__pmDiscoverServicesWithOptions(3) — Linux manual page



NAME         top

       pmDiscoverServices,  __pmDiscoverServicesWithOptions  -  discover PCP
       services on the network

C SYNOPSIS         top

       #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

CAVEAT         top

       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.

DESCRIPTION         top

       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


       pmDiscoverServices(service, mechanism, urls)

       is equivalent to calling

       __pmDiscoverServicesWithOptions(service, mechanism, NULL, NULL,

       service specifies the PCP service to be discovered.  Currently
       supported services are PM_SERVER_SERVICE_SPEC and
       PM_PROXY_SERVICE_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.

              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, defines an 8 bit subnet
              consisting of the addresses through
              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:

              This requests that DNS name resolution be attempted for the
              addresses of any discovered services.

              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:

              Specifying this flag is equivalent to specifying resolve in
              the optionsString

              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)

SEE ALSO         top

       pmcd(1), pmfind(1), pmproxy(1), pcp-kube-pods(1), PMAPI(3),
       pmGetConfig(3), pcp.conf(5), pcp.env(5) and avahi-daemon(8).

DIAGNOSTICS         top

              An invalid argument has been specified.

              Unable to allocate memory required to process the request.

              The specified mechanism is not supported.

COLOPHON         top

       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
       2020-09-18.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-09-18.)  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

Performance Co-Pilot                 PCP               PMDISCOVERSERVICES(3)