SQL/XML Dumps/Wikibase dumps via cron

All about Wikibase dumps via cron

Okay, maybe not all about them, but enough to get you adding your own scripts for new datasets.

Much of this is specific to the WMF puppet repo, but it builds on scripts in the Wikibase extension that are used to dump wikidata entities in various formats. We can just look at one of these formats to see how it works. It may be helpful for you to have a look at SQL/XML_Dumps/"Other"_dump_jobs_via_cron in combination with the current document.

All dumps except for xml/sql dumps run from cron via shell scripts which can be found in our puppet manifests. See modules/snapshot/files/cron [1] for these. We’ll start by looking at common functions available to all scripts.

Common functions for dump scripts

The script dump_functions.sh ([2]) provides paths to a number of directories, such as the base directory tree for all of these dumps, and the path to the dumps configuration files. It also provides a function for extracting values from the output of a little python script that gets multiple values from those config files, such as paths to useful executables, and the directory tree for temporary files. You should always source dump_functions.sh at the top of your script.

Configuration files

We have a few dumps configuration files available; one is for xml/sql dumps and you won’t want that. One is for WMCS instances and you won’t want that either. The one you do want is wikidump.conf.other in the config dir, available to you in the $confsdir variable. This name is historical; everything other than xml/sql dumps was considered “other” and is put in a separate directory tree, and even generated by separate hosts writing to a separate filesystem.

Where to write files, what to name them

We like output files to have the wiki db name, the date in YYYYMMDD format, and the sort of dump being produced in the name, the type of output (json, txt, ttl etc) as well as the compression type as the extension. Typically files are arranged in directories by dump type and then date. For example, cirrussearch dumps are in the subdirectory cirrussearch under a further subdirectory of YYYYMMDD for the date that run was started, with files for all wikis in the same directory. Output files for mediainfo data from commons in rdf format might be in wikibase/commonswiki/20200830/commons-20200830-mediainfo.nt.gz for example.

Thus, at the beginning of the script you should save the date in the right format. The base directory tree for these dump output files is available to you in $crondir so you can just tack on the dump name and the date as subdirs after that.

Getting config values for your script

We use absolute paths for everything including e.g. gzip and php. This makes things a bit safer and also lets us switch between versions of php on a rolling basis when we start moving to a new version. We also need to be able to get the directory where MWScript.php and its ilk reside. The getconfigvals.py script ([3]) is available for retrieving these values. You will set up a single argument with the config file sections and setting names you want to retrieve, call the script once, get the output, and then use the getsetting() function (included in the dump_functions.sh script we saw earlier) to extract each value to its own shell variable. You’ll want to check that the value isn’t empty (that something horrible hasn’t gone wrong with the config file or whatever) by using checkval(), also provided in dump_functions.sh.

Variables and settings for wikibase dumps

Enough blah blah, let’s look at code right from wikibasedumps-shared.sh ([4]) and see for ourselves. This code does all of the above for you, but it’s a good idea to know what all the pieces are before you start building on top of them.

 

#!/bin/bash
#############################################################
# This file is maintained by puppet!
# modules/snapshot/cron/wikibase/wikibasedumps-shared.sh
#############################################################
#
# Shared variable and function declarations for creating Wikibase dumps
# of any sort
#
# Marius Hoch < hoo@online.de >
​

 

Here we source the dump_functions script to get those directory paths and the settings retrieval/check functions. We now have the config dir path so we can pick up the right config file.

 

 

source /usr/local/etc/dump_functions.sh
configfile="${confsdir}/wikidump.conf.other"
​

 

Stash the date for the entire run in YYYYMMDD format. The other two variables have to do with how many runs we keep around (not really true as we have aggressive cleanup scripts running on all hosts) and how many pages to process in a batch. We dump output in batches so that if any batch fails it can be retried up to some reasonable number of times without having to start the whole job over from the beginning.

 

 

today=`date +'%Y%m%d'`
daysToKeep=70
pagesPerBatch=200000
​

 

Here we get the path to the multiversion directory, the path to the temporary directory tree, and the paths for php and lbzip2 (you may want gzip or something else here instead).

 

 

args="wiki:multiversion;output:temp;tools:php,lbzip2"
results=`python3 "${repodir}/getconfigvals.py" --configfile "$configfile" --args "$args"`

multiversion=`getsetting "$results" "wiki" "multiversion"` || exit 1
tempDir=`getsetting "$results" "output" "temp"` || exit 1
php=`getsetting "$results" "tools" "php"` || exit 1
lbzip2=`getsetting "$results" "tools" "lbzip2"` || exit 1
​

 

Once we have the settings we make sure they all have actual values in them (sanity check).

 

 

for settingname in "multiversion" "tempDir"; do
    checkval "$settingname" "${!settingname}"
done
​

 

Stash the directory for the specific wiki and run date.

 

 

targetDirBase=${cronsdir}/wikibase/${projectName}wiki
targetDir=$targetDirBase/$today
​

 

We need this in order to run our maintenance script.

 

 

multiversionscript="${multiversion}/MWScript.php"

# Create the dir for the day: This may or may not already exist, we don't care
mkdir -p $targetDir

Reminder that all of this is done for you in wikibasedumps-shared.sh so you need only source that in your dumpwikibase(somenewformat).sh script.

There is more here, but we don't need to look at all of the code for it. Instead, we summarize the interesting parts below.

Shared functions for wikibase dumps

A number of convenience functions are provided for you in wikibasedumps-shared.sh so please make use of them:

• pruneOldLogs() tosses old log files, typically written to files in /var/log/wikidatadump/ or commonsdump/
• runDcat() runs DCAT.php on the output files if there is a config specified for it.
• putDumpChecksums() generates md5 and sha1 checksums for and output file and stashes them in files to be made available for download.
• getNumberOfBatchesNeeded() gets the number of batches we’ll need to run, based on the number of processes we run at once and the max page id and some other stuffs.
• setPerBatchVars() sets the first and last page id we want to retrieve in a specific batch, etc.
• getTempFiles() gets a properly sorted list of all the output files matching some wildcard.
• getFileSize() gets the byte count of one or more files. This is used as a sanity check to make sure we don’t suddenly have much tinier output files than expected.
• handleBatchFailure() logs errors and handles retries of a batch.
• getContinueBatchNumber() is used in the case that we have run this script manually to continue a previously failed run. It will determine where we left off.
• moveLinkFile() is used at the end to move the temporary files we write into their permanent name and location.

These are all pretty self-explanatory, and the calls to them in e.g. dumpwikibaserdf.sh should be good examples.

Per-project functions for wikibase rdf dumps

You may want to set up for some other format but these are the sort of things you’ll want to provide.

Let’s look at the example for commons rdf dumps: commonsrdf_functions.sh ([5])

 

The usage message is because I will not remember 5 minutes later how to run these things and neither will you by the time you come back to fix the next bug.

 

#!/bin/bash
#############################################################
# This file is maintained by puppet!
# puppet:///modules/snapshot/cron/wikibase/commonsrdf_functions.sh
#############################################################
# function used by wikibase rdf dumps, customized for Commons

usage() {
    echo -e "Usage: $0 commons [--continue] mediainfo ttl|nt [nt|ttl]\n"
    echo -e "\t--continue\tAttempt to continue a previous dump run."
    echo -e "\tttl|nt\t\tOutput format."
    echo -e "\t[nt|ttl]\t\tOutput format for extra dump, converted from above (optional)."

    exit 1
}
​

 

You can see we set the project name to commons, the filename to wiki-date-dumptype as described earlier, a cutoff output files size below which the script should complain if the output is smaller, and the dcat config which in the case of commons does not exist yet.

 

 

setProjectName() {
    projectName="commons"
}

setEntityType() {
	entityTypes="--entity-type mediainfo --ignore-missing"
}

setDumpFlavor() {
	dumpFlavor="full-dump"
}

setFilename() {
    filename=commons-$today-$dumpName
}

setDumpNameToMinSize() {
	# TODO: figure out what number makes sense here
    dumpNameToMinSize=(["mediainfo"]=1000)
}

setDcatConfig() {
	# TODO: add DCAT info
    dcatConfig=""
}

Pretty simple stuff.

Now let’s see how all that gets used in dumpwikibaserdf.sh ([6])

Bringing it all together for wikbase rdf dumps

This does everything from grabbing all those shared definitions and functions, to setting up the output location and the number of parallel processes to run, to running the php script, checking for errors, and finally processing the output and moving it into its final location.

prep before php script execution

 

#!/bin/bash
#############################################################
# This file is maintained by puppet!
# puppet:///modules/snapshot/cron/wikibase/dumpwikibaserdf.sh
#############################################################
#
# Generate a RDF dump for wikibase datasets and remove old ones.
# This script requires a second shell script with function definitions
# in it specific to the given wikibase project and entity types;
# place it in modules/snapshot/cron/wikibase/<projectname>rdf_functions.sh
# using one of the existing files as a guide, and then add the
# project name to PROJECTS below.
# The project name should be the wiki db name without the 'wiki'
# suffix. If someday we move to run wikibase on wiktionaries
# or what have you, we'll redo the project and file name logic!
​

 

This code works only for commons and wikidata (db names commonswiki, wikidatawiki).

 

 

PROJECTS="wikidata|commons"

if [[ "$1" == '--help' ]]; then
    echo -e "$0 $PROJECTS --help for help"
    exit 1
fi

projectName=$1
if [ -z "$projectName" ]; then
    echo -e "Missing project name."
    echo -e "$0 $PROJECTS --help for help"
    exit 1
fi
if [ "$projectName" != "wikidata" -a  "$projectName" != "commons" ]; then
    echo -e "Unknown project name."
    echo -e "$0 $PROJECTS --help for help"
    exit 1
fi
​

 

Source all those common settings and functions.

 

 

. /usr/local/bin/wikibasedumps-shared.sh
. /usr/local/bin/${projectName}rdf_functions.sh

if [[ "$2" == '--help' ]]; then
     usage
     exit 1
fi
​

 

In case we are doing a manual run to finish up a run that broke partway through.

 

 

continue=0
if [[ "$2" == '--continue' ]]; then
	shift
	continue=1
fi
​

 

For rdf dumps this can currently be “all”, “truthy”, or “nt”.

 

 

dumpName=$2
if [ -z "$dumpName" ]; then
	echo "No dump name given."
	usage
	exit 1
fi

if [ $continue -gt 0 ]; then
	# Remove old leftovers, as we start from scratch.
	rm -f $tempDir/$projectName$dumpFormat-$dumpName.*-batch*.gz
fi
​

 

For rdf dumps this varies according to the dumpName, the dumpFlavor variable eventually gets passed in as an arg to the maintenance script. For other formats you may want something else or to not even have this.

 

 

setDumpFlavor
​

 

Yeah more special format stuff for the rdf jobs.

 

 

dumpFormat=$3
extraFormat=$4

if [[ "$dumpFormat" != "ttl" ]] && [[ "$dumpFormat" != "nt" ]]; then
	echo "Unknown format: $dumpFormat"
	usage
	exit 1
fi

if [ -n "$extraFormat" ]; then
	declare -A serdiDumpFormats
	serdiDumpFormats=(["ttl"]="turtle" ["nt"]="ntriples")
	extraIn=${serdiDumpFormats[$dumpFormat]}
	extraOut=${serdiDumpFormats[$extraFormat]}
	if [ -z "$extraIn" -o -z "$extraOut" -o "$extraIn" = "$extraOut" ]; then
		extraFormat=""
	fi
fi
​

 

Set up that dump output file name though!

 

 

setFilename

failureFile="/tmp/dump${projectName}${dumpFormat}-${dumpName}-failure"
logLocation="/var/log/${projectName}dump"
mainLogFile="${logLocation}/dump${projectName}${dumpFormat}-${filename}-main.log"
​

 

This is hardcoded in; how many batches are we dumping at once? Increases to this are inevitable but should be coordinated with the dba and whoever is managing the host(s) generating the dumps.

 

 

shards=8

i=0
rm -f $failureFile
​

 

When is the output so small that it’s probably broken?

 

 

setDumpNameToMinSize
​

 

Set up batch info.

 

 

getNumberOfBatchesNeeded ${projectName}wiki
numberOfBatchesNeeded=$(($numberOfBatchesNeeded / $shards))

if [[ $numberOfBatchesNeeded -lt 1 ]]; then
# wiki is too small for default settings, change settings to something sane
# this assumes wiki has at least four entities, which sounds plausible
	shards=4
	numberOfBatchesNeeded=1
	pagesPerBatch=$(( $maxPageId / $shards ))
fi
​

 

What are we dumping again? This sets the entity-type arg for the rdf dumps maintenance script.

 

 

setEntityType
​

running the MediaWiki maintenance script

 

while [ $i -lt $shards ]; do
	(

 

Gotta get errors from anywhere in the pipeline.

 

 

​		set -o pipefail
		errorLog=${logLocation}/dump$projectName$dumpFormat-$filename-$i.log

		batch=0

		if [ $continue -gt 0 ]; then
			getContinueBatchNumber "$tempDir/$projectName$dumpFormat-$dumpName.$i-batch*.gz"
		fi

		retries=0
		while [ $batch -lt $numberOfBatchesNeeded ] && [ ! -f $failureFile ]; do
			setPerBatchVars
​

 

Actually run the script, woo hoo!

 

 

​			echo "(`date --iso-8601=minutes`) Starting batch $batch" >> $errorLog
			$php $multiversionscript extensions/Wikibase/repo/maintenance/dumpRdf.php \
				--wiki ${projectName}wiki \
				--shard $i \
				--sharding-factor $shards \
				--batch-size $(($shards * 250)) \
				--format $dumpFormat ${dumpFlavor:+--flavor} ${dumpFlavor:+"$dumpFlavor"} \
				$entityTypes \
				--dbgroupdefault dump \
				--part-id $i-$batch \
				$firstPageIdParam \
				$lastPageIdParam 2>> $errorLog | gzip -9 > $tempDir/$projectName$dumpFormat-$dumpName.$i-batch$batch.gz

			exitCode=$?
			if [ $exitCode -gt 0 ]; then
				handleBatchFailure
				continue
			fi

			retries=0
			let batch++
		done
	) &
	let i++
done

wait
​

 

This failureFile thing is literally “did something fail”

 

 

if [ -f $failureFile ]; then
	echo -e "\n\n(`date --iso-8601=minutes`) Giving up after a shard failed." >> $mainLogFile
	rm -f $failureFile

	exit 1
fi

i=0
while [ $i -lt $shards ]; do
	getTempFiles "$tempDir/$projectName$dumpFormat-$dumpName.$i-batch*.gz"
	if [ -z "$tempFiles" ]; then
		echo "No files for shard $i!" >> $mainLogFile
		exit 1
	fi
	getFileSize "$tempFiles"
	if [ $fileSize -lt ${dumpNameToMinSize[$dumpName]} ]; then
		echo "File size of $tempFile is only $fileSize. Aborting." >> $mainLogFile
		exit 1
	fi
	cat $tempFiles >> $tempDir/$projectName$dumpFormat-$dumpName.gz
	let i++
done
​

 

This is rdf specific stuff.

 

 

if [ -n "$extraFormat" ]; then
	# Convert primary format to extra format
	i=0
	while [ $i -lt $shards ]; do
		getTempFiles "$tempDir/$projectName$dumpFormat-$dumpName.$i-batch*.gz"
		(
			set -o pipefail
			for tempFile in $tempFiles; do
				extraFile=${tempFile/$projectName$dumpFormat/$projectName$extraFormat}
				gzip -dc $tempFile | serdi -i $extraIn -o $extraOut -b -q - | gzip -9 > $extraFile
				exitCode=$?
				if [ $exitCode -gt 0 ]; then
					echo -e "\n\n(`date --iso-8601=minutes`) Converting $tempFile failed with exit code $exitCode" >> $errorLog
				fi
			done
		) &
		let i++
	done
	wait
fi

i=0

process the output files

 

Everything got written to temp files in the temp dir, do size sanity check, then concat them all together

 

 

while [ $i -lt $shards ]; do
	getTempFiles "$tempDir/$projectName$dumpFormat-$dumpName.$i-batch*.gz"
	rm -f $tempFiles
	if [ -n "$extraFormat" ]; then
		getTempFiles "$tempDir/$projectName$extraFormat-$dumpName.$i-batch*.gz"
		cat $tempFiles >> $tempDir/$projectName$extraFormat-$dumpName.gz
		rm -f $tempFiles
	fi
	let i++
done
​

 

We recompress the gzip output to bzip2 here, ymmv

 

 

nthreads=$(( $shards / 2))
if [ $nthreads -lt 1 ]; then
    nthreads=1
fi
​

 

But first we move the concatted temp file into place.

 

 

moveLinkFile $projectName$dumpFormat-$dumpName.gz $filename.$dumpFormat.gz latest-$dumpName.$dumpFormat.gz $projectName
gzip -dc "$targetDir/$filename.$dumpFormat.gz" | "$lbzip2" -n $nthreads -c > $tempDir/$projectName$dumpFormat-$dumpName.bz2
moveLinkFile $projectName$dumpFormat-$dumpName.bz2 $filename.$dumpFormat.bz2 latest-$dumpName.$dumpFormat.bz2 $projectName
​

 

The rdf specific extra format stuff, more of it

 

 

if [ -n "$extraFormat" ]; then
	moveLinkFile $projectName$extraFormat-$dumpName.gz $filename.$extraFormat.gz latest-$dumpName.$extraFormat.gz $projectName
	gzip -dc "$targetDir/$filename.$extraFormat.gz" | "$lbzip2" -n $nthreads -c > $tempDir/$projectName$extraFormat-$dumpName.bz2
	moveLinkFile $projectName$extraFormat-$dumpName.bz2 $filename.$extraFormat.bz2 latest-$dumpName.$extraFormat.bz2 $projectName
fi
​

 

Clean up old logs, run dcat if there’s a config, and we’re done at last!

 

 

pruneOldLogs
setDcatConfig
runDcat