myservicename

How to create a simple HTTP service for a SOA environment and run it under systemd. Replace myservicename and myservicedir. Install the build requirements: [source,bash] ---- nimble install jester ---- === Basic HTTP service Create myservice.nim : [source,nim] ---- import jester, posix, json const config_file_name = "conf.json" # the "debug" and "info" macros from the logging module are not flushing the buffer proc log_debug(args: varargs[string, `$`]) = debug args fl.file.flushFile() proc log_info(args: varargs[string, `$`]) = info args fl.file.flushFile() onSignal(SIGABRT): ## Handle SIGABRT from systemd # Lines printed to stdout will be received by systemd and logged # Start with "" from 0 to 7 echo "<2>Received SIGABRT" quit(1) # Add handlers for SIGSTOP, SIGQUIT as needed let conf = parseFile(config_file_name) # Traditional logging to file. To use the more featureful journald you might # use https://github.com/FedericoCeratto/nim-morelogging let fl = newFileLogger(conf["log_fname"].str, fmtStr = "$datetime $levelname ") fl.addHandler include "templates/base.tmpl" include "templates/home.tmpl" routes: get "/": resp base_page(generate_home_page()) when isMainModule: log_info "starting" runForever() ---- === Example templates Simple HTML templates. Create /var/lib/myservicename/templates/base.tmpl [source,nim] ---- #? stdtmpl | standard #proc base_page(content: string): string = # result = "" myservicename

${content}

---- Create /var/lib/myservicename/temaplates/home.tmpl [source,nim] ---- #? stdtmpl | standard #proc generate_home_page(): string = # result = ""

Welcome to myservicename

---- === Configure the running environment Create /lib/systemd/system/myservicename.service file. Configure CapabilityBoundingSet as needed. [source,ini] ---- [Unit] Description=myservicename # Optional documentation hints Documentation=man:myservicename Documentation=https://github.com/REPLACEME/myservicename After=network.target httpd.service squid.service nfs-server.service mysqld.service named.service postfix.service Wants=network-online.target [Service] Type=simple WorkingDirectory=/var/lib/myservicedir/ # stdbuf buffers the stdout in order not to block your application ExecStart=/usr/bin/stdbuf -oL /var/lib/myservicedir/myservicename # wait 10s when stopping TimeoutStopSec=10 # SIGTERM the master process and later on SIGKILL any stray process KillMode=mixed KillSignal=SIGTERM User=myservicename #Group=myservicename # Restart the daemon if crashes or is killed Restart=always RestartSec=2s LimitNOFILE=65536 # Hardening NoNewPrivileges=yes # Set process capabilities. Fine-tune as needed. CapabilityBoundingSet=CAP_DAC_READ_SEARCH # Create private /dev /tmp /home to isolate the process PrivateDevices=yes PrivateTmp=yes ProtectHome=yes ProtectSystem=full # Log any stdout/stderr to syslog/journald StandardOutput=syslog+console StandardError=syslog+console # Allow RW access to some dirs. Add yours as needed. ReadWriteDirectories=/proc/self ReadWriteDirectories=-/var/run [Install] WantedBy=multi-user.target ---- An example variable config file for your application. Create /var/lib/myservicedir/conf.json [source,json] ---- { "log_fname": "/var/log/myservicename.log", } ---- [source,bash] ---- sudo adduser myservicename --system --home /var/lib/myservicedir sudo touch /var/log/myservicename.log sudo chown myservicename:myservicename /var/log/myservicename.log sudo systemctl enable myservicename sudo systemctl start myservicename ---- === Systemd watchdog The watchdog automatically restarts the application if a "ping" is not received within 10 seconds. Useful to detect a frozen process. To enable a watchdog, add "WatchdogSec=10s" to the service file. Install https://github.com/FedericoCeratto/nim-sdnotify[sdnotify client] [source,nim] ---- import sdnotify let sd = newSDNotify() sd.notify_ready() # Every 5 seconds in a dedicated thread: sd.ping_watchdog() ---- === Application metrics To generate application metrics for StatsD use https://github.com/FedericoCeratto/nim-statsd-client[StatsD client] === Running Jester behind Nginx Nginx is commonly used as a reverse proxy for webservices. Edit /etc/nginx/sites-enabled/default and add: [source,php] ---- server { listen 443; server_name www.REPLACEME.org; # Comment out the next 3 lines to disable SSL ssl on; ssl_certificate /etc/REPLACEME/fullchain.pem; ssl_certificate_key /etc/REPLACEME/privkey.pem; access_log /var/log/REPLACEME.log; location / { proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $host; # Jester listens on port 5000 by default proxy_pass http://127.0.0.1:5000; } } ---- Reload Nginx and monitor the logfile: [source,bash] ---- sudo service nginx reload ----