2. `Statistics Categories`_
3. `Running a Tahoe Stats-Gatherer Service`_
4. `Using Munin To Graph Stats Values`_
Each Tahoe node collects and publishes statistics about its operations as it
runs. These include counters of how many files have been uploaded and
downloaded, CPU usage information, performance numbers like latency of
storage server operations, and available disk space.
The easiest way to see the stats for any given node is use the web interface.
From the main "Welcome Page", follow the "Operational Statistics" link inside
the small "This Client" box. If the welcome page lives at
http://localhost:3456/, then the statistics page will live at
http://localhost:3456/statistics . This presents a summary of the stats
block, along with a copy of the raw counters. To obtain just the raw counters
(in JSON format), use /statistics?t=json instead.
The stats dictionary contains two keys: 'counters' and 'stats'. 'counters'
are strictly counters: they are reset to zero when the node is started, and
grow upwards. 'stats' are non-incrementing values, used to measure the
current state of various systems. Some stats are actually booleans, expressed
as '1' for true and '0' for false (internal restrictions require all stats
values to be numbers).
Under both the 'counters' and 'stats' dictionaries, each individual stat has
a key with a dot-separated name, breaking them up into groups like
'cpu_monitor' and 'storage_server'.
The currently available stats (as of release 1.6.0 or so) are described here:
this group counts inbound storage-server operations. They are not provided
by client-only nodes which have been configured to not run a storage server
(with [storage]enabled=false in tahoe.cfg)
allocate, write, close, abort
these are for immutable file uploads. 'allocate' is incremented when a
client asks if it can upload a share to the server. 'write' is
incremented for each chunk of data written. 'close' is incremented when
the share is finished. 'abort' is incremented if the client abandons
these are for immutable file downloads. 'get' is incremented
when a client asks if the server has a specific share. 'read' is
incremented for each chunk of data read.
these are for immutable file creation, publish, and retrieve. 'readv'
is incremented each time a client reads part of a mutable share.
'writev' is incremented each time a client sends a modification
add-lease, renew, cancel
these are for share lease modifications. 'add-lease' is incremented
when an 'add-lease' operation is performed (which either adds a new
lease or renews an existing lease). 'renew' is for the 'renew-lease'
operation (which can only be used to renew an existing one). 'cancel'
is used for the 'cancel-lease' operation.
this counts how many bytes were freed when a 'cancel-lease'
operation removed the last lease from a share and the share
was thus deleted.
this counts how many bytes were consumed by immutable share
uploads. It is incremented at the same time as the 'close'
this counts how many bytes are currently 'allocated', which
tracks the space that will eventually be consumed by immutable
share upload operations. The stat is increased as soon as the
upload begins (at the same time the 'allocated' counter is
incremented), and goes back to zero when the 'close' or 'abort'
message is received (at which point the 'disk_used' stat should
incremented by the same amount).
disk_total, disk_used, disk_free_for_root, disk_free_for_nonroot, disk_avail, reserved_space
these all reflect disk-space usage policies and status.
'disk_total' is the total size of disk where the storage
server's BASEDIR/storage/shares directory lives, as reported
by /bin/df or equivalent. 'disk_used', 'disk_free_for_root',
and 'disk_free_for_nonroot' show related information.
'reserved_space' reports the reservation configured by the
tahoe.cfg [storage]reserved_space value. 'disk_avail'
reports the remaining disk space available for the Tahoe
server after subtracting reserved_space from disk_avail. All
values are in bytes.
this is '1' if the storage server is currently accepting uploads of
immutable shares. It may be '0' if a server is disabled by
configuration, or if the disk is full (i.e. disk_avail is less than
this counts the number of 'buckets' (i.e. unique
storage-index values) currently managed by the storage
server. It indicates roughly how many files are managed
by the server.
these stats keep track of local disk latencies for
storage-server operations. A number of percentile values are
tracked for many operations. For example,
'storage_server.latencies.readv.50_0_percentile' records the
median response time for a 'readv' request. All values are in
seconds. These are recorded by the storage server, starting
from the time the request arrives (post-deserialization) and
ending when the response begins serialization. As such, they
are mostly useful for measuring disk speeds. The operations
tracked are the same as the counters.storage_server.* counter
values (allocate, write, close, get, read, add-lease, renew,
cancel, readv, writev). The percentile values tracked are:
mean, 01_0_percentile, 10_0_percentile, 50_0_percentile,
90_0_percentile, 95_0_percentile, 99_0_percentile,
99_9_percentile. (the last value, 99.9 percentile, means that
999 out of the last 1000 operations were faster than the
given number, and is the same threshold used by Amazon's
internal SLA, according to the Dynamo paper).
Percentiles are only reported in the case of a sufficient
number of observations for unambiguous interpretation. For
example, the 99.9th percentile is (at the level of thousandths
precision) 9 thousandths greater than the 99th
percentile for sample sizes greater than or equal to 1000,
thus the 99.9th percentile is only reported for samples of 1000
or more observations.
These count client activity: a Tahoe client will increment these when it
uploads or downloads an immutable file. 'files_uploaded' is incremented by
one for each operation, while 'bytes_uploaded' is incremented by the size of
These count client activity for mutable files. 'published' is the act of
changing an existing mutable file (or creating a brand-new mutable file).
'retrieved' is the act of reading its current contents.
These count activity of the "Helper", which receives ciphertext from clients
and performs erasure-coding and share upload for files that are not already
in the grid. The code which implements these counters is in
incremented each time a client asks to upload a file
upload_already_present: incremented when the file is already in the grid
incremented when the file is not already in the grid
incremented when the helper already has partial ciphertext for
the requested upload, indicating that the client is resuming an
this counts how many bytes of ciphertext have been fetched
from uploading clients
this counts how many bytes of ciphertext have been
encoded and turned into successfully-uploaded shares. If no
uploads have failed or been abandoned, encoded_bytes should
eventually equal fetched_bytes.
These also track Helper activity:
how many files are currently being uploaded. 0 when idle.
how many cache files are present in the incoming/ directory,
which holds ciphertext files that are still being fetched
from the client
total size of cache files in the incoming/ directory
total size of 'old' cache files (more than 48 hours)
how many cache files are present in the encoding/ directory,
which holds ciphertext files that are being encoded and
total size of cache files in the encoding/ directory
total size of 'old' cache files (more than 48 hours)
how many seconds since the node process was started
1min_avg, 5min_avg, 15min_avg
estimate of what percentage of system CPU time was consumed by the
node process, over the given time interval. Expressed as a float, 0.0
for 0%, 1.0 for 100%
estimate of total number of CPU seconds consumed by node since
the process was started. Ticket #472 indicates that .total may
sometimes be negative due to wraparound of the kernel's counter.
When enabled, the "load monitor" continually schedules a one-second
callback, and measures how late the response is. This estimates system load
(if the system is idle, the response should be on time). This is only
enabled if a stats-gatherer is configured.
average "load" value (seconds late) over the last minute
maximum "load" value over the last minute
Running a Tahoe Stats-Gatherer Service
The "stats-gatherer" is a simple daemon that periodically collects stats from
several tahoe nodes. It could be useful, e.g., in a production environment,
where you want to monitor dozens of storage servers from a central management
host. It merely gatherers statistics from many nodes into a single place: it
does not do any actual analysis.
The stats gatherer listens on a network port using the same Foolscap_
connection library that Tahoe clients use to connect to storage servers.
Tahoe nodes can be configured to connect to the stats gatherer and publish
their stats on a periodic basis. (In fact, what happens is that nodes connect
to the gatherer and offer it a second FURL which points back to the node's
"stats port", which the gatherer then uses to pull stats on a periodic basis.
The initial connection is flipped to allow the nodes to live behind NAT
boxes, as long as the stats-gatherer has a reachable IP address.)
.. _Foolscap: http://foolscap.lothar.com/trac
The stats-gatherer is created in the same fashion as regular tahoe client
nodes and introducer nodes. Choose a base directory for the gatherer to live
in (but do not create the directory). Then run:
tahoe create-stats-gatherer $BASEDIR
and start it with "tahoe start $BASEDIR". Once running, the gatherer will
write a FURL into $BASEDIR/stats_gatherer.furl .
To configure a Tahoe client/server node to contact the stats gatherer, copy
this FURL into the node's tahoe.cfg file, in a section named "[client]",
under a key named "stats_gatherer.furl", like so:
stats_gatherer.furl = pb://firstname.lastname@example.org:49997/wxycb4kaexzskubjnauxeoptympyf45y
or simply copy the stats_gatherer.furl file into the node's base directory
(next to the tahoe.cfg file): it will be interpreted in the same way.
The first time it is started, the gatherer will listen on a random unused TCP
port, so it should not conflict with anything else that you have running on
that host at that time. On subsequent runs, it will re-use the same port (to
keep its FURL consistent). To explicitly control which port it uses, write
the desired portnumber into a file named "portnum" (i.e. $BASEDIR/portnum),
and the next time the gatherer is started, it will start listening on the
given port. The portnum file is actually a "strports specification string",
as described in `docs/configuration.rst <configuration.rst>`_.
Once running, the stats gatherer will create a standard python "pickle" file
in $BASEDIR/stats.pickle . Once a minute, the gatherer will pull stats
information from every connected node and write them into the pickle. The
pickle will contain a dictionary, in which node identifiers (known as "tubid"
strings) are the keys, and the values are a dict with 'timestamp',
'nickname', and 'stats' keys. d[tubid][stats] will contain the stats
dictionary as made available at http://localhost:3456/statistics?t=json . The
pickle file will only contain the most recent update from each node.
Other tools can be built to examine these stats and render them into
something useful. For example, a tool could sum the
"storage_server.disk_avail' values from all servers to compute a
total-disk-available number for the entire grid (however, the "disk watcher"
daemon, in misc/operations_helpers/spacetime/, is better suited for this specific task).
Using Munin To Graph Stats Values
The misc/munin/ directory contains various plugins to graph stats for Tahoe
nodes. They are intended for use with the Munin_ system-management tool, which
typically polls target systems every 5 minutes and produces a web page with
graphs of various things over multiple time scales (last hour, last month,
.. _Munin: http://munin-monitoring.org/
Most of the plugins are designed to pull stats from a single Tahoe node, and
are configured with the e.g. http://localhost:3456/statistics?t=json URL. The
"tahoe_stats" plugin is designed to read from the pickle file created by the
stats-gatherer. Some plugins are to be used with the disk watcher, and a few
(like tahoe_nodememory) are designed to watch the node processes directly
(and must therefore run on the same host as the target node).
Please see the docstrings at the beginning of each plugin for details, and
the "tahoe-conf" file for notes about configuration and installing these
plugins into a Munin environment.