BUG: Redis instrumentation crashes when using client.call([:command, args])

[brafales]

Hi,

We've encountered an issue when upgrading to version 0.25.1 of the gem. We have code in our application that uses the redis-rb Redis class call method by calling it the following way:

Redis.call([:del, "key1", "key2", "key3"])

As per the docs: https://www.rubydoc.info/github/redis/redis-rb/Redis#call-instance_method.

As far as we know this is a valid way to interact with Redis, but raises an error in the following line: https://github.com/DataDog/dd-trace-rb/blob/master/lib/ddtrace/contrib/redis/quantize.rb#L30 since command_args.first evaluates to an Array and therefore calling to_sym on an Array raises an error.

Here's a stack trace I can provide:

vendor/bundle/ruby/2.6.0/gems/ddtrace-0.26.0/lib/ddtrace/contrib/redis/quantize.rb:30:in `auth_command?': undefined method `to_sym' for #<Array:0x00007f573a3671b0>
Did you mean?  to_s
               to_set (NoMethodError)
    from vendor/bundle/ruby/2.6.0/gems/ddtrace-0.26.0/lib/ddtrace/contrib/redis/quantize.rb:23:in `format_command_args'
    from vendor/bundle/ruby/2.6.0/gems/ddtrace-0.26.0/lib/ddtrace/contrib/redis/patcher.rb:67:in `block in call'
    from vendor/bundle/ruby/2.6.0/gems/ddtrace-0.26.0/lib/ddtrace/tracer.rb:303:in `trace'
    from vendor/bundle/ruby/2.6.0/gems/ddtrace-0.26.0/lib/ddtrace/contrib/redis/patcher.rb:64:in `call'
    from vendor/bundle/ruby/2.6.0/gems/redis-4.1.2/lib/redis.rb:88:in `block in call'
    from vendor/bundle/ruby/2.6.0/gems/redis-4.1.2/lib/redis.rb:52:in `block in synchronize'
    from /usr/local/lib/ruby/2.6.0/monitor.rb:230:in `mon_synchronize'
    from vendor/bundle/ruby/2.6.0/gems/redis-4.1.2/lib/redis.rb:52:in `synchronize'
    from vendor/bundle/ruby/2.6.0/gems/redis-4.1.2/lib/redis.rb:87:in `call'

We have since changed our code to use REDIS.del("key1", "key2") instead but we think given the other command is expected to be valid, the gem should be prepared to process it.

To reproduce:
In any ddtrace enabled ruby project using redis instrumentation, open a ruby console and type: Redis.call([:del, "key1", "key2", "key3"]) where Redis is a Redis client using the redis-rb gem.

Expected result:

• ddtracer should report metrics of a DEL command in Redis

Actual result:
Error is raised.

[delner]

Hey @brafales, sorry for the late response, but thank you for the thorough report! We will try to reproduce this on our end; the details you provided should make that pretty simple.

[dustMason]

We also just bumped into this bug while trying to upgrade.

[marcotc]

Hey @brafales @dustMason, we've just released version 0.28.0 with a fix to this issue.

I'm going to close this issue for now, let us know if the problem persists.