I get this error from time to time in the MDrivenServer log. What does it mean and how do I fix it?
When you upload a model to the MDrivenServer it is associated a checksum that is based on the contents of the model. The model-version uploaded is used to evolve and change your database so that it match the new model.
If you have client-applications running while doing this they will be based on the prior version of the model.
If someone with a different model tries to write to your database it may cause data inconsistency in the database (suppose you added an attribute in the new model that has a mandatory value - the old version does not know and cannot possibly comply - resulting in a illegal state).
MDrivenServer stops updates from models with wrong checksum in order to prevent data inconsistency - it then writes "Client has a different model than the server. Save is not allowed" in the log.
Related
Is there anyway to check duplicate the message control id (MSH:10) in MSH segment using Mirth connect?
MSH|^~&|sss|xxx|INSTANCE2|KKLIU 0063/2021|20190905162034||ADT^A28^ADT_A05|Zx20190905162034|P|2.4|||NE|NE|||||
whenever message enters it needs to be validated whether duplicate of control id Zx20190905162034 is already processed or not?
Mirth will not do this for you, but you can write your own JavaScript transformer to check a database or your own set of previously encountered control ids.
Your JavaScript can make use of any appropriate Java classes.
The database check (you can implement this using code template) is the easier way out. You might want to designate the column storing MSH:10 values as a primary key or define an index on it. Queries against unique entries would be faster. Other alternatives include periodically redeploying the Channel while reading all MSH:10 values already in the database and placing them in a global map variable or maintained in an API that you can make a GET request to when processing every message. Any of the options depends on the number of records we are speaking about.
I'm using Copy Data.
When there is some data error. I would export them to a blob.
But in this case, the Pipelines's status is still Succeeded. I want to set it to false. Is it possible?
When there is some data error.
It depends on what error you mentioned here.
1.If you mean it's common incompatibility or mismatch error, ADF supports built-in feature named Fault tolerance in Copy Activity which supports below 3 scenarios:
Incompatibility between the source data type and the sink native
type.
Mismatch in the number of columns between the source and the sink.
Primary key violation when writing to SQL Server/Azure SQL
Database/Azure Cosmos DB.
If you configure to log the incompatible rows, you can find the log file at this path: https://[your-blob-account].blob.core.windows.net/[path-if-configured]/[copy-activity-run-id]/[auto-generated-GUID].csv.
If you want to abort the job as soon as any error occurs,you could set as below:
Please see this case: Fault tolerance and log the incompatible rows in Azure Blob storage
2.If you are talking about your own logic for the data error,may some business logic. I'm afraid that ADF can't detect that for you, though it's also a common requirement I think. However,you could follow this case (How to control data failures in Azure Data Factory Pipelines?) to do a workaround. The main idea is using custom activity to divert the bad rows before the execution of copy activity. In custom activity, you could upload the bad rows into Azure Blob Storage with .net SDK as you want.
Update:
Since you want to log all incompatible rows and enforce the job failed at the same time, I'm afraid that it can not be implemented in the copy activity directly.
However, I came up with an idea that you could use If Condition activity after Copy Activity to judge if the output contains rowsSkipped. If so, output False,then you will know there are some skip data so that you could check them in the blob storage.
I have a 3-tier application:
Client application
Server application
Database server
The server uses Entity Framework 4 to read and write data to/from the database.
Imagine following situation:
Client application creates an instance of an entity with a RowVersion property. At this point in time, the property is equal to null.
Client application sends a request "Save this instance in the database" to the server.
Server saves the object in the database and automatically sets the value of the RowVersion property. But at the client side, that value is still equal to null.
Client application modifies the object it created in the first step, sends a request to the server and the server gets a concurrency exception when trying to save the new version of the object.
Are there any standard mechanisms for solving this type of problem?
I dont know how the system works inside (think communication between Client and Server goes using some API). As I see you trying to handle the situation when 2 clients modifying same entity and you need to notify the client if he is trying to save the version that is older that current.
So I will do next:
On step 3 server must return the version ID (first save of entity)
Next modification of entity by client will have a version id and you need to check if current version id is equal or older than you
have on server (think that rowversion is timestamp)
Server logic will handle this states and send to client response: saved a new version (if current version is equal and will send back
new version id) or false state if version is older (other client made
modification already).
This is it in simplified way.
[Update]
Looks like in this article you will find the implementation that is very close to your needs:
http://weblogs.asp.net/ricardoperes/archive/2012/05/28/yet-another-asp-net-mvc-crud-tutorial.aspx
Baseline info:
I'm using an external OAuth provider for login. If the user logs into the external OAuth, they are OK to enter my system. However this user may not yet exist in my system. It's not really a technology issue, but I'm using JOliver EventStore for what it's worth.
Logic:
I'm not given a guid for new users. I just have an email address.
I check my read model before sending a command, if the user email
exists, I issue a Login command with the ID, if not I issue a
CreateUser command with a generated ID. My issue is in the case of a new user.
A save occurs in the event store with the new ID.
Issue:
Assume two create commands are somehow issued before the read model is updated due to browser refresh or some other anomaly that occurs before consistency with the read model is achieved. That's OK that's not my problem.
What Happens:
Because the new ID is a Guid comb, there's no chance the event store will know that these two CreateUser commands represent the same user. By the time they get to the read model, the read model will know (because they have the same email) and can merge the two records or take some other compensating action. But now my read model is out of sync with the event store which still thinks these are two separate entities.
Perhaps it doesn't matter because:
Replaying the events will have the same effect on the read model
so that should be OK.
Because both commands are duplicate "Create" commands, they should contain identical information, so it's not like I'm losing anything in the event store.
Can anybody illuminate how they handled similar issues? If some compensating action needs to occur does the read model service issue some kind of compensation command when it realizes it's got a duplicate entry? Is there a simpler methodology I'm not considering?
You're very close to what I'd consider a proper possible solution. The scenario, if I may summarize, is somewhat like this:
Perform the OAuth-entication.
Using the read model decide between a recurring visitor and a new visitor, based on the email address.
In case of a new visitor, send a RegisterNewVisitor command message that gets handled and stored in the eventstore.
Assume there is some concurrency going on that, for the same email address, causes two RegisterNewVisitor messages, each containing what the system thinks is the key associated with the email address. These keys (guids) are different.
Detect this duplicate key issue in the read model and merge both read model records into one record.
Now instead of merging the records in the read model, why not send a ResolveDuplicateVisitorEmailAddress { Key1, Key2 } towards your domain model, leaving it up to the domain model (the codified form of the business decision to be taken) to resolve this issue. You could even have a dedicated read model to deal with these kind of issues, the other read model will just get a kind of DuplicateVisitorEmailAddressResolved event, and project it into the proper records.
Word of warning: You've asked a technical question and I gave you a technical, possible solution. In general, I would not apply this technique unless I had some business indicator that this is worth investing in (what's the frequency of a user logging in concurrently for the first time - maybe solving it this way is just a way of ignoring the root cause (flakey OAuth, no register new visitor process in place, etc)). There are other technical solutions to this problem but I wanted to give you the one closest to what you already have in place. They range from registering new visitors sequentially to keeping an in-memory projection of the visitors not yet in the read model.
Say that I have a User table in my ReadDatabase (use SQL Server). In a regulare read/write database I can put like a index on the table to make sure that 2 users aren't addedd to the table with the same emailadress.
So if I try to add a user with a emailadress that already exist in my table for a diffrent user, the sql server will throw an exception back.
In Cqrs I can't do that since if I decouple the write to my readdatabas from the domain model, by puting it on an asyncronus queue I wont get the exception thrown back to me, and I will return "OK" to the UI and the user will think that he is added to the database, when infact he will never be added to the read database.
I can do a search in the read database checking if there is a user already in my database with the emailadress, and if there is one, then thru an exception back to the UI. But if they press the save button the same time, I will do 2 checks to the database and see that there isn't any user in the database with the emailadress, I send back that it's okay. Put it on my queue and later it will fail (by hitting the unique identifier).
Am I suppose to load all users from my EventSource (it's a SQL Server) and then do the check on that collection, to see if I have a User that already has this emailadress. That sounds a bit crazy too me...
How have you people solved it?
The way I can see is to not using an asyncronized queue, but use a syncronized one but that will affect perfomance really bad, specially when you have many "read storages" to write to...
Need some help here...
Searching for CQRS Set Based Validation will give you solutions to this issue.
Greg Young posted about the business impact of embracing eventual consistency http://codebetter.com/gregyoung/2010/08/12/eventual-consistency-and-set-validation/
Jérémie Chassaing posted about discovering missing aggregate roots in the domain http://thinkbeforecoding.com/post/2009/10/28/Uniqueness-validation-in-CQRS-Architecture
Related stack overflow questions:
How to handle set based consistency validation in CQRS?
CQRS Validation & uniqueness