prometheus-exporters-releases.sh

#!/bin/bash

set -Eeuo pipefail

# This script fetches various Prometheus exporters from GitHub.

# It checks if the latest release has already been downloaded for each repository
# in the list. If there is a new release, it downloads it, and performs standard
# steps like compilation or copying, depending on the options specified.

# It depends on the exporters being stored in the following structure:
#
# $EXPORTER_DIR
#     $exporter
#         version.txt - latest version
#         repo.txt - repository url, like https://github.com/prometheus/node_exporter/releases
#         process_assets - shell script to process the assets, like turning
#                         node_exporter-1.5.0.linux-amd64.tar.gz into
#                         node_exporter-amd64

# Set the destination directory for the exporters and the working directory
EXPORTER_DIR="/usr/local/prometheus/exporters"
WORKING_DIR="/root/prometheus/exporters"

# Check if the required dependencies are installed
for dependency in git curl go jq; do
    if ! command -v "$dependency" >/dev/null; then
        printf "Error: %s is required but not installed. Aborting.\n" "$dependency"
        exit 1
    fi
done

# Check if the exporter directory exists and is writable
for dir in $EXPORTER_DIR $WORKING_DIR; do
    if [[ ! -d "$dir" || ! -w "$dir" ]]; then
        printf "Error: %s does not exist or is not writable.\n" "$dir"
        exit 1
    fi
done

# Find the list of exporters and their repositories from the directory structure, and iterate over them
for exporter_repo in $EXPORTER_DIR/*/repo.txt; do
    exporter="$(echo "$exporter_repo" | rev | cut -d / -f 2 | rev)"
    repo=$(cat "$EXPORTER_DIR/$exporter/repo.txt")

    # Check if the required metadata files exist for the exporter
    for metafile in patterns.txt process_assets; do
        if [[ ! -f "$metafile" ]]; then
            echo "Error: $exporter/$metafile does not exist."
            exit 1
        fi
    done

    # Check if the directory for the repository exists
    if [[ -f "$EXPORTER_DIR/$exporter/version.txt" ]]; then
        # The directory and version file exist, so check the version of the downloaded release
        downloaded_version=$(cat "$EXPORTER_DIR/$exporter/version.txt")
    else
        # The directory or version file does not exist, so set the downloaded version to an empty string
        downloaded_version=""
    fi

        # Get the latest version from GitHub
    latest_release_api_response=$(curl -s https://api.github.com/repos/$repo/releases/latest)
    if [[ $? -ne 0 ]]; then
        # Curl encountered an error when fetching the latest release API response
        echo "Error: Failed to fetch latest release for $exporter from GitHub."
        exit 1
    fi
    latest_version=$(echo "$latest_release_api_response" | jq -r '.tag_name' 2>/dev/null)
    if [[ $? -ne 0 ]]; then
        # Jq encountered an error when parsing the latest release API response
        echo "Error: Failed to parse latest release for $exporter from GitHub."
        exit 1
    fi

    # Compare the versions
    if [[ "$downloaded_version" != "$latest_version" ]]; then
        # The downloaded version is older, so download the latest release
        printf "Info: %s has updates available (current: %s, latest: %s).\n" "$exporter" "$downloaded_version" "$latest_version"
        assets=$(echo "$latest_release_api_response" | jq -r '.assets[].name' 2>/dev/null)
        if [[ $? -ne 0 ]]; then
            # Jq encountered an error when parsing the list of assets from the latest release API response
            echo "Error: Failed to parse list of assets for $exporter from GitHub at $repo."
            exit 1
        fi
        if [[ -z "$assets" ]]; then
            # The list of assets is empty
            echo "Error: No assets found for latest release of $exporter on GitHub at $repo."
            exit 1
        fi
        # Loop through the list of assets
        for asset in $assets; do
            # Loop through the list of patterns
            matched=false
            while IFS='' read -r pattern || [[ -n "$pattern" ]]; do
                # Check if the asset's filename matches the pattern
                if [[ $asset =~ $pattern ]]; then
                    # The asset's filename matches the pattern, so download it
                    matched=true
                    break
                fi
            done < "$EXPORTER_DIR/$exporter/patterns.txt"
            if [[ "$matched" = true ]]; then
                # The asset's filename matches a pattern in the list, so download it

                # Get the URL of the asset
                asset_url=$(echo "$latest_release_api_response" | jq -r ".assets[] | select(.name == \"$asset\") | .browser_download_url" 2>/dev/null)
                if [[ $? -ne 0 ]]; then
                    # Jq encountered an error when parsing the URL of the asset from the latest release API response
                    echo "Error: Failed to parse URL for asset $asset for $exporter from GitHub."
                    exit 1
                fi

                # Download the asset
                mkdir -p $WORKING_DIR/$exporter
                if [[ $? -ne 0 ]]; then
                    # Mkdir encountered an error when creating the working directory for the exporter
                    echo "Error: Failed to create working directory for $exporter."
                    exit 1
                fi
                curl -L "$asset_url" -o "$WORKING_DIR/$exporter/$asset"
                if [[ $? -ne 0 ]]; then
                    # Curl encountered an error when downloading the asset
                    echo "Error: Failed to download asset $asset for $exporter from GitHub."
                    exit 1
                fi

                # Process the asset
                "$EXPORTER_DIR/$exporter/process_assets" "$WORKING_DIR/$exporter/$asset"
                if [[ $? -ne 0 ]]; then
                    # The process_assets script encountered an error
                    echo "Error: Failed to process asset $asset for $exporter."
                    exit 1
                fi
            fi
        done
        # Update the version file
        echo "$latest_version" > "$EXPORTER_DIR/$exporter/version.txt"
    else
        # The downloaded version is up to date
        printf "Info: %s is up to date (current: %s, latest: %s).\n" "$exporter" "$downloaded_version" "$latest_version"
    fi
done