I have been researching Spring Data Rest especially for cassandra and one of the questions my coworkers and I had was when does Spring Data connect to the database. We don't always want a rest controller to connect to the database so when does spring establish a connection if say we had a class extend the CRUDRepository? Does it connect to the database during the start of application itself? Is that something we can control?
For example, I implemented this example on Spring's website:
https://spring.io/guides/gs/accessing-data-rest/
At what point in the code does spring connect to the database?
Spring will connect to the DB as soon as the Datasource get initialized. Basically, Spring contexts will become alive somehow (Web listeners, manually calling them) and start creating beans. As soon as it reaches the Datasource, connection will be made and the connection pool will be populated.
Of course the above is based on a normal out of the box configuration and everything can be setup up to your taste.
So unless, you decide to control the connections yourself, DB connections will be sitting there waiting to be used.
Disagree with the above answer.
As part of research i initiated the datasource using a bean configuration and then changed my database password(not in my spring application but the real db username password)
The connection stays for a while and then in some point of time (maybe idle time) it stops working and throws credential exception.
This is enough to say the JPA does not keep the connection sitting and waiting to be used but uses some mechanism to occupy/release the db connection as per the need.
Related
I was reviewing a code which seems to lose connection to DB approximately once a month intermittently. It leaves no logs on DB side but server prints a log of Connection closed by peer.
Its a Spring Boot App (2.1.9) which uses Spring Integration to read from queues (JMS).
Under pom.xml spring-boot-started-jdbc , Hikari is excluded and tomcat is used.
The app is designed in such a way that it has an in-queue to get traffic, then series of internal queues to split the workload and finally an out queue to the destination.
This app has 4 datasources created all pointing to the same oracle database.
First datasource is used for all CRUD operations in the flow between in-queue and first internal queue. Second datasource is used for all CRUD operations in the flow between first and second internal queue. Third datasource is used between second internal queue and destination queue. Fourth datasource is not used anywhere which suggests some flow was commented but datasource was never removed.
Each datasource has different min and max connections but rest of the properties are same.
Wanted to understand is that a good practice to create
datasources for each spring integration flow pointing to same database?
Can it cause any problems to leave a datasource initialized without using it anywhere?
Is there any obvious reason why HikariCP shouldn't be chosen for production when lot of matrix online show Hikari is superior to Tomcat and Spring boot 2 has chosen it as default for a reason?
So i am running a spring boot server which i use to query a MySQL database. So far i have been using the auto-configured HikariCP connection pool with JOOQ so i had almost nothing to do with the connection pool. But now i need to query two different schemas (on the same server) and it seems like i can't auto-configure two connection pools so i have to tinker with the DataSource myself. I would like to conserve the native behavior of the connection, i.e have a set of persistent connections so that the server can dispatch the queries and once the query is resolved, the connection is still there and free to use again. I have found multiple implementations of connection pools allowing to have multiple DataSource to query multiple servers but i don't know if each of them is using the behavior that i just described.
Implementation #1 :
https://www.ru-rocker.com/2018/01/28/configure-multiple-data-source-spring-boot/
Implementation #2 :
https://www.stubbornjava.com/posts/database-connection-pooling-in-java-with-hikaricp
I feel like #2 is the most straight forward solution but i am sceptical to the idea of creating a new DataSource everytime i want to query. If i don't close it, am i just opening now connections over and over again? So obviously i would have to close them once finished but then it's not really a connection pool anymore. (Or am i misunderstanding this?)
Meanwhile #1 seems more reliable but again, i would be calling new HikariDataSource everytime so is that what i am looking for?
(Or is there a more simple solution that i have been missing out because i need to query two different schemas but still on the same server and dialect)
Ok so it turns out i don't have to setup multiple connections in my case. As i am querying the same server with the same credentials, i don't have to setup a connection for each shema. I just removed the schema that i specified in my jdbc url config:
spring.datasource.url=jdbc:mysql://localhost:5656/db_name?useUnicode=true&serverTimezone=UTC
Becomes
spring.datasource.url=jdbc:mysql://localhost:5656/?useUnicode=true&serverTimezone=UTC
And then as i had already generated the POJO with the JOOQ generator i could reference my table from the schema object, i.e: Client.CLIENT.ID.as("idClient") becomes ClientSchema.CLIENTSCHEMA.CLIENT.ID.as("idClient"). This way i can query multiple schemas without setting up any new additional connection.
How to configure MAVEN and JOOQ to generate sources from multiple schemas:
https://www.jooq.org/doc/3.13/manual/code-generation/codegen-advanced/codegen-config-database/codegen-database-catalog-and-schema-mapping/
We have an application that uses several data sources. A DB underlying one of those data sources is down at the moment: IOError. Network adapter couldn't establish the connection & Socket read timed out.
Is there an annotation (or other means) of configuring Spring Boot such that it bypasses the culprit data source and still starts up: the DB is not essential in current development work. spring.datasource.continue-on-error=true doesn't seem to work. This is Spring 2.2.2.RELEASE.
using multiple datasource, so when your apps fail at start up your apps still work, i mean using memory db / sqlite to handle fail at connection error...
We have an old EJB based web application which we are supposed to migrate into Spring boot. For database connectivity, it is a plain old jdbc connection approach as of now.
We want to use Spring transactions and remove EJB transactions but willing to keep plain old jdbc connectivity same. In short we don't want to make changes in our DAO layer to convert plain old jdbc to Spring JdbcTemplate.
Please note that we have our own connection pooling algorithm and we create connection object and close it in the pool.
Along with this we want our application to be multi-tenant that can work with multiple databases on the basis of 'tenantID' that we will provide.
I actually tried to implement this but it is not working. I had to manually do con.commit(); and con.rollback();
Is there any way to use Spring transactions with plain old jdbc connectivity with above scenario?
my problem is a bit complicated to explain, but basically seems that there some relation between my number of active connections and the delay to get some data from a remote server (web service). I mean I have a query to get some data in the database and after that a I do a call to this webserver, but everytime the latency of this webservice increase my connection in the database start to increase as well. I'm using Spring data jpa and Spring Boot.