Just to let you know:
Based on my finished Oracle implementation and the last blog post, I’ve dropped Vincent Rogier, developer of ocilib a few lines about my work experience with ocilib.
This small diary entry describes the way how Icinga and ocilib happened 🙂
Just to let you know:
As mentioned in the last post, there are other improvements for Icinga and IDOUtils.
This time, I want to give you a deeper look onto database performance and the housekeeping stuff.
As you might know, selecting, updating or even deleting a row from a table heavily depends on the row count. If table size grows bigger e.g. in the historical tables from IDOUtils, those queries will be slower and hold back the main process. Current approach of IDOUtils is one forked child of ido2db for one idomod connection – working sequentially on the gotten data.
So even one select taking longer will slow down the data processing and worst case the socket will get blocking and idomod complains about writing to data sink.
But how to resolve those issues?
First of all there were several approaches originally found in mysql-mods.sql – setting indexes on table columns which are being used within the WHERE clause. Regarding the fact that ido2db is not just an insert application, but also deletes historical data on demand (table trimming options), selects objects for caching and furthermore updates existing rows (service/hoststatus e.g.) we decided to apply most useful indexes on the table creation statements. It does slow down an insert a bit, but the overall benefit is much bigger than that 🙂
Also the upcoming Icinga Web benefits from that – e.g. the logentries tables select performs a lot faster when using the API and a RDBMS.
But that’s not all – indexes are only one approach of improvement. In the last few months, Hendrik, Christoph and myself discussed a lot about the periodic housekeeping. The basic approach was to remove housekeeping function from the main data processing. Simply because historical deletes on large tables will take even longer and prevent new data being written to the database.
There have been discussions about a cronjob and seperated forked processes for housekeeping, but we wanted something within ido2db and simple to use. So Hendrik came up with the idea to create an own thread within each ido2db child which runs completely seperated from the main data processing flow – the so-called threaded housekeeper.
The thread just waits for the appropriate instance getting connected and then performs the periodic housekeeping – independant from the main flow. And it does not interfere with the normal data processing. So to speak it resolves a big performance issue within IDOUtils.
Basically, this is the way it performs:
- sleep a while after creation and intialization
- idle wait for database connection and connected instance from main process
- perform periodic maintenance not interferring with main process
- will be terminated when ido2db shuts down
Best thing so far – it has been implemented and tested and improved quite a while. Mostly done in our own git branches, but the final solution is within current git master and will be one of the outstanding new features for Icinga IDOUtils in the upcoming Icinga 1.0.1 release.
Stay tuned for more updates!
… and prepare for Icinga 1.0.1! =)
It’s been a while since I made several changes to the initial Oracle implementation in Icinga IDOUtils. Code has been split, first start of using prepared statements and binded params with ocilib and some other changes to the code.
In the last few weeks I have been investigating a lot on how to implement more improvements and optimize the critical path of data input from Icinga Core.
I want to start with IDOUtils Oracle, more information on other improvements for Icinga and IDOUtils will follow 🙂
Oracle implementation splits up into several parts taken care of:
- Rewrite all queries to prepared statements and bind params at runtime
- Add dynamic procedures for DELETE statements
- Drop autoincrement emulation by one sequence and insert triggers
- Add sequences for each table and use INSERT INTO … (id, …) VALUES (seq_name.nextval, …)
- Add RETURNING id INTO :id for INSERT statements to save one round trip
- MERGE does not support returning INTO, added SELECT seq_name.currval query instead for fetching last inserted id
- Rewrite selecting cached objects from DB
The rewritten queries are divided as follows:
- 1x SELECT latest data time as is (called only at startup)
- dynamic procedure for DELETE on table by instance_id called at startup for cleaning config/status
- dynamic procedure for DELETE on tably by instance_id, field compared to time called during periodic cleanup
- all other queries are prepared with their own statement handler
- 4x DELETE
- 52x MERGE
- 9x INSERT
- 9x UPDATE
- 5x SELECT
This summarizes into about 8000 lines (+) and 2000 lines (-) of code modifications 🙂
Furthermore I have been thinking on how to provide an upgrade path for all existing IDOUtils Oracle users. Importing data using the newly applied sequences might lead into errors regarding currval of each sequence. A basic upgrade procedure has been provided already – if you want to try, get the latest GIT master.
Stay tuned for more interesting stories to tell 🙂
… and watch out for Icinga 1.0.1 and fresh IDOUtils Oracle!