PT-2080 Add JSON logging to pt-kill (#543)

* Add JSON output support to pt-kill

Introduces new flags `--log-json` and `--log-json-fields` to control JSON output:
- `--log-json`: when combined with `--print`, outputs kill information in JSON format instead of plain text, with the same fields as the `kill_log` table when using `--log-dsn`
- `--log-json-fields`: when combined with `--log-json`, adds user-defined key-value pairs to the JSON document that is output (such as cluster name or hostname); parameter value is in the format of `key1:value1,key2:value2`

* Convert --log-json to write to file, remove dependency on --print, update docs

The `--log-json` parameter now takes a file path value, and writes JSON output to this file.

The `--print` parameter is now independent and does not need to be specified to use `--log-json`.

Docs updated for clarity.

* Add chksm to JSON output, make JSON key names consistent

- Adds chksm outout to JSON output to make it easier to group similar queries
- Moves chksm code so that it is always executed, is accessible within the `log-json` scope, and isn't duplicated
- Change JSON key names to consistently use uppercase letters at start of words, change `ts` to `Timestamp`

* Update docs to match changed field names

* Rename JSON parameter, output to STDOUT, fix tests, add test for --json, bug fix for --query-id

- `--json` parameter must now be used in conjunction with `--print`; JSON output replaces normal `--print` output when `--json` is also specified
- `--json` output is now sent to STDOUT instead of a specified file, as its new behaviour is to change the output format of `--print` instead of logging to a file
- Renamed `--log-json` and `--log-json-fields` parameters to `--json` and `--json-fields` to better represent their new behaviour
- Refactored checksum code to prevent test failures when `$query->{'Info'}` is empty
- Added test for `--json` and `--json-fields` parameters
- Fixed bug where specifying `--query-id` would cause errors when `$query->{'Info'}` is empty

* Fix typo: Unkown -> Unknown

bin/pt-kill

@@ -7373,20 +7373,49 @@ sub main {
 
          MATCHING_QUERY:
          foreach my $query ( @queries ) {
-            if ( $o->get('print') ) {
             my $qinfo = ( $query->{Info} || 'NULL' );
             if( $o->get('fingerprint') && $qinfo ne 'NULL' ) {
                $qinfo = $qr->fingerprint($query->{'Info'});
             }
-
+            my $chksm = '';
+            if ( $qinfo ne 'NULL' ) {
+               my $fp = $qr->fingerprint($query->{'Info'});
+               # $chksm is used by query-id and json
+               $chksm = Transformers::make_checksum($fp);
+            }
+            if ( $o->get('print') ) {
+               if ( $o->get('json') ) {
+                  my $reasons = join "\n", map {
+                        defined($_) ? $_ : "Unknown reason"
+                     } @{ $pl->{_reasons_for_matching}->{$query} };
+                  my %jsonOutput = (
+                        Timestamp   => ts(time),
+                        Reason      => $reasons,
+                        Kill_Error  => $EVAL_ERROR,
+                        Id          => $query->{Id},
+                        User        => $query->{User},
+                        Host        => $query->{Host},
+                        Db          => $query->{db},
+                        Command     => $query->{Command},
+                        Time        => $query->{Time},
+                        State       => $query->{State},
+                        Info        => $qinfo,
+                        Digest      => $chksm
+                  );
+                  if ( $o->get('json-fields') ) {
+                     my @logFieldKVs = split(",", $o->get('json-fields'));
+                     my %logFields = map { split(":", $_) } @logFieldKVs;
+                     %jsonOutput = (%jsonOutput, %logFields);
+                  }
+                  printf "%s\n", Transformers::hash_to_json(\%jsonOutput);
+               } else {
                   printf "# %s %s %d (%s %d sec) %s\n",
                      ts(time), $o->get('kill-query') ? 'KILL QUERY' : 'KILL',
                      $query->{Id}, ($query->{Command} || 'NULL'), $query->{Time},
                      $qinfo;
                }
+            }
             if ( $o->get('query-id') ) {
-                  my $fp = $qr->fingerprint($query->{'Info'});
-                  my $chksm = Transformers::make_checksum($fp);
                print "Query ID: 0x$chksm\n";
             }
             if ( $o->get('execute-command') ) {
@@ -7484,7 +7513,7 @@ sub log_to_table {
 
    my $ts      = Transformers::ts(time());
    my $reasons = join "\n", map {
-         defined($_) ? $_ : "Unkown reason"
+         defined($_) ? $_ : "Unknown reason"
       } @{ $pl->{_reasons_for_matching}->{$query} };
    $log->(
          $ts, $reasons, $args{eval_error},
@@ -7869,6 +7898,67 @@ MAGIC_create_log_table:
       PRIMARY KEY (kill_id)
    ) DEFAULT CHARSET=utf8
 
+=item --json
+
+Prints killed queries as JSON, must be used with L<"--print">. For example:
+
+   --print --json
+
+The usual plain-text output from L<"--print"> will not be displayed.
+
+JSON output will be in the format of:
+
+   {
+      "Command": "Query",
+      "Host": "10.0.0.1:9999",
+      "Id": 1234,
+      "Info": "SELECT SLEEP(5)",
+      "State": "User sleep",
+      "Time": 10,
+      "User": "my_user",
+      "Db": "my_db",
+      "Kill_Error": "",
+      "Digest": "58A43A7DA83F58C1",
+      "Reason": "Exceeds busy time\nQuery matches Command spec",
+      "Timestamp": "2022-01-01T00:00:00"
+   }
+
+=item --json-fields
+
+type: string
+
+Specify a list of additional key:value pairs to include in JSON output when
+using L<"--json">, the value of this parameter must be specified in the
+format of:
+
+   --json-fields key1:value1,key2:value2
+
+Any fields specified using L<"--json-fields"> will be included in the
+L<"--json"> output.
+
+For example:
+
+   --print --json --json-fields hostname:$(hostname),tag:my_tag
+
+Will result in JSON records being written to "kill_log.json" using this format:
+
+   {
+      "Command": "Query",
+      "Host": "10.0.0.1:9999",
+      "Id": 1234,
+      "Info": "SELECT SLEEP(5)",
+      "State": "User sleep",
+      "Time": 10,
+      "User": "my_user",
+      "Db": "my_db",
+      "Kill_Error": "",
+      "Digest": "58A43A7DA83F58C1",
+      "Reason": "Exceeds busy time\nQuery matches Command spec",
+      "Timestamp": "2022-01-01T00:00:00",
+      "hostname": "my_host",
+      "tag": "my_tag"
+   }
+
 =item --password
 
 short form: -p; type: string

t/pt-kill/match.t

@@ -9,7 +9,7 @@ BEGIN {
 use strict;
 use warnings FATAL => 'all';
 use English qw(-no_match_vars);
-use Test::More tests => 16;
+use Test::More tests => 17;
 
 use PerconaTest;
 use Sandbox;
@@ -147,6 +147,16 @@ like(
    '--query-id'
 );
 
+# --json option
+$output = output(
+   sub { pt_kill::main(@args, "$trunk/t/lib/samples/pl/recset011.txt", qw(--match-all --print --json --json-fields key:value)); }
+);
+like(
+   $output,
+   qr/\{"Command"\:"Query","Db"\:"db","Digest"\:"69962191E64980E6","Host"\:"127\.0\.0\.1\:3306","Id"\:"4","Info"\:"\\\/\* fruit\=orange \*\\\/ select 1 from fuits;","Kill_Error"\:"","Reason"\:"","State"\:"statistics","Time"\:"6","Timestamp"\:".*","User"\:"foo","key"\:"value"\}/,
+   '--json'
+);
+
 # #############################################################################
 # Live tests.
 # #############################################################################