I need to log the last time the user signed in using my node.js server. I am looking into three options. The persistence requirement is not super high, meaning that the margin of error of this record being recorded is open.
Use SQL DB and whenever the user logs in it modifies their profile account.
Record it in a server text file. So whenever the user logs on, this file will be opened and updated. The opening, recording and closing of the file will all be done asynchronously.
I'm thinking that the second option is the better on because I'm using SQL for many other operations so I prefer to not interrupting my DB as much as possible.
One concern I have for the second option is the performance hit on the server that will be caused by the frequently read and write to a local text file.
I'm curious what other people who have gone through this path thought about my thought process. Any opinions or tips are highly welcomed. Thank you.
Normally you should use a SQL database, it is a much more better way than the plain text.
The main problem with a text file is that when you log in, you can simply append a line (but what about a couple of user loggin in at the same moment ? You have not any warranty that all the access are logged), but when you want to extact the last login for a user, you should read (and then load) all the file from the start (or the end), which can cause a really worst problem than the access to the DB.
Naturally you can work out all the problems with a text file, but then you have written a lot of code to avoid a simple update query.
I don't think that, with the information you give, you should be worried about the performance of a database access in this case.
Related
I am working on migrating a MS Access Database over to a newer SQL platform.
But, with all of the users who are currently using it, we're migrating slowly/carefully.
The first step is that we are re-writing the VBA code into C#, which is then deployed in a .dll along with the database.
Now, the VBA code calls into the C# to do the business logic, then the VBA continues to do the displays/UI, while Access still hosts the database.
The problem comes in that I have a report that is being run after the business logic from the C# in one place, and apparently MS Access has a cache, which clears every 5 seconds. So, the transaction that occurs in the C# code writes to the database, but the VBA code is still using the cache. This is causing errors, as the records added to the database (which the VBA report is trying to report on) don't exist in the cache yet...
I'm guessing that the C# .dll must be getting treated as a "second connection" to the MS Access database, which is what seems to typically cause this error in my searches (thinks that one process is writing, and the other is reading).
Since the cache is cleared out every 5 seconds, we can just put the process to sleep, and wake it up after 5 seconds, and then run the report, but that's pretty terrible for an end user.
And, making things difficult, the cache seems like it only gets used in the deployed version (so, when running from source / in debug mode, the error never happens).
Doing some searches, there seems to be plenty of people who have said "just refresh the cache." But, the question is: within VBA, how do you refresh the cache?
Any advice would be welcome.
Thanks
I've been fighting the same issue for years as I write a lot of tools around an old Powerbuilder application that has an Access MDB back end.
The cache does exist and it is VERY real. When data is inserted on a different connection than it is queried on, the cache can be directly observed and measured. It was also documented by Microsoft before they blackholed a bunch of their old articles...
Microsoft Jet has a read-cache that is updated every PageTimeout milliseconds (default is 5000ms = 5 seconds). It also has a lazy-write mechanism that operates on a separate thread to main processing and thus writes changes to disk asynchronously. These two mechanisms help boost performance, but in certain situations that require high concurrency, they may create problems.
I've found a couple workarounds that are not the best, but somewhat make due until I find something better or can re-write the app with a better back end database.
The seemingly best answer I've found (that may actually work for you since you say you need VBA) is to use JRO.RefreshCache. I've been trying to figure out how to implement this using C# or VB.net without any luck. Below is a link to a code example where you execute the RefreshCache method on your 2nd connection that needs to pull the data. I have not tested this myself.
https://documentation.help/MSJRO/jrmthrefreshcachex.htm
A workaround I've found that will deliver the query results within 500ms to 1000ms of insert time (instead of anywhere between 500 and 5000 ms - or more):
Use System.Data.ODBC instead of OleDB, with connection string: Driver={Microsoft Access Driver (*.mdb, *.accdb)};Dbq=;
If someone knows how to use the JRO.RefreshCache method with OLEDB and C# or VB.net, I'd be forever grateful. I believe the issue is it's looking for an ADO connection to be passed in, not an OLEDB connection.
I not aware of ANY suggesting that some 5 second cache exits? Where did this idea come from????
Furthermore, if you have 5 users, then you not going to be able to update their cache, are you?
In other words, the issue of some cache for one user still not going to solve or work with mutli-users anyway, is it?
The simple matter is if you load up a form with 100 reocrds, and then other users are ALSO working on that 100 rows, then all users will not see other changes until such time you tell access to re-load the form.
You can do this with a me.Refresh in the form, and then it will show changes made by other users (or even your c# code!!!).
However, that not really the soluion here.
How does near EVERY system deal with this issue?
Answer:
You don't, you "design" the software to take the user work flow into account.
So, in place of loading up a form with 100 rows of data? (which you should not, unless SUPER DUPER reason exists for doing that).
The you provide a UI in which the user FIRST searches for whatever it is they want to work on.
In other words, say you just booked a user on a tour. Now, they call the office back, and want to change some details of that tour. But, a different tour staff might pick up the phone. So, now a 2nd user opens the tour?
So, you solve that issue by NOT loading all the tours into that form in the first place.
you provide a search screen, so they can search for the user, find the user, maybe type in a invoice number or whatever.
You display the results in a pick list, and then launch the form to the ONE record (and perhaps detail records from child tables).
So there no concpet of a cache in Access anymore then there is in c#.
However, if you load up a datatable in c#, and then display that data?
Well, what about the other users on that system. They will not see changes to that data ANY MORE then the current access form.
So, if you want to update some data in c#? Then fine, but you need/want to do two things:
First, before you call any c# code that may update the current form reocrd? You need to FORCE a data save of that current record BEFORE you call any code, be it VBA code, or c# code that going to update that current reocrd the user is working on.
You can in Access save the current reocrd in MANY different ways, but the typical approach is:
' single record save - current record
if me.dirty then me.dirty = false
' VBA or c# code goes here.
' optional refresh the current form to reflect changes
me.Refresh
So, in most cases, it is the "design" of your software that will solve this issue.
For example, in the tour example, or in fact ANY system, the user can't work, can't update, and can't do their job UNLESS they first find/search and have a means to bring up that form + record data in the first place.
So, ANY typical good design will:
Ask the user for that name, invoce number or whatever.
Display the results of the search, and THEN allow the user to pick the record/data to work on. When they are done, they close that form and are RIGHT BACK to the search form to do battle with the next customer or task or phone call or whatever.
So, a search form might look like this:
In above, I typed in smi, and then displayed a pick list.
The user can further type in say part of the first name, and thus now get this:
So, maybe they type in a invoice number, customer number, booking number or whatever.
So, you display the results, and then they can select the row or "thing" to work on.
thus, we click on the row (or above glasses button), and then jump to the ONE record.
so, the user does whatever they have to do with the customer. Now, when done, they close the ONE thing, the ONE main reocrd.
This not only saves the data (so others in the office can now use that booking data), but it also means the data is saved. and they are NOW right back at the search screen, ready to do battle with the next customer.
So, not only does this mean we have a VERY bandwith friednly design (we only pull the one main reocrd into that form), but it also is better for work flow.
The Access form's cache thus becomes a non issue, since we only dealing with the one record.
And as I pointed out, if the system is multi-user, then you NOT going to be able to udpate and deal with multiple users cached data anyway, are you?
Think of ANY system you EVER used from a software point of view.
When you use google, does it download the WHOLE internet, and then you use ctrl-f to search megs and megs of data in the browser?
Nope!
you search first, get a list of that search, and THEN pick one!!
And when that list is display, maybe others on the internet are udpateing, and add new data - but if that was cached in your browser, then it would not work!!!
And same goes for a desktop accounting system. You don't load up all accounts, and THEN have the user go ctrl-f to search all the data. You search for the customer, invoice number and PICK ONE to work on.
And it does not make sense to load up a form with 1000 customers, and then go ctrl-f to find that customer. Same goes for a instant banking machine. It does not download ALL customers and THEN let you search. It asks you FIRST to get what you need. So, be it browser based, desktop based, or JUST ABOUT ANY software you use?
You quite much elminate the cache issue, since not pre-loading boatloads of data, but asking and letting the user search for the data they need.
So, in regards to the Access form data and cache?
If you are on a form, and call VBA code, or c# code or whatever?
If that code update the current form, you have NO MORE OR LESS of a issue when calling VBA code, or c# code!!!! If that code updates the current form, and the reocrd is dirty (has pending edits), then you get that message about the current form's reocrd having been udpated by another user!!!
So, your cache issue does NOT IN ANY WAY exist MORE or LESS as a issue in typical Access software.
As a genreal rule, if you are on a form with pending edits, and say want to pop up some form to edit releated data?
You have to ensure that pending edits are SAVED before you launch an form that can edit the same data, or run code that can/may edit that data.
As a result, ZERO cache issues should exist, and they no more or no less exist when calling sql or VBA update code in a form then calling some c# code from that form.
So, write the pending update for that form.
Then run your VBA, SQL, or c# code.
And then do a me.Refresh to display any changes made by those external routines.
there is no documetjion, or ANY article I can find that suggests some kind of 5 seocnd cache or update - it is a urban myth, and your software challenge here in regards to use c# or VBA, or even SQL server stored procedures?
They are all the same issue, and I dare say that often access is used as a front end to SQL server, and ALL OF the SAME issues exist when using SQL server with ms-access.
I need to extract some data from my client's SAP ECC (the SUIM -> Users by Complex Selection Criteria -program RSUSR002)
Normally I give them a table of values that I they have to fill some field to extract what I need.
They have to make 63 different extractions (with different values of objects, for example - but inside the same transaction - you can see in the print) from their SAP, to later send to me all extracted files.
Do you know if there is an automated way to extract that, so they don't have to make 63 extractions?
My biggest problem is that every time they make mistakes. It's a lot of things to fill..
Can I create a variant and send it to them? Is it possible to export my variant so they can import it without the need to fill 63x different data?
Thank you.
When this is a task which takes considerable effort by multiple people each year, then it is something which might be worth automatizing.
First you need to find out where that transaction gets its data from. If you spend some time analyzing and debugging the program behind the transaction, you will surely find which SELECT's on which database table(s) provide that data. If you are lucky, there might even be a function module for it.
Then you just need to write an own ABAP program which performs the same selections.
Now about the interesting part: How to get that data to you. There are several approaches here. The best one depends on your requirements and your technical infrastructure. Some possibilities are:
Let users run the program in foreground, use the method cl_gui_frontend_services=>gui_download to save the data to a file on the user's PC and ask them to send it to you via email
Run the program in background and save the file on the application server. Then ask your sysadmins how to get that file from their application server to you. The simplest way would be to just map a network fileserver so they all write to the same place, but there might be some organizational hurdles in the way which prevent that. (Our security people would call me crazy if I proposed to allow access to SMB shares from outside of our network, but your mileage may vary)
Have the program send the data to you directly via email. You can send emails from an SAP system using the function module SO_NEW_DOCUMENT_ATT_SEND_API1. This of course requires that the system was configured to be able to send emails (which you can do with transaction code SCOT). Again, security considerations apply. When it's PII or other confidential data, then you should not send it in an unencrypted email.
Use an RFC call to send the data to your own SAP system which aggregates the data
Use a webservice call to send the data to your own non-SAP system which aggregates the data
You can create a recording in transaction SM35.
There you fill a tcode (SUIM), start recording, make some input in transaction SUIM and then press 'Execute'. Then you can go back to recording (F3 multiple times) and the system will generate some table with commands (structure is BDCDATA). You can delete unnecessary part (i.e. BACK button click) and save it to use as a 'macro'. Then you can replay this recording and it will do exactly what you did.
Also it's possible to export/import the recording to text file, so you can explore it's structure, write some VBA script to create such recording from your parameters and sent it to users. But keep in mind that blanks are meaningful.
It's a standard tools so there's no any coding in the system.
You can save the selection as a variant.
Fill in the selection criteria and press Save.
It can be reused.
You can also transport Variants if the they have a special name
We have an ERP Program used to create and manage stock / orders. Somehow an order has vanished - this should not be possible. It should be possible to cancel an unwanted order, but never delete it completely.
The order in question was created, printed and sent to a customer - and then disappeared. I know the Primary key and Table info, and want to search the log to see if this was somehow deleted, or perhaps there was a rollback.
How can I translate/search the log in this way?
Please note: I did not write this program, and its not my job to fix it.
I just need to diagnose the issue and contact the SW Vendor, if required, and have them fix it. As such I cannot post any code.
With so little information it is hard to give a definitive answer.
I'd start by searching the regular logs. If you have some kind of audit trail mechanism that would be a great help!
If a search through the regular logs doesn't find you the answer then I would:
Get a copy of the database
Go through the REDO logs using the appropriate DBA tools. Since I'm not an sqlanywhere DBA I would get help from one.
When I found the place in time where the order was deleted I would find any other information I could get. The user that did the commit or users that where logged on at the time (I don't know exactly what kind of information you can get here). Also, go back to the other logs you may have and check around that time stamp.
To learn exactly how to go through the redo logs of an SQL Anywhere database you should first try your google luck and then ask in Database Administrators.
Solved!!!!
The Sybase Central tool has an option (which I couldn't find in the manual and missed the first time I looked), which can translate a log file into a series of statements and create a *.SQL file.
Tools -> SQL Anywhere -> Translate Log File -> Follow wizard (which hopefully for you is in a language that you speak, for me it was not).
Background
I have an SQL CE database, that is constantly updated (every second).
I have a (web) application that allows a user to look at the data in real-time. At some point a user can click "take a snapshot" button, and it will open the snapshot in a different window.
And then on that form, there is "print" and "download" buttons that will either generate a page for printing, or will stream the data as CSV file - but same data snapshot has to be used, i.e. I can't go to the DB to get latest data for that.
Details
SQL CE dabatase is exposed through WCF web service.
Snapshot consists of up to 500 records, 10 columns each. Expiration time on the snapshot of 2 hours is sufficient.
It is a low-traffic application, so I don't expect more than few (5) connections at the same time.
Loosing snapshot is not a big deal, user can simply generate new one.
database is accessed by self-hosted WCF web service using Linq-to-SQL.
Web site is ASP.NET MVC hosted on UltiDev Cassini.
database, and web site are most likely be on the same box, when deployed. The entire app is intranet bound.
Problem
I need to cache the snapshot of the data at the moment user pressed "take a snapshot" button, so that I can use same data to generate print page, or generate a file for download.
Solution 1:
Each time there is a need to generate a snapshot, I will create a table in the database. Since there are no temp tables in SQL CE, I will need to clean it up myself.
Solution 2:
Cache the snapshot in-memory on either DB server, or web server.
Question:
Is there anything wrong with proposed solutions? Any different solution suggestions?
A consideration is the typical usage pattern. Do most snapshots eventually result in either being printed or exported or both?
If such is the case, we might as well "get it in memory" (temporarily) in the form of a non blocking (asynchronous) select statement from the device to the server. In this fashion the data will "be there" or well on its way when user decides to use it.
If on the other hand many snapshot end up not being effectively used, Solution #1 seems quite ok (maybe the table could be named after the account/user, hence guaranteeing "self clean up" based on the number of snapshot a user can maintain at a given time (though it seems to be just one, with even the tolerance of loosing it sometimes).
500 rows by 10 columns isn't really very large at all. For the sake of simplicity in this case, I might just generate the CSV data at the same time I generate the initial snapshot page, and then place the CSV data in a hidden field in the snapshot page. The "Print" and "Download CSV" buttons would then POST the form that contains the CSV data to a Print page that generates the printable version from the posted CSV data, or a page that streams the CSV directly back to the client's browser, respectively. This way, at least, you wouldn't have any clean-up issues to deal with, and you avoid having to cache something on the server (either in the cache proper or in the database) that might well end up never being used at all.
If you cached the CSV data in a hidden field client-side, you could even handle both the printing and the CSV display completely client-side with javascript, although I don't know if that's worth the trouble or not.
Every once in awhile I am fed a large data file that my client uploads and that needs to be processed through CMFL. The problem is that if I put the processing on a CF page, then it runs into a timeout issue after 120 seconds. I was able to move the processing code to a CFC where it seems to not have the timeout issue. However, sometime during the processing, it causes ColdFusion to crash and has to restarted. There are a number of database queries (5 or more, mixture of updates and selects) required for each line (8,000+) of the file I go through as well as other logic provided by me in the form of CFML.
My question is what would be the best way to go through this file. One caveat, I am not able to move the file to the database server and process it entirely with the DB. However, would it be more efficient to pass each line to a stored procedure that took care of everything? It would still be a lot of calls to the database, but nothing compared to what I have now. Also, what would be the best way to provide feedback to the user about how much of the file has been processed?
Edit:
I'm running CF 6.1
I just did a similar thing and use CF often for data parsing.
1) Maintain a file upload table (Parent table). For every file you upload you should be able to keep a list of each file and what status it is in (uploaded, processed, unprocessed)
2) Temp table to store all the rows of the data file. (child table) Import the entire data file into a temporary table. Attempting to do it all in memory will inevitably lead to some errors. Each row in this table will link to a file upload table entry above.
3) Maintain a processing status - For each row of the datafile you bring in, set a "process/unprocessed" tag. This way if it breaks, you can start from where you left off. As you run through each line, set it to be "processed".
4) Transaction - use cftransaction if possible to commit all of it at once, or at least one line at a time (with your 5 queries). That way if something goes boom, you don't have one row of data that is half computed/processed/updated/tested.
5) Once you're done processing, set the file name entry in the table in step 1 to be "processed"
By using the approach above, if something fails, you can set it to start where it left off, or at least have a clearer path of where to start investigating, or worst case clean up in your data. You will have a clear way of displaying to the user the status of the current upload processing, where it's at, and where it left off if there was an error.
If you have any questions, let me know.
Other thoughts:
You can increase timeouts, give the VM more memory, put it in 64 bit but all of those will only increase the capacity of your system so much. It's a good idea to do these per call and do it in conjunction with the above.
Java has some neat file processing libraries that are available as CFCS. if you run into a lot of issues with speed, you can use one of those to read it into a variable and then into the database
If you are playing with XML, do not use coldfusion's xml parsing. It works well for smaller files and has fits when things get bigger. There are several cfc's written out there (check riaforge, etc) that wrap some excellent java libraries for parsing xml data. You can then create a cfquery manually if need be with this data.
It's hard to tell without more info, but from what you have said I shoot out three ideas.
The first thing, is with so many database operations, it's possible that you are generating too much debugging. Make sure that under Debug Output settings in the administrator that the following settings are turned off.
Enable Robust Exception Information
Enable AJAX Debug Log Window
Request Debugging Output
The second thing I would do is look at those DB queries and make sure they are optimized. Make sure selects are happening with indicies, etc.
The third thing I would suspect is that the file hanging out in memory is probably suboptimal.
I would try looping through the file using file looping:
<cfloop file="#VARIABLES.filePath#" index="VARIABLES.line">
<!--- Code to go here --->
</cfloop>
Have you tried an event gateway? I believe those threads are not subject to the same timeout settings as page request threads.
SQL Server Integration Services (SSIS) is the recommended tool for complex ETL (Extract, Transform, and Load) work, which is what this sounds like. (It can be configured to access files on other servers.) The question might be, can you work up an interface between Cold Fusion and SSIS?
If you can upgrade to cf8 and take advantage of cfloop file="" which would give you greater speed and the file would not be put in memory (which is probably the cause of the crashing).
Depending on the situation you are encountering you could also use cfthread to speed up processing.
Currently, an event gateway is the only way to get around the timeout limits of an HTTP request cycle. CF does not have a way to process CF pages offline, that is, there is no command-line invocation (one of my biggest gripes about CF - very little offling processing).
Your best bet is to use an Event Gateway or rewrite your parsing logic in straight Java.
I had to do the same thing, Ben Nadel has written a bunch of great articles uses java file io, to allow you to more speedily read files, write files etc...
Really helped improve the performance of our csv importing application.