usertools/dpdk-telemetry: print name of app when connected

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

---
  usertools/dpdk-telemetry.py | 5 +++++
  1 file changed, 5 insertions(+)

usertools/dpdk-telemetry.py +0 -0

index 181859658f..82b91f346f 100755

usertools/dpdk-telemetry.py +0 -0

      # get list of commands for readline completion
      sock.send("/".encode())
 

Quoted 16 lines · Bruce Richardson

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

---
  usertools/dpdk-telemetry.py | 5 +++++
  1 file changed, 5 insertions(+)

usertools/dpdk-telemetry.py +0 -0

index 181859658f..82b91f346f 100755

usertools/dpdk-telemetry.py def handle_socket(path): · line 50

Quoted 6 lines

usertools/dpdk-telemetry.py +3 -0

@@ -45,6 +45,11 @@ def handle_socket(path):
          return
      json_reply = read_socket(sock, 1024)
      output_buf_len = json_reply["max_output_len"]
+    pid = json_reply["pid"]
+    if os.path.exists('/proc/' + str(pid) + '/cmdline'):
+        with open('/proc/' + str(pid) + '/cmdline') as f:

First of all, this is better done using os.path.join:

path = os.path.join('/proc', str(pid), 'cmdline')
if os.path.exists(path):
with open(path) as f:
...

More importantly this isn't terribly Pythonic as it's not over-using exceptions :) IMO a better way would be:

try:
with open(path) as f:
...
except IOError as e:

    # ignore if doesn't exist
    if e.errno != errno.ENOENT:
        raise

usertools/dpdk-telemetry.py def handle_socket(path): · line 52

Quoted 2 lines

usertools/dpdk-telemetry.py +2 -0

+            argv0 = f.read(1024).split('\0')[0]
+            print("Connected to application: '" + os.path.basename(argv0) + "'")

Also, formatting is better than concatenation, e.g. at least:

bname = os.path.basename(argv0) print("Connected to application: '{}'".format(bname))

Quoted 26 lines · Anatoly

Quoted 16 lines · Bruce Richardson

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

---
   usertools/dpdk-telemetry.py | 5 +++++
   1 file changed, 5 insertions(+)

usertools/dpdk-telemetry.py +0 -0

index 181859658f..82b91f346f 100755

usertools/dpdk-telemetry.py def handle_socket(path): · line 50

Quoted 6 lines

usertools/dpdk-telemetry.py +3 -0

@@ -45,6 +45,11 @@ def handle_socket(path):
           return
       json_reply = read_socket(sock, 1024)
       output_buf_len = json_reply["max_output_len"]
+    pid = json_reply["pid"]
+    if os.path.exists('/proc/' + str(pid) + '/cmdline'):
+        with open('/proc/' + str(pid) + '/cmdline') as f:

First of all, this is better done using os.path.join:

Quoted 4 lines

path = os.path.join('/proc', str(pid), 'cmdline')
if os.path.exists(path):
with open(path) as f:
...

Ok, I forgot that os.path.join can take > 2 parameters.

Quoted 4 lines

More importantly this isn't terribly Pythonic as it's not over-using exceptions :) IMO a better way would be:

Quoted 8 lines

try:
with open(path) as f:
...
except IOError as e:

     # ignore if doesn't exist
     if e.errno != errno.ENOENT:
         raise

Yes, I was thinking that I just wanted any exceptions to be raised, but you right that I should just ignore the not-found one and skip the printout.

Quoted 9 lines

usertools/dpdk-telemetry.py def handle_socket(path): · line 52

Quoted 3 lines

usertools/dpdk-telemetry.py +2 -0

+            argv0 = f.read(1024).split('\0')[0]
+            print("Connected to application: '" + os.path.basename(argv0) + "'")

Also, formatting is better than concatenation, e.g. at least:

bname = os.path.basename(argv0) print("Connected to application: '{}'".format(bname))

And f-strings are best of all, but we need python 3.6 for those. :-) I consider use of format vs concat a matter of taste, but I'll update as you suggest.

Thanks for the review.

/Bruce

PS: Python 3.5 has had its final release late last year:
https://www.python.org/downloads/release/python-3510/
We should soon consider updating our minimum required version to Python 3.6, allowing us to use f-strings in our python code rather than concatenation or explicit format calls.

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

---
V2:
Updated with stylistic feedback from Anatoly, and split name query into a separate function.

---
  usertools/dpdk-telemetry.py | 18 ++++++++++++++++++
  1 file changed, 18 insertions(+)

usertools/dpdk-telemetry.py +18 -1

index 181859658..b2acd92ba 100755
@@ -11,6 +11,7 @@
  import os
  import glob
  import json
+import errno
  import readline
 
  # global vars

@@ -32,6 +33,20 @@ def read_socket(sock, buf_len, echo=True):
      return ret
 
 
+def get_app_name(pid):
+    """ return the app name for a given pid, for printing """
+    proc_cmdline = os.path.join('/proc', str(pid), 'cmdline')
+    try:
+        with open(proc_cmdline) as f:
+            argv0 = f.read(1024).split('\0')[0]
+            return os.path.basename(argv0)
+    except IOError as e:
+        # ignore file not found errors
+        if e.errno != errno.ENOENT:
+            raise
+    return None
+
+
  def handle_socket(path):
      """ Connect to socket and handle user input """
      sock = socket.socket(socket.AF_UNIX, socket.SOCK_SEQPACKET)

@@ -45,6 +60,9 @@ def handle_socket(path):
          return
      json_reply = read_socket(sock, 1024)
      output_buf_len = json_reply["max_output_len"]
+    app_name = get_app_name(json_reply["pid"])
+    if app_name:
+        print('Connected to application: "%s"' % app_name)
 
      # get list of commands for readline completion
      sock.send("/".encode())
--

2.27.0

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

Quoted 7 lines

When the dpdk-telemetry client connects to a DPDK instance, we can use the PID provided in the initial connection message to query from /proc the name of the process we are connected to, and display that to the user. We use the "cmdline" procfs entry for the query since that is available on both Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by Bruce Richardson <[email protected]>

Acked-by Anatoly Burakov <[email protected]>

Acked-by Kevin Laatz <[email protected]>