Well-known EventCounters in .NET

The .NET runtime and libraries implement and publish several EventCounters that can be used to identify and diagnose various performance issues. This article is a reference on the providers that can be used to monitor these counters and their descriptions.

System.Runtime counters

The following counters are published as part of .NET runtime (CoreCLR) and are maintained in the RuntimeEventSource.cs.

Counter Description First available in
% Time in GC since last GC (time-in-gc) The percent of time in GC since the last GC .NET Core 3.1
Allocation Rate (alloc-rate) The number of bytes allocated per update interval .NET Core 3.1
CPU Usage (cpu-usage) The percent of the process's CPU usage relative to all of the system CPU resources .NET Core 3.1
Exception Count (exception-count) The number of exceptions that have occurred .NET Core 3.1
GC Heap Size (gc-heap-size) The number of bytes thought to be allocated based on GC.GetTotalMemory(Boolean) .NET Core 3.1
Gen 0 GC Count (gen-0-gc-count) The number of times GC has occurred for Gen 0 per update interval .NET Core 3.1
Gen 0 Size (gen-0-size) The number of bytes for Gen 0 GC .NET Core 3.1
Gen 1 GC Count (gen-1-gc-count) The number of times GC has occurred for Gen 1 per update interval .NET Core 3.1
Gen 1 Size (gen-1-size) The number of bytes for Gen 1 GC .NET Core 3.1
Gen 2 GC Count (gen-2-gc-count) The number of times GC has occurred for Gen 2 per update interval .NET Core 3.1
Gen 2 Size (gen-2-size) The number of bytes for Gen 2 GC .NET Core 3.1
LOH Size (loh-size) The number of bytes for the large object heap .NET Core 3.1
POH Size (poh-size) The number of bytes for the pinned object heap (available on .NET 5 and later versions) .NET Core 3.1
GC Fragmentation (gc-fragmentation) The GC Heap Fragmentation (available on .NET 5 and later versions) .NET Core 3.1
Monitor Lock Contention Count (monitor-lock-contention-count) The number of times there was contention when trying to take the monitor's lock, based on Monitor.LockContentionCount .NET Core 3.1
Number of Active Timers (active-timer-count) The number of Timer instances that are currently active, based on Timer.ActiveCount .NET Core 3.1
Number of Assemblies Loaded (assembly-count) The number of Assembly instances loaded into a process at a point in time .NET Core 3.1
ThreadPool Completed Work Item Count (threadpool-completed-items-count) The number of work items that have been processed so far in the ThreadPool .NET Core 3.1
ThreadPool Queue Length (threadpool-queue-length) The number of work items that are currently queued to be processed in the ThreadPool .NET Core 3.1
ThreadPool Thread Count (threadpool-thread-count) The number of thread pool threads that currently exist in the ThreadPool, based on ThreadPool.ThreadCount .NET Core 3.1
Working Set (working-set) The amount of physical memory mapped to the process context at a point in time base on Environment.WorkingSet .NET Core 3.1
IL Bytes Jitted (il-bytes-jitted) The total size of ILs that are JIT-compiled, in bytes .NET 5
Method Jitted Count (method-jitted-count) The number of methods that are JIT-compiled .NET 5
GC Committed Bytes (gc-committed-bytes) The number of bytes committed by the GC .NET 6

Microsoft.AspNetCore.Hosting counters

The following counters are published as part of ASP.NET Core and are maintained in HostingEventSource.cs.

Counter Description First available in
Current Requests (current-requests) The total number of requests that have started, but not yet stopped .NET Core 3.1
Failed Requests (failed-requests) The total number of failed requests that have occurred for the life of the app .NET Core 3.1
Request Rate (requests-per-second) The number of requests that occur per update interval .NET Core 3.1
Total Requests (total-requests) The total number of requests that have occurred for the life of the app .NET Core 3.1

Microsoft.AspNetCore.Http.Connections counters

The following counters are published as part of ASP.NET Core SignalR and are maintained in HttpConnectionsEventSource.cs.

Counter Description First available in
Average Connection Duration (connections-duration) The average duration of a connection in milliseconds .NET Core 3.1
Current Connections (current-connections) The number of active connections that have started, but not yet stopped .NET Core 3.1
Total Connections Started (connections-started) The total number of connections that have started .NET Core 3.1
Total Connections Stopped (connections-stopped) The total number of connections that have stopped .NET Core 3.1
Total Connections Timed Out (connections-timed-out) The total number of connections that have timed out .NET Core 3.1

Microsoft-AspNetCore-Server-Kestrel counters

The following counters are published as part of the ASP.NET Core Kestrel web server and are maintained in KestrelEventSource.cs.

Counter Description First available in
Connection Queue Length (connection-queue-length) The current length of the connection queue .NET 5
Connection Rate (connections-per-second) The number of connections per update interval to the web server .NET 5
Current Connections (current-connections) The current number of active connections to the web server .NET 5
Current TLS Handshakes (current-tls-handshakes) The current number of TLS handshakes .NET 5
Current Upgraded Requests (WebSockets) (current-upgraded-requests) The current number of upgraded requests (WebSockets) .NET 5
Failed TLS Handshakes (failed-tls-handshakes) The total number of failed TLS handshakes .NET 5
Request Queue Length (request-queue-length) The current length of the request queue .NET 5
TLS Handshake Rate (tls-handshakes-per-second) The number of TLS handshakes per update interval .NET 5
Total Connections (total-connections) The total number of connections to the web server .NET 5
Total TLS Handshakes (total-tls-handshakes) The total number of TLS handshakes with the web server .NET 5

System.Net.Http counters

The following counters are published by the HTTP stack.

Counter Description First available in
Requests Started (requests-started) The number of requests started since the process started .NET 5
Requests Started Rate (requests-started-rate) The number of requests started per update interval .NET 5
Requests Failed (requests-failed) The number of failed requests since the process started .NET 5
Requests Failed Rate (requests-failed-rate) The number of failed requests per update interval .NET 5
Current Requests (current-requests) Current number of active HTTP requests that have started but not yet completed or failed .NET 5
Current HTTP 1.1 Connections (http11-connections-current-total) The current number of HTTP 1.1 connections that have started but not yet completed or failed .NET 5
Current HTTP 2.0 Connections (http20-connections-current-total) The current number of HTTP 2.0 connections that have started but not yet completed or failed .NET 5
HTTP 1.1 Requests Queue Duration (http11-requests-queue-duration) The average duration of the time HTTP 1.1 requests spent in the request queue .NET 5
HTTP 2.0 Requests Queue Duration (http20-requests-queue-duration) The average duration of the time HTTP 2.0 requests spent in the request queue .NET 5

System.Net.NameResolution counters

The following counters track metrics related to DNS lookups.

Counter Description First available in
DNS Lookups Requested (dns-lookups-requested) The number of DNS lookups requested since the process started .NET 5
Average DNS Lookup Duration (dns-lookups-duration) The average time taken for a DNS lookup .NET 5

System.Net.Security counters

The following counters track metrics related to the Transport Layer Security protocol.

Counter Description First available in
TLS handshakes completed (tls-handshake-rate) The number of TLS handshakes completed per update interval .NET 5
Total TLS handshakes completed (total-tls-handshakes) The total number of TLS handshakes completed since the process started .NET 5
Current TLS handshakes (current-tls-handshakes) The current number of TLS handshakes that have started but not yet completed .NET 5
Total TLS handshakes failed (failed-tls-handshakes) The total number of failed TLS handshakes since the process started .NET 5
All TLS Sessions Active (all-tls-sessions-open) The number of active TLS sessions of any version .NET 5
TLS 1.0 Sessions Active (tls10-sessions-open) The number of active TLS 1.0 sessions .NET 5
TLS 1.1 Sessions Active (tls11-sessions-open) The number of active TLS 1.1 sessions .NET 5
TLS 1.2 Sessions Active (tls12-sessions-open) The number of active TLS 1.2 sessions .NET 5
TLS 1.3 Sessions Active (tls13-sessions-open) The number of active TLS 1.3 sessions .NET 5
TLS Handshake Duration (all-tls-handshake-duration) The average duration of all TLS handshakes .NET 5
TLS 1.0 Handshake Duration (tls10-handshake-duration) The average duration of TLS 1.0 handshakes .NET 5
TLS 1.1 Handshake Duration (tls11-handshake-duration) The average duration of TLS 1.1 handshakes .NET 5
TLS 1.2 Handshake Duration (tls12-handshake-duration) The average duration of TLS 1.2 handshakes .NET 5
TLS 1.3 Handshake Duration (tls13-handshake-duration) The average duration of TLS 1.3 handshakes .NET 5

System.Net.Sockets counters

The following counters track metrics related to Socket.

Counter Description First available in
Outgoing Connections Established (outgoing-connections-established) The total number of outgoing connections established since the process started .NET 5
Incoming Connections Established (incoming-connections-established) The total number of incoming connections established since the process started .NET 5
Bytes Received (bytes-received) The total number of bytes received since the process started .NET 5
Bytes Sent (bytes-sent) The total number of bytes sent since the process started .NET 5
Datagrams Received (datagrams-received) The total number of datagrams received since the process started .NET 5
Datagrams Sent (datagrams-sent) The total number of datagrams sent since the process started .NET 5