Service Commander for IBM i

A utility for unifying the daunting task of managing various services and applications running on IBM i. Its objective is to provide an intuitive, easy-to-use command line interface for managing services or jobs.

This tool can be used to manage a number of services, for instance:

IBM i host server jobs
IBM i standard TCP servers (*TCP, *SSHD, etc.)
Programs you wrote using open source technology (Node.js, Python, PHP, etc.)
Apache Tomcat instances
Apache Camel routes
Kafka, Zookeeper, ActiveMQ servers, etc
Jenkins
The Cron daemon
OSS Database servers (PostgreSQL, MariaDB)

Current features

Some of the features of the tool include:

The ability to specify dependencies (for instance, if one application or service dependds on another), and it will start any dependencies as needed
The ability to submit jobs to batch easily, even with custom batch settings (use your own job description or submit as another user, for instance)
The ability to check the “liveliness” of your service by either port status or job name
Customize the runtime environment variables of your job
Define custom groups for your services, and perform operations on those groups (by default, a group of “all” is defined)
Query basic performance attributes of the services
Assistance in providing/managing log files. This is a best-guess only and naively assumes the service uses stdout/stderr as its logging mechanism. Service Commander has its own primitive logging system that works well only for certain types of services
Ability to define manage ad hoc services specified on the command line
Ability to see what ports are currently opening (have a job listening)

Hands-on Exercise

Want to walk through a quick exercise to get some basic “hands-on” experience with this tool? If so, please see our very simple hands-on exercise

Have feedback or want to contribute?

Feel free to open an issue with any questions, problems, or other comments. If you’d like to contribute to the project, see CONTRIBUTING.md for more information on how to get started.

In any event, we’re glad to have you aboard in any capacity, whether as a user, spectator, or contributor!

Service Commander’s design is fundamentally different from other tools that accomplish similar tasks, like init.d, supervisord, and so on. Namely, the functions within Service Commander are intended to work regardless of:

Who else may start or stop the service
What other tools may be used to start or stop the service. For instance, Service Commander may start/stop an IBM i host server, but so could the STRHOSTSVR/ENDHOSTSVR CL commands.
Whether the service runs in the initially spawned job or a secondary job

Also, this tool doesn’t have the privilege of being the unified, integrated solution with the operating system that other tools may have. Therefore, Service Commander cannot take the liberty of assuming that it can keep track of the resources tied to the services that it manages. So, for example, this tool does not keep track of process IDs of launched processes. Similarly, it doesn’t have special access to kernel data structures, etc.

Instead, this tool makes strong assumptions based on checks for a particular job name or port usage (see check_alive_criteria in the file format documentation). A known limitation, therefore, is that Service Commander may mistake another job for a configured service based on one of these attributes. For example, if you configure a service that is supposed to be listening on port 80, Service Commander will assume that any job listening on port 80 is indeed that service.

Service Commander’s unique design is intended to offer a great deal of flexibility and ease of management through the use of simple .yaml files.

Installation

System Requirements

For most of the features of this tool, the following is required to be installed (the installation steps should handle these for you):

db2util (yum install db2util)
OpenJDK (yum install openjdk-11)
bash (yum install bash)
GNU coreutils (yum install coreutils-gnu)

The performance information support (perfinfo) has additional requirements that are not automatically installed, including:

Python 3 with the ibm_db database connector (yum install python3-ibm_db)
Required operating system support, which depends on your IBM i operating system level, as follows:
IBM i 7.4: included with base OS
IBM i 7.3: Group PTF SF99703 Level 11
IBM i 7.2: Group PTF SF99702 Level 23
IBM i 7.1 (and earlier): not supported

Option 1: Binary distribution

You can install the binary distribution by installing the service-commander package:

If you are not familiar with IBM i RPMs, see this documentation to get started.

Option 2: Build from source (for development or fix evaluation)

Feel free to build from the main branch to start making code contributions or to evaluate a fix/feature not yet publish. This process assumes your PATH environment variable is set up properly, otherwise:

The build itself can be done with the following steps:

Basic usage

Usage of the command is summarized as:

The above usage assumes the program is installed with the above installation steps and is therefore
launched with the sc script. Otherwise, if you’ve hand-built with maven (mvn compile), you can specify arguments in exec.args (for instance, mvn exec:java -Dexec.args=’start kafka’).

Specifying options in environment variables
If you would like to set some of the tool’s options via environment variable, you may do so with one of the following:

SC_TCPSVR_OPTIONS, which will be processed when invoked via the STRTCPSVR/ENDTCPSVR commands
SC_OPTIONS, which will be processed on all invocations
For example, to gather verbose output when using STRTCPSVR, run the following before your STRTCPSVR command:

Usage examples

Start the service named kafka:

Stop the service named zookeeper:

Check status of all configured services (all services belong to a special group named “all”)

Try to start all configured services

Print information about all configured services

Try to start all services in “host_servers” group

List all services

List jobs running on port 8080

Stop jobs running on port 8080

Check if anything is running on port 8080

Start the service defined in a local file, myservice.yml

Checking which ports are currently open

As of version 0.7.x, Service Commander also comes with a utility, scopenports that allow you to see which ports are open.
Usage is as follows:

Example output when invoked with the –mine option:

The value in the service name column can be used with the sc command. For instance, with
the above example, if I wanted to see which job was running on port 62006, I could run

Important Note: Currently, the scopenports utility can only show human-readable descriptions for services that have
been configured for sc’s use. To populate some common defaults, run sc_install_defaults.

Configuring Services

Initializing your configuration with defaults

If you’d like to start with pre-made configurations for common services, simply run:

This will install service definitions for:

IBM i TCP servers
IBM i Host Servers
The Cron daemon (if you have cron installed)
MariaDB (if you have mariadb installed)

Through YAML configuration files

This tool allows you to define any services of interest in .yaml files. These files can be stored in any of the following locations:

A global directory (/QOpenSys/etc/sc/services). This, of coures, requires you to have admin access (*ALLOBJ special authority).
A user-specific directory($HOME/.sc/services)
If defined, whatever the value of the services.dir system property is. The file name must be in the format of service_name.yaml (or service_name.yml), where “service_name” is the “simple name” of the service as to be used with this tool’s CLI. The service name must consist of only lowercase letters, numbers, hyphens, and underscores.

The file can also be located in any arbitrary directory, but it must be explicitly passed along to the sc command, for instance

YAML File Format

See the samples directory for some sample service definitions. The following attributes may be specified in the service definition (.yaml) file:

Required fields

start_cmd: the command used to start the service
check_alive: the technique used to check whether the service is alive or not. This is either “jobname” or “port”.
check_alive_criteria: The criteria used when checking whether the service is alive or not. If check_alive is set to “port”, this is expected to be a port number. If check_alive is set to “jobname”, this is expect to be be a job name, either in the format “jobname” or “subsystem/jobname”.

Optional fields that are often needed/wanted

name: A “friendly” name of the service
dir: The working directory in which to run the startup/shutdown commands

Other optional fields

stop_cmd: The service shutdown command. If unspecified, the service will be located by port number or job name.
startup_wait_time: The wait time, in seconds, to wait for the service to start up (the default is 60 seconds if unspecified)
stop_wait_time: The wait time, in seconds, to wait for the service to stop (the default is 45 seconds if unspecified)
batch_mode: Whether or not to submit the service to batch
sbmjob_jobname: If submitting to batch, the custom job name to be used for the batch job
sbmjob_opts: If submitting to batch, custom options for the SBMJOB command (for instance, a custom JOBD)
environment_is_inheriting_vars: Whether the service inherits environment variables from the current environment (default is true)
environment_vars: Custom environment variables to be set when launching the service. Specify as an array of strings in “KEY=VALUE” format
service_dependencies: An array of services that this service depends on. This is the simple name of the service (for instance, if the dependency is defined as “myservice”, then it is expected to be defined in a file named myservice.yaml), not the “friendly” name of the service.
groups: Custom groups that this service belongs to. Groups can be used to start and stop sets of services in a single operation. Specify as an array of strings.

You can use the scinit tool can be used to create the YAML configuration files for you. Basic usage of the tool is simply:

The idea is that you would simply:

cd to the directory where you’d normally start the service
Run the command you’d normally use to start the service, prefixed by scinit
Answer a series of questions about how you would like the service deployed
In doing so, the scinit will create the YAML configuration file for you and also show you information about the newly-configured service.

For instance, if you would normally launch a Node.js application from /home/MYUSR/mydir by running node app.js, you would run:

The scinit tool will ask you for a “short name” among other things. When done, a service configuration will be saved under that short
name. So, for instance, if your short name is “my_node_app”, you can run sc start my_node_app.

Ad hoc service definition

Ad hoc services can be specified on the sc command line in the format job:jobname or port:portname. In these instances, the operations will be performed on the specified jobs. This is determined by looking for
jobs matching the given job name or listening on the given port. The job name can be specified either in
jobname or subsystem/jobname format.

If an existing service definition is found (configured via YAML, as in the preceding section) that matches the
job name or port criteria, that service will be used. For instance, if you have a service configured to run on
port 80, then specifying sc info port:80 will show information about the service configured to run on port 80.

Ad hoc service definition is useful for quick checks without the need to create a YAML definition. It’s also
useful if you do not recall the service name, but remember the job name or port.

It is also useful for cases where you just want to find out who (if anyone) is using a certain port. For instance,
sc jobinfo port:8080 will show you which job is listening on port 8080. Similarly, sc stop port:8080 will kill
whatever job is running on port 8080.

Demo (video)

Automatically restarting a service if it fails

Currently, this tool does not have built-in monitoring and restart capabilities. This may be a future enhancement. In the meantime, one can use simple scripting to accomplish a similar task. For instance, to check every 40 seconds and ensure that the navigator service is running, you could submit a job like this (replace the sleep time, service name, and submitted job name to match your use case):

This will result in several jobs that continuously check on the service and attempt to start it if the service is dead. If you wish to stop this behavior, simply kill the jobs. In the above example, the job name is NAVMON, so the WRKACTJOB command to do this interactively looks like:

Testimonials

“I use this a lot for my own personal use. Might be useless for the rest of the world. I don’t know, though.”

  –@ThePrez, creator of Service Commander

STRTCPSVR Integration

Service Commander now has integration with system STRTCPSVR and ENDTCPSVR commands. This feature is experimental and may be removed
if too problematic.

To integrate with the STRTCPSVR and ENDTCPSVR commands, you can run the following command as an admin user:

This will install create the SCOMMANDER library and compile/install the TCP program into that library. To use a different
library, just set the SCTARGET variable. For instance:

If you need to compile to a previous release of IBM i, set the SCTGTRLS variable to the required value of CRTCMOD parameter TGTRLS. Example for IBM i 7.1:

After doing so, you can run the *SC TCP server commands, specifying the simple name of the sc-managed service as the instance name. For example:

Important Notes about AUTOSTART(*YES)

You can set the *SC server to autostart via CHGTCPSVR SVRSPCVAL(*SC) AUTOSTART(*YES). However, great care must be taken in order for this to work properly and not create a security exposure. When STRTCPSVR runs at IPL time, the task will run under the QTCP user profile. This user profile does not have *ALLOBJ authority, nor does it have authority to submit jobs as other user profiles. Thus, in order for the autostart job to function properly, the QTCP user profile must have access to run the commands needed to start the service, and the service must not submit jobs to batch as a specific user. Be are that adding QTCP to new group profiles or granting special authorities may represent a security exposure. Also, due to the highly-flexible nature of this tool, it is not good practice to run this command as an elevated user in an unattended fashion. In summary, it is likely not a good idea to use AUTOSTART(*YES).

Special groups used by STRTCPSVR/ENDTCPSVR
There are a couple special groups used by the TCP server support. You can define your services to be members of one or more of these groups:

default, which is what’s started or ended if no instance is specified (i.e. STRTCPSVR SERVER(*SC))
autostart, which is what’s started when invoked on the *AUTOSTART instance (i.e. STRTCPSVR SERVER(*SC) INSTANCE(*AUTOSTART))