I am receiving the following error when I submit a transaction to Hedera:
failed precheck with status INVALID_TRANSACTION_START
This hasn't happened to me before and I'm confused.
Why is this error happening?
INVALID_TRANSACTION_START is returned if your device clock is ahead of time. As transactions include the valid start time (it's in the TransactionId) in the payload the user signs, keeping the device synced with a time server (set date to auto) is the solution for now. The SDK removes a few seconds from the client's time to take into account minor time differences.
There have been suggestions of adding an API to Hedera enabling the query of a node's time and using this instead of the client's clock. The client would use the return value from the query to set its transaction id.
This could be an opportunity for a HIP.
Related
I want to implement an incremental load process using SQL Server Change Data Capture. Every example I find takes the "happy path."
In other words, they assume that the CDC history exceeds the time since the last successful incremental load.
Suppose we leave the cleanup job with the default of 3 days, and for some reason our load hasn't successfully completed for longer than that. I need to check for this and run a full extract instead.
I'm logging the successful execution datetime in SQL Server tables. So, if I compare the last successful date to the earliest record in the cdc.lsn_time_mapping table, will this accomplish my task?
Basically something like:
Select #LastSuccessfulDate from audit....
Select #MinCdCDate = min(tran_begin_time) from cdc.lsn_time_mapping
if #MinCdCDate > #LastSuccessfulDate then 'Full' else 'Incremental'
Should this work? Is there a better way to accomplish it?
I would always stay in the "log domain" not the "time domain" when working directly with CDC. So track the last LSN of the last run and compare it against sys.fn_cdc_get_min_lsn every time you syncronize.
So if you last synchronized at lsn=100, and the min_lsn=110, then you've got a gap of 10 missing log records.
But this is only one of many scenarios that will require you to reinitialize the replication with a full sync, so you should also have an input parameter or somesuch to force a full sync.
We are facing DUPLICATE_VALUE error while assigning permission set .
We are having 1 future method called from event trigger and another from user trigger.
for salesforce internal users its working fine , because that time event trigger is not triggering.
But for community user both future method executing in same transaction.
So basically
futurePermissionSetAssignment1 executes from UserTrigger , so it assign permission set
futurePermissionSetAssignment2 executes after futurePermissionSetAssignment1 , although we are verifying if permission is not assigned to user already but it didnt take result of futurePermissionSetAssignment1.
Experts please guide if it can be handle.
PS: I cant put community user check.
Your description is bit messy and some code samples would help.
If it looks like you have parallel execution problem (operation A running a query, deciding to do X, in meantime operation B changes the state faster and A will fail because it works on old query results)...
You could do your thing as "save what you can" with Database.insert(myAssignments, false);: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/langCon_apex_dml_database.htm
Have a look at record locking with "FOR UPDATE". If both your futures start with say SELECT Id FROM User WHERE Id IN :... FOR UPDATE they should detect a lock and one will wait for the other to finish (or will fail after 10 seconds)
I need some guidance from anyone who has deployed a real-world, in-production application that uses the Sql Server Service Broker external activation mechanism (via the Service Broker External Activator from the Feature Pack).
Current mindset:
My specs are rather simple (or at least I think so), so I'm thinking of the following basic flow:
order-like entity gets inserted into a Table_Orders with state "confirmed"
SP_BeginOrder gets executed and does the following:
begins a TRANSACTION
starts a DIALOG from Service_HandleOrderState to Service_PreprocessOrder
stores the conversation handle (from now on PreprocessingHandle) in a specific column of the Orders table
sends a MESSAGE of type Message_PreprocessOrder containing the order id using PreprocessingHandle
ends the TRANSACTION
Note that I'm not ending the conversation, I don't want "fire-and-forget"
event notification on Queue_PreprocessOrder activates an instance of PreprocessOrder.exe (max concurrent of 1) which does the following:
begins a SqlTransaction
receives top 1 MESSAGE from Queue_PreprocessOrder
if message type is Message_PreprocessOrder (format XML):
sets the order state to "preprocessing" in Table_Orders using the order id in the message body
loads n collections of data of which computes an n-ary Carthesian product (via Linq, AFAIK this is not possible in T-SQL) to determine the order items collection
inserts the order items rows into a Table_OrderItems
sends a MESSAGE of type Message_PreprocessingDone, containing the same order id, using PreprocessingHandle
ends the conversation pertaining to PreprocessingHandle
commits the SqlTransaction
exits with Environment.Exit(0)
internal activation on Queue_HandleOrderState executes a SP (max concurrent of 1) that:
begins a TRANSACTION
receives top 1 MESSAGE from Queue_InitiatePreprocessOrder
if message type is Message_PreprocessingDone:
sets the order state to "processing" in Table_Orders using the order id in the message body
starts a DIALOG from Service_HandleOrderState to Service_ProcessOrderItem
stores the conversation handle (from now on ProcessOrderItemsHandle) in a specific column of Table_Orders
creates a cursor for rows in Table_OrderItems for current order id and for each row:
sends a MESSAGE of type Message_ProcessOrderItem, containing the order item id, using ProcessOrderItemsHandle
if message type is Message_ProcessingDone:
sets the order state to "processed" in Table_Orders using the order id in the message body
if message type is http://schemas.microsoft.com/SQL/ServiceBroker/EndDialog (END DIALOG):
ends the conversation pertaining to conversation handle of the message
ends the TRANSACTION
event notification on Queue_ProcessOrderItem activates an instance of ProcessOrderItem.exe (max concurrent of 1) which does the following:
begins a SqlTransaction
receives top 1 MESSAGE from Queue_ProcessOrderItem
if message type is Message_ProcessOrderItem (format XML):
sets the order item state to "processing" in Table_OrdersItems using the order item id in the message body, then:
loads a collection of order item parameters
makes a HttpRequest to a URL using the parameters
stores the HttpResponse as a PDF on filesystem
if any errors occurred in above substeps, sets the order item state to "error", otherwise "ok"
performs a lookup in the Table_OrdersItems to determine if all order items are processed (state is "ok" or "error")
if all order items are processed:
sends a MESSAGE of type Message_ProcessingDone, containing the order id, using ProcessOrderItemsHandle
ends the conversation pertaining to ProcessOrderItemsHandle
commits the SqlTransaction
exits with Environment.Exit(0)
Notes:
specs specify MSSQL compatibility 2005 through 2012, so:
no CONVERSATION GROUPS
no CONVERSATION PRIORITY
no POISON_MESSAGE_HANDLING ( STATUS = OFF )
I am striving to achieve overall flow integrity and continuity, not speed
given that tables and SPs reside in DB1 whilst Service Broker objects (messages, contracts, queues, services) reside in DB2, DB2 is SET TRUSTWORTHY
Questions:
Are there any major design flaws in the described architecture ?
Order completion state tracking doesn't seem right. Is there a better method ? Maybe using QUEUE RETENTION ?
My intuition tells me that in no case whatsoever should the activated external exe terminate with an exit code other than 0, so there should be try{..}catch(Exception e){..} finally{ Environment.Exit(0) } in Main. Is this assumption correct ?
How would you organize error handling in DB code ? Is an error log table enough?
How would you organize error handling in external exe C# code ? Same error logging
table ?
I've seen the SQL Server Service Broker Product Samples, but the Service Broker Interface seems overkill for my seemingly simpler case. Any alternatives for a simpler Service Broker object model ?
Any cross-version "portable" admin tool for Service Broker capable of at least draining poison messages ?
Have you any decent code samples for any of the above ?
Q: Are there any major design flaws in the described architecture ?
A: Couple of minor perks:
- waiting for an HTTP request to complete while holding open a transaction is bad. You can't achieve transactional consistency between a database and HTTP anyway, so don't risk to have a transaction stretch for minutes when the HTTP is slow. The typical pattern is to {begin tran/receive/begin conversation timer/commit} then issue the HTTP call w/o any DB xact. If the HTTP call succeeds then {begin xact/send response/end conversation/commit}. If the HTTP fails (or client crashes) then let the conversation time activate you again. You'll get a timer message (no body), you need to pick up the item id associated with the handle from your table(s).
Q: Order completion state tracking doesn't seem right. Is there a better method ? Maybe using QUEUE RETENTION ?
A: My one critique of your state tracking is the dependency on scanning the order items to determine that the current processed one is the last one (5.3.4). For example you could add the information that this is the 'last' item to be processed in the item state so you know, when processing it, that you need to report the completion. RETENTION is only useful in debugging or when you have logic that require to run 'logical rollback' and to compensating actions on conversation error.
Q: My intuition tells me that in no case whatsoever should the activated external exe terminate with an exit code other than 0, so there should be try{..}catch(Exception e){..} finally{ Environment.Exit(0) } in Main. Is this assumption correct ?
A: The most important thing is for the activated process to issue a RECEIVE statement on the queue. If it fails to do so the queue monitor may enter the notified state forever. Exit code is, if I remember correctly, irrelevant. As with any background process is important to catch and log exceptions, otherwise you'll never even know it has a problem when it start failing. In addition to disciplined try/catch blocks, Hookup Application.ThreadException for UI apps and AppDomain.UnhandledException for both UI and non-UI apps.
Q: How would you organize error handling in DB code ? Is an error log table enough?
A: I will follow up later on this. Error log table is sufficient imho.
Q: How would you organize error handling in external exe C# code ? Same error logging table ?
A: I created bugcollect.com exactly because I had to handle such problems with my own apps. The problem is more than logging, you also want some aggregation and analysis (at least detect duplicate reports) and suppress floods of errors from some deployment config mishap 'on the field'. Truth be told nowadays there are more options, eg. exceptron.com. And of course I think FogBugs also has logging capabilities.
Q: I've seen the SQL Server Service Broker Product Samples, but the Service Broker Interface seems overkill for my seemingly simpler case. Any alternatives for a simpler Service Broker object model ?
finally, an easy question: Yes, it is overkill. There is no simple model.
Q: Any cross-version "portable" admin tool for Service Broker capable of at least draining poison messages ?
A: The problem with poison messages is that the definition of poison message changes with your code: the poison message is whatever message breaks the current guards set in place to detect it.
Q: Have you any decent code samples for any of the above ?
A: No
One more point: try to avoid any reference from DB1 to DB2 (eg. 4.3.4 is activated in DB1 and reads the items table from DB2). This creates cross DB dependencies which break when a) one DB is offline (eg. for maintenance) or overloaded or b) you add database mirroring for HA/DR and one DB fails over. Try to make the code to work even if DB1 and DB2 are on different machines (and no linked servers). If necessary, add more info to the messages payload. And if you architect it that way that DB2 can be on a different machine and even multiple DB2 machines can exists to scale out the HTTP/PDF writing work.
And finally: this design will be very slow. I'm talking low tens messages per second slow, with so many dialogs/messages involved and everything with max_queue_readers 1. This may or may not be acceptable for you.
I have a queue that stops without any aparently reason, in this queue i have implemented a posion message handling. And during processing, it records and discards any poison messages.
It has worked fine for more than a year without stopping. But recently (the problem began four weeks ago), it stops once or twice a week. And only in this week it stopped twice.
And when I check the table with the new poisoned messages, there is none!! And when I enable the queue, processing resumes successfully and the 'poison message' situation does not reproduce.
About the task of the queue: Receives about 2-3000 messages per day. It is used to run stored procedures outside the transaction. And each message can last a little to be processed (doing a lot of selects, inserts, updates).
Let me explain this point: the database has triggers that are fired inside a transaction, the trigger sends a message to run some code outside the trigger. The asynchronous behavior prevents droping the performance of the database.
I have detected that even when a dead-lock occurs while proccessing the messages, the queue treats the message as poisoned. So in principle it shouldn't be a performance problem. But, can it be? Maybe the database is growing and it lasts too long to proces a messages?
But how can I find it out if it is not detected as posioned?
Why other reason a queue stops?
How can save when and with which message the queue got disabled?
Does anybody has any idea how I can do any forensics analysis?
Any idea?
UPDATE EXPOSING A PSEUDO-SOLUTION:
According Remus' post, I've tried to use the event notification to get the exact moment when the queue stops.
CREATE EVENT NOTIFICATION [QueueDisabledEN]
ON QUEUE [dbo].[ProcessQueue]
FOR BROKER_QUEUE_DISABLED
TO SERVICE 'Queue Watch Service', 'current database';
And then checking the event log:
select * from sys.event_notificiation
But since it is difficult to know the environment in which the event occurred, (what else was running at the momment??), forensic analysis ends there. Fortunately my broker service implementation stores the messages with the date of shipment, the date of receipt, date processing, ... This has helped me to detect that within 3 seconds the queue is flooded with hundreds of messages that take too long to be processed.
While I find a real solution the only temporary solution is to check with an agent job every x minutes the status of the queue and enable it:
IF (EXISTS(SELECT * FROM sys.service_queues WHERE name like 'ProcessQueue' AND (is_receive_enabled = 0 OR is_enqueue_enabled = 0))) BEGIN
PRINT convert(nvarchar, getdate(), 121)+ ': Activando la cola ProcessQueue'
ALTER QUEUE ProcessQueue WITH STATUS = ON
END
Thanks Remus!
When you find the queue in disabled state and you enable back the queue, I assume that the processing resumes successfully and the 'poison message' situation does not reproduce. This would indicate that the cause is transient or time related. It could be a SQL Agent job that is running and causes deadlocks with the queue processing, forcing the queue processing to rollback. Deadlocks are in my experience the most typical poison message cause. Your best forensics tool is the system event log, as the activated procedure does output errors into the ERRORLOG and hence into the system Event Log.
Whenever a queue is disabled by the poison message trigger (5 consecutive rollbacks) an event notification of type QUEUE_DISABLED is fired. You can capture more forensic information in the handling this event, as it will run shortly after the moment the queue was disabled.
As a side note, you can never have true 'poison message handling'. Whenever you enhance the processing to handle some error cases, the definition of the 'poison message' changes to be the message capable of disabling the new error handling.
Is it possible in DB2 to detect if the table is locked or not. Actually whenever we use Select statement and if that table is locked [ may be because of on going execution of insertion or deletion ] , then we have to wait till the table is unlocked.
In our application sometimes it goes to even 2-3 mins. What i think is, if i can have some mechanism by which i can detect the locked table, then i will not even try to fetch the records, instead i will splash some message.
Not only in DB2, but is it possible to detect this in any Database.
I've never used DB2, but according to the documentation it seems you can use the following to make queries not wait for a lock:
SET CURRENT LOCK TIMEOUT NOT WAIT
Alternatively, you can set the lock timeout value to 0
SET CURRENT LOCK TIMEOUT 0
Both the statements have the same effect.
Once you have this, you can try to select from the table and catch the error.
I would recommend against NO WAIT, and rather, specify a low LOCK TIMEOUT (10-30s). If the target table is only locked temporarily (small update, say for 1 second), your second app will timeout immediately. If you have a 10s timeout, the second app would simply wait for the first app to COMMIT or ROLLBACK (1 sec) then move forward.
Also consider there's a bit of a "first come, first served" policy when it comes to handing out locks - if the second app "gives up", a third app could get in and grab the locks needed by the second. It's possible that the second app experiences lock starvation because it keeps giving up.
If you are experiencing ongoing concurrency issues, consider lock monitoring to get a handle on how the database is being accessed. There's lots of useful statistics (such as average lock-wait time, etc.) that can help you tune your parameters and application behaviour.
DB2 V9.7 Infocenter - Database Monitoring