Enhance PCAP Command

[a18e]

Changes:

• Start tcpdump commands in parallel, so the captures start at the same time on each VM
  • Uses the global --parallel parameter of the bosh-cli (which defaults to 5)
• Allow for multiple Instance Groups/InstanceID capture targets, e.g.:
  bosh -d cf pcap nats router/0 -o test.pcap
  • Overlaps between Instance Groups/IDs are handled gracefully (e.g. router router/0 will merge to router)
• Reduce verbosity of pcap command
• Show a table of all the VMs where the capture will be started and prompt if capturing should begin. Include a warning if the number of VMs is > 5 (-n/--non-interactive is supported):

./bosh pcap -d cf  -o test.pcap
[...]

Expected VMs for SSH capture

Job              IP         ID
uaa              10.1.1.65  d5033e83-5750-4e46-bc9c-e69d93cc107c
router           10.1.1.8   37747b53-7a56-460f-bdc7-f991d373cd7f
log-api          10.1.1.71  b65ed4a2-529c-45db-a0dc-50249f06e983
scheduler        10.1.1.68  da38fc60-6938-40d1-9e7d-0e65f313277c
router           10.1.1.9   5fff48d8-1456-4e7c-8a74-63f9b23096eb
cc-worker        10.1.1.67  9cd001cb-d1be-46c4-994d-6f53539710f4
diego-api        10.1.1.64  185b8031-0db4-4e19-92b5-05c7f7481d61
api              10.1.1.66  0cc45a0f-47ce-4a2d-9842-77a137de691d
doppler          10.1.1.70  b3054bbc-a02b-426f-9c3f-9f419888c8e5
nats             10.1.1.3   d6effa85-1cbd-4915-a5ff-93add8c77d4b
graphite-nozzle  10.1.1.72  9dccedaa-6138-4618-9ee9-56354f0af1ec
log-cache        10.1.1.69  1968bd85-f1fd-4007-9c94-8a83815f8124

Traffic on 12 VMs will be captured.

Warning: This could put a significant load on the BOSH Director. Use at your own discretion.

Continue? [yN]:

(Prompt can be omitted via -n/--non-interactive flag)

Correspondings docs PR: cloudfoundry/docs-bosh#858

[ramonskie]

lgtm. as this only have impact on pcap subcmd

[a18e]

Thanks for the reviews everyone, could someone please hit the merge button?
(My team is from ARP WG so nobody has any permissions here 😅 )

[lnguyen]

done @a18e