EvmEvent(5) File Formats Manual EvmEvent(5)
NAME
EvmEvent - The structure of an EVM Event
DESCRIPTION
An EVM event is a self-contained data structure, which can be manipulated and accessed using EVM API functions. Application code can: Cre-
ate, duplicate and destroy an event Set and retrieve the values of standard data items contained within the event Add variable data items
to the event, and set and retrieve their values Post the event to the EVM daemon for distribution to subscribers Read events from an open
file descriptor Write events to an open file descriptor
Command line utilities are provided that allow users access to these capabilities.
The Contents of an Event
The event structure includes two types of data items: Standard data items, with predefined names Variable data items, with names and types
defined at the time they are added to the event
When you create an event you can include as many data items as you like. When you post the event, the API functions automatically add the
standard items which pertain to the current environment, such as the host name and timestamp.
Standard Data Items
Standard data items are those which are commonly required in an event, and which are understood and may be acted upon by EVM. The follow-
ing table is a list of the standard data items that may be contained in an event. The identifier is the keyword used to post, display, or
format the item.
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Data item/Id Description
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Event Name
NAME Names the event. Must match a name in the dae-
mon's template database if the event is to be
posted.
Time Posted
TIMESTAMP UNIX system time when the first occurrence of
this event was generated.
Repeat Count
REPEAT_COUNT Number of instances of the same event that have
been combined into a single stored event. The
Time Posted and Last Timestamp items indicate
when the first and last instances of the event
were posted.
Last Timestamp
LAST_TIMESTAMP If Repeat Count is present and non-zero, the sys-
tem time when the latest occurrence of this event
was generated.
Event Identifier
EVENT_ID Identifies the event. See the description fol-
lowing this table.
Host Name
HOST_NAME Name of the posting node.
Host IP Address
HOST_IP IP address of the posting node.
Cluster Event
CLUSTER_EVENT In a cluster environment, a value of EvmTRUE
indicates that the event was posted on behalf of
the cluster, not the individual node, and will be
distributed to every node in the cluster.
Cluster Name
CLUSTER_NAME In a cluster environment, the name of the posting
cluster.
Cluster IP Address
CLUSTER_IP In a cluster environment, the IP address of the
posting cluster.
Cluster Member ID
MEMBER_ID In a cluster environment, the node's cluster ID.
Kernel Only
KERNEL_ONLY If present and EvmTRUE for an event generated in
the kernel, the event will not be propagated from
the kernel to user space.
Process ID
PID PID of the process which posted the event.
Parent Process ID
PPID PID of the parent of the process which posted the
event.
User name
USER_NAME Name of the owner of the posting process.
Priority
PRIORITY Indicates the importance of the event. Does not
affect the order of event distribution. See the
description following this table.
I18N catalog
I18N_CATALOG Name of I18N catalog file for internationalized
events.
I18N msgset id
I18N_SET_ID Identifies the message set within the I18N mes-
sage catalog.
I18N message id
I18N_MSG_ID I18N message id for the event.
Format
FORMAT Event format text. See the EvmEventFormat(3) and
evmtemplate(4) reference pages for a description
of the format string.
Reference
REF Reference to event explanation text.
Event Name
The event name is the primary means of identifying an event. It must be present for an event to be posted. Although it can be any syntac-
tically-valid string, the name should generally identify the posting facility and indicate what happened.
The event name is an ASCII character string, made up of a dot-separated series of components, with the left-most component representing the
top of a notational hierarchy. Component substrings may include any combination of letters, digits and underbar characters. There is no
restriction on the number of components that can be included in an event name. An event template must contain at least two components. An
event must contain at least three components to be accepted for posting.
The naming scheme provides an open-ended way to identify events, letting you provide detail to any level. Careful naming gives the system
administrator an intuitive and precise way to select events for viewing and monitoring and facilitates the identification of the system
components which issue events and the recognition of patterns that warn of problems. The more detail included in the event name, the more
precise the specification criteria can be.
Event Identifier
The event identifier data item is a numeric quantity, assigned to an event by the EVM daemon as the event is posted. In combination with
the host and timestamp data items, the value can be used to produce a unique identity for an event.
The daemon assigns identifiers according to the following rules: Each posted event receives an unsigned integer event identification num-
ber, with a value greater by one than that of the previous event posted through the same EVM daemon. The event identifier of the first
event posted after the daemon is started or restarted is zero. The event identifier wraps back to zero after it has reached its maximum
value. If a daemon receives an event that already contains an identifier, it does not generate a new identifier for the event. This may
happen if the event is a cluster event posted in another node. New event identifiers are assigned only to events which the daemon vali-
dates and accepts for distribution. If an event is accepted and does not already contain an identifier, a new identifier is assigned to it
even if there are no subscribers for the event.
Event Priority
EVM uses an event's priority value solely for filtering, sorting and presentation purposes - it does not use it to prioritize the distribu-
tion sequence. The priority is an integer value in the range 0-700, with zero being the least significant priority. This table indicates
the event priority, the default action taken by evmlogger for that priority, and a description of the priority.
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Default
EVM Priority/Name Notification Description
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700
Emergency Log, mail to root A dangerous situation has been
detected and immediate action either
is required or has been taken.
600 - 699
Alert Log, mail to root A dangerous situation is imminent
and immediate action either is
required or has been taken.
500 - 599
Critical Log, mail to root A failure has been detected that
renders some part of the system
inoperable.
400 - 499
Error Log A non-critical failure has been
detected in or by some component of
the system or application.
300 - 399
Warning Log Some aspect of the system or appli-
cation requires attention.
200 - 299
Notice Log Notification of an expected opera-
tional event that the component is
designed to deal with.
100 - 199
Information None A normal operational event - for
example, an application has started
or terminated normally. Events in
this range typically will not be
saved in the system EVM log file.
1 - 99
Debug None Program debug information. Events in
this range may be monitored for
informational purposes, but typi-
cally will not be saved in the sys-
tem EVM log file.
0
None Application Priority 0 should be used for events
that are specifically intended to be
subscribed to by programs, and are
not expected to be interesting to
administrators.
Catalog Name and Message Set Id
If you plan to internationalize your events, you will need to supply an I18N catalog file containing the format strings for all of the
events, and include the name of the file in the event. You also can break the file into multiple message sets, and give the message set id
in the event - but note that all messages pertaining to a particular event must belong to the same set. If all events described in a single
template file use messages from the same catalog or message set or both, you will probably want to supply these items as global values, so
that you need only to specify them once.
Cluster event
You should set the cluster event data item only if your application is cluster-aware, and is posting the event on behalf of the cluster,
rather than an individual node. Cluster events are distributed to all nodes in the cluster.
Formatting an Event for Display
Although an event is an opaque binary structure, it can be formatted into a human-readable string by using the evmshow(1) command or by
calling the EvmEventFormat(3) function. Formatting is essential for human-oriented output, but may not be necessary for an application
program that will simply extract any variable data the event contains, and take the necessary action.
The starting point for formatting an event is the format data item. A format is a text string that may contain a simple piece of text, the
names of standard data items, or the names of variables whose values are to be substituted into the text, or any combination of these.
You include variable names for substitution by preceding them with a $ character - for example $temp. You include standard data items by
preceding their names with @ - for example, @timestamp.
The EvmEventFormat(3) routine automatically converts data items or variables into displayable form, regardless of their types.
You can escape the special meaning of a $ or @ characters in the format text by preceding it with a backslash (). To include a literal
backslash in the text, use a double backslash.
If an event does not include a format data item, formatting it will result in a default text string that includes the event name and any
variables the event may contain.
If the event includes a repeat count, then the repeat count is prepended to the output in the form [repeat_count times].
Variable Data Items
You can use variable data items in your events to provide data that may be different each time the event is posted.
You can give the variable any name you like - the name is a string that is carried with the event, and can be used by a subscriber to
extract the data in its original form. A variable name can be made up of any combination of upper or lower case alphanumeric characters
and the underscore character. By convention, names beginning with an underscore are reserved for system use.
EVM's variable data items have these properties: A name A type A value A size (implicit for most types) An I18N message id (for string
variables only)
The following table shows the variable types that EVM supports:
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Type Identification Remarks
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EvmTYPE_BOOLEAN 8-bit integer
EvmTYPE_CHAR 8-bit character
EvmTYPE_INT16 16-bit signed integer
EvmTYPE_INT32 32-bit signed integer
EvmTYPE_INT64 64-bit signed integer
EvmTYPE_UINT8 8-bit unsigned integer
EvmTYPE_UINT16 16-bit unsigned integer
EvmTYPE_UINT32 32-bit unsigned integer
EvmTYPE_UINT64 64-bit unsigned integer
EvmTYPE_FLOAT 32-bit floating point value
EvmTYPE_DOUBLE 64-bit floating point value
EvmTYPE_STRING Null-terminated character string
EvmTYPE_OPAQUE Binary data - cannot be interpreted directly.
The size must be specified explicitly.
RESTRICTIONS
Data types EvmTYPE_FLOAT and EvmTYPE_DOUBLE cannot be used for events posted within the kernel.
SEE ALSO
Commands: evmshow(1)
Routines: EvmEventFormat(3)
Files: evmtemplate(4)
Event Management: EVM(5)
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EvmEvent(5)