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Add an introductory Upjet-based provider monitoring guide #181

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116 changes: 116 additions & 0 deletions docs/monitoring.md
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## Monitoring the Upjet Runtime
The [Kubernetes controller-runtime] library provides a Prometheus metrics
endpoint by default. The Upjet based providers including the
[upbound/provider-aws], [upbound/provider-azure], [upbound/provider-azuread] and
[upbound/provider-gcp] expose [various
metrics](https://book.kubebuilder.io/reference/metrics-reference.html)
from the controller-runtime to help monitor the health of the various runtime
components, such as the [`controller-runtime` client], the [leader election
client], the [controller workqueues], etc. In addition to these metrics, each
controller also
[exposes](https://github.com/kubernetes-sigs/controller-runtime/blob/60af59f5b22335516850ca11c974c8f614d5d073/pkg/internal/controller/metrics/metrics.go#L25)
various metrics related to the reconciliation of the custom resources and active
reconciliation worker goroutines.

In addition to these metrics exposed by the `controller-runtime`, the Upjet
based providers also expose metrics specific to the Upjet runtime. The Upjet
runtime registers some custom metrics using the [available extension
mechanism](https://book.kubebuilder.io/reference/metrics.html#publishing-additional-metrics),
and are available from the default `/metrics` endpoint of the provider pod. Here
are these custom metrics exposed from the Upjet runtime:
- `upjet_terraform_cli_duration`: This is a histogram metric and reports
statistics, in seconds, on how long it takes a Terraform CLI invocation to
complete.
- `upjet_terraform_active_cli_invocations`: This is a gauge metric and it's the
number of active (running) Terraform CLI invocations.
- `upjet_terraform_running_processes`: This is a gauge metric and it's the
number of running Terraform CLI and Terraform provider processes.
- `upjet_resource_ttr`: This is a histogram metric and it measures, in seconds,
the time-to-readiness for managed resources.

Prometheus metrics can have [labels] associated with them to differentiate the
characteristics of the measurements being made, such as differentiating between
the CLI processes and the Terraform provider processes when counting the number
of active Terraform processes running. Here is a list of labels associated with
each of the above custom Upjet metrics:
- Labels associated with the `upjet_terraform_cli_duration` metric:
- `subcommand`: The `terraform` subcommand that's run, e.g., `init`,
`apply`, `plan`, `destroy`, etc.
- `mode`: The execution mode of the Terraform CLI, one of `sync` (so that
the CLI was invoked synchronously as part of a reconcile loop), `async`
(so that the CLI was invoked asynchronously, the reconciler goroutine will
poll and collect results in future).
- Labels associated with the `upjet_terraform_active_cli_invocations` metric:
- `subcommand`: The `terraform` subcommand that's run, e.g., `init`,
`apply`, `plan`, `destroy`, etc.
- `mode`: The execution mode of the Terraform CLI, one of `sync` (so that
the CLI was invoked synchronously as part of a reconcile loop), `async`
(so that the CLI was invoked asynchronously, the reconciler goroutine will
poll and collect results in future).
- Labels associated with the `upjet_terraform_running_processes` metric:
- `type`: Either `cli` for Terraform CLI (the `terraform` process) processes
or `provider` for the Terraform provider processes. Please note that this
is a best effort metric that may not be able to precisely catch & report
all relevant processes. We may, in the future, improve this if needed by
for example watching the `fork` system calls. But currently, it may prove
to be useful to watch rouge Terraform provider processes.
- Labels associated with the `upjet_resource_ttr` metric:
- `group`, `version`, `kind` labels record the [API group, version and
kind](https://kubernetes.io/docs/reference/using-api/api-concepts/) for
the managed resource, whose
[time-to-readiness](https://github.com/crossplane/terrajet/issues/55#issuecomment-929494212)
measurement is captured.

## Examples
You can [export](https://book.kubebuilder.io/reference/metrics.html) all these
custom metrics and the `controller-runtime` metrics from the provider pod for
Prometheus. Here are some examples showing the custom metrics in action from the
Prometheus console:

- `upjet_terraform_active_cli_invocations` gauge metric showing the sync & async
`terraform init/apply/plan/destroy` invocations: <img width="3000" alt="image"
src="https://user-images.githubusercontent.com/9376684/223296539-94e7d634-58b0-4d3f-942e-8b857eb92ef7.png">

- `upjet_terraform_running_processes` gauge metric showing both `cli` and
`provider` labels: <img width="2999" alt="image"
src="https://user-images.githubusercontent.com/9376684/223297575-18c2232e-b5af-4cc1-916a-d61fe5dfb527.png">

- `upjet_terraform_cli_duration` histogram metric, showing average Terraform CLI
running times for the last 5m: <img width="2993" alt="image"
src="https://user-images.githubusercontent.com/9376684/223299401-8f128b74-8d9c-4c82-86c5-26870385bee7.png">

- The medians (0.5-quantiles) for these observations aggregated by the mode and
Terraform subcommand being invoked: <img width="2999" alt="image"
src="https://user-images.githubusercontent.com/9376684/223300766-c1adebb9-bd19-4a38-9941-116185d8d39f.png">

- `upjet_resource_ttr` histogram metric, showing average resource TTR for the
last 10m: <img width="2999" alt="image"
src="https://user-images.githubusercontent.com/9376684/223309711-edef690e-2a59-419b-bb93-8f837496bec8.png">

- The median (0.5-quantile) for these TTR observations: <img width="3002"
alt="image"
src="https://user-images.githubusercontent.com/9376684/223309727-d1a0f4e2-1ed2-414b-be67-478a0575ee49.png">

These samples have been collected by provisioning 10 [upbound/provider-aws]
`cognitoidp.UserPool` resources by running the provider with a poll interval of
1m. In these examples, one can observe that the resources were polled
(reconciled) twice after they acquired the `Ready=True` condition and after
that, they were destroyed.

## Reference
You can find a full reference of the exposed metrics from the Upjet-based
providers [here](provider_metrics_help.txt).

[Kubernetes controller-runtime]:
https://github.com/kubernetes-sigs/controller-runtime
[upbound/provider-aws]: https://github.com/upbound/provider-aws
[upbound/provider-azure]: https://github.com/upbound/provider-azure
[upbound/provider-azuread]: https://github.com/upbound/provider-azuread
[upbound/provider-gcp]: https://github.com/upbound/provider-gcp
[`controller-runtime` client]:
https://github.com/kubernetes-sigs/controller-runtime/blob/60af59f5b22335516850ca11c974c8f614d5d073/pkg/metrics/client_go_adapter.go#L40
[leader election client]:
https://github.com/kubernetes-sigs/controller-runtime/blob/60af59f5b22335516850ca11c974c8f614d5d073/pkg/metrics/leaderelection.go#L12
[controller workqueues]:
https://github.com/kubernetes-sigs/controller-runtime/blob/60af59f5b22335516850ca11c974c8f614d5d073/pkg/metrics/workqueue.go#L40
[labels]: https://prometheus.io/docs/practices/naming/#labels
147 changes: 147 additions & 0 deletions docs/provider_metrics_help.txt
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# HELP upjet_terraform_cli_duration Measures in seconds how long it takes a Terraform CLI invocation to complete
# TYPE upjet_terraform_cli_duration histogram

# HELP upjet_terraform_running_processes The number of running Terraform CLI and Terraform provider processes
# TYPE upjet_terraform_running_processes gauge

# HELP upjet_resource_ttr Measures in seconds the time-to-readiness (TTR) for managed resources
# TYPE upjet_resource_ttr histogram

# HELP upjet_terraform_active_cli_invocations The number of active (running) Terraform CLI invocations
# TYPE upjet_terraform_active_cli_invocations gauge

# HELP certwatcher_read_certificate_errors_total Total number of certificate read errors
# TYPE certwatcher_read_certificate_errors_total counter

# HELP certwatcher_read_certificate_total Total number of certificate reads
# TYPE certwatcher_read_certificate_total counter

# HELP controller_runtime_active_workers Number of currently used workers per controller
# TYPE controller_runtime_active_workers gauge

# HELP controller_runtime_max_concurrent_reconciles Maximum number of concurrent reconciles per controller
# TYPE controller_runtime_max_concurrent_reconciles gauge

# HELP controller_runtime_reconcile_errors_total Total number of reconciliation errors per controller
# TYPE controller_runtime_reconcile_errors_total counter

# HELP controller_runtime_reconcile_time_seconds Length of time per reconciliation per controller
# TYPE controller_runtime_reconcile_time_seconds histogram

# HELP controller_runtime_reconcile_total Total number of reconciliations per controller
# TYPE controller_runtime_reconcile_total counter

# HELP go_gc_duration_seconds A summary of the pause duration of garbage collection cycles.
# TYPE go_gc_duration_seconds summary

# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge

# HELP go_info Information about the Go environment.
# TYPE go_info gauge

# HELP go_memstats_alloc_bytes Number of bytes allocated and still in use.
# TYPE go_memstats_alloc_bytes gauge

# HELP go_memstats_alloc_bytes_total Total number of bytes allocated, even if freed.
# TYPE go_memstats_alloc_bytes_total counter

# HELP go_memstats_buck_hash_sys_bytes Number of bytes used by the profiling bucket hash table.
# TYPE go_memstats_buck_hash_sys_bytes gauge

# HELP go_memstats_frees_total Total number of frees.
# TYPE go_memstats_frees_total counter

# HELP go_memstats_gc_sys_bytes Number of bytes used for garbage collection system metadata.
# TYPE go_memstats_gc_sys_bytes gauge

# HELP go_memstats_heap_alloc_bytes Number of heap bytes allocated and still in use.
# TYPE go_memstats_heap_alloc_bytes gauge

# HELP go_memstats_heap_idle_bytes Number of heap bytes waiting to be used.
# TYPE go_memstats_heap_idle_bytes gauge

# HELP go_memstats_heap_inuse_bytes Number of heap bytes that are in use.
# TYPE go_memstats_heap_inuse_bytes gauge

# HELP go_memstats_heap_objects Number of allocated objects.
# TYPE go_memstats_heap_objects gauge

# HELP go_memstats_heap_released_bytes Number of heap bytes released to OS.
# TYPE go_memstats_heap_released_bytes gauge

# HELP go_memstats_heap_sys_bytes Number of heap bytes obtained from system.
# TYPE go_memstats_heap_sys_bytes gauge

# HELP go_memstats_last_gc_time_seconds Number of seconds since 1970 of last garbage collection.
# TYPE go_memstats_last_gc_time_seconds gauge

# HELP go_memstats_lookups_total Total number of pointer lookups.
# TYPE go_memstats_lookups_total counter

# HELP go_memstats_mallocs_total Total number of mallocs.
# TYPE go_memstats_mallocs_total counter

# HELP go_memstats_mcache_inuse_bytes Number of bytes in use by mcache structures.
# TYPE go_memstats_mcache_inuse_bytes gauge

# HELP go_memstats_mcache_sys_bytes Number of bytes used for mcache structures obtained from system.
# TYPE go_memstats_mcache_sys_bytes gauge

# HELP go_memstats_mspan_inuse_bytes Number of bytes in use by mspan structures.
# TYPE go_memstats_mspan_inuse_bytes gauge

# HELP go_memstats_mspan_sys_bytes Number of bytes used for mspan structures obtained from system.
# TYPE go_memstats_mspan_sys_bytes gauge

# HELP go_memstats_next_gc_bytes Number of heap bytes when next garbage collection will take place.
# TYPE go_memstats_next_gc_bytes gauge

# HELP go_memstats_other_sys_bytes Number of bytes used for other system allocations.
# TYPE go_memstats_other_sys_bytes gauge

# HELP go_memstats_stack_inuse_bytes Number of bytes in use by the stack allocator.
# TYPE go_memstats_stack_inuse_bytes gauge

# HELP go_memstats_stack_sys_bytes Number of bytes obtained from system for stack allocator.
# TYPE go_memstats_stack_sys_bytes gauge

# HELP go_memstats_sys_bytes Number of bytes obtained from system.
# TYPE go_memstats_sys_bytes gauge

# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge

# HELP rest_client_request_duration_seconds Request latency in seconds. Broken down by verb, and host.
# TYPE rest_client_request_duration_seconds histogram

# HELP rest_client_request_size_bytes Request size in bytes. Broken down by verb and host.
# TYPE rest_client_request_size_bytes histogram

# HELP rest_client_requests_total Number of HTTP requests, partitioned by status code, method, and host.
# TYPE rest_client_requests_total counter

# HELP rest_client_response_size_bytes Response size in bytes. Broken down by verb and host.
# TYPE rest_client_response_size_bytes histogram

# HELP workqueue_adds_total Total number of adds handled by workqueue
# TYPE workqueue_adds_total counter

# HELP workqueue_depth Current depth of workqueue
# TYPE workqueue_depth gauge

# HELP workqueue_longest_running_processor_seconds How many seconds has the longest running processor for workqueue been running.
# TYPE workqueue_longest_running_processor_seconds gauge

# HELP workqueue_queue_duration_seconds How long in seconds an item stays in workqueue before being requested
# TYPE workqueue_queue_duration_seconds histogram

# HELP workqueue_retries_total Total number of retries handled by workqueue
# TYPE workqueue_retries_total counter

# HELP workqueue_unfinished_work_seconds How many seconds of work has been done that is in progress and hasn't been observed by work_duration. Large values indicate stuck threads. One can deduce the number of stuck threads by observing the rate at which this increases.
# TYPE workqueue_unfinished_work_seconds gauge

# HELP workqueue_work_duration_seconds How long in seconds processing an item from workqueue takes.
# TYPE workqueue_work_duration_seconds histogram