ctlv3: support ETCDCTL_WATCH_KEY, ETCDCTL_WATCH_RANGE_END

[gyuho]

Parsing logic became more complicated, but added test cases should cover all edge cases.

Can you give this a try @debovema @vikin91 @wwyiwzhang @pldmgg ?

ETCDCTL_API=3 ETCDCTL_WATCH_KEY=foo ./bin/etcdctl watch
ETCDCTL_API=3 ETCDCTL_WATCH_KEY=foo ./bin/etcdctl watch --rev 5
ETCDCTL_API=3 ETCDCTL_WATCH_KEY=foo ./bin/etcdctl watch -i

ref. #8919 (comment)
#8814

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@7a8c192). Click here to learn what that means.
The diff coverage is 73.33%.

@@            Coverage Diff            @@
##             master    #9142   +/-   ##
=========================================
  Coverage          ?   76.01%           
=========================================
  Files             ?      359           
  Lines             ?    30038           
  Branches          ?        0           
=========================================
  Hits              ?    22833           
  Misses            ?     5618           
  Partials          ?     1587

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/global.go	60.6% <60%> (ø)
etcdctl/ctlv3/command/watch_command.go	50.34% <75%> (ø)

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[vikin91]

I will give it a try in the next days. However, in the comments #8919 (comment) and #8919 (comment) me and @debovema meant different set of variables. The variables (ETCD_WATCH_KEY, ETCD_WATCH_VALUE, ...) shall be set by the etcdctl watch command. In this PR, the env variables are the inputs to the etcdctl watch command, which is only a nice addition, but not the feature that is missing in APIv3.

In this comment, you referenced the proper values that should be set before the execution of the command.

Consider this trivial scenario:

etcdctl watch foo -- echo "key: $ETCD_WATCH_KEY value: $ETCD_WATCH_VALUE"
# The output shall be non-empty and contain the key (prefix) and value that have changed in etcd

[gyuho]

@vikin91 Just added

./etcdctl watch foo -- sh -c "env | grep ETCD_WATCH_"

# PUT
# foo
# bar
# ETCD_WATCH_REVISION=11
# ETCD_WATCH_KEY="foo"
# ETCD_WATCH_EVENT_TYPE="PUT"
# ETCD_WATCH_VALUE="bar"

It will be set for each event. Think of ETCD_WATCH_REVISION as v2 exec-watch's ETCD_WATCH_MODIFIED_INDEX. It is the latest revision at the time of watch response from server.

[vikin91]

Fantastic, thanks! I will get back to you as soon as I test it. Hopefully in the next 48hrs.

[jpbetz]

This looks right to me. Docs and tests look comprehensive.

lgtm

[vikin91]

Sorry for reporting back so late - so far it works for me as expected. Many thanks for this PR!

[rajnishahuja]

1. Is below not supposed to work ?
   etcdctl watch foo -- echo "key: $ETCD_WATCH_KEY value: $ETCD_WATCH_VALUE"
   PUT
   foo
   bar
   key: value:

2. I want to take action only for PUT entries for a specific prefix and ignore the DELETEs . While setting the key via env variable works, it does NOT work for WATCH_EVENT_TYPE

Below works and reports only events on foo (and ignore foo1)
ETCDCTL_WATCH_KEY=foo etcdctl watch -- sh -c 'env |grep ETCD_WATCH' , (and it monitors only the foo key and ignores foo1)

This DOES NOT work and reports all types of events (PUT OR DELETE).

ETCD_WATCH_EVENT_TYPE=PUT etcdctl watch foo -- sh -c 'env |grep ETCD_WATCH'
PUT
foo
bar
ETCD_WATCH_KEY="foo"
ETCD_WATCH_REVISION=630
ETCD_WATCH_VALUE="bar"
ETCD_WATCH_EVENT_TYPE="PUT"
DELETE
foo

ETCD_WATCH_KEY="foo"
ETCD_WATCH_REVISION=631
ETCD_WATCH_VALUE=""
ETCD_WATCH_EVENT_TYPE="DELETE"

3. While ETCDCTL_WATCH_KEY works ; ETCDCTL_WATCH_EVENT_TYPE throws an error ;

2023-05-11 16:22:39.793490 W | pkg/flags: unrecognized environment variable ETCDCTL_WATCH_EVENT_TYPE=PUT

Any way of making this work ?