Roll back to JDK 21 for now, and make Java version configurable in the root build.gradle
The project has run into no less than three distinct show-stopping bugs in JDK22, across multiple vendors, and gradle still doesn't fully support it, meaning you need multiple JDK versions installed.
Look, this will make the git history look funny, but trimming unnecessary depth from the source tree is a very necessary sanity-preserving measure when dealing with a super-modularized codebase like this one.
While it makes the project configuration a bit less conventional, it will save you several clicks every time you jump between modules. Which you'll do a lot, because it's *modul*ar. The src/main/java convention makes a lot of sense for a non-modular project though. This ain't that.
To avoid having to either hard-code or manually configure service addresses (possibly several dozen), and to reduce the project's dependency on docker to deal with routing and discovery, the option to use [Zookeeper](https://zookeeper.apache.org/) to manage services and discovery has been added.
A service registry interface was added, with a Zookeeper implementation and a basic implementation that only works on docker and hard-codes everything.
The last remaining REST service, the assistant-service, has been migrated to gRPC.
This also proved a good time to clear out primordial technical debt from the root of the codebase. The 'service-client' library has been taken behind the barn and given a last farewell. It's replaced by a small library for managing gRPC channels.
Since it's no longer used by anything, RxJava has been removed as a dependency from the project.
Although the current state seems reasonably stable, this is a work-in-progress commit.
In the scenario where an operator
* Performs a new crawl from spec
* Doesn't load the data into the index
* Recrawls the data
The recrawl will not find the domains in the database, and the crawl log will be overwritten with an empty file,
irrecoverably losing the crawl log making it impossible to load!
To mitigate the impact similar problems, the change saves a backup of the old crawl log, as well as complains about this happening.
More specifically to this exact scenario however, the parquet-loaded domains are also preemptively inserted into the domain database at the start of the crawl. This should help the DbCrawlSpecProvider to find them regardless of loaded state.
This may seem a bit redundant, but losing crawl data is arguably the worst type of disaster scenario for this software, so it's arguably merited.
Modified the DbCrawlSpecProvider to shuffle domains after loading to ensure a good mix for each crawl. This change prevents overload of crawling the same server in parallel from different subdomains or crawling big domains all at once.
The WARC specification says the records should transparently remove compression. This was not done, leading to the WARC typically being a bit of a gzip-Matryoshka.
The WARC specification says the records should transparently remove compression. This was not done, leading to the WARC typically being a bit of a gzip-Matryoshka.
Wrote a new test to examine the redirect behavior of the crawler, ensuring that the redirect URL is the URL that is reported in the parquet file. This works as intended.
Noticed in the course of this that the crawler doesn't add links from meta-tag redirects to the crawl frontier. Added logic to handle this case, amended the test case to verify the new behavior. Added the meta-redirect case to the HtmlDocumentProcessorPlugin as well, so that we consider it a link between documents in the unlikely case that a meta redirect is to another domain.
This commit extracts several previously hardcoded configuration properties, and makes then available through system.properties.
The documentation is updated to reflect the change.
Dead code was also removed in the process. CrawlSpecGenerator is left feeling a bit over-engineered still, since it's built for a more general case, where all other implementations but the current one are removed, but we'll leave it like this for now as it's fairly readable still.
Use a system.properties file to configure the system. This is loaded statically by MainClass or ProcessMainClass. Update the property names to be more consistent, and update the documentations to reflect the changes.
Add a toggle for saving the WARC data generated by the search engine's crawler. Normally this is discarded, but for debugging or archival purposes, retaining it may be of interest.
The warc files are concatenated into larger archives, up to about 1 GB each.
An index is also created containing filenames, domain names, offsets and sizes
to help navigate these larger archives.
The warc data is saved in a directory warc/ under the crawl data storage.
The changeset also makes the control service responsible for flyway migrations. This helps reduce the number of places the database configuration needs to be spread out. These automatic migrations can be disabled with -DdisableFlyway=true.
The commit also adds curl to the docker container, to enable docker health checks and interdependencies.
The new converter logic assumes that the crawl data is ordered where the domain record comes first, and then a sequence of document records. This is true for the new parquet format, but not for the old zstd/gson format.
To make the new converter compatible with the old format, a specialized reader is introduced that scans for the domain record before running through the sequence of document records; and presenting them in the new order.
This is slower than just reading the file beginning to end, so in order to retain performance when this ordering isn't necessary, a CompatibilityLevel flag is added to CrawledDomainReader, permitting the caller to decide how compatible the data needs to be.
Down the line when all the old data is purged, this should be removed, as it amounts to technical debt.
The URI query string is now URL encoded in the WarcProtocolReconstructor. This change ensures proper encoding of special characters as per the standard URL encoding rules and improves URL validity during the crawling process.
Guava's hashers are a bit allocation hungry, and a big driver of GC churn in the crawler. This switches to the modified Murmur hash function used throughout Marginalia.
