Describes the behaviour and configuration of the cache_critical_dns
script, mainly cribbed from commit messages. Tries to make this program
a bit less of an enigma.
The `PG::Connection#ping` method is only reliable for checking if the
given host is accepting connections, and not if the authentication
details are valid.
This extends the healthcheck to confirm that the auth details are
able to both create a connection and execute queries against the
database.
We expect the empty query to return an empty result set, so we can
assert on that. If a failure occurs for any reason, the healthcheck will
return false.
An SRV RR contains a priority value for each of the SRV targets that
are present, ranging from 0 - 65535. When caching SRV records we may want to
filter out any targets above or below a particular threshold.
This change adds support for specifying a lower and/or upper bound on
target priorities for any SRV RRs. Any targets returned when resolving
the SRV RR whose priority does not fall between the lower and upper
thresholds are ignored.
For example: Let's say we are running two Redis servers, a primary and
cold server as a backup (but not a replica). Both servers would pass health
checks, but clearly the primary should be preferred over the backup
server. In this case, we could configure our SRV RR with the primary
target as priority 1 and backup target as priority 10. The
`DISCOURSE_REDIS_HOST_SRV_LE` could then be set to 1 and the target with
priority 10 would be ignored.
See /t/66045.
This removes the option to override the sleep time between caching of
DNS records. The override was invalid because `''.to_i` is 0 in Ruby,
causing a tight loop calling the `run` method.
For Redis connections that operate over TLS, we need to ensure that we
are setting the correct arguments for the Redis client. We can utilise
the existing environment variable `DISCOURSE_REDIS_USE_SSL` to toggle
this behaviour.
No SSL verification is performed for two reasons:
- the Discourse application will perform a verification against any FQDN
as specified for the Redis host
- the healthcheck is run against the _resolved_ IP address for the Redis
hostname, and any SSL verification will always fail against a direct
IP address
If no SSL arguments are provided, the IP address is never cached against
the hostname as no healthy address is ever found in the HealthyCache.
Modify the cache_critical_dns script for SRV RR awareness. The new
behaviour is only enabled when one or more of the following environment
variables are present (and only for a host where the `DISCOURSE_*_HOST_SRV`
variable is present):
- `DISCOURSE_DB_HOST_SRV`
- `DISCOURSE_DB_REPLICA_HOST_SRV`
- `DISCOURSE_REDIS_HOST_SRV`
- `DISCOURSE_REDIS_REPLICA_HOST_SRV`
Some minor changes in refactor to original script behaviour:
- add Name and SRVName classes for storing resolved addresses for a hostname
- pass DNS client into main run loop instead of creating inside the loop
- ensure all times are UTC
- add environment override for system hosts file path and time between DNS
checks mainly for testing purposes
The environment variable for `BUNDLE_GEMFILE` is set to enables Ruby to
load gems that are installed and vendored via the project's Gemfile.
This script is usually not run from the project directory as it is
configured as a system service (see
71ba9fb7b5/templates/cache-dns.template.yml (L19))
and therefore cannot load gems like `pg` or `redis` from the default
load paths. Setting this environment variable configures bundler to look
in the correct project directory during it's setup phase.
When a `DISCOURSE_*_HOST_SRV` environment variable is present, the
decision for which target to cache is as follows:
- resolve the SRV targets for the provided hostname
- lookup the addresses for all of the resolved SRV targets via the
A and AAAA RRs for the target's hostname
- perform a protocol-aware healthcheck (PostgreSQL or Redis pings)
- pick the newest target that passes the healthcheck
From there, the resolved address for the SRV target is cached against
the hostname as specified by the original form of the environment
variable.
For example: The hostname specified by the `DISCOURSE_DB_HOST` record
is `database.example.com`, and the `DISCOURSE_DB_HOST_SRV` record is
`database._postgresql._tcp.sd.example.com`. An SRV RR lookup will return
zero or more targets. Each of the targets will be queried for A and AAAA
RRs. For each of the addresses returned, the newest address that passes
a protocol-aware healthcheck will be cached. This address is cached so
that if any newer address for the SRV target appears we can perform a
health check and prefer the newer address if the check passes.
All resolved SRV targets are cached for a minimum of 30 minutes in memory
so that we can prefer newer hosts over older hosts when more than one target
is returned. Any host in the cache that hasn't been seen for more than 30
minutes is purged.
See /t/61485.
* File.exists? is deprecated and removed in Ruby 3.2 in favor of
File.exist?
* Dir.exists? is deprecated and removed in Ruby 3.2 in favor of
Dir.exist?
The discourse base image already contains a postgres installation, so pulling a separate postgres image is a little wasteful. Using the copy of Postgres in the discourse image saves about 20 seconds on every GitHub actions run.
This commit sets up Postgres with a few performance-improving flags, which we were already using for the `rake docker:test` task (used on our internal CI system).
Some tables in the database have constraints on columns with dates. Because of them, the script for moving timestamps can fail from time to time. This PR makes the script work with such tables.
In general, in PostgreSQL it is not always possible to defer constraint checks to the transaction commit (Primary Keys and Unique Constraints can be deferred, but them should be declared as DEFERRABLE to make it possible. Indices created with CREATE UNIQUE INDEX can't be deferred at all).
Since we can't defer constraint checks, I've made it work using a little hack. For example, if we need to move all timestamps by one day, the script will move timestamps by 1000 years and one day, and then return timestamps back by 1000 years. The script use this hack only for columns that have unique constraints.
This will fix the try-reset build that failed today. Probably this going to happen again with other tables that have constraints on date columns. I'm going to modify the script to make it work without ignoring such tables. After that, the only table we're going to need to ignore will be the 2FA table.
Before I fixed that, don't hesitate to tag me if the try-reset build fail again.
Without checking if t.table_schema = '#{@schema}' the SELECT with JOIN in the script were returning every column twice in case there is a 'backup' scheme with exactly the same tables as in the 'public scheme'
We're going to use this script for updating timestamps on Try, but it can be used with a local database during development as well.
Usage:
Commands:
ruby db_timestamp_updater.rb yesterday <date> move all timestamps by x days so that <date> will be moved to yesterday
ruby db_timestamp_updater.rb 100 move all timestamps forward by 100 days
ruby db_timestamp_updater.rb -100 move all timestamps backward by 100 days
The script moves all timestamps in the database by the same amount of days forward or backward. No need to change the script if we add a new column in the future.
The more simple solution would be just to move timestamps in several tables (topics, posts, and so on). I didn't want to go that way because it could generate additional work in the future. For example, if we add a new column with a timestamp and users can see that timestamp we'd need to add that column to the script. Or, for example, if we move a post's timestamp to the future but forget to move a timestamp of topic timer or user action it can cause weird bugs.
Post-deploy migrations exist to allow for seamless Discourse upgrades. By design, they cause migrations to run out of numerical order. This has the potential to cause some unexpected edge cases. To reduce the likelihood of these edge cases, we will promote historical post_deploy migrations to regular migrations after a full Discourse stable release cycle.
This script is intended to be run at least during every Discourse release cycle.
This means that truly seamless upgrades will not be possible between non-consecutive Discourse versions. (Upgrades will still work, but may cause some server errors for users during the upgrade)
Setting a random value in the interval 1 week ago ... now works better
because this spreads digest scheduling over a week because digests are
sent one week from the date of the last digest.
Over the years we accrued many spelling mistakes in the code base.
This PR attempts to fix spelling mistakes and typos in all areas of the code that are extremely safe to change
- comments
- test descriptions
- other low risk areas
This is a pretty straightforward bulk importer, just tailored to the vBulletin 5 database structure.
Also made a few minor improvements to the base importer -- should be self explanatory in the code.
Wrote up a new script to import from Higher Logic. Nothing too crazy going on here. Two major things about this script:
It requires you to convert a Microsoft SQL file to a format MySQL can read.
Higher Logic stores posts (at least in the case of the import I ran) with the email thread shown in the post body. The script does its best to truncate this out, but the logic may need to be improved on future imports. For the import I ran, it worked just fine as is. 🤷♂️
Made some improvements to the Vanilla MySQL script -- mainly because not all SQL imports require use of the VanillaBodyParser. Still left it as an option to turn on and use if so desired. Also added subcategory support, importing of likes, and solve status.
