flent - Flent: The FLExible Network Tester
Flent is a wrapper around netperf and similar tools to run
predefined tests and aggregate and plot the results. It defines several
tests that can be run against one or more hosts, primarily targeted at
testing for the presence of bufferbloat under various conditions.
The aggregated data is saved in (gzipped) JSON format for later
processing and/or import into other tools. The JSON format is documented
below.
Apart from the JSON format, the data can be output as csv values,
emacs org mode tables or plots. Each test can specify several different
plots, including time-series plots of the values against each other, as well
as CDF plots of (e.g.) ping times.
Plots can be output to the formats supported by matplotlib by
specifying the output filename with -o
output.{png,ps,pdf,svg}. If no output file is specified, the plot is
displayed using matplotlib’s interactive plot browser, which also
allows saving of the output (in .png format).
Flent runs on Python, versions 2.7+ and 3.3+. Plotting requires a
functional matplotlib installation (but everything else can run
without matplotlib). For the interactive plot viewer, a graphical
display (and suitably configured matplotlib) is required.
Most tests employ the netperf benchmarking tool to run the
tests. Version 2.6 or higher is required, and netperf must be compiled with
the --enable-demo option passed to ./configure. Some tests use
iperf in addition to, or instead of netperf. Both tools must be available in
the PATH.
For ICMP ping measurements, the version of ping employed must
support output timestamping (the -D parameter to GNU ping). This is not
supported by the BSD and OSX versions of ping. As an alternative to the
regular ping command, the fping utility (see http://fping.org)
can be employed. In that case fping must be version 3.5 or greater. Flent
will attempt to detect the presence of fping in the PATH and check
for support for the -D parameter. If this check is successful, fping
will be employed for ping data, otherwise the system ping will be used.
The irtt tool is highly recommended for UDP measurements.
See https://github.com/peteheist/irtt. Flent will automatically
detect if irtt is available in the PATH and use it if it is detected.
Note that the server component of irtt needs to be running on the target
host(s) as well.
When run, flent must be supplied either (a) a test name and one or
more host names to connect to, or (b) one or more input files containing
data from previous runs to post-process.
Test names, hostnames and input file names can all be specified as
unqualified arguments, and flent will do its best to guess which is which.
For each argument, if it is an existing file, it is assumed to be an input
file, if it is the name of an existing test configuration it’s
assumed to be a test name, and if neither of those are true, it is assumed
to be a host name. The -i and -H switches can be used to
explicitly specify the interpretation of an argument.
flent [options] <host|test|input file
...>
- -i INPUT,
--input=INPUT
- File to read input from (instead of running tests). Input files can also
be specified as unqualified arguments without using the -i
switch.
- -f FORMAT,
--format=FORMAT
- Select output format (plot, csv, org_table, stats). Default is no
processed output (just writes the JSON data file).
- -p PLOT, --plot=PLOT
- Select which plot to output for the given test (implies -f plot).
Use the --list-plots option to see available plots.
- -n NOTE, --note=NOTE
- Add arbitrary text as a note to be stored in the JSON data file (under the
NOTE key in the metadata object).
- -r RCFILE,
--rcfile=RCFILE
- Load configuration data from RCFILE (default ~/.flentrc).
See section below for information on the rc file format.
- -x,
--extended-metadata
- Collect extended metadata and store it with the data file. May include
details of your machine you don’t want to distribute; see the
section on the data format below.
- --remote-metadata=HOSTNAME
- Collect extended metadata from a remote host. HOSTNAME is passed
verbatim to ssh, so can include hosts specified in ~/.ssh/config. Note
that gathering the data can take some time, since it involves executing
several remote commands. This option can be specified multiple times and
implies --extended-metadata.
- --gui
- Run the flent GUI. All other options are used as defaults in the GUI, but
can be changed once it is running. The GUI can also be started by running
the flent-gui binary. For more information on the GUI, see the
The Flent GUI section.
- --new-gui-instance
- Start a new GUI instance. Otherwise, flent will try to connect to an
already running GUI instance and have that load any new data files
specified as arguments. Implies --gui when passed on the command
line, but not when set in the rc file. Note that when multiple GUI
instances are running, there is no guarantee as to which instance will get
a subsequent open request (if run again without
--new-gui-instance).
- --gui-no-defer
- Normally, the GUI defers redrawing plots until they are needed to avoid
redrawing all open plots every time an option changes. This switch turns
off that optimisation in favour of always redrawing everything straight
away. This is useful when loading a bunch of plots from the command line
and then wanting to flip through them without drawing delay.
- -B BATCH_FILE,
--batch-file=BATCH_FILE
- Load batch file BATCH_FILE. Can be specified multiple times, in which case
the files will be combined (with identically-named sections being
overridden by later files). See appropriate section below for an
explanation of the batch file format.
- --batch-override=key=value
- Override parameter ’key’ in the batch config and set it to
’value’. The key name will be case folded to lower case. Can
be specified multiple times.
- --batch-dry-run
- Dry batch run. Prints what would be done, but doesn’t actually run
any tests.
- --batch-resume=DIR
- Try to resume a previously interrupted batch run. The argument is the
top-level output directory from the previous run.
This will attempt to find a data file in the resume directory
and load the BATCH_TIME from the previous run from that and continue.
The assumption is that the output directory and filenames are generated
from the batch time, so that they will match with the previous run when
the same time is used. Then, tests for which data files already exist
will be skipped on this run. If the rest of the batch invocation is
different from the one being resumed, results may not be what you
want.
There's a check to ensure that the generated output path is a
subdirectory of the resume directory, and the whole run will be aborted
if it isn't.
These options affect the behaviour of the test being run and have
no effect when parsing input files.
- -H HOST, --host=HOST
- Host to connect to for tests. For tests that support it, multiple hosts
can be specified by supplying this option multiple times. Hosts can also
be specified as unqualified arguments; this parameter guarantees that the
argument be interpreted as a host name (rather than being subject to
auto-detection between input files, hostnames and test names).
- --local-bind=IP
- Local hostname or IP address to bind to (for test tools that support
this). Can be specified multiple times for tests that connect to more than
one host; if it is, it must be specified as many times as there are
hosts.
- --remote-host=idx=HOSTNAME
- A remote hostname to connect to when starting a test. The idx is the
runner index, which is assigned sequentially to each runner (and so
it is not the same as the sequence of hostnames). Look for the
'IDX' key in SERIES_META for a test get the idx used here, but note that
the idx assignment depends on the exact arguments to the test.
This works by simply prepending 'ssh HOSTNAME' to the runner
command, so it relies on the same binaries being in the same places on
both machines, and won't work for all runners.
This option can be specified multiple times to have multiple
runners run on remote hosts.
- -4, --ipv4
- Use IPv4 for tests (some tests may ignore this).
- -6, --ipv6
- Use IPv6 for tests (some tests may ignore this).
- --socket-timeout=SOCKET_TIMEOUT
- Socket timeout (in seconds) used for UDP delay measurement, to prevent
stalls on packet loss. Only enabled if the installed netperf version is
detected to support this (requires SVN version of netperf).
For the default value, see the output of flent -h. The
value of this parameter is an implicit upper bound on how long a
round-trip time that can be measured. As such you may need to adjust it
if you are experiencing latency above the default value. Set to 0 to
disable.
- --send-size=SEND_SIZE
- Send size (in bytes) used for TCP tests. Netperf uses the socket buffer
size by default, which if too large can cause spikes in the throughput
results. Lowering this value will increase CPU usage but also improves the
fidelity of the throughput results without having to decrease the socket
buffer size.
Can be specified multiple times, with each value corresponding
to a stream of a test. If only specified once, the same value will be
applied to all flows.
- --test-parameter=key=value
- Arbitrary test parameter in key=value format. Key will be case folded to
lower case. The values are stored with the results metadata, and so can be
used for storing arbitrary information relevant for a particular test run.
In addition to serving as simple metadata, the test parameters
can also affect the behaviour of some test configurations. See the
Supplied Tests section for information on these.
This option can be specified multiple times to set multiple
test parameters.
- --swap-up-down
- Switch upstream and downstream directions for data transfer. This means
that ’upload’ will become ’download’ and vice
versa. Works by exchanging netperf TCP_MAERTS and TCP_STREAM
parameters, so only works for tests that employ these as their data
transfer, and only for the TCP streams.
- --socket-stats
- Parse socket stats during test. This will capture and parse socket
statistics for all TCP upload flows during a test, adding TCP cwnd and RTT
values to the test data. Requires the 'ss' utility to be present on the
system, and can fail if there are too many simultaneous upload flows;
which is why this option is not enabled by default.
- --marking-name
- Define a new symbolic name that can be used when specifying flow markings
using the 'markings' test parameter. This can be used to make it easier to
specify custom diffserv markings on flows by using symbolic names for each
marking value instead of the hex codes. Values specified here will be used
in addition to the common values (listed below), and cannot override the
built-in names. Names will be case-folded when matching.
The list of symbolic markings natively supported, along with
their hex expansions, are:
AF11: 0x28 CS0: 0x00
AF12: 0x30 CS1: 0x20
AF13: 0x38 CS2: 0x40
AF21: 0x48 CS3: 0x60
AF22: 0x50 CS4: 0x80
AF23: 0x58 CS5: 0xa0
AF31: 0x68 CS6: 0xc0
AF32: 0x70 CS7: 0xe0
AF33: 0x78 EF: 0xb8
AF41: 0x88
AF42: 0x90
AF43: 0x98
Note that the hexadecimal values denote the value of the full ToS
byte (including the two ECN bits), so they need to be right-shifted by two
bits to get the corresponding diffserv code points.
These options are used to configure the appearance of plot output
and only make sense combined with -f plot.
- --label-y=LABEL
- Override the figure axis labels. Can be specified twice, corresponding to
figures with multiple axes.
- -I,
--invert-latency-y
- Invert latency data series axis (typically the Y-axis), making plots show
’better' values upwards.
- -z, --zero-y
- Always start Y axis of plot at zero, instead of autoscaling the axis.
Autoscaling is still enabled for the upper bound. This also disables log
scale if enabled.
- --norm-factor=FACTOR
- Data normalisation factor. Divide all data points by this value. Can be
specified multiple times, in which case each value corresponds to a data
series.
- --bounds-y=BOUNDS
- Specify bounds of the plot axes. If specifying one number, that will
become the upper bound. Specify two numbers separated by a comma to
specify both upper and lower bounds. To specify just the lower bound, add
a comma afterwards. Can be specified twice, corresponding to figures with
multiple axes.
- -S, --scale-mode
- Treat file names (except for the first one) passed as unqualified
arguments as if passed as --scale-data (default as if passed as
--input).
- --concatenate
- Concatenate multiple result sets into one data series. This means that
each data file will have its time axis shifted by the preceding series
duration and appended to the first data set specified. Only works for data
sets from the same test, obviously.
- --absolute-time
- Plot data points with absolute UNIX time on the x-axis. This requires the
absolute starting time for the test run to be stored in the data file, and
so it won’t work with data files that predates this feature.
- --subplot-combine
- When plotting multiple data series, plot each one on a separate subplot
instead of combining them into one plot. This mode is not supported for
all plot types, and only works when --scale-mode is disabled.
- --skip-missing-series
- Skip missing series entirely from bar plots, instead of leaving an empty
space for it.
- --no-print-n
- Do not print the number of data points on combined plots. When using plot
types that combines results from several test runs, the number of data
series in each combined data point is normally added after the series
name, (n=X) for X data series. This option turns that off.
- --no-annotation
- Exclude annotation with hostnames, time and test length from plots.
- --override-title=TITLE
- Override plot title with this string. Completely discards the configured
title (from the test configuration), as well as the title stored in the
data set, and replaces it with the value supplied here. This is useful to
override the plot title at the time of plotting, for instance to
add a title to an aggregate plot from several data series. When this
parameter is specified, --no-title has no effect.
- --no-markers
- Don’t use line markers to differentiate data series on plots.
- --horizontal-legend
- Place a horizontal legend below the plot instead of a vertical one next to
it. Doesn't always work well if there are too many items in the
legend.
- --legend-placement=LEGEND_PLACEMENT
- Control legend placement. Enabling this option will place the legend
inside the plot at the specified location. Can be one of 'best', 'upper
right', 'upper left', 'lower left', 'lower right', 'right', 'center left',
'center right', 'lower center', 'upper center' or 'center'.
- --reverse-legend
- Reverse the order of items in the legend. This can be useful to make the
legend order match the data series in some cases.
- --filter-legend
- Filter legend labels by removing the longest common substring from all
entries. This is not particularly smart, so use with care.
- --filter-regexp=REGEXP
- Filter the plot legend by the supplied regular expression (removing any
text from the legend that matches the expression). Can be specified
multiple times, in which case the filters will be applied in the order
specified. Note that for combining several plot results, the regular
expression is also applied before the grouping logic, meaning that a too
wide filter can mess up the grouping.
- --override-label=LABEL
- Override dataset label. Can be specified multiple times when multiple
datasets are being plotted, in which case the order of labels corresponds
to the order of datasets.
Like --override-title, this is applied at the time
of plotting.
- --split-group=LABEL
- Split data sets into groups when creating box plots. Specify this option
multiple times to define the new groups; the value of each option is the
group name.
Say you're plotting nine datasets which are really testing two
variables with three values each. In this case, it can be useful to have
the box plot of the results be split into three parts (corresponding to
the values of one variable) with each three boxes in each of them
(corresponding to the values of the second variable). This option makes
this possible; simply specify it three times with the labels to be used
for the three groups.
A constraint on this option is that the number of datasets
being plotted must be divisible by the number of groups.
- --colours=COLOURS
- Comma-separated list of colours to be used for the plot colour cycle. Can
be specified in any format understood by matplotlib (including HTML hex
values prefixed with a #).
Yes, this option uses British spelling. No, American spelling
is not supported.
- --override-colour-mode=MODE
- Override colour_mode attribute. This changes the way colours are assigned
to bar plots. The default is 'groups' which assigns a separate colour to
each group of data series. The alternative is 'series' which assigns a
separate colour to each series, repeating them for each data group.
- --override-group-by=GROUP
- Override the group_by setting for combination plots. This is useful
to, for instance, switch to splitting up combined data sets by batch run
instead of by file name.
- --combine-save-dir=DIRNAME
- When doing a combination plot save the intermediate data to
DIRNAME. This can then be used for subsequent plotting to avoid
having to load all the source data files again on each plot.
- --figure-width=FIG_WIDTH
- Figure width in inches. Used when saving plots to file and for default
size of the interactive plot window.
- --figure-height=FIG_HEIGHT
- Figure height in inches. Used when saving plots to file and for default
size of the interactive plot window.
- --fallback-layout
- Use the fallback layout engine (tight_layout built in to matplotlib). Use
this if text is cut off on saved figures. The downside to the fallback
engine is that the size of the figure (as specified by
--figure-width and --figure-height) is no longer kept
constant.)
- --no-matplotlibrc
- Don’t load included matplotlibrc values. Use this if autodetection
of custom matplotlibrc fails and flent is inadvertently overriding rc
values.
- --no-hover-highlight
- Don't highlight data series on hover in interactive plot views. Use this
if redrawing is too slow, or the highlighting is undesired for other
reasons.
- --scale-data=SCALE_DATA
- Additional data files to consider when scaling the plot axes (for plotting
several plots with identical axes). Note, this displays only the first
data set, but with axis scaling taking into account the additional data
sets. Can be supplied multiple times; see also --scale-mode.
- --control-host=HOST
- Hostname for the test control connection (for test tools that support
this). Default: First hostname of test target.
When running tests that uses D-ITG as a test tool (such as the
voip-* tests), this switch controls where flent will look for the D-ITG
control server (see section below on running tests with D-ITG). For
Netperf-based tests, this option is passed to Netperf to control where
to point the control connection. This is useful to, for instance, to run
the control server communication over a separate control network so as
to not interfere with test traffic.
There is also a per-flow setting for this for tests that
connect to multiple hosts; see the control_hosts test parameter
in Supplied Tests. If both are set, the per-flow setting takes
precedence for those tests that use it.
- --control-local-bind=IP
- Local hostname or IP to bind control connection to (for test tools that
support it; currently netperf). If not supplied, the value for
--local-bind will be used. Note that if this value is passed but
--local-bind is not, netperf will use the value specified
here to bind the data connections to as well.
- --http-getter-urllist=FILENAME
- When running HTTP tests, the http-getter tool is used to fetch URLs (see
https://github.com/tohojo/http-getter). This option specifies the
filename containing the list of HTTP URLs to get. Can also be a URL, which
will then be downloaded as part of each test iteration. If not specified,
this is set to http://<hostname>/filelist.txt where
<hostname> is the first test hostname.
- --http-getter-dns-servers=DNS_SERVERS
- DNS servers to use for http-getter lookups. Format is
host[:port][,host[:port]]... This option will only work if libcurl
supports it (needs to be built with the ares resolver). Default is none
(use the system resolver).
- --irtt-sampling-interval=MILLISECONDS
- Override the sampling interval passed to irtt, in milliseconds. Can be
used to run irtt with a higher sampling frequency than the rest of the
test. If set, this will override the sampling interval for all instances
of irtt used in the test.
- --list-plots
- List available plots for selected test and exit.
- -q, --quiet
- Disable normal logging to console (and only log warnings and errors).
Flent will abort what it is currently doing on receiving a
SIGINT -- this includes killing all runners, cleaning up temporary
files and shutting down as gracefully as possible. Runners are killed with
SIGTERM in this mode, and their output is discarded. If a batch run
is in progress, the current test will be interrupted in this way, and the
rest of the batch run is aborted. Previously completed tests and their
results are not aborted. Post-commands marked as ’essential’
will be run after the test is interrupted. Additionally, flent converts
SIGTERM into SIGINT internally and reacts accordingly.
Upon receiving a SIGUSR1, flent will try to gracefully
abort the test it is currently running, and parse the output of the runners
to the extent that any such output exists. That is, each runner will be
killed by a SIGINT, which will cause a graceful shutdown for at least
ping and netperf (although netperf running in TCP_MAERTS mode will
bug out when interrupted like this, so end-of-tests statistics will be
missing). Flent will only react once to a SIGUSR1, sending exactly
one SIGINT to the active runners, then wait for them to exit. This
may take several seconds in the case of netperf. If the runners for some
reason fail to exit, flent will be stuck and will need to be killed with
SIGINT. If running in batch mode, SIGUSR1 will only affect the
currently running test; subsequent tests will still be run.
Test are supplied as Python files and can specify commands to run
etc. For a full list of the tests supported by flent, see the
--list-tests option.
This test exists in a couple of variants and is a partial
implementation of the RRUL specification as written by Dave Taht (see
https://www.bufferbloat.net/projects/bloat/wiki/RRUL_Spec/). It works
by running RTT measurement using ICMP ping and UDP roundtrip time
measurement, while loading up the link with eight TCP streams (four
downloads, four uploads). This quite reliably saturates the measured link
(wherever the bottleneck might be), and thus exposes bufferbloat when it is
present.
These tests combine a TCP flow (either in one direction, or both)
with an ICMP ping measurement. It’s a simpler test than RRUL, but in
some cases the single TCP flow can be sufficient to saturate the link.
This test runs iperf configured to emit 100Mbps of UDP
packets targeted at the test host, while measuring RTT using ICMP ping. It
is useful for observing latency in the face of a completely unresponsive
packet stream.
Some test parameters (set with --test-parameter) affect the
way tests behave. These are:
- bidir_streams
- These set the number of streams for the tests that are configurable. The
tcp_nup, tcp_ndown and rrul_be_nflows tests
understand upload_streams and download_streams, while the
rrul_var test understands bidir_streams. If any of these
parameter is set to the special value num_cpus the number of
streams will be set to the number of CPUs on the system (if this
information is available).
- tcp_cong_control
- Set the congestion control used for TCP flows, for platforms that supports
setting it. This can be specified as a simple string to set the same value
for upstream and downstream, or two comma-separated values to set it
separately for the upstream and downstream directions. On Linux, any value
in the sysctl net.ipv4.tcp_allowed_congestion_control can be used.
If a congestion control is specified that is not available on
the system running the test, setting it will simply fail. In addition,
some tests override the congestion control for one or more flows. The
actual congestion control used is stored in the CONG_CONTROL
per-test metadata field.
- udp_pktsizes
- This sets the bandwidth and packet size of each UDP stream in the
udp_* tests. The option is passed to iperf so can be in any
syntax the iperf understands (e.g. 20M for 20 Mbps).
When running multiple UDP streams use the plural versions of
the options (udp_bandwidths and udp_pktsizes) to specify
individual per-stream values (comma-separated per stream), or the
singular versions to specify the same value for all streams.
- burst_tos
- These set the length, number of ports to use, packet size and TOS value
for the packet bursts generated in the burst* tests.
- wifi_stats_hosts
- These set hostnames to gather statistics from from during the test. The
hostnames are passed to SSH, so can be anything understood by SSH
(including using username@host syntax, or using hosts defined in
~/.ssh/config). This will attempt to run remote commands on these
hosts to gather the required statistics, so passwordless login has to be
enabled for. Multiple hostnames can be specified, separated by commas.
CPU stats and netstat output is global to the machine being
connected to. The qdisc and WiFi stats need extra parameters to work.
These are qdisc_stats_interfaces, wifi_stats_interfaces
and wifi_stats_stations. The two former specify which interfaces
to gather statistics from. These are paired with the hostnames, and so
must contain the same number of elements (also comma-separated) as the
_hosts variables. To specify multiple interfaces on the same
host, duplicate the hostname. The wifi_stats_stations parameter
specifies MAC addresses of stations to gather statistics for. This list
is the same for all hosts, but only stations present in debugfs on each
host are actually captured.
The qdisc stats gather statistics output from tc -s,
while the WiFi stats gather statistics from debugfs. These are gathered
by looping in a shell script; however, for better performance, the
tc_iterate and wifistats_iterate programmes available in
the misc/ directory of the source code tarball can be installed.
On low-powered systems this can be critical to get correct statistics.
The helper programmes are packaged for LEDE/OpenWrt in the
flent-tools package.
- ping_labels
- These are used to define one or more extra host names that will receive a
ping flow while a test is run. The ping_hosts variable simply
specifies hostnames to ping (several can be specified by separating them
with commas). The ping_local_binds variable sets local IP
address(es) to bind to for the extra ping flows. If specified, it must
contain the same number of local addresses as the number of ping hosts.
The same local address can be specified multiple times, however. The
ping_labels variable is used to label each of the ping flows; if
not specified, Flent will create a default label based on the target
hostname for each flow.
- voip_marking
- Similar to the ping variants above, these parameters specify a hostname
that will receive a VoIP test. However, unlike the ping parameters, only
one hostname can be specified for VoIP tests, and that end-host needs to
have either D-ITG (and the control server) or the IRTT server running. The
marking setting controls which DiffServ marking is applied to the VoIP
flow and defaults to no marking being set.
- control_hosts
- Hostnames to use for the control connections for the rtt_fair*
tests. Comma-separated. If specified, it must contain as many hostnames as
the number of target hostnames specified for the test.
- labels
- Flow markings to use for each of the flows in the rtt_fair* tests.
Comma-separated values of markings understood by Netperf (such as
"CS0"). Only supports setting the same marking on both the
upstream and downstream packets of each flow (so no "CS0,CS0"
setting as can be used for Netperf). If not set, defaults to CS0 (best
effort). If set, each value corresponds to a flow, and any extra flows
will be set to CS0. By default each flow will be labelled according to its
marking; to override these labels, use the labels parameter.
- stream_delays
- Specify a per-stream delay (in seconds) for the different streams started
up by a test. Use commas to separate values for the different streams.
This can be used to create tests with staggered start times, for example
to test TCP flow startup convergence times. What exactly constitutes a
stream depends on the test. For example, the rtt_fair* tests considers
each hostname a stream, whether or not there is one or two flows going to
that host.
Flent comes equipped with a GUI to browse and plot previously
captured datasets. The GUI requires PyQt4; if this is installed, it can be
launched with the --gui parameter, or by launching the
flent-gui binary. Additionally, if Flent is launched without
parameters and without a controlling terminal, the GUI will be launched
automatically.
The GUI can be used for interactively plotting previously captured
datasets, and makes it easy to compare results from several test runs. It
presents a tabbed interface to graphs of data files, allows dynamic
configuration of plots, and includes a metadata browser. For each loaded
data file, additional data files can be loaded and added to the plot,
similar to what happens when specifying multiple input files for plotting on
the command line. A checkbox controls whether the added data files are added
as separate entries to the plot, or whether they are used for scaling the
output (mirroring the --scale-mode) command line switch.
The GUI also incorporates matplotlib’s interactive browsing
toolbar, enabling panning and zooming of the plot area, dynamic
configuration of plot and axis parameters and labels and saving the plots to
file. The exact dynamic features supported depends on the installed version
of matplotlib.
Some of the command line options can be specified in an rc file.
By default, flent looks for this in ~/.flentrc, but an alternative
location can be specified with the --rcfile command line option.
The rc file allows options to be specified globally, an optionally
overridden for specific tests. For an explanation of the options, refer to
the annotated example rc file, by default installed to
/usr/share/doc/flent/flentrc.example.
Flent supports reading batch files to automate running several
tests and do setup/teardown of test environment etc. This greatly aids
reproducibility of tests.
The batch file is parsed as an ini file, and can have three types
of sections: batches, commands and args. Each section also has a name; type
and name are separated with two colons. 'Batches' are named tests that can
be selected from the command line, 'commands' are system commands to be run
before or after each test run, and 'args' are used in the looping mechanism
(which allows repeating tests multiple times with different parameters).
Variables in sections control the operation of Flent and can be
modified in several ways: Sections of the same type can inherit from each
other and the variables in an 'arg' section will be interpolated into the
batch definition on each iteration of a loop. In addition, variable contents
can be substituted into other variables by using the ${varname} syntax.
These three operations are resolved in this order (inheritance, arg
interpolation and variable substitution).
An annotated example batchfile is distributed with the source
code, and is by default installed to
/usr/share/doc/flent/batchfile.example.
The aggregated test data is saved in a file called
<test_name>-<date>.<title>.flent.gz (the title part
is omitted if no title is specified by the -t parameter). This file
contains the data points generated during the test, as well as some
metadata.
- version
- The file format version as an integer.
- x_values
- An array of the x values for the test data (typically the time values for
timeseries data).
- results
- A JSON object containing the result data series. The keys are the data
series names; the value for each key is an array of y values for that data
series. The data array has the same length as the x_values array,
but there may be missing data points (signified by null values).
- metadata
- An object containing various data points about the test run. The metadata
values are read in as configuration parameters when the data set is loaded
in for further processing. Not all tests use all the parameters, but they
are saved anyway.
- raw_values
- An array of objects for each data series. Each element of the array
contains the raw values as parsed from the test tool corresponding to that
data series.
- TITLE
- Any extra title specified by the --title-extra parameter when the
test was run.
- HOSTS
- List of the server hostnames connected to during the test.
- LOCAL_HOST
- The hostname of the machine that ran the test.
- LENGTH
- Test length in seconds, as specified by the --length
parameter.
- TOTAL_LENGTH
- Actual data series length, after the test has added time to the
LENGTH.
- TIME
- ISO timestamp of the time the test was initiated.
- NOTE
- Arbitrary text as entered with the --note switch when the test was
run.
- IP_VERSION
- IP version used to run test (as specified by command line parameters, or
auto-detected from getaddrinfo() if unspecified).
- MODULE_VERSIONS
- The sha1sum of certain interesting Linux kernel modules, if available. Can
be used to match test data to specific code versions, if the kernel build
is instrumented to, e.g., set the build ID to a git revision.
- SYSCTLS
- The values of several networking-related sysctls on the host (if
available; Linux only).
- EGRESS_INFO
- Interface name, qdisc, offload, driver and BQL configuration of the
interface used to reach the test target. This requires that the ip
binary is present on Linux, but can be extracted from route on BSD.
Qdisc information requires the tc binary to be present, and offload
information requires ethtool.
If the --remote-metadata is used, the extended metadata
info is gathered for each of the hostnames specified. This is gathered
under the REMOTE_METADATA key in the metadata object, keyed by
the hostname values passed to --remote-metadata. Additionally,
the REMOTE_METADATA object will contain an object called
INGRESS_INFO which is a duplicate of EGRESS_INFO, but with
the destination IP exchanged for the source address of the host running
flent. The assumption here is that --remote-metadata is used to
capture metadata of a router known to be in the test path, in which case
INGRESS_INFO will contain information about the reverse path from
the router (which is ingress from the point of view of the host running
flent). If the host being queried for remote metadata is off the path,
the contents of INGRESS_INFO will probably be the same as that of
EGRESS_INFO .
If the --extended-metadata switch is turned on, the
following additional values are collected and stored (to the extent they are
available from the platform):
- IP_ADDRS
- IP addresses assigned to the machine running flent.
- GATEWAYS
- IP addresses of all detected default gateways on the system, and the
interfaces they are reachable through. Only available if the
netstat binary is present on the system.
- EGRESS_INFO
- In the EGRESS_INFO key, the IP address of the next-hop router and
the interface MAC address are added if extended metadata is enabled.
The following output formats are currently supported by Flent:
Output test data as one of a series of graphical plots of
timeseries data or summarised as a CDF plot. Each test supplies a number of
different plots; the list of plots for a given test is output by the
--list-plots switch (which must be supplied along with a test
name).
The plots are drawn by matplotlib, and can be displayed on the
screen interactively (requires a graphical display), or output to a file in
svg, pdf, ps and png formats. Using the -o switch turns out file
output (the file format is inferred from the file name), while not supplying
the switch turns on the interactive plot viewer.
These formats output the numeric data in a tabulated format to be
consumed by other applications. The csv output format is a
comma-separated output that can be imported into e.g. spreadsheets, while
org_table outputs a tabulated output in the table format supported by
Emacs org mode. The data is output in text format to standard output, or
written to a file if invoked with the -o parameter.
This output format outputs various statistics about the test data,
such as total bandwidth consumed, and various statistical measures
(min/max/mean/median/std dev/variance) for each data source specified in the
relevant test (this can include some data sources not includes on plots).
The data is output in text format to standard output, or written to a file
if invoked with the -o parameter.
This output format outputs the test metadata as pretty-printed
JSON (also suitable for human consumption). It is output as a list of
objects, where each object corresponds to the metadata of one test. Mostly
useful for inspecting metadata of stored data files.
This version of flent has experimental support for running and
parsing the output of the D-ITG test tool (see
http://traffic.comics.unina.it/software/ITG/). Flent supports parsing
the one-way delay as measured by D-ITG. However, in order to do so, the data
needs to be collected at the receiver end, statistics extracted, and the
result passed back to flent on the sending side.
To perform this function, flent supports a control server which
will listen to XML-RPC requests, spawn an appropriate ITGRecv instance and,
after the test is done, parse its output and make it available for flent to
retrieve. This control server is available as a Python file that by default
is installed in /usr/share/doc/flent/misc. It currently requires a
patched version of D-ITG v2.8.1. The patch is also included in the same
directory.
Note that the D-ITG server is finicky and not designed with
security in mind. For this reason, the control server includes HMAC
authentication to only allow authenticated clients to run a test against the
server; however there is currently no support for enforcement of this in
e.g. firewall rules. Please bear this in mind when running a publicly
reachable ITGRecv instance (with or without the control server). Another
security issue with the control server is that the Python XML-RPC library by
default is vulnerable to XML entity expansion attacks. For this reason, it
is highly recommended to install the defusedxml library (available at
https://pypi.python.org/pypi/defusedxml/) on the host running the
control server. The server will try to find the library on startup and
refuse to run if it is not available, unless explicitly told otherwise.
Due to the hassle of using D-ITG, it is recommended to install
irtt instead and use that for VoIP tests.
Under some conditions (such as severe bufferbloat), the UDP RTT
measurements done by netperf can experience packet loss to the extent that
the test aborts completely, which can cause missing data points for some
measurement series. The --socket-timeout feature can alleviate this, but
requires a recent SVN version of netperf to work. Flent tries to detect if
netperf supports this option and enables it for the UDP measurements if it
does. Using irtt for UDP measurements is a way to alleviate this;
Flent will automatically detect the availability of irtt and use it if
available.
Probably many other bugs. Please report any found to
https://github.com/tohojo/flent/issues and include the output of
flent --version in the report. A debug log (as obtained with
flent --log-file) is also often useful.
2012-2022, Toke Høiland-Jørgensen and contributors.
Source code is GPLv3. Documentation is CC-BY-SA. Neither license affects any
output produced by Flent