# NFS Client Input Plugin

The NFS Client input plugin collects data from /proc/self/mountstats. By
default, only a limited number of general system-level metrics are collected,
including basic read/write counts.  If `fullstat` is set, a great deal of
additional metrics are collected, detailed below.

__NOTE__ Many of the metrics, even if tagged with a mount point, are really
_per-server_.  Thus, if you mount these two shares: `nfs01:/vol/foo/bar` and
`nfs01:/vol/foo/baz`, there will be two near identical entries in
/proc/self/mountstats.  This is a limitation of the metrics exposed by the
kernel, not the telegraf plugin.

## Configuration

```toml @sample.conf
# Read per-mount NFS client metrics from /proc/self/mountstats
[[inputs.nfsclient]]
  ## Read more low-level metrics (optional, defaults to false)
  # fullstat = false

  ## List of mounts to explictly include or exclude (optional)
  ## The pattern (Go regexp) is matched against the mount point (not the
  ## device being mounted).  If include_mounts is set, all mounts are ignored
  ## unless present in the list. If a mount is listed in both include_mounts
  ## and exclude_mounts, it is excluded.  Go regexp patterns can be used.
  # include_mounts = []
  # exclude_mounts = []

  ## List of operations to include or exclude from collecting.  This applies
  ## only when fullstat=true.  Symantics are similar to {include,exclude}_mounts:
  ## the default is to collect everything; when include_operations is set, only
  ## those OPs are collected; when exclude_operations is set, all are collected
  ## except those listed.  If include and exclude are set, the OP is excluded.
  ## See /proc/self/mountstats for a list of valid operations; note that
  ## NFSv3 and NFSv4 have different lists.  While it is not possible to
  ## have different include/exclude lists for NFSv3/4, unused elements
  ## in the list should be okay.  It is possible to have different lists
  ## for different mountpoints:  use mulitple [[input.nfsclient]] stanzas,
  ## with their own lists.  See "include_mounts" above, and be careful of
  ## duplicate metrics.
  # include_operations = []
  # exclude_operations = []
```

### Configuration Options

- __fullstat__ bool: Collect per-operation type metrics.  Defaults to false.
- __include_mounts__ list(string): gather metrics for only these mounts.  Default is to watch all mounts.
- __exclude_mounts__ list(string): gather metrics for all mounts, except those listed in this option. Excludes take precedence over includes.
- __include_operations__ list(string): List of specific NFS operations to track.  See /proc/self/mountstats (the "per-op statistics" section) for complete lists of valid options for NFSv3 and NFSV4.  The default is to gather all metrics, but this is almost certainly _not_ what you want (there are 22 operations for NFSv3, and well over 50 for NFSv4).  A suggested 'minimal' list of operations to collect for basic usage:  `['READ','WRITE','ACCESS','GETATTR','READDIR','LOOKUP','LOOKUP']`
- __exclude_operations__ list(string): Gather all metrics, except those listed.  Excludes take precedence over includes.

_N.B._ the `include_mounts` and `exclude_mounts` arguments are both applied to
the local mount location (e.g. /mnt/NFS), not the server export
(e.g. nfsserver:/vol/NFS).  Go regexp patterns can be used in either.

### References

1. [nfsiostat](http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=summary)
2. [net/sunrpc/stats.c - Linux source code](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/net/sunrpc/stats.c)
3. [What is in /proc/self/mountstats for NFS mounts: an introduction](https://utcc.utoronto.ca/~cks/space/blog/linux/NFSMountstatsIndex)
4. [The xprt: data for NFS mounts in /proc/self/mountstats](https://utcc.utoronto.ca/~cks/space/blog/linux/NFSMountstatsXprt)

## Metrics

### Fields

- nfsstat
  - bytes (integer, bytes) - The total number of bytes exchanged doing this operation. This is bytes sent _and_ received, including overhead _and_ payload.  (bytes = OP_bytes_sent + OP_bytes_recv.  See nfs_ops below)
  - ops (integer, count) - The number of operations of this type executed.
  - retrans (integer, count) - The number of times an operation had to be retried (retrans = OP_trans - OP_ops.  See nfs_ops below)
  - exe (integer, miliseconds) - The number of miliseconds it took to process the operations.
  - rtt (integer, miliseconds) - The total round-trip time for all operations.
  - rtt_per_op (float, miliseconds) - The average round-trip time per operation.

In addition enabling `fullstat` will make many more metrics available.

### Tags

- All measurements have the following tags:
  - mountpoint - The local mountpoint, for instance: "/var/www"
  - serverexport - The full server export, for instance: "nfsserver.example.org:/export"

- Measurements nfsstat and nfs_ops will also include:
  - operation - the NFS operation in question.  `READ` or `WRITE` for nfsstat, but potentially one of ~20 or ~50, depending on NFS version.  A complete list of operations supported is visible in `/proc/self/mountstats`.

## Additional metrics

When `fullstat` is true, additional measurements are collected.  Tags are the
same as above.

### NFS Operations

Most descriptions come from [Reference][ref] and `nfs_iostat.h`.  Field order
and names are the same as in `/proc/self/mountstats` and the Kernel source.

Please refer to `/proc/self/mountstats` for a list of supported NFS operations,
as it changes occasionally.

- nfs_bytes
  - fields:
    - normalreadbytes (int, bytes): Bytes read from the server via `read()`
    - normalwritebytes (int, bytes): Bytes written to the server via `write()`
    - directreadbytes (int, bytes): Bytes read with O_DIRECT set
    - directwritebytes (int, bytes): Bytes written with O_DIRECT set
    - serverreadbytes (int, bytes): Bytes read via NFS READ (via `mmap()`)
    - serverwritebytes (int, bytes): Bytes written via NFS WRITE (via `mmap()`)
    - readpages (int, count): Number of pages read
    - writepages (int, count): Number of pages written

- nfs_events (Per-event metrics)
  - fields:
    - inoderevalidates (int, count): How many times cached inode attributes have to be re-validated from the server.
    - dentryrevalidates (int, count): How many times cached dentry nodes have to be re-validated.
    - datainvalidates (int, count): How many times an inode had its cached data thrown out.
    - attrinvalidates (int, count): How many times an inode has had cached inode attributes invalidated.
    - vfsopen (int, count): How many times files or directories have been `open()`'d.
    - vfslookup (int, count): How many name lookups in directories there have been.
    - vfsaccess (int, count): Number of calls to `access()`. (formerly called "vfspermission")
    - vfsupdatepage (int, count): Count of updates (and potential writes) to pages.
    - vfsreadpage (int, count): Number of pages read.
    - vfsreadpages (int, count): Count of how many times a _group_ of pages was read (possibly via `mmap()`?).
    - vfswritepage (int, count): Number of pages written.
    - vfswritepages (int, count): Count of how many times a _group_ of pages was written (possibly via `mmap()`?)
    - vfsgetdents (int, count): Count of directory entry reads with getdents(). These reads can be served from cache and don't necessarily imply actual NFS requests. (formerly called "vfsreaddir")
    - vfssetattr (int, count): How many times we've set attributes on inodes.
    - vfsflush (int, count): Count of times pending writes have been forcibly flushed to the server.
    - vfsfsync (int, count): Count of calls to `fsync()` on directories and files.
    - vfslock (int, count): Number of times a lock was attempted on a file (regardless of success or not).
    - vfsrelease (int, count): Number of calls to `close()`.
    - congestionwait (int, count): Believe unused by the Linux kernel, but it is part of the NFS spec.
    - setattrtrunc (int, count): How many times files have had their size truncated.
    - extendwrite (int, count): How many times a file has been grown because you're writing beyond the existing end of the file.
    - sillyrenames (int, count): Number of times an in-use file was removed (thus creating a temporary ".nfsXXXXXX" file)
    - shortreads (int, count): Number of times the NFS server returned less data than requested.
    - shortwrites (int, count): Number of times NFS server reports it wrote less data than requested.
    - delay (int, count): Occurances of EJUKEBOX ("Jukebox Delay", probably unused)
    - pnfsreads (int, count): Count of NFS v4.1+ pNFS reads.
    - pnfswrites (int, count): Count of NFS v4.1+ pNFS writes.

- nfs_xprt_tcp
  - fields:
    - bind_count (int, count): Number of_completely new_ mounts to this server (sometimes 0?)
    - connect_count (int, count): How many times the client has connected to the server in question
    - connect_time (int, jiffies): How long the NFS client has spent waiting for its connection(s) to the server to be established.
    - idle_time (int, seconds): How long (in seconds) since the NFS mount saw any RPC traffic.
    - rpcsends (int, count): How many RPC requests this mount has sent to the server.
    - rpcreceives (int, count): How many RPC replies this mount has received from the server.
    - badxids (int, count): Count of XIDs sent by the server that the client doesn't know about.
    - inflightsends (int, count): Number of outstanding requests; always >1. (See reference #4 for comment on this field)
    - backlogutil (int, count): Cumulative backlog count

- nfs_xprt_udp
  - fields:
    - [same as nfs_xprt_tcp, except for connect_count, connect_time, and idle_time]

- nfs_ops
  - fields (In all cases, the `operations` tag is set to the uppercase name of the NFS operation, _e.g._ "READ", "FSINFO", _etc_.  See /proc/self/mountstats for a full list):
    - ops (int, count): Total operations of this type.
    - trans (int, count): Total transmissions of this type, including retransmissions: `OP_ops - OP_trans = total_retransmissions` (lower is better).
    - timeouts (int, count): Number of major timeouts.
    - bytes_sent (int, count): Bytes sent, including headers (should also be close to on-wire size).
    - bytes_recv (int, count): Bytes received, including headers (should be close to on-wire size).
    - queue_time (int, milliseconds): Cumulative time a request waited in the queue before sending this OP type.
    - response_time (int, milliseconds): Cumulative time waiting for a response for this OP type.
    - total_time (int, milliseconds): Cumulative time a request waited in the queue before sending.
    - errors (int, count): Total number operations that complete with tk_status < 0 (usually errors).  This is a new field, present in kernel >=5.3, mountstats version 1.1

[ref]: https://utcc.utoronto.ca/~cks/space/blog/linux/NFSMountstatsIndex

## Example Output

For basic metrics showing server-wise read and write data.

```shell
nfsstat,mountpoint=/NFS,operation=READ,serverexport=1.2.3.4:/storage/NFS ops=600i,retrans=1i,bytes=1207i,rtt=606i,exe=607i 1612651512000000000
nfsstat,mountpoint=/NFS,operation=WRITE,serverexport=1.2.3.4:/storage/NFS bytes=1407i,rtt=706i,exe=707i,ops=700i,retrans=1i 1612651512000000000

```

For `fullstat=true` metrics, which includes additional measurements for
`nfs_bytes`, `nfs_events`, and `nfs_xprt_tcp` (and `nfs_xprt_udp` if present).
Additionally, per-OP metrics are collected, with examples for READ, LOOKUP, and
NULL shown.  Please refer to `/proc/self/mountstats` for a list of supported NFS
operations, as it changes as it changes periodically.

```shell
nfs_bytes,mountpoint=/home,serverexport=nfs01:/vol/home directreadbytes=0i,directwritebytes=0i,normalreadbytes=42648757667i,normalwritebytes=0i,readpages=10404603i,serverreadbytes=42617098139i,serverwritebytes=0i,writepages=0i 1608787697000000000
nfs_events,mountpoint=/home,serverexport=nfs01:/vol/home attrinvalidates=116i,congestionwait=0i,datainvalidates=65i,delay=0i,dentryrevalidates=5911243i,extendwrite=0i,inoderevalidates=200378i,pnfsreads=0i,pnfswrites=0i,setattrtrunc=0i,shortreads=0i,shortwrites=0i,sillyrenames=0i,vfsaccess=7203852i,vfsflush=117405i,vfsfsync=0i,vfsgetdents=3368i,vfslock=0i,vfslookup=740i,vfsopen=157281i,vfsreadpage=16i,vfsreadpages=86874i,vfsrelease=155526i,vfssetattr=0i,vfsupdatepage=0i,vfswritepage=0i,vfswritepages=215514i 1608787697000000000
nfs_xprt_tcp,mountpoint=/home,serverexport=nfs01:/vol/home backlogutil=0i,badxids=0i,bind_count=1i,connect_count=1i,connect_time=0i,idle_time=0i,inflightsends=15659826i,rpcreceives=2173896i,rpcsends=2173896i 1608787697000000000

nfs_ops,mountpoint=/NFS,operation=NULL,serverexport=1.2.3.4:/storage/NFS trans=0i,timeouts=0i,bytes_sent=0i,bytes_recv=0i,queue_time=0i,response_time=0i,total_time=0i,ops=0i 1612651512000000000
nfs_ops,mountpoint=/NFS,operation=READ,serverexport=1.2.3.4:/storage/NFS bytes=1207i,timeouts=602i,total_time=607i,exe=607i,trans=601i,bytes_sent=603i,bytes_recv=604i,queue_time=605i,ops=600i,retrans=1i,rtt=606i,response_time=606i 1612651512000000000
nfs_ops,mountpoint=/NFS,operation=WRITE,serverexport=1.2.3.4:/storage/NFS ops=700i,bytes=1407i,exe=707i,trans=701i,timeouts=702i,response_time=706i,total_time=707i,retrans=1i,rtt=706i,bytes_sent=703i,bytes_recv=704i,queue_time=705i 1612651512000000000
```
