What is the pending requests gauge?

Hi all,

I have been referring to https://twitter.github.io/finagle/guide/Metrics.html to understand and figure out the most important metrics to monitor.

What does the “pending: A gauge of the current total number of outstanding requests.” refer to? Are these connections which have been accepted by linkerd, but are waiting to be dispatched to the client? What determines/controls the size of this outstanding requests “queue”?


Pending the the number of requests that Linkerd has sent to a destination but has not yet received a response for. This can be thought of as the number of “currently in-flight requests”.

Thanks Alex. Is there any limit on the maximum number of pending requests
per destination host beyond which linkerd will stop sending requests to it?

Nope, I don’t believe we have any limit on the maximum number of pending requests.

That being said, the number of pending requests (or the amount of time taken to satisfy a request, depending on the lb algorithm) is used by the load balancer to weight traffic. If a particular host slows down and has many pending requests, the load balancer will shift more traffic to less loaded hosts.

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