'\"macro stdmacro
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.TH PMWEBD 1 "PCP" "Performance Co-Pilot"
.SH NAME
\f3pmwebd\f1 \- web access to PCP
.SH SYNOPSIS
\f3pmwebd\f1
[\f3\-p\f1 \f2port\f1]
[\f3\-4\f1]
[\f3\-6\f1]
[\f3\-t\f1 \f2timeout\f1]
[\f3\-R\f1 \f2resdir\f1]
[\f3\-c\f1 \f2number\f1]
[\f3\-h\f1 \f2hostname\f1]
[\f3\-a\f1 \f2archive\f1]
[\f3\-C\f1]
[\f3\-P\f1]
[\f3\-L\f1]
[\f3\-N\f1]
[\f3\-G\f1]
[\f3\-X\f1]
[\f3\-i\f1 \f2min-interval\f1]
[\f3\-J\f1
[\f3\-K\f1 \f2spec\f1]
[\f3\-A\f1 \f2archivesdir\f1]
[\f3\-S\f1]
[\f3\-l\f1 \f2logfile\f1]
[\f3\-U\f1 \f2username\f1]
[\f3\-v\f1]
[\f3\-?\f1]
.SH DESCRIPTION
.B pmwebd
is a network daemon that binds a subset of the
Performance Co-Pilot (PCP) client API (\c
.BR PMAPI (3))
to RESTful web
applications using the HTTP (\c
.BR PMWEBAPI (3))
protocol.
Web clients request a URI with the prefix
.B /pmapi
to access the bindings.
.B 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.
.PP
In addition to the API binding,
.B 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 
.B /pmapi
prefix are mapped to files under the configured resource directory, if
the \f3\-R\f1 option was given.
.PP
In addition,
.B pmwebd
may be optionally configured as a server of a subset
of the graphite 0.9.12 web API, for URLs with the
.B /graphite
prefix, in order to expose PCP archives to interactive data-graphing web
applications.
.PP
The options to
.B pmwebd
are as follows.
.TP
\f3\-p\f1 \f2port\f1
Set the TCP port number on which
.B pmwebd
will listen for HTTP requests.
The default is 44323.
.TP
\f3\-4\f1 or \f3\-6\f1
Listen only on IPv4 or IPv6.  By default,
.B pmwebd
will listen on both
protocols, if possible.
.TP
\f3\-A\f1 \f2archdir\f1
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
.B pmwebd
working directory may
be accessed.
.TP
\f3\-R\f1 \f2resdir\f1
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.
.TP
\f3\-G\f1
Activate servicing of a subset of the graphite webapi.  This exposes all
PCP archives under the \f3\-A\f1 directory to remote clients.  By default,
graphite webapi serving is disabled.  To use the graphite and/or grafana
web applications included with
.BR pmwebd ,
use both \f3\-G\f1 and \f3\-R\f1, and connect your web browser to
.nh
.B http://127.0.0.1:43323/
.hy
.TP
\f3\-X\f1
Disable encoding of common characters for metric names, which allows
shorter graphite metric names.
.TP
\f3\-i\f1 \f2min-interval\f1
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
.B pmwebd
or the web browser; and vice versa.
.TP
\f3\-J\f1
When constructing graphite metric names, use the stored \f2hostname\f1
instead of a archive pathname as the first component.  This virtually
unifies \f2all\f1 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).
.TP
\f3\-t\f1 \f2timeout\f1
Set the maximum timeout (in seconds) after the last operation on a pmapi web
context, before it is closed by
.BR pmwebd .
A smaller timeout may be requested
by the web client. The default is 300.
.TP
\f3\-c\f1 \f2number\f1
Reset the next PMWEBAPI permanent context identifier as given.
The default is 1.
.TP
\f3\-h\f1 \f2hostname\f1 or \f3\-a\f1 \f2archive\f1 or \f3\-L\f1
Assign the next permanent PMWEBAPI context identifier to a PMAPI connection
to the given host (with an extended syntax as given in 
.BR PCPIntro (1)),
or archive file, or the PM_CONTEXT_LOCAL.
.TP
\f3\-C\f1
Mandatory authentication mode, where all host specifications at context
creation time must be accompanied by credentials (username and password).
These are then passed to
.BR 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.
.TP
\f3\-P\f1
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
.B pmwebd
accesses will be from benevolent users.
If enabled, unauthenticated remote
.BR PMWEBAPI (3)
clients will be able to access
potentially sensitive performance metric values which an unauthenticated
.BR PMAPI (3)
client usually would not be able to.
Refer to CVE-2012-3419 for additional details.
.TP
\f3\-N\f1
Disable creation of new PMWEBAPI contexts via HTTP requests, leaving only
permanent ones accessible.
.TP
\f3\-K\f1 \f2spec\f1
When
fetching metrics from a local context, the \f3\-K\f1
option may be used to control the DSO PMDAs that should be
made accessible.  The
.I spec
argument conforms to the syntax described in
.BR pmSpecLocalPMDA (3).
More than one
.B \-K
option may be used.
.TP
\f3\-l\f1 \f2logfile\f1
By default, logging goes to standard output/error file handles.
The verbosity flag \f3\-v\f1 affects the amount of traffic.  The
.B \-l
option causes the log file to be written to
.I logfile
instead.
If the log file cannot be created or is not writable, output is
written to the standard error instead.
.TP
\f3\-U\f1 \f2username\f1
If invoked as root, assume the identity of
.I username
before starting to accept incoming requests from web clients.
.TP
\f3\-S\f1
Disable service advertisement.
By default,
.B 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.
.TP
\f3\-v\f1
Increase the verbosity of
.B pmwebd
as it logs to its standard output/error.
.TP
\f3\-?\f1
Show
.B pmwebd
invocation help and exit.
.SH SECURITY
.PP
.B 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
.BR pmwebd .
Such configuration is beyond the scope of this document.
.TP
encryption/confidentiality
.BR pmwebd
does not currently support HTTPS (SSL/TLS), so
the HTTP traffic is not protected against network-level attacks.
.TP
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
.IR pcps://hostname?method=plain&user=userid&pass=password .
Use of resulting pmwebapi contexts later requires matching HTTP PLAIN
authentication; see below.
.TP
inbound admission control
.B 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.
.TP
outbound admission control
.B pmwebd
does not impose access control on outbound connections
when a new PMAPI context is created for a PMCD.
(Without the
.BR \-P
option, connections to UNIX-domain / local PMCDs are blocked.)
This enables hypothetical use of a
.B pmwebd
instance to be used as a network proxy/scanner.
For an archive type context, the files must be located under the
.B pmwebd
current directory, or another directory specified by 
.BR \-A .
One may entirely disable remotely specified PMAPI context creation using the 
.B \-N
option; in this case, specify a static set of contexts using the
.BR \-h ,
.BR \-a ,
and/or
.B \-L
options.
You may assign them arbitrary context numbers with the
.B \-c
option.
.TP
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
.B \-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.
.SH "STARTING AND STOPPING PMWEBD"
The
.B pmwebd
server may be started automatically at boot time and
stopped when the system is being brought down.  Users may also run
customized
.B pmwebd
instances (under separate \f3\-p\f1 PORT numbers), for
example for their own archive farms.
.B
For management fo the system
.BR pmwebd ,
become superuser and type
.PP
.ft CS
# $PCP_RC_DIR/pmwebd start
.ft
.PP
to start
.BR pmwebd ,
or
.PP
.ft CS
# $PCP_RC_DIR/pmwebd stop
.ft
.PP
to stop
.BR pmwebd .
Starting
.B pmwebd
when it is already running is the same as stopping
it and then starting it again.
.SH FILES
.PD 0
.TP
.B $PCP_PMWEBDOPTIONS_PATH
command line options
and environment variable settings for
.B pmwebd
when launched from
.B $PCP_RC_DIR/pmwebd
This file is interpreted as a Bourne Shell script, expecting
variable settings of the form "OPTIONS=value" and possibly others.
.TP
.B $PCP_LOG_DIR/pmwebd/pmwebd.log
Log file for system
.B pmwebd
service. 
.TP
.B $PCP_LOG_DIR
Default directory for \f3\-A\f1 option: a base directory containing PCP archives.
.TP
.B $PCP_SHARE_DIR/webapps
Default directory for \f3\-R\f1 option: a base directory containing web applications.
.PD
.SH "PCP ENVIRONMENT"
Environment variables with the prefix
.B PCP_
are used to parameterize the file and directory names
used by PCP.
On each installation, the file
.I /etc/pcp.conf
contains the local values for these variables.
The
.B $PCP_CONF
variable may be used to specify an alternative
configuration file,
as described in
.BR pcp.conf (5).
.SH SEE ALSO
.BR PCPIntro (1),
.BR PMAPI (3),
.BR PMWEBAPI (3),
.BR pmSpecLocalPMDA (3),
.BR pcp.conf (5),
.BR pcp.env (5)
.nh
.BR http://graphite.readthedocs.org/
.hy
and
.BR pmns (5).