10. DPDK Telemetry User Guide

The Telemetry library provides users with the ability to query DPDK for telemetry information, currently including information such as ethdev stats, ethdev port list, and eal parameters.

10.1. Telemetry Interface

The Telemetry Library opens a socket with path <runtime_directory>/dpdk_telemetry.<version>. The version represents the telemetry version, the latest is v2. For example, a client would connect to a socket with path /var/run/dpdk/*/dpdk_telemetry.v2 (when the primary process is run by a root user).

10.2. Telemetry Initialization

The library is enabled by default, however an EAL flag to enable the library exists, to provide backward compatibility for the previous telemetry library interface:

--telemetry

A flag exists to disable Telemetry also:

--no-telemetry

10.3. Running Telemetry

The following steps show how to run an application with telemetry support, and query information using the telemetry client python script.

Launch testpmd as the primary application with telemetry:
```
./app/dpdk-testpmd
```
Launch the telemetry client script:
```
./usertools/dpdk-telemetry.py
```

When connected, the script displays the following, waiting for user input:

Connecting to /var/run/dpdk/rte/dpdk_telemetry.v2
{"version": "DPDK 20.05.0-rc2", "pid": 60285, "max_output_len": 16384}
-->

The user can now input commands to send across the socket, and receive the response. Some available commands are shown below.

List all commands:

--> /
{"/": ["/", "/eal/app_params", "/eal/params", "/ethdev/list",
"/ethdev/link_status", "/ethdev/xstats", "/help", "/info"]}

Get the list of ethdev ports:

--> /ethdev/list
{"/ethdev/list": [0, 1]}

Note

For commands that expect a parameter, use “,” to separate the command and parameter. See examples below.

Get extended statistics for an ethdev port:

--> /ethdev/xstats,0
{"/ethdev/xstats": {"rx_good_packets": 0, "tx_good_packets": 0,
"rx_good_bytes": 0, "tx_good_bytes": 0, "rx_missed_errors": 0,
...
"tx_priority7_xon_to_xoff_packets": 0}}

Get the help text for a command. This will indicate what parameters are required. Pass the command as a parameter:

--> /help,/ethdev/xstats
{"/help": {"/ethdev/xstats": "Returns the extended stats for a port.
Parameters: int port_id"}}

10.4. Connecting to Different DPDK Processes

When multiple DPDK process instances are running on a system, the user will naturally wish to be able to select the instance to which the connection is being made. The method to select the instance depends on how the individual instances are run:

For DPDK processes run using a non-default file-prefix, i.e. using the –file-prefix EAL option flag, the file-prefix for the process should be passed via the -f or –file-prefix script flag.

For example, to connect to testpmd run as:
```
$ ./build/app/dpdk-testpmd -l 2,3 --file-prefix="tpmd"
```
One would use the telemetry script command:
```
$ ./usertools/dpdk-telemetry -f "tpmd"
```
To list all running telemetry-enabled file-prefixes, the -l or --list flags can be used:
```
$ ./usertools/dpdk-telemetry -l
```
For the case where multiple processes are run using the –in-memory EAL flag, but no –file-prefix flag, or the same –file-prefix flag, those processes will all share the same runtime directory. In this case, each process after the first will add an increasing count suffix to the telemetry socket name, with each one taking the first available free socket name. This suffix count can be passed to the telemetry script using the -i or –instance flag.

For example, if the following two applications are run in separate terminals:
```
$ ./build/app/dpdk-testpmd -l 2,3 --in-memory    # will use socket "dpdk_telemetry.v2"

$ ./build/app/test/dpdk-test -l 4,5 --in-memory  # will use "dpdk_telemetry.v2:1"
```
The following telemetry script commands would allow one to connect to each binary:
```
$ ./usertools/dpdk-telemetry.py       # will connect to testpmd

$ ./usertools/dpdk-telemetry.py -i 1  # will connect to test binary
```