OS_Mon Release Notes

## 1 OS_Mon Release Notes

This document describes the changes made to the OS_Mon application.

### 1.1 Os_Mon 2.1.1

#### 1.1.1 Fixed Bugs and Malfunctions

- Did not build on Mac OS X.
  Added support for IRIX. (Thanks to Michel Urvoy and Daniel Solaz.)
  Own Id: OTP-6136

#### 1.1.2 Improvements and New Features

- `disksup`: Now using `round(T*100)` instead of `trunc(T*100)` when setting the threshold value given a float `T`.
  Own Id: OTP-6153

### 1.2 Os_Mon 2.1

#### 1.2.1 Fixed Bugs and Malfunctions

- In 2.0, a call to `alarm_handler:get_alarms/0` was introduced in `memsup` and `disksup`. This will lead to problems if the default `alarm_handler` event handler is not used, however, and the call has now been removed. (Thanks to Serge Aleynikov for pointing this out.)
  Own Id: OTP-6029
- A bug that in rare cases caused `cpu_sup` to crash has been corrected.
  Own Id: OTP-6102 Aux Id: seq10312

### 1.3 OS_Mon 2.0

A note on backwards compatibility: The behaviour of OS_Mon 2.0 is backwards compatible under normal operation, but has changed somewhat in error situations: The services do not terminate and the API functions do not raise exceptions in all cases where they did before. Also, in the case where a service does terminate, the exit reason may be different. See below for details.

#### 1.3.1 Fixed Bugs and Malfunctions

- A call to a OS_Mon service (cpu_sup, disksup, ...) when OS_Mon is not running, or when the service is not available for the OS, or when the service is not started, will no longer result in an exception. Instead a warning is issued via error_logger and a dummy value is returned, which one is specified in the man pages for the respective service.
  The reason is that it should not be necessary for a service to be started on each and every node of a distributed Erlang system for the OS-MON-MIB and other OS_Mon users to work properly.
  Own Id: OTP-4332 Aux Id: seq7358
- References to the obsolete EVA application in OTP-OS-MON-MIB has been removed.
  Own Id: OTP-5699
- Setting the option `memsup_system_only` to `true` did not work, but would crash the `memsup` process.
  Own Id: OTP-5890 Aux Id: seq10185
- `cpu_sup:nprocs/0` returned 0 on FreeBsd.
  Own Id: OTP-5901
- If the OS_Mon service `disksup` or `memsup` was restarted, the same alarm could be set twice. Also, set alarms were not cleared when the application was stopped.
  Own Id: OTP-5910

#### 1.3.2 Improvements and New Features

- Thresholds and time intervals in `disksup` and `memsup` are now configurable in run-time.
  Own Id: OTP-4246 Aux Id: Seq7230
- `memsup` can now handle systems with more than 4GB of RAM.
  Own Id: OTP-5800 Aux Id: seq10130
- The entire OS_Mon application (code and documentation) has been reviewed and consequently updated with the goal to make the application more robust, homogeneous and easier to configure.
  The behaviour under normal operation is backwards compatible. However, recoverable errors now no longer terminate the affected service (and thus possible the entire application), instead `error_logger` is used to warn the user if/when such errors occurs. Also, in the case of unrecoverable errors, the services have been made more homogeneous with respect to behavior and exit reasons. See below for more information and refer to the man pages for details.
  Port handling has been unified, meaning that if a port program sends garbage or unexpectedly dies, this is now handled the same way by all OS_Mon services, namely immediate process termination with the exit reason `{port_error,Garbage}` or `{port_died,Reason}`, respectively.
  Application configuration parameter handling has been unified. Bad parameter values are no longer silently ignored (`disksup`) or cause application termination (`memsup`, `os_sup`). Instead a warning is issued and the default value for the parameter is used. Also, some cases where a bad parameter value accidentally could be accepted have been corrected.
  Message handling has been unified. Unknown (`gen_server-`) calls cause process termination, whereas unknown casts and messages are now ignored by all OS_Mon services.
  Own Id: OTP-5897
- The following changes have been made to the `os_sup` service:
  It is now available on Windows, using `nteventlog` as backend.
  On Solaris, enabling the service (that is, installing a new configuration file for `syslogd` etc.) can now be done outside the `os_sup` process. The reason for this is that the Erlang emulator should normally not be run with `root` privileges, as is otherwise required. The new application configuration parameter `os_sup_config` must be set to `false`.
  Also, `os_sup` can now be configured using a new configuration parameter `os_sup_mfa` to call an arbitrary Erlang function when a message is received from the OS.
  Own Id: OTP-5925
- The `memsup` service has been rewritten, replacing the supervised `memsup_helper` with a linked help process. This gives the `memsup` process more control and prevents a situation where it gets out of synch with the received memory data and thus possibly returns erroneous results.
  Own Id: OTP-5927

### 1.4 OS_Mon 1.8.1

#### 1.4.1 Fixed Bugs and Malfunctions

- `cpu_sup:util/0` failed with error reason `negative_diff` when called the first time on a machine (hw) that had been up for a very long time.
  Own Id: OTP-5869 Aux Id: seq10166

### 1.5 OS_Mon 1.8

#### 1.5.1 Improvements and New Features

- The memsup part of the OS_Mon application has been made more stable. If there are (possibly temporary) problems collecting memory data, the interface functions (`get_memory_data/0`, `get_system_memory_data/0`) now do not fail, but return the previously collected value, if any, or a dummy value otherwise. Also, a warning message is printed.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-5798

### 1.6 OS_Mon 1.7.4

#### 1.6.1 Fixed Bugs and Malfunctions

- Corrected several problems in the error handling/error recovery (especially when OS_Mon is starting up).
  Own Id: OTP-5559

### 1.7 OS_Mon 1.7.3

#### 1.7.1 Improvements and New Features

- `memsup.c` will now compile on OpenBSD. (Thanks to Geoff White and Jay Nelson.)
  The `disksup` and `cpu_sup` modules now work on Mac OS X (tested on Mac OS 10.3.8).
  The `memsup` module should now work on Linux 2.6.* as well as on older Linuxes. (`/proc/meminfo` has slightly different formats in different releases of Linux.)
  Own Id: OTP-5421
  Aux Id: OTP-5194, OTP-5228, OTP-5291

### 1.8 OS_Mon 1.7.2

This version is identical with 1.7.

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