Bulk delete gitlab pipelines older than a given date

cleanup-gitlab-pipelines.sh

#!/bin/bash
# Purpose: Bulk-delete GitLab pipelines older than a given date
# Author: github.com/chrishoerl
# GitLab API: v4
# Requirements: jq must be instaled ($ sudo apt install jq)
# API example: https://gitlab.example.com/api/v4/projects
# API example: https://gitlab.example.com/api/v4/projects/<projectid>/pipelines
#
# NOTE: Script is just a dryrun. To really delete pipelines, simply uncomment line 49 to activate
#
################### FIRST REPLACE VARIABLES WITH YOR VALUES ############
# Define some variables
GITLABURL="https://gitlab.example.com"
ACCESSTOKEN="XXXXXXXXXXXXX" #must have API r/w access
# Pipelines older than this date will be deleted by this script
DELETEBEFORE="2020-01-16" #date range format: yyyy-mm-dd
########################################################################

# Get all project names and write to array
project_array=( $(curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" "$GITLABURL/api/v4/projects?per_page=100" 2> /dev/null | jq -r '.[] | .path_with_namespace') )

# Now let's work with the project names from the array
COUNTER=1
for PROJECTNAME in "${project_array[@]}"
do
   # debug
   #echo "Project: $PROJECTNAME"

   # Determine project id of given project name
   PROJECTID=`curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" $GITLABURL/api/v4/projects?per_page=100 2> /dev/null | jq '.[]|select(.path_with_namespace=="'$PROJECTNAME'")|.id'`

   # Find out pipeline IDs of our project which match the date range and write results into array
   pipeline_array=( $(curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" "$GITLABURL/api/v4/projects/$PROJECTID/pipelines?per_page=100&updated_before="$DELETEBEFORE"T23:01:00.000Z" 2> /dev/null | jq -r '.[] | .id') )

   # Count how many pipelines we found out
   NUMOFPIPES=`echo ${#pipeline_array[@]}`

   # Print statistics
   echo -e "---\nTask $COUNTER: Project $PROJECTNAME (ID:$PROJECTID) has $NUMOFPIPES pipelines to delete."

   # Print all pipeline IDs from the array
   for pipelineid in "${pipeline_array[@]}"
   do
      echo "Deleting pipeline ID: ${pipelineid}"
      echo "$GITLABURL/api/v4/projects/$PROJECTID/pipelines/${pipelineid}"

      ## ACTIVATE THIS TO START CLEANUP JOB
      ## Create DELETE query for each pipeline matching our date range
      #curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" --request "DELETE" "$GITLABURL/api/v4/projects/$PROJECTID/pipelines/$pipelineid"
   done
   # Raise counter
   COUNTER=$((COUNTER + 1))
done

Your script doesn't work when number of projects is more than 100. Besides I found some troubles with archived projects. And is't easier to have array from project id numbers and find project name by id, I changed this also because of some problems after updating to Gitlab 14.10.5.
There is a new way to get a list of all projects in Giltab 15.x, but I didn't test it yet? I'll test after upgrade.
Your script also doesn't delete pipelines more than 100, so I add a while cycle to get it work. Here is my script. Please test and check If you can make it clear.
https://gist.github.com/anutator/7f24f83db93bf7cc5d159de4fabd77a7

#!/bin/bash
# Purpose: Bulk-delete GitLab pipelines older than a given date
# Author: github.com/chrishoerl  Updated github.com/LeeRoyManea
# GitLab API: v4
# Requirements: jq must be instaled ($ sudo apt install jq)
# API example: https://gitlab.example.com/api/v4/projects
# API example: https://gitlab.example.com/api/v4/projects/<projectid>/pipelines
#
# NOTE: Script is just a dryrun. To really delete pipelines, simply uncomment line 49 to activate
################### FIRST REPLACE VARIABLES WITH YOUR VALUES ############
# Define some variables
GITLABURL=""
ACCESSTOKEN="" # must have API r/w access
########################################################################

# Function to get all items from a paginated GitLab API endpoint
get_all_items() {
  local endpoint=$1
  local array_name=$2
  local page=1
  while true; do
    response=$(curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" "$GITLABURL/$endpoint?page=$page&per_page=100" 2>/dev/null)
    #current_items=$(echo "$response" | jq -r '.[]? | .id // empty')
    current_items=$(echo "$response" | jq -r 'if length > 0 then .[] | .id else empty end')
    if [ -z "$current_items" ]; then
      break
    fi
    eval "$array_name+=( $current_items )"
    page=$((page + 1))
    #echo "loading Page: ${page} of '${GITLABURL}/${endpoint}'"
  done
}

# Get all project IDs and write to array
project_ids=()
get_all_items "api/v4/projects" project_ids

# Now let's work with the project IDs from the array
COUNTER=1
for PROJECTID in "${project_ids[@]}"; do
  # Get project name
  PROJECTNAME=$(curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" "$GITLABURL/api/v4/projects/$PROJECTID" 2>/dev/null | jq -r '.path_with_namespace')

  # Find out pipeline IDs of our project which match the date range and write results into array
  pipeline_array=()
  get_all_items "api/v4/projects/$PROJECTID/pipelines" pipeline_array

  # Count how many pipelines we found out
  NUMOFPIPES=${#pipeline_array[@]}

  # Print statistics
  echo -e "---\nTask $COUNTER: Project $PROJECTNAME (ID:$PROJECTID) has $NUMOFPIPES pipelines to delete."

  # Print all pipeline IDs from the array
  for pipelineid in "${pipeline_array[@]}"; do
    echo "Deleting pipeline ID: ${pipelineid} -> $GITLABURL/api/v4/projects/$PROJECTID/pipelines/${pipelineid}"
    curl --header "PRIVATE-TOKEN: $ACCESSTOKEN" --request "DELETE" "$GITLABURL/api/v4/projects/$PROJECTID/pipelines/$pipelineid"
  done
  # Raise counter
  COUNTER=$((COUNTER + 1))
done

this is working for me to delete all pipelines in all projects. not only the top 100. sadly the datetime filter causing issues for me