tcollector is a client-side process that gathers data from local collectors and pushes the data to OpenTSDB. You run it on all your hosts, and it does the work of sending each host's data to the TSD.

OpenTSDB is designed to make it easy to collect and write data to it. It has a simple protocol, simple enough for even a shell script to start sending data. However, to do so reliably and consistently is a bit harder. What do you do when your TSD server is down? How do you make sure your collectors stay running? This is where tcollector comes in.

Tcollector does several things for you:

  • Runs all of your data collectors and gathers their data
  • Does all of the connection management work of sending data to the TSD
  • You don't have to embed all of this code in every collector you write
  • Does de-duplication of repeated values
  • Handles all of the wire protocol work for you, as well as future enhancements


Typically you want to gather data about everything in your system. This generates a lot of datapoints, the majority of which don't change very often over time (if ever). However, you want fine-grained resolution when they do change. Tcollector remembers the last value and timestamp that was sent for all of the time series for all of the collectors it manages. If the value doesn't change between sample intervals, it suppresses sending that datapoint. Once the value does change (or 10 minutes have passed), it sends the last suppressed value and timestamp, plus the current value and timestamp. In this way all of your graphs and such are correct. Deduplication typically reduces the number of datapoints TSD needs to collect by a large fraction. This reduces network load and storage in the backend. A future OpenTSDB release however will improve on the storage format by using RLE (among other things), making it essentially free to store repeated values.

Collecting lots of metrics with tcollector

Collectors in tcollector can be written in any language. They just need to be executable and output the data to stdout. Tcollector will handle the rest. The collectors are placed in the collectors directory. Tcollector iterates over every directory named with a number in that directory and runs all the collectors in each directory. If you name the directory 60, then tcollector will try to run every collector in that directory every 60 seconds. The shortest supported interval is 15 seconds, you should use a long-running collector in the 0 folder for intervals shorter than 15 seconds. TCollector will sleep for 15 seconds after each time it runs the collectors so intervals of 15 seconds are the only actually supported intervals. For example, this would allow you to run a collector every 15, 30, 45, 60, 75, or 90 seconds, but not 80 or 55 seconds. Use the directory 0 for any collectors that are long-lived and run continuously. Tcollector will read their output and respawn them if they die. Generally you want to write long-lived collectors since that has less overhead. OpenTSDB is designed to have lots of datapoints for each metric (for most metrics we send datapoints every 15 seconds).

If there any non-numeric named directories in the collectors directory, then they are ignored. We've included a lib and etc directory for library and config data used by all collectors.

Installation of tcollector

You need to clone tcollector from GitHub:

git clone git://

and edit 'tcollector/startstop' script to set following variable:

To avoid having to run mkmetric for every metric that tcollector tracks you can to start TSD with the --auto-metric flag. This is useful to get started quickly, but it's not recommended to keep this flag in the long term, to avoid accidental metric creation.

Collectors bundled with tcollector

The following are the collectors we've included as part of the base package, together with all of the metric names they report on and what they mean. If you have any others you'd like to contribute, we'd love to hear about them so we can reference them or include them with your permission in a future release.

General collectors


These stats are similar to ones provided by /usr/bin/df util.


    total size of data

  • df.bytes.used

    bytes used


    bytes free


    total number of inodes

  • df.inodes.used

    number of inodes used


    number of inodes free

These metrics include time series tagged with each mount point and the filesystem's fstype. This collector filters out any cgroup, debugfs, devtmpfs, rpc_pipefs, rootfs filesystems, as well as any any mountpoints mounted under /dev/, /sys/, /proc/, and /lib/.

With these tags you can select to graph just a specific filesystem, or all filesystems with a particular fstype (e.g. ext3).


These stats are from /proc/net/dev.


    (rate) Bytes in/out


    (rate) Packets in/out


    (rate) Packet errors in/out


    (rate) Dropped packets in/out

These are interface counters, tagged with the interface, iface=, and direction= in or out. Only ethN interfaces are tracked. We intentionally exclude bondN interfaces, because bonded interfaces still keep counters on their child ethN interfaces and we don't want to double-count a box's network traffic if you don't select on iface=.


Data is from /proc/diskstats.

  • iostat.disk.*

    per-disk stats

  • iostat.part.*

    per-partition stats (see note below on different metrics, depending on if you have a 2.6 kernel before 2.6.25 or after.)

See iostats.txt

/proc/diskstats has 11 stats for a given physical device. These are all rate counters, except ios_in_progress.

.read_requests       Number of reads completed
.read_merged         Number of reads merged
.read_sectors        Number of sectors read
.msec_read           Time in msec spent reading
.write_requests      Number of writes completed
.write_merged        Number of writes merged
.write_sectors       Number of sectors written
.msec_write          Time in msec spent writing
.ios_in_progress     Number of I/O operations in progress
.msec_total          Time in msec doing I/O
.msec_weighted_total Weighted time doing I/O (multiplied by ios_in_progress)

in 2.6.25 and later, by-partition stats are reported the same as disks.


in 2.6 before 2.6.25, partitions have only 4 stats per partition


For partitions, these *_issued are counters collected before requests are merged, so aren't the same as *_requests (which is post-merge, which more closely represents represents the actual number of disk transactions).

Given that diskstats provides both per-disk and per-partition data, for TSDB purposes we put them under different metrics (versus the same metric and different tags). Otherwise, if you look at a given metric, the data for a given box will be double-counted, since a given operation will increment both the disk series and the partition series. To fix this, we output by-disk data to iostat.disk.* and by-partition data to iostat.part.*.


Socket allocation and network statistics.

Metrics from /proc/net/sockstat.

  • net.sockstat.num_sockets

    Number of sockets allocated (only TCP)

  • net.sockstat.num_timewait

    Number of TCP sockets currently in TIME_WAIT state

  • net.sockstat.sockets_inuse

    Number of sockets in use (TCP/UDP/raw)

  • net.sockstat.num_orphans

    Number of orphan TCP sockets (not attached to any file descriptor)

  • net.sockstat.memory

    Memory allocated for this socket type (in bytes)

  • net.sockstat.ipfragqueues

    Number of IP flows for which there are currently fragments queued for reassembly

Metrics from /proc/net/netstat (netstat -s command).

  • net.stat.tcp.abort

    Number of connections that the kernel had to abort. <code>type=memory</code> is especially bad, the kernel had to drop a connection due to having too many orphaned sockets. Other types are normal (e.g. timeout)

  • net.stat.tcp.abort.failed

    Number of times the kernel failed to abort a connection because it didn't even have enough memory to reset it (bad)

  • net.stat.tcp.congestion.recovery

    Number of times the kernel detected spurious retransmits and was able to recover part or all of the CWND

  • net.stat.tcp.delayedack

    Number of delayed ACKs sent of different types.

  • net.stat.tcp.failed_accept

    Number of times a connection had to be dropped after the 3WHS. reason=full_acceptq indicates that the application isn't accepting connections fast enough. You should see SYN cookies too

  • net.stat.tcp.invalid_sack

    Number of invalid SACKs we saw of diff types. (requires Linux v2.6.24-rc1 or newer)

  • net.stat.tcp.memory.pressure

    Number of times a socket entered the "memory pressure" mode (not great).

  • net.stat.tcp.memory.prune

    Number of times a socket had to discard received data due to low memory conditions (bad)

  • net.stat.tcp.packetloss.recovery

    Number of times we recovered from packet loss by type of recovery (e.g. fast retransmit vs SACK)

  • net.stat.tcp.receive.queue.full

    Number of times a received packet had to be dropped because the socket's receive queue was full. (requires Linux v2.6.34-rc2 or newer)

  • net.stat.tcp.reording

    Number of times we detected re-ordering and how

  • net.stat.tcp.syncookies

    SYN cookies (both sent &amp; received)


These stats are from /proc/net/rpc/nfs.

  • nfs.client.rpc.stats

    RPC stats counter

It tagged with the type (<code>type=</code>) of operation. There are 3 operations: authrefrsh - number of times the authentication information refreshed, calls - number of calls conducted, and retrans - number of retransmissions

  • nfs.client.rpc

    RPC calls counter

It tagged with the version (version=) of NFS server that conducted the operation, and name of operation (op=)

Description of operations can be found at appropriate RFC: NFS ver. 3 RFC1813, NFS ver. 4 RFC3530, NFS ver. 4.1 RFC5661.


These stats are all from /proc/net/tcp{,6}. (Note if IPv6 is enabled, some IPv4 connections seem to get put into /proc/net/tcp6). Collector sleeps 60 seconds in between intervals. Due in part to a kernel performance issue in older kernels and in part due to systems with many TCP connections, this collector can take sometimes 5 minutes or more to run one interval, so the frequency of datapoints can be highly variable depending on the system.


    Number of TCP connections

For each run of the collector, we classify each connection and generate subtotals. TSD will automatically total these up when displaying the graph, but you can drill down for each possible total or a particular one. Each connection is broken down with a tag for user=username (with a fixed list of users we care about or put under "other" if not in the list). It is also broken down into state with state=, (established, time_wait, etc). It is also broken down into services with <code>service=</code> (http, mysql, memcache, etc) Note that once a connection is closed, Linux seems to forget who opened/handled the connection. For connections in time_wait, for example, they will always show user=root. This collector does generate a large amount of datapoints, as the number of points is (S*(U+1)*V), where S=number of TCP states, U=Number of users you track, and V=number of services (collections of ports). The deduper does dedup this down very well, as only 3 of the 10 TCP states are generally ever seen. On a typical server this can dedup down to under 10 values per interval.


Miscellaneous stats from /proc.

  • proc.stat.cpu

    (rate) CPU counters (jiffies), tagged by cpu type (type=user, nice, system, idle, iowait, irq, softirq, etc). As a rate they should aggregate up to approximately 100*numcpu per host. Best viewed as type=* or maybe type={user|nice|system|iowait|irq}

  • proc.stat.intr

    (rate) Number of interrupts

  • proc.stat.ctxt

    (rate) Number of context switches


  • proc.vmstat.*

    A subset of VM Stats from /proc/vmstat (mix of rate and non-rate). See .

  • proc.meminfo.*

    Memory usage stats from /proc/meminfo. See the Linux kernel documentation

  • proc.loadavg.*

    1min, 5min, 15min, runnable, total_threads metrics from /proc/loadavg


    (rate) Seconds since boot


    (rate) Seconds since boot that the system has been idle

  • proc.kernel.entropy_avail

    Amount of entropy (in bits) available in the input pool (the one that's cryptographically strong and backing /dev/random among other things). Watch this value on your frontend servers that do SSL unwrapping, if it gets too low, your SSL performance will suffer

  • sys.numa.zoneallocs

    Number of pages allocated from the preferred node (type=hit) or not (type=miss)

  • sys.numa.foreign_allocs

    Number of pages this node allocated because the preferred node didn't have a free page to accommodate the request

  • sys.numa.allocation

    Number of pages allocated locally (type=local) or remotely (type=remote) for processes executing on this node

  • sys.numa.interleave

    Number of pages allocated successfully by the interleave strategy


Stats from SMART disks.

  • smart.raw_read_error_rate

    Data related to the rate of hardware read errors that occurred when reading data from a disk surface. The raw value has different structure for different vendors and is often not meaningful as a decimal number. (vendor specific)

  • smart.throughput_performance

    Overall throughput performance of a hard disk drive

  • smart.spin_up_time

    Average time of spindle spin up (from zero RPM to fully operational [millisecs])

  • smart.start_stop_count

    A tally of spindle start/stop cycles

  • smart.reallocated_sector_ct

    Count of reallocated sectors

  • smart.seek_error_rate

    Rate of seek errors of the magnetic heads. (vendor specific)

  • smart.seek_time_performance

    Average performance of seek operations of the magnetic heads

  • smart.power_on_hours

    Count of hours in power-on state, shows total count of hours (or minutes, or seconds) in power-on state. (vendor specific)

  • smart.spin_retry_count

    Count of retry of spin start attempts

  • smart.recalibration_retries

    The count that recalibration was requested (under the condition that the first attempt was unsuccessful)

  • smart.power_cycle_count

    The count of full hard disk power on/off cycles

  • smart.soft_read_error_rate

    Uncorrected read errors reported to the operating system

  • smart.program_fail_count_chip

    Total number of Flash program operation failures since the drive was deployed

  • smart.erase_fail_count_chip

    "Pre-Fail" Attribute

  • smart.wear_leveling_count

    The maximum number of erase operations performed on a single flash memory block

  • smart.used_rsvd_blk_cnt_chip

    The number of a chip’s used reserved blocks

  • smart.used_rsvd_blk_cnt_tot

    "Pre-Fail" Attribute (at least HP devices)

  • smart.unused_rsvd_blk_cnt_tot

    "Pre-Fail" Attribute (at least Samsung devices)

  • smart.program_fail_cnt_total

    Total number of Flash program operation failures since the drive was deployed

  • smart.erase_fail_count_total

    "Pre-Fail" Attribute

  • smart.runtime_bad_block

    The total count of all read/program/erase failures

  • smart.end_to_end_error

    The count of parity errors which occur in the data path to the media via the drive's cache RAM (at least Hewlett-Packard)

  • smart.reported_uncorrect

    The count of errors that could not be recovered using hardware ECC

  • smart.command_timeout

    The count of aborted operations due to HDD timeout

  • smart.high_fly_writes

    HDD producers implement a Fly Height Monitor that attempts to provide additional protections for write operations by detecting when a recording head is flying outside its normal operating range. If an unsafe fly height condition is encountered, the write process is stopped, and the information is rewritten or reallocated to a safe region of the hard drive. This attribute indicates the count of these errors detected over the lifetime of the drive

  • smart.airflow_temperature_celsius

    Airflow temperature

  • smart.g_sense_error_rate

    The count of errors resulting from externally induced shock & vibration

  • smart.power-off_retract_count

    The count of times the heads are loaded off the media

  • smart.load_cycle_count

    Count of load/unload cycles into head landing zone position

  • smart.temperature_celsius

    Current internal temperature

  • smart.hardware_ecc_recovered

    The count of errors that were recovered using hardware ECC

  • smart.reallocated_event_count

    Count of remap operations. The raw value of this attribute shows the total count of attempts to transfer data from reallocated sectors to a spare area

  • smart.current_pending_sector

    Count of "unstable" sectors (waiting to be remapped, because of unrecoverable read errors)

  • smart.offline_uncorrectable

    The total count of uncorrectable errors when reading/writing a sector

  • smart.udma_crc_error_count

    The count of errors in data transfer via the interface cable as determined by ICRC (Interface Cyclic Redundancy Check)

  • smart.write_error_rate

    The total count of errors when writing a sector

  • smart.media_wearout_indicator

    The normalized value of 100 (when the SSD is new) and declines to a minimum value of 1

  • smart.transfer_error_rate

    Count of times the link is reset during a data transfer

  • smart.total_lba_writes

    Total count of LBAs written

  • smart.total_lba_read

    Total count of LBAs read

Description of metrics can be found at: S.M.A.R.T. article on wikipedia. The best way to understand/find metric is to look at producer's specification.

Other collectors


Stats from couchbase (document-oriented NoSQL database).

All metrics are tagged with name of related bucket(bucket=). A bucket is a logical grouping of physical resources within a cluster of Couchbase Servers. They can be used by multiple client applications across a cluster. Buckets provide a secure mechanism for organizing, managing, and analyzing data storage resources.

Refer to the following documentation for metrics description: Cbstats documentation.


Stats from Elastic Search (search and analytics engine).

Refer to the following documentation for metrics description: ElasticSearch cluster APIs.


Stats from Hadoop (framework for the distributed processing), DataNode stats.

Following metrics are disabled at the collector by default: revision, hdfsUser, hdfsDate, hdfsUrl, date, hdfsRevision, user, hdfsVersion, url, version, NamenodeAddress, Version, RpcPort, HttpPort, CurrentThreadCpuTime, CurrentThreadUserTime, StorageInfo, VolumeInfo.

Refer to the following documentation for metrics description: HBase metrics.


Stats from Haproxy (TCP/HTTP load balancer).

  • haproxy.current_sessions

    Current number of sessions

  • haproxy.session_rate

    Number of new sessions per second

All metrics are tagged with server (server=) and cluster (cluster=).

Refer to the following documentation for metrics description: Haproxy configuration # section 9.2.Unix Socket commands


Stats from Hadoop (framework for the distributed processing), RegionServer stats.

Following metrics are disabled at the collector by default: revision, hdfsUser, hdfsDate, hdfsUrl, date, hdfsRevision, user, hdfsVersion, url, version, Version, RpcPort, HttpPort,HeapMemoryUsage, NonHeapMemoryUsage.

Refer to the following documentation for metrics description: HBase metrics.


Stats from Mongo (document NoSQL database).

Refer to the following documentation for metrics description: Mongo DB server-status.


Stats from MySQL (relational database).

Refer to the following documentation for metrics description: InnoDB Innodb monitors, Global Show status, Engine Show engine, Slave Show slave status, Process list Show process list.


Stats from PostgreSQL (relational database).

Refer to the following documentation for metrics description: PostgreSQL monitoring stats.


Stats from Redis (key-value store).

Refer to the following documentation for metrics description: Redis info comands.


Stats from Riak (document NoSQL database).

Refer to the following documentation for metrics description: Riak statistics.


Stats from Varnish (HTTP accelerator).

By default all metrics collected, it can be changed by editing "vstats" array of the collector.

Refer to the following documentation for metrics description: run "varnishstat -l" to have lists the available metrics.


Stats from Zookeeper (centralized service for distributed synchronization).

Refer to the following documentation for metrics description: Zookeeper admin commands.