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...
Related
In a Spring Boot application using Log4j2, I have setup a DataSource via yaml-configuration. But since Log4j2 needs a connection pool already in the startup phase for its JDBC Appender, a second data source must be provided separately. This results in the application having two connection pools running, both writing to the same database.
My first question is:
Are there any concerns about this setup, or is this the normal approach anyway?
Alternatively, the following setup would come to mind: we programmatically initialize the DataSource, so that we have access to it. Further on, we can then programmatically extend the existing Log4j2 configuration that doesn't have a JDBC Appender yet. By doing so we can pass the pooled DataSource that we also use for the application itself.
My second question is therefore:
Are there any caveats to using the same DataSource for both the application and the Log4j2 logging framework?
Many thanks for any information that helps to clarify the situation.
I would like to know if changing the password of the DB associated with the Spring boot application affects the existing connections.
If Hikari tries to connect by reading the properties at regular intervals when managing the connection, I think there could be a connection error in this process, is that right?
Yes it does affects the connection, it will cause something like "Error establishing a database connection".
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/
I configured Hikari following this tutorial: https://www.baeldung.com/spring-boot-hikari
When Spring Boot starts Hikari starts too, as follows in the next image:
Is it possible to configure Hikari to start when the first ReST request is being received?
Quoted from Hikari's official document on Github:
connectionTestQuery
If your driver supports JDBC4 we strongly recommend not setting this property. This is for "legacy" drivers that do not support the JDBC4
Connection.isValid() API. This is the query that will be executed just
before a connection is given to you from the pool to validate that the
connection to the database is still alive. Again, try running the pool
without this property, HikariCP will log an error if your driver is
not JDBC4 compliant to let you know. Default: none
As documentation:
"For a pooling DataSource to be created, we need to be able to verify that a valid Driver class is available, so we check for that before doing anything. In other words, if you set spring.datasource.driver-class-name=com.mysql.jdbc.Driver, then that class has to be loadable."(https://docs.spring.io/spring-boot/docs/2.1.6.RELEASE/reference/htmlsingle/)
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.