Hi: I run stateless (REST) web services written in PHP7.0 OO-style, under Apache. They use mysqli to connect to mariaDB instance on AWS. We discovered a db synchronization issue, and not sure where the problem is or how to solve it.
client call to service 1 will insert a record, and return the autogenerated primary key retrieved by $i_primary_key = $this->db->insert_id, post-successful insertion;
next client call will use that primary key to execute a service 2, which will UPDATE the record
since service 1 and 2 are separate https calls, they create their own connections, resources, etc.
The problem is that sometimes service 2 fails, complaining the record with such a primary key does not exist. Try again, or artificially delay calling service 2, after obtaining results from Service 1, and things work as they should.
How do I tell the mariaDB engine, or mysqli API to flush their cache after the insert? I am only guessing that the engine/connection in Service 1 has not yet made its resources available to its own internal server, hence other clients of the engine do not see the latest changes/data.
Any advice...?
Thanks
There is only one way for the "flush" not to have happened: If the INSERT is in a transaction that is not committed.
To investigate, find out what value of autocommit is being used in "service 1". If it is "on" (or "1"), then there is no way for the problem to occur.
If autocommit is off (0), the the code in service 1 failed to COMMIT the implicit transaction. That is a user error. I prefer, instead, to have explicit BEGIN...COMMIT statements.
I found this reading up on mariaDB:
https://mariadb.com/kb/en/library/server-system-variables/#flush
flush
Description: Usually, MariaDB writes changes to disk after each SQL statement, and the operating system handles synchronizing (flushing) it to disk. If set to ON, the server will synchronize all changes to disk after each statement.
Commandline: --flush
Scope: Global
Dynamic: Yes
Data Type: boolean
Default Value: OFF
...So I'm going to set it to ON. Once I have results I'll update confirming it working...
Related
I am running into a very strange issue with Spring Boot and Spring Data: after I manually close a connection, the formerly working application seems to "forget" which schema it's using and complains about missing relations.
Here's the code snippet in question:
try (Connection connection = this.dataSource.getConnection()) {
ScriptUtils.executeSqlScript(connection, new ClassPathResource("/script.sql"));
}
This code works fine, but after it executes, the application immediately starts throwing errors like the following:
org.postgresql.util.PSQLException: ERROR: relation "some_table" does not exist
Prior to executing the code above, the application works fine (including referencing the table it later complains about). If I remove the try-resource block, and do not close the Connection, everything also works fine, except that I've now created a resource leak. I have also tried explicitly setting the default schema (public) in the following ways:
In the JDBC URL with the currentSchema parameter
With the the spring.datasource.hikari.schema parameter
With the spring.datasource.jpa.properties.hibernate.default_schema property
The last does alleviate the issue with respect to Hibernate managed classes, but the issue persists with native queries. I could, of course, make the schema explicit in those queries, but that doesn't seem to address the root issue. Why would closing a connection trigger this behavior?
My environment:
Spring Boot 2.5.1
PostgreSQL 12.7
Thanks to several users above who immediately saw what I did not. The script, adapted from an older pg_dump run, was indeed mucking with the search_path:
SELECT pg_catalog.set_config('search_path', '', false);
Removing that line, and some other unnecessary ones, resolved the problem. Big duh on my part.
I am writing restful API with Yii, but I am getting an SQL error in create function. My purpose is to add new data to the news table, but it asks me for the author_id. How can I do it without crushing the default create method?
Solution 1. Run this below query on mysql/phpmyadmin and restart server
SET GLOBAL sql_mode = 'NO_ENGINE_SUBSTITUTION';
Solution 2.
Open the my.ini or my.cnf file for editing (the file you have depends on whether you are running Windows or Linux).
Find the following line:
sql_mode = "STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
Replace it with the line below:
If the line is not found, insert the line under the [mysqld] section (if there is no [mysqld] section, create it).
sql_mode= ""
Restart the MySQL service for the change to take effect.
If restarting is not a feasible option at the moment, you may log into the database server and execute the below command for the changes to take effect immediately. However, the change will be discarded the next time the MySQL service restarts unless the above process is performed.
set global sql_mode='';
In the PostgreSQL documentation https://www.postgresql.org/docs/10/libpq-connect.html, it has been said that multiple hosts can be specified in a single connection string such that all the hosts will be tried in order one after the other until one of the server gets succeeds.
But when i tried to implement the same setting in the tag present in my ASP.net web.config file, it is throwing error as no such host name. I am using NpgSQL provider in order to connect to PostgreSQL database.
I need to add multiple server names in the connection string such that if the server#1 fails then it should try for the next server server#2 immediately provided in the order until it succeeds
Can you please suggest on how multiple hosts can be provided in the connection string?
The Npgsql driver does not currently support this functionality. The issue tracking this is https://github.com/npgsql/npgsql/issues/732, I'm still hoping we can get this into the next release but there's a lot going on.
Load balancing and failover is avaialble in Npgsql version 6. At the time of writing v.6 is in preview.
Simple failover example (server2 is only used if a connection could not be established to server1):
Host=server1,server2;Username=test;Password=test
Example with load balancing (round robin I guess):
Host=server1,server2,server3,server4,server5;Username=test;Password=test;Load
Balance Hosts=true;Target Session Attributes=prefer-standby
https://www.npgsql.org/doc/failover-and-load-balancing.html
there. I want to tune Google Cloud SQL for PostgreSQL instance. Currently, I'm trying to eliminate sorting speed degradation:
Sort Method: external merge Disk: 39592kB
Right now work_mem is set to 4MB, and it seems that is too small. After reading docs, I didn't find the way how to change this setting. It's impossible via Web GUI and via command line:
$ gcloud sql instances patch reporting-dev --database-flags work_mem=128MB
The following message will be used for the patch API method.
{"project": "xxx-153410", "name": "reporting-dev", "settings": {"databaseFlags": [{"name": "work_mem", "value": "128MB"}]}}
WARNING: This patch modifies a value that requires your instance to be
restarted. Submitting this patch will immediately restart your
instance if it's running.
Do you want to continue (Y/n)? Y
ERROR: (gcloud.sql.instances.patch) HTTPError 404: Flag requested cannot be set.
Any thoughts on that?
You can change it by user or by database.
alter database db1 set work_mem='64MB';
alter user stan set work_mem='32MB';
User overides db, db overrides postgresql.conf / cluster settings. Both override alter system set ... which you might not be able to use due to security settings.
Im new to chef and trying to understand why this code does not return any error while if i do the same with 'start' i will get an error for such service does not exist.
service 'non-existing-service' do
action :stop
end
# chef-apply test.rb
Recipe: (chef-apply cookbook)::(chef-apply recipe)
* service[non-existing-service] action stop (up to date)
Don't know which plattform you are running on if you are running on Windows it should at least log
Chef::Log.debug "#{#new_resource} does not exist - nothing to do"
given that you have debug as log level.
You could argue this is the wrong behaviour, but if the service dose not exist it for sure isen't running.
Source code
https://github.com/chef/chef/blob/master/lib/chef/provider/service/windows.rb#L147
If you are getting one of the variants of the init.d provider, they default to getting the current status of a service by grepping the process table. Because Chef does its own idempotence checks internally before calling the provider's stop method, it would see there is no such process in the table and assume it was already stopped.