Ubuntu Manpage: pmwebd - web access to PCP

NAME

       pmwebd - web access to PCP

SYNOPSIS

       pmwebd [-p port] [-4] [-6] [-t timeout] [-R resdir] [-c number] [-h hostname] [-a archive]
       [-C] [-P] [-L] [-N] [-G] [-X] [-i min-interval] [-J [-K spec] [-A  archivesdir]  [-S]  [-l
       logfile] [-U username] [-x file] [-v] [-?]

DESCRIPTION

pmwebd is a network daemon that binds a subset of the Performance Co-Pilot (PCP) client
API (PMAPI(3)) to RESTful web applications using the HTTP (PMWEBAPI(3)) protocol. Web
clients request a URI with the prefix /pmapi to access the bindings. pmwebd creates PCP
contexts as requested by a dynamic pool of remote clients, and maintains them as long as
the clients regularly reconnect to request PMAPI operations. Otherwise, PCP contexts are
closed after a timeout. Permanent contexts may be requested on the command line.

In addition to the API binding, pmwebd may be optionally configured as a simple HTTP file
server, in order to feed the web application itself to a web browser. URIs not matching
the /pmapi prefix are mapped to files under the configured resource directory, if the -R
option was given.

In addition, pmwebd may be optionally configured as a server of a subset of the graphite
0.9.12 web API, for URLs with the /graphite prefix, in order to expose PCP archives to
interactive data-graphing web applications.

The options to pmwebd are as follows.

-p port
Set the TCP port number on which pmwebd will listen for HTTP requests. The default
is 44323.

-4 or -6
Listen only on IPv4 or IPv6. By default, pmwebd will listen on both protocols, if
possible.

-A archdir
Limit remote access to archives to only those beneath the given directory. For
performance, symbolic links to other directories may not be followed. By default,
only files beneath the initial pmwebd working directory may be accessed.

-R resdir
Activate file serving beneath the given resource directory. All regular files
there may be read and transcribed to remote clients. By default, file serving is
disabled.

-G Activate servicing of a subset of the graphite webapi. This exposes all PCP
archives under the -A directory to remote clients. By default, graphite webapi
serving is disabled. To use the graphite and/or grafana web applications included
with pmwebd, use both -G and -R, and connect your web browser to
http://127.0.0.1:43323/

-X Disable encoding of common characters for metric names, which allows shorter
graphite metric names.

-i min-interval
Set the minimum sampling interval for graphite time series in seconds. The default
is 60. Smaller values give higher precision (but not necessarily accuracy) data,
but may cost extra processing time at pmwebd or the web browser; and vice versa.

-J When constructing graphite metric names, use the stored hostname instead of a
archive pathname as the first component. This virtually unifies all archives found
with the same hostname into a single time series. The host name is canonicalized:
any symbol characters other than _ (underscore), space, - (hyphen), and / (slash)
are replaced by _ (underscore).

-t timeout
Set the maximum timeout (in seconds) after the last operation on a pmapi web
context, before it is closed by pmwebd. A smaller timeout may be requested by the
web client. The default is 300.

-c number
Reset the next PMWEBAPI permanent context identifier as given. The default is 1.

-h hostname or -a archive or -L
Assign the next permanent PMWEBAPI context identifier to a PMAPI connection to the
given host (with an extended syntax as given in PCPIntro(1)), or archive file, or
the PM_CONTEXT_LOCAL.

-C Mandatory authentication mode, where all host specifications at context creation
time must be accompanied by credentials (username and password). These are then
passed to pmcd(1) when creating the context. In addition, subsequent PMAPI context
operations require matching HTTP Basic authentication credentials. This setting is
incompatible with the permissive mode of operation.

-P Run in permissive mode, allowing Unix domain socket connections and/or local PMDA
contexts. By default these are not allowed due to the automatic authentication
that is performed on the server in these modes. Only enable this option if you
understand the risks involved, and are sure that all remote pmwebd accesses will be
from benevolent users. If enabled, unauthenticated remote PMWEBAPI(3) clients will
be able to access potentially sensitive performance metric values which an
unauthenticated PMAPI(3) client usually would not be able to. Refer to
CVE-2012-3419 for additional details.

-N Disable creation of new PMWEBAPI contexts via HTTP requests, leaving only permanent
ones accessible.

-K spec
When fetching metrics from a local context, the -K option may be used to control
the DSO PMDAs that should be made accessible. The spec argument conforms to the
syntax described in pmSpecLocalPMDA(3). More than one -K option may be used.

-l logfile
By default, logging goes to standard output/error file handles. The verbosity flag
-v affects the amount of traffic. The -l option causes the log file to be written
to logfile instead. If the log file cannot be created or is not writable, output
is written to the standard error instead.

-U username
If invoked as root, assume the identity of username before starting to accept
incoming requests from web clients.

-S Disable service advertisement. By default, pmwebd will advertise its presence on
the network using any available mechanisms (such as Avahi/DNS-SD), assisting remote
monitoring tools with finding it. These mechanisms are disabled with this option.

-x file
Before the pmwebd logfile can be opened, pmwebd may encounter a fatal error which
prevents it from starting. By default, the output describing this error is sent to
/dev/tty but it may redirected to file.

-v Increase the verbosity of pmwebd as it logs to its standard output/error.

-? Show pmwebd invocation help and exit.

SECURITY

pmwebd is suitable for direct exposure to trusted networks only, due to several security
limitations. Most or all of these limitations may be worked around by use of a web
application firewall (for example, an Apache HTTP proxy), which would add the constraints
and capabilities absent within pmwebd. Such configuration is beyond the scope of this
document.

encryption/confidentiality
pmwebd does not currently support HTTPS (SSL/TLS), so the HTTP traffic is not
protected against network-level attacks.

authentication
The PMAPI layer does not possess a mandatory authentication mechanism, so any
remote connection can access any metric exposed by suchly connected PMAPI contexts.
However, a new host-context string may use authentication clauses of the longer
host URLs, for example pcps://hostname?method=plain&user=userid&pass=password. Use
of resulting pmwebapi contexts later requires matching HTTP PLAIN authentication;
see below.

inbound admission control
pmwebd does not impose access control on the origin or rate of its incoming
requests. It may be possible for some clients to starve others.

outbound admission control
pmwebd does not impose access control on outbound connections when a new PMAPI
context is created for a PMCD. (Without the -P option, connections to UNIX-domain
/ local PMCDs are blocked.) This enables hypothetical use of a pmwebd instance to
be used as a network proxy/scanner. For an archive type context, the files must be
located under the pmwebd current directory, or another directory specified by -A.
One may entirely disable remotely specified PMAPI context creation using the -N
option; in this case, specify a static set of contexts using the -h, -a, and/or -L
options. You may assign them arbitrary context numbers with the -c option.

context ownership
Authenticated PCP contexts are protected by requiring the same HTTP PLAIN/simple
userid/password credentials for related /pmapi requests. However, unauthenticated
contexts for different web clients are kept distinct only by the assignment of
large pseudorandom identifiers. It may be possible to find these by brute-force
search or other techniques, thereby letting a web client impersonate another. For
more privacy of the permanent contexts, use the -c option to reset their starting
web context identifiers to a number much different from 1. On the other hand,
context ownership is not that precious, since there exist no state-destructive
operations for them, except perhaps metric store or instance profile settings.

STARTING AND STOPPING PMWEBD

       The pmwebd server may be started automatically at boot time and stopped when the system is
       being  brought  down.   Users  may also run customized pmwebd instances (under separate -p
       PORT numbers), for example for their own archive farms.   For  management  fo  the  system
       pmwebd, become superuser and type

       # $PCP_RC_DIR/pmwebd start

       to start pmwebd, or

       # $PCP_RC_DIR/pmwebd stop

       to stop pmwebd.  Starting pmwebd when it is already running is the same as stopping it and
       then starting it again.

FILES

       $PCP_PMWEBDOPTIONS_PATH
              command line options and environment variable settings  for  pmwebd  when  launched
              from  $PCP_RC_DIR/pmwebd  This  file  is  interpreted  as  a  Bourne  Shell script,
              expecting variable settings of the form "OPTIONS=value" and possibly others.
       $PCP_LOG_DIR/pmwebd/pmwebd.log
              Log file for system pmwebd service.
       $PCP_LOG_DIR
              Default directory for -A option: a base directory containing PCP archives.
       $PCP_SHARE_DIR/webapps
              Default directory for -R option: a base directory containing web applications.

PCP ENVIRONMENT

       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).