ASPNET Core Zero Downtime Deployment to Linux with Nginx

aspnetcore-linux-deployment.sh

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

# How to use?
# https://medium.com/@ozgurtrgy/aspnet-core-zero-downtime-deployment-to-linux-with-nginx-b8b230bf1577

# the variables depend on you.
PACKAGE_TAR_NAME="artifacts.tar.gz"
VERSION="1005"
ASPNETCORE_ENV="Production"
APP_NAME="Example.Application.Name"
DLL_NAME="Example.Web.dll"
HEALTHCHECK_PORT=8081 # should be between 8000 and 9000.
DOMAIN_NAME="example.com"
REMOVE_NON_ASCII_COOKIES="true" # true if you are using ASPNET Core version 2.1 or below, otherwise false.

# other variables.
SERVICE_FILE_DIR="/etc/systemd/system"
NGINX_FILE_DIR="/etc/nginx/sites-available"
APP_ROOT_DIR="/var/aspnetcore"
APP_DIR="$APP_ROOT_DIR/$APP_NAME"
HEALTHCHECK_PATH="healthcheck"
APP_URL_LOCAL="http://localhost"

##
# Main routine
##
main() {
    local randomFreePort=$(getRandomFreePort)
    local deploypath=$(getDeployPath)
    local suffix=$(getSuffix)
    local appurl="$APP_URL_LOCAL:$randomFreePort";
    local healthcheckurl="$appurl/$HEALTHCHECK_PATH"
    local servicefile=$(getServiceFilePath ${suffix})
    
    extractPackage $deploypath
    replaceSettings $deploypath
    configureDataProtection
    configurePermissions $deploypath
    runService $servicefile $deploypath $appurl $healthcheckurl $suffix
    configureNginx $deploypath $appurl $healthcheckurl
    checkCorrectVersionIsUp $HEALTHCHECK_PORT $suffix
    destroyOldService $servicefile

    echo "Successfully finished." > /dev/stdout
}

##
# Get the directory that created recently. It should be created when new package fetched.
##
getLatestDir() {
    echo $(echo $(cd "$APP_DIR" && echo $(ls -t | head -1)))
}

##
# Get the current deployment path with version.
##
getDeployPath() {
    echo "$APP_DIR/$(getLatestDir)"
}

##
# Get the suffix from current deployment dir name. Suffix is the number that comes after the "-"
##
getSuffix() {
    local latestdir=$(getLatestDir)
    [[ $latestdir =~ "-" ]] && echo "-${latestdir##*-}" || echo ""
}

##
# Get random port between 5000 and 5300 that free.
##
getRandomFreePort() {
    while :; do randomport="`shuf -i 5000-5300 -n 1`"; ss -lpn | grep -q ":$randomport " || break; done
    echo $randomport
}

##
# Extract the deployment package.
##
extractPackage() {
    local deploypath=$1
    (cd $deploypath
        sudo tar -xzf $PACKAGE_TAR_NAME --strip-components=1 && sudo rm $PACKAGE_TAR_NAME
    )
}

##
# Replace app setting tmpl variables to environment variables.
##
replaceSettings() {
    local deploypath=$1
    (cd $deploypath
        keys=($(grep -o '{{.*}}' appsettings.json.tmpl | sed "s/{{.//g" | sed "s/}}//g"))

        echo "Variables are replacing..." > /dev/stdout

        #set appsetting.environment.json from environment variables.
        for key in "${keys[@]}"
        do
            value=${!key} # Fetched from environment variables. You can fetch your variables whereever you want.
            [[ $value =~ Unrecognized* ]] && (>&2 echo $value; exit 1;)

            sudo sed -i -e "s%{{.$key}}%$value%g" appsettings.json.tmpl
        done

        sudo mv appsettings.json.tmpl appsettings.$ASPNETCORE_ENV.json
    )
}

##
# Get the service file path.
##
getServiceFilePath() {
    local suffix=${1-""}
    local servicefilename="$APP_NAME-$VERSION$suffix.service"
    echo "$SERVICE_FILE_DIR/$servicefilename"
}

##
# Configure and run the new service.
##
runService() {
    local servicefile=$1
    local deploypath=$2
    local appurl=$3
    local healthcheckurl=$4
    local suffix=${5-""}

    local servicefilename="${servicefile##*/}"

    local service=(
        "[Unit]"
        "Description=Example .ASPNET Web App running on Ubuntu. app: $APP_NAME version: $VERSION"
        ""
        "[Service]"
        "WorkingDirectory=$deploypath"
        "ExecStart=/usr/bin/dotnet $deploypath/$DLL_NAME"
        "Restart=always"
        "RestartSec=30"
        "KillMode=mixed" # https://stackoverflow.com/a/40971615
        "SyslogIdentifier=$APP_NAME"
        "User=www-data"
        "LimitNOFILE=640000"
        "Environment=ASPNETCORE_ENVIRONMENT=$ASPNETCORE_ENV"
        "Environment=ASPNETCORE_URLS=$appurl"
        "Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false"
        "Environment=DEPLOYMENT_VERSION=$VERSION$suffix"
        ""
        "[Install]"
        "WantedBy=multi-user.target" )

    echo "Service is updating..." > /dev/stdout
    
    #configure
    [ -f $servicefile ] && sudo rm $servicefile

    for line in "${service[@]}"; do
        echo $line | sudo tee --append $servicefile > /dev/null
    done

    #run
    echo "Start the service..." > /dev/stdout
    sudo systemctl daemon-reload
    sudo systemctl restart $servicefilename
    sudo systemctl enable $servicefilename 2>&1 # to run on startup.
    echo "The service successfully started." > /dev/stdout

    #wait for the service is up.
    echo "Waiting for the service to up and running..." > /dev/stdout
    local end=$((SECONDS+180)) # 3 min to wait service up.
    local serviceisup=0
    while [ $SECONDS -lt $end ]; do 
        if [[ "$(curl -s -o /dev/null -w ''%{http_code}'' $healthcheckurl)" != "200" ]]; then
            sleep 10; # seconds
        else
            serviceisup=1
            break;
        fi    
    done
    [ $serviceisup -ne 1 ] && ( (>&2 echo "Service not responding :("); sudo rm $servicefile; sudo systemctl daemon-reload; exit 1; )
    echo "Service is up and running!" > /dev/stdout
}

##
# Configure the nginx config file.
##
configureNginx() {
    local deploypath=$1
    local appurl=$2
    local healthcheckurl=$3
    
    # to removing non-ascii characters from cookie. This is a workaround for kerstel 400 issue that will be fixed in 2.2 relase.
    # https://github.com/aspnet/KestrelHttpServer/issues/2884
    local removenonasciiblock=("") 
    local setnonasciicookieline=""

    if [ $REMOVE_NON_ASCII_COOKIES == "True" ]; then
        local removenonasciiblock=(
                '        set_by_lua_block $cookie_ascii {'
                '            local cookie = ngx.var.http_cookie'
                "            if cookie == nil or cookie == '' then return cookie end"
                '            local cookie_ascii, n, err = ngx.re.gsub(cookie, "[^\\x00-\\x7F]", "")'
                '            return cookie_ascii'
                '        }'
            )
        local setnonasciicookieline='        proxy_set_header    Cookie $cookie_ascii;'
    fi

    local rootlocation=(
        "    location / {"
        "${removenonasciiblock[@]}"
        "        root                $deploypath;"
        "        proxy_pass          $appurl;"
        "        proxy_buffering     off;" # https://medium.com/@mshanak/soved-dotnet-core-too-many-open-files-in-system-when-using-postgress-with-entity-framework-c6e30eeff6d1
        "        proxy_read_timeout  7200;"
        "        proxy_http_version  1.1;"
        "        proxy_set_header    Upgrade \$http_upgrade;"
        "        proxy_set_header    Connection keep-alive;"
        "        proxy_set_header    Host \$host;"
        "        proxy_cache_bypass  \$http_upgrade;"
        "        proxy_set_header    X-Forwarded-For \$proxy_add_x_forwarded_for;"
        "        proxy_set_header    X-Forwarded-Proto \$scheme;"
        "$setnonasciicookieline"
        "        fastcgi_buffers     16 16k;"
        "        fastcgi_buffer_size 32k;"
        "    }"
    )

    local server=(
        "server {"
        "    listen 80;"
        "    server_name $DOMAIN_NAME;"
        "${rootlocation[@]}"
        "}" )

    local healthcheckserver=(
        "server {"
        "    listen $healthcheckport;"
        "${rootlocation[@]}"
        "}"
    )

    local nginxconfigfile="$NGINX_FILE_DIR/$APP_NAME"

    echo "nginx configuring..." > /dev/stdout
    [ -f $nginxconfigfile ] && sudo rm $nginxconfigfile

    # server for all of environments.
    for line in "${server[@]}"; do
        echo $line | sudo tee --append $nginxconfigfile > /dev/null
    done
    # healtcheck server to use the app by ip.
    if [[ $healthcheckport =~ ^8[0-9]{3}$ ]]; then # healthcheckport should be between 8000 and 9000.
        for line in "${healthcheckserver[@]}"; do
            echo $line | sudo tee --append $nginxconfigfile > /dev/null
        done
    fi
    sudo ln -sfn $nginxconfigfile /etc/nginx/sites-enabled/
    sudo systemctl reload nginx
    echo "nginx successfully configured." > /dev/stdout
}

##
# After the request directly to nginx, check the correct version number we see.
##
checkCorrectVersionIsUp() {
    local healthcheckport=$1
    local suffix=${2-""}

    local machineip=$(hostname -I)
    local versioncheckurl="http://${machineip}:${healthcheckport}/healthcheck"
    local versioncheckurl=$(echo ${versioncheckurl//[[:blank:]]/})

    echo "Waiting for the correct version is up to deleting old one... Check url: $versioncheckurl" > /dev/stdout
    
    local end=$((SECONDS+60)) # 1 min to wait service switch.
    while [ $SECONDS -lt $end ]; do 
        if [[ "$(curl -s -o /dev/null -w ''%{http_code}'' $versioncheckurl)" == "200" ]]; then
            local deploynumber=$(curl -s "$versioncheckurl" | jq -r '.Version')
            if [ "$deploynumber" == "$VERSION$suffix" ]; then
                echo "The correct version is up now!" > /dev/stdout
                break;
            else
                sleep 2; # seconds
            fi    
        fi    
    done
}

##
# Destroy old one.
##
destroyOldService() {
    local serviceFile=$1

    echo "Stopping and deleting old service..." > /dev/stdout
    for oldservicefile in $SERVICE_FILE_DIR/$APP_NAME-*; do
        if [[ -f "$oldservicefile" ]] && [[ "$servicefile" != "$oldservicefile" ]]; then
            local oldservicefilename="${oldservicefile##*/}"
            sudo systemctl stop $oldservicefilename || true
            sudo systemctl disable $oldservicefilename 2>&1 || true
            sudo rm $oldservicefile
            sudo systemctl daemon-reload
            echo "$oldservicefile stopped and deleted." > /dev/stdout
        fi
    done
    echo "Old services stopped and deleted." > /dev/stdout
}

##
# Execute main routine.
##
main $@