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NAME | C SYNOPSIS | CAVEAT | DESCRIPTION | PCP ENVIRONMENT | DIAGNOSTICS | SEE ALSO | COLOPHON |
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PMDISCOVERSERVICES(3) Library Functions Manual PMDISCOVERSERVICES(3)
pmDiscoverServices, __pmDiscoverServicesWithOptions - discover
PCP services on the network
#include <pcp/pmapi.h>
int pmDiscoverServices(const char *service, const char *mechanism, char ***urls);
#include <pcp/libpcp.h>
int __pmDiscoverServicesWithOptions(const char *service, const char *mechanism, const char *optionsString, const volatile unsigned *flags, char ***urls);
cc ... -lpcp
This documentation is intended for internal Performance Co-Pilot
(PCP) developer use.
These interfaces are not part of the PCP APIs that are guaranteed
to remain fixed across releases, and they may not work, or may
provide different semantics at some point in the future.
Given a PCP service name, as identified by service, and using the
type of discovery optionally specified in mechanism,
pmDiscoverServices returns, via urls, a list of URLs representing
the services discovered on the network.
The internal function __pmDiscoverServicesWithOptions performs
the same function and adds arguments for global options and a
mechanism for interrupting the discovery process.
The pmfind(1) utility provides command line access to both of
these interfaces.
Calling
pmDiscoverServices(service, mechanism, urls)
is equivalent to calling
__pmDiscoverServicesWithOptions(service, mechanism, NULL, NULL,
urls);
service specifies the PCP service to be discovered. Currently
supported services are PM_SERVER_SERVICE_SPEC and
PM_SERVER_PROXY_SPEC which search for pmcd(1), and pmproxy(1)
servers respectively.
mechanism specifies the style of discovery to be used.
The currently supported mechanisms are:
avahi This searches for services which are broadcasting using
mDNS via avahi-daemon(8). An optional suffix ",timeout=N"
may be added to specify the discovery timeout in floating-
point multiples of one second. The default timeout is 0.5
seconds, which may be overridden by the
AVAHI_DISCOVERY_TIMEOUT environment variable, also
specified in floating-point multiples of one second. If
both are specified, then the value specified in the
environment variable takes precedence.
probe=<net-address>/<mask-bits>
Actively probes the given subnet for the requested PCP
service(s). <net-address> is an inet or ipv6 network
address and <mask-bits> is the number of bits used to
define the subnet. For example, 192.168.1.0/24 defines an
8 bit subnet consisting of the addresses 192.168.1.0
through 192.168.1.255. An optional suffix ",maxThreads=N"
may be added to limit the number of threads used while
probing. The default is the value of __FD_SETSIZE (which
is typically 1024) or the number of addresses in the
subnet, whichever is less. An optional suffix
",timeout=N" may be added to specify the timeout for each
connection attempt in floating-point multiples of one
second. The default is 0.02 seconds (20 milliseconds).
shell Probes the list of addresses provided by scripts for
requested PCP service(s). Several optional, comma-
separated parameters can also be provided. Firstly, the
"path=DIR" option specifies the directory where commands
like pcp-kube-pods(1) are located (defaults to
$PCP_BINADM_DIR/discover/). This setting can be further
restricted to an individual command using the command=CMD
option, but the default is to use all available commands
from the path. The "maxThreads=N" option limits the
number of threads used while probing. The default is the
value of __FD_SETSIZE (which is typically 1024) or the
number of addresses returned by the scripts, whichever is
less. The "timeout=N" option may be added to limit the
amount of time spent waiting for each connection attempt.
N is a floating point number specifying the number of
seconds to wait. The default is 0.02 seconds (20
milliseconds).
mechanism may also be NULL, which means to use all available
discovery mechanisms.
For __pmDiscoverServicesWithOptions, optionsString specifies
global options to be applied to the discovery process. Options
are comma-separated and may be one or more of the following:
resolve
This requests that DNS name resolution be attempted for
the addresses of any discovered services.
timeout=N
This specifies a timeout period after which the discovery
process will be interrupted. N is a floating point number
representing the number of seconds before timing out.
optionsString may also be NULL, which means that no global
options are specified.
For __pmDiscoverServicesWithOptions, flags specifies a pointer to
an object of type unsigned which is a bit mask of options/status
flags for the discovery process. The supported flags are:
PM_SERVICE_DISCOVERY_RESOLVE
Specifying this flag is equivalent to specifying resolve
in the optionsString
PM_SERVICE_DISCOVERY_INTERRUPTED
This flag must be unset when calling
__pmDiscoverServicesWithOptions but may be set
asynchronously (by an interrupt handler, for example) in
order to interrupt the service discovery process.
flags may also be NULL, which indicates that no flags are set.
pmDiscoverServices and __pmDiscoverServicesWithOptions will
return the number of services discovered, else a value less than
zero for an error. The value zero indicates that no services
were discovered.
The resulting list of pointers, urls, and the values (the URLs)
that the pointers reference will have been allocated by
pmDiscoverServices or __pmDiscoverServicesWithOptions with a
single call to malloc(3), and it is the responsibility of the
pmDiscoverServices or __pmDiscoverServicesWithOptions caller to
free(urls) to release the space when it is no longer required.
When an error occurs, or no services are discovered, urls is
undefined (no space will have been allocated, and so calling
free(3) is a singularly bad idea).
Environment variables with the prefix PCP_ are used to
parameterize the file and directory names used by PCP. On each
installation, the file /etc/pcp.conf contains the local values
for these variables. The $PCP_CONF variable may be used to
specify an alternative configuration file, as described in
pcp.conf(5). Values for these variables may be obtained
programmatically using the pmGetConfig(3) function.
-EINVAL
An invalid argument has been specified.
-ENOMEM
Unable to allocate memory required to process the request.
-EOPNOTSUPP
The specified mechanism is not supported.
pmcd(1), pmfind(1), pmproxy(1), pcp-kube-pods(1), PMAPI(3),
pmGetConfig(3), pcp.conf(5), pcp.env(5) and avahi-daemon(8).
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at
⟨http://www.pcp.io/⟩. If you have a bug report for this manual
page, send it to pcp@groups.io. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-14.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Performance Co-Pilot PCP PMDISCOVERSERVICES(3)
Pages that refer to this page: pcp-kube-pods(1), pmfind(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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