in rowsForParent)
{
list.Add(row);
}
}
}
else //single main row
{
if (rowsForParent != null)
{
daton = rowsForParent?[0] as Daton;
}
}
//child tables
var rowsByPK = RestructureByPrimaryKey(datondef.MainTableDef, loadResult.RowsByParentKey);
await LoadChildTablesRecursive(rowsByPK, db, dbdef, datondef.MainTableDef);
daton.Key = key;
daton.Recompute(datondef);
return(new LoadResult {
Daton = daton
});
}
public PersistonDiff(DatonDef datondef, DatonKey key, string version)
{
DatonDef = datondef;
Key = key;
BasedOnVersion = version;
}