Can anyone help me understand how to keep a connection alive on Heroku using Sequelize? Currently I am following the instructions on the Sequelize site to establish a connection to the postgres DB on Heroku.
Here is the link that shows the current model/index.js file I am following.
http://sequelizejs.com/heroku
In this example for the site. Every time we call global.db.User we have to reestablish a connection for each time we want to access the DB. It would better optimized if there was a way to keep the only connection alive during each client session.
Related
I'm working on logs. I want to reproduce a log in which the application fails to connect to the server.
Currently the commands I'm using are
db2 force applications all
This closes all the connections and then one by one I deactivate each database using
db2 deactivate db "database_name"
What happens is that it temporary blocks the connections and after a minute my application is able to create the connection again, due to which I am not able to regenerate the log. Any Ideas how can I do this?
What you are looking for is QUIESCE.
By default users can connect to a database. It becomes active and internal in-memory data structures are initialized. When the last connection closes, the database becomes inactive. Activating a database puts and leaves them initialized and "ready to use".
Quiescing the database puts them into an administrative state. Regular users cannot connect. You can quiesce a single database or the entire instance. See the docs for some options to manage access to quiesced instances. The following forces all users off the current database and keeps them away:
db2 quiesce db immediate
If you want to produce a connection error for an app, there are other options. Have you ever tried to connect to a non-estisting port, Db2 not listening on it? Or revoke connect privilege for that user trying to connect.
There are several testing strategies that can be used, they involve disrupting the network connection between client and server:
Alter the IP routing table on the client to route the DB2 server address to a non-existent subnet
Use the connection via a proxy software that can be turned off, there is a special proxy ToxiProxy, which was designed for the purpose of testing network disruptions
Pull the Ethernet cable from the client machine, observe then plug it back in (I've done this)
This has the advantage of not disabling the DB2 server for other testing in progress.
So , i'm creating a datasnap TCP/IP server multiitier data base in Delphi XE7, i used in the server a mssql Database then connected it used a datasetprovider
in the Client Side i made a sqlConnection for connecting to DataSnap Server then i used a dsproviderconnection then i used "ClientDataSet"
when i run the Client Application i will a serval rows and post the modifcation but if i desactivate the ClientDataSet then reactivate it the data will be lost
so help me please i cant see what is the probleme there no error or something like that?
and thank you
Either don't deactivate the ClientDataSet (the data will get lost as you found) or save the data to a file or stream and reload it afterwards (SaveToFile/Stream, LoadFromFile/Stream).
(I am a sql noob and I just can not figure this out on my own)
For some time now I have been trying to establish a connection to a SQL database in codename one but to no avail. First I tried connecting to a MariaDB database from one.com. All that's needed for the connection is
Database db = Display.getInstance().openOrCreate("databaseName");
if I am not mistaken, but I am guessing this implies that I have somehow already established a connection to the database. This is not the case however so it creates a new .sql file, right? I can recall that you can connect to a database in the services tab in Netbeans. I chose the MySQL(Connector/ J Driver) which should work with MariaDB, or should it? I entered all my data and i says that it can not establish connection to the database.
the error i get
So I thought I might as well try using localhost. I used XAMPP to host a database and connected in the netbeans services tab.
connected?
Now testing was needed to see if this works. I started the SQL journey with this https://www.codenameone.com/manual/files-storage-networking.html#_sql and integrated the part after "You can probably integrate this code into your app as a debugging tool". I changed database name to "mybase" (it's existance can be confirmed in picture 2). Ran the app, opened the dialog, entered "select ID from customers" and got: java.sql.SQLException: [SQLITE_ERROR] SQL error or missing database (no such table: customers) It does not get past the first call to "executeQuery". The customers table definitely exists so what am I missing to establish connection?
I really need instructions to connect to the localhost database and ideally also to the one hosted by my webhost provider.
Thanks,
Jona
The Database class is to access the SQLite DB on the mobile device. To connect to external databases, you'd have to do something different, such as a ConnectionRequest or Socket I think.
I need to test a web application.So I copied the database file and connected to the dulicate databse on different sql server.. The application is running fine when I connected to the live database but when I connected to the duplicate database on my server.. it is throwing entity command execution exception. I changed the connection string details in the webapp( source,username, pwd) and also connected in vs. Did I miss anything(in connecting to database file) ? I searched a lot.. but couldn't figure out.. what was it I am doing wrong which throws exception ? I made it run once, but it didn't work again after please throw some light on how could I approach it...?
I am using Apache2 and php 5.6.,12. I decided to host my database remotely at Heroku(Using postgresql 9.4) and keep my server at Digital ocean.
In my yii 1 framework, the connection string that I have added is the following:
'db'=>array(
'connectionString' =>
'pgsql:host=ec2-XX-XX-XX-XX.compute-1.amazonaws.com;port=6372;dbname=dddqXXXXX;sslmode=require',
'emulatePrepare' => true,
'username' => 'XXXX4dcXXXX',
'password' => 'XXXXXXXXXc34XXXXXXX123',
'charset' => 'utf8',
),
The connection is successful but remote access is making it slow for even simple query in my server at digital ocean. I read from Heroku that for remote access, ssl mode has to be enabled. So I did and and I am still unable to figured out why the database connection is slow. It can be slow up to even 5 seconds. I tried with a locally installed postgresql database server and everything is running as expected. I am not sure how can I solve this else I will have to move away from Herokku and do it in the traditional way which is going to be very depressing. I hope that someone can help me.
Here is my php info og pgsql:
Is there some settings that need to be done to speed up remote heroku database access in apache2 or php?
I was unable to ping Postgres Heroku Server as advised by Richard (Heroku has prevented pinging) . It was very obvious that connection between digital ocean server and Heroku Postgres server is slow. Thus I emailed Heroku directly to ask for their advice.
Heroku's Solution:
They claimed that applications which are connecting from long distance outside the Heroku platform will have initial connection latency and this latency is a big problem.
Thus, Application has to establish a TCP connection which Postgres protocol will upgrade that to an SSL connection. This takes quite a few packets and introduces a lot of latency, particularly if the app is creating a new connection for each query or page load.
Heroku recommended me to configure the app to use something like heroku-pgbouncer connection pool. That uses pgbouncer and stunnel to provide a configurable connection pool for the app endpoints.
The recommendation sound too expensive and highly challenging for me to deal with.
My Solution :: Use Database Labs
I found out another postgres as a service provider called Database Labs . They allow users to select data center region for better performance.Database Labs has easy backend managing platform and friendly support team. The backend had minimum backend functionality and I do understand as they started in year 2014.
However, after migrating to their service, the performance of my web page improved remarkably. The connection was like any standard connection without the need for SSL. I am inputing my solution for the benefit of others who could face similar problem like me.
Heroku is definitely a good provider if we host our application in Heroku and use their database service. However If you are a Digital Ocean user, I recommend that you use Use Database Labs . This saves a lot of time
There isn't really a question here exactly, so this answer is more a guide to how to test the situation.
If you don't know enough to run a packet trace, you probably want to make sure your servers are all on the same network. However, try logging in to your Digital Ocean server and just ping the Heroku one. Repeat for www.google.com and compare the times. That's assuming the Heroku server responds to pings.
You should be able to connect with "psql -h ...". Then you can run a "SELECT count(*) FROM " then "SELECT * FROM LIMIT 10000", then "LIMIT 20000". That will let you figure out how much time is spent just transferring data vs running the query.
It might just be that the connection between your servers is very slow. Can't say without testing.