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Collection Rules

dotnet monitor can be configured to automatically collect diagnostic artifacts based on conditions within the discovered processes.

Note

Collection rules are only enabled when running dotnet-monitor in Listen mode. See Connection Mode configuration for details.

A collection rule is composed of four key aspects:

  • Filters: Describes for which processes the rule is applied. Can filter on aspects such as process name, ID, and command line.
  • Trigger: A condition to monitor in the target process.
  • Actions: A list of actions to execute when the trigger condition is satisfied.
  • Limits: Limits applied to the rule or action execution.

Behavior

When a process is newly discovered by dotnet monitor, the tool will attempt to apply all of the configured collection rules. If a process matches the filters on a rule or the rule does not have any filters, then the rule is applied to the process.

An applied rule will start its trigger on the process, monitoring for the condition that the trigger describes. If the trigger is the Startup trigger, the trigger is immediately satisfied.

Once a trigger is satisfied, the action list is executed. Each action is started (see Action List Execution for more details) in the order as specified by the list of actions. When the execution of the action list is completed, the rule will restart the trigger to begin monitoring for the condition that the trigger describes.

Limits can be applied to inform the rule of how long the rule may run, how many times the action list may be executed, etc.

Filters

A rule can describe for which processes that the rule is applied. If a discovered process does not match the filters, then the rule is not applied to the process. If filters are not configured, the rule is applied to the process.

Note

dotnet monitor is capable of observing multiple processes simultaneously. The filter mechanism for collection rules allows the user to specify which subset of the observed processes that each individual rule should be applied.

The filter criteria are the same as those used for the default process configuration.

See Filters configuration for details and an example of how to specify the filters.

Triggers

A trigger will monitor for a specific condition in the target application and raise a notification when that condition has been observed.

The following are the currently available triggers:

Name Type Description
Startup Startup Satisfied immediately when the rule is applied to a process.
AspNetRequestCount Event Pipe Satisfied when the number of HTTP requests is above the threshold count.
AspNetRequestDuration Event Pipe Satisfied when the number of HTTP requests have response times longer than the threshold duration.
AspNetResponseStatus Event Pipe Satisfied when the number of HTTP responses that have status codes matching the pattern list is above the specified threshold.
EventCounter Event Pipe Satisfied when the value of a counter falls above, below, or between the described threshold.
EventMeter Event Pipe Satisfied when the value of an instrument falls above, below, or between the described threshold.

Actions

Actions allow executing an operation or an external executable in response to a trigger condition being satisfied. Each type of action may have outputs that are consumable by other action settings using an action output dependency (see Action Output Dependencies below).

The following are the currently available actions:

Name Description
CollectDump Collects a memory dump of the target process.
CollectExceptions Collects exceptions from the target process.
CollectGCDump Collects a gcdump of the target process.
CollectLiveMetrics Collects live metrics from the target process.
CollectLogs Collects logs from the target process.
CollectStacks Collects call stacks from the target process.
CollectTrace Collects an event trace of the target process.
Execute Executes an external executable with command line parameters.
LoadProfiler Loads an ICorProfilerCallback implementation into the target process.
SetEnvironmentVariable Sets an environment variable value in the target process.
GetEnvironmentVariable Gets an environment variable value from the target process.

Limits

See Limits for details on the configurable limits.

Advanced Behavior

Action Output Dependencies

Actions may reference the outputs of other actions that have started before them in the same action list execution. These dependencies are described using a simple syntax within the settings of the action. The syntax is:

$(Actions.<ActionName>.<OutputName>)

where <ActionName> is the name of the action from which to get an output value and <OutputName> is the name of an output from that action.

For example, if action A has an output named EgressPath, and action B has a settings property named Arguments, then action B can reference the EgressPath from within the Arguments property setting:

JSON 
{
    "Actions": [{
        "Name": "A",
        "Type": "CollectTrace",
        "Settings": {
            "Profile": "Cpu",
            "Egress": "AzureBlob"
        }
    },{
        "Name": "B",
        "Type": "Execute",
        "Settings": {
            "Path": "path-to-dotnet",
            "Arguments": "MyApp.dll $(Actions.A.EgressPath)"
        }
    }]
}
Kubernetes ConfigMap 
CollectionRules__RuleName__Actions__0__Name: "A"
CollectionRules__RuleName__Actions__0__Type: "CollectTrace"
CollectionRules__RuleName__Actions__0__Settings__Profile: "Cpu"
CollectionRules__RuleName__Actions__0__Settings__Egress: "AzureBlob"
CollectionRules__RuleName__Actions__1__Name: "B"
CollectionRules__RuleName__Actions__1__Type: "Execute"
CollectionRules__RuleName__Actions__1__Settings__Path: "path-to-dotnet"
CollectionRules__RuleName__Actions__1__Settings__Arguments: "MyApp.dll $(Actions.A.EgressPath)"
Kubernetes Environment Variables 
- name: DotnetMonitor_CollectionRules__RuleName__Actions__0__Name
  value: "A"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__0__Type
  value: "CollectTrace"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__0__Settings__Profile
  value: "Cpu"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__0__Settings__Egress
  value: "AzureBlob"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__1__Name
  value: "B"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__1__Type
  value: "Execute"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__1__Settings__Path
  value: "path-to-dotnet"
- name: DotnetMonitor_CollectionRules__RuleName__Actions__1__Settings__Arguments
  value: "MyApp.dll $(Actions.A.EgressPath)"

At this time, only the Arguments property of the Execute action may use an action output dependency.

Additional token substitution

In addition to dependencies, the following list of token substitutions are also available for action settings:

Name Description
$(Process.RuntimeId) The unique identifier of the target process. Note for 3.1 applications, this will be the empty Guid.
$(Process.ProcessId) Process id of the target process.
$(Process.Name) Name of the target process.
$(Process.CommandLine) Command line of the target process.

Action List Execution

When the action list of a rule is executed, the actions are started in the order in which they were specified within the list. However, each action may be completed asynchronously (this is the default behavior). For example, if an action list has actions A, B, C, then the execution of the list is:

  1. Start A
  2. Start B
  3. Start C
  4. Wait for all actions to complete.

The execution of this list does not wait for action A to complete before starting action B; similarly, action B completion is not awaited before starting action C. The execution of the list will wait for all actions to complete before the execution of the list is considered completed.

The above behavior can be changed with the WaitForCompletion property on individual actions or using action output dependencies.

If WaitForCompletion is set to true on an action, the execution of the list will wait for that action to complete before starting the next action. Using the same A, B, C example, if action B has WaitForCompletion set to true, then the execution of the list is:

  1. Start A
  2. Start B
  3. Wait for B to complete
  4. Start C
  5. Wait for all remaining actions (namely, A and C) to complete.

If an action has an output dependency on another action, the execution of the list will wait for the dependency to complete before starting the dependent action. Using the same A, B, C example, if action C has has an output dependency on action A, then the execution of the list is:

  1. Start A
  2. Start B
  3. Wait for A to complete
  4. Start C
  5. Wait for all remaining actions (namely, B and C) to complete.

Resume Runtime

Typically, when a target process is connecting to a dotnet monitor instance running in Listen mode, the target process runtime is suspended until dotnet monitor instructs it to resume. This allows starting diagnostic operations before the runtime starts, so that events that occur early in the runtime execution may be captured.

The rule system plays a part in this process by starting the triggers of all of the applicable rules on a process before its runtime is resumed. For the Startup trigger, the rule will not yield back to the runtime for resumption until all actions are started; the caveat is that when starting the actions, if either an explicit wait is specified via the WaitForCompletion setting or an action dependency forces an implicit wait, then the runtime is resumed at that point. For non-Startup trigger rules, the rule will yield back to the runtime for resumption as soon as the trigger has started.

Examples

For examples of how to configure collection rules, see Collection Rule Examples.