eb22c2a8c8
* Also dump diagnostics when a read times out while active (not queued). * Add the "Trigger permit" line, containing the details of the permit which caused the diagnostics dump (by e.g. timing out). * Add the "Identified bottleneck(s)" line, containing the identified bottlenecks which lead to permits being queued. This line is missing if no such bottleneck can be identified. * Document the new features, as well as the stat dump, which was added some time ago. Example of the new dump format: ``` INFO 2024-09-12 08:09:48,046 [shard 0:main] reader_concurrency_semaphore - Semaphore reader_concurrency_semaphore_dump_reader_diganostics with 8/10 count and 106192275/32768 memory resources: timed out, dumping permit diagnostics: Trigger permit: count=0, memory=0, table=ks.tbl0, operation=mutation-query, state=waiting_for_admission Identified bottleneck(s): memory permits count memory table/operation/state 3 2 26M *.*/push-view-updates-2/active 3 2 16M ks.tbl1/push-view-updates-1/active 1 1 15M ks.tbl2/push-view-updates-1/active 1 0 13M ks.tbl1/multishard-mutation-query/active 1 0 12M ks.tbl0/push-view-updates-1/active 1 1 10M ks.tbl3/push-view-updates-2/active 1 1 6060K ks.tbl3/multishard-mutation-query/active 2 1 1930K ks.tbl0/push-view-updates-2/active 1 0 1216K ks.tbl0/multishard-mutation-query/active 6 0 0B ks.tbl1/shard-reader/waiting_for_admission 3 0 0B *.*/data-query/waiting_for_admission 9 0 0B ks.tbl0/mutation-query/waiting_for_admission 2 0 0B ks.tbl2/shard-reader/waiting_for_admission 4 0 0B ks.tbl0/shard-reader/waiting_for_admission 9 0 0B ks.tbl0/data-query/waiting_for_admission 7 0 0B ks.tbl3/mutation-query/waiting_for_admission 5 0 0B ks.tbl1/mutation-query/waiting_for_admission 2 0 0B ks.tbl2/mutation-query/waiting_for_admission 8 0 0B ks.tbl1/data-query/waiting_for_admission 1 0 0B *.*/mutation-query/waiting_for_admission 26 0 0B permits omitted for brevity 96 8 101M total Stats: permit_based_evictions: 0 time_based_evictions: 0 inactive_reads: 0 total_successful_reads: 0 total_failed_reads: 0 total_reads_shed_due_to_overload: 0 total_reads_killed_due_to_kill_limit: 0 reads_admitted: 1 reads_enqueued_for_admission: 82 reads_enqueued_for_memory: 0 reads_admitted_immediately: 1 reads_queued_because_ready_list: 0 reads_queued_because_need_cpu_permits: 82 reads_queued_because_memory_resources: 0 reads_queued_because_count_resources: 0 reads_queued_with_eviction: 0 total_permits: 97 current_permits: 96 need_cpu_permits: 0 awaits_permits: 0 disk_reads: 0 sstables_read: 0 ``` Fixes: https://github.com/scylladb/scylladb/issues/19535 Improvement, no backport needed. Closes scylladb/scylladb#20545 * github.com:scylladb/scylladb: docs/dev/reader-concurrency-semaphore.md: update the documentation on diagnostics dumps test/boost/reader_concurrency_semaphore_test: test the new diagnostics functionality reader_concurrency_semaphore: add bottleneck self-diagnosis to diagnosis dump reader_concurrency_semaphore: include trigger permit in diagnostic dump reader_concurrency_semaphore: propagate permit to do_dump_reader_permit_diagnostics() reader_concurrency_semaphore: use consistent exception type for timeout reader_concurrency_semaphore: dump diagnostics when non-waiting reader times out
ScyllaDB Documentation
This repository contains the source files for ScyllaDB Open Source documentation.
- The
devfolder contains developer-oriented documentation related to the ScyllaDB code base. It is not published and is only available via GitHub. - All other folders and files contain user-oriented documentation related to ScyllaDB Open Source and are sources for docs.scylladb.com.
To report a documentation bug or suggest an improvement, open an issue in GitHub issues for this project.
To contribute to the documentation, open a GitHub pull request.
Key Guidelines for Contributors
- Follow the ScyllaDB Style Guide.
- The user documentation is written in reStructuredText (RST) - a plaintext markup language similar to Markdown. If you're not familiar with RST, see ScyllaDB RST Examples.
- The developer documentation is written in Markdown. See Basic Markdown Syntax for reference.
Creating Knowledge Base Articles
The kb/ directory holds source files for knowledge base articles in the Knowledge Base section of the ScyllaDB documentation.
The kb/kb_common subdirectory contains a template for knowledge base articles to help you create new articles.
To create a new knowledge base article (KB):
- Copy the
kb-article-template.rstfile from/kb/kb_commonto/kband rename it with a unique name. - Open the new file and fill in the required information.
- Remove what is not needed.
- Run
make previewto build the docs and preview them locally. - Send a PR with "KB" in its title.
Building User Documentation
Prerequisites
- Python 3. Check your version with
$ python --version. - poetry 1.12 or later
- make
Mac OS X
You must have a working Homebrew in order to install the needed tools.
You also need the standard utility make.
Check if you have these two items with the following commands:
brew help
make -h
Linux Distributions
Building the user docs should work out of the box on most Linux distributions.
Windows
Use "Bash on Ubuntu on Windows" for the same tools and capabilities as on Linux distributions.
Building the Docs
- Run
make previewto build the documentation. - Preview the built documentation locally at http://127.0.0.1:5500/.
Cleanup
You can clean up all the build products and auto-installed Python stuff with:
make pristine
Information for Contributors
If you are interested in contributing to Scylla docs, please read the Scylla open source page at http://www.scylladb.com/opensource/ and complete a Scylla contributor agreement if needed. We can only accept documentation pull requests if we have a contributor agreement on file for you.
Third-party Documentation
-
Do any copying as a separate commit. Always commit an unmodified version first and then do any editing in a separate commit.
-
We already have a copy of the Apache license in our tree, so you do not need to commit a copy of the license.
-
Include the copyright header from the source file in the edited version. If you are copying an Apache Cassandra document with no copyright header, use:
This document includes material from Apache Cassandra.
Apache Cassandra is Copyright 2009-2014 The Apache Software Foundation.