Add prometheus-gate catalog task to await prometheus range query results

task/prometheus-gate/0.1/README.md

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+# Prometheus Gate
+
+A simple gate task which will query the prometheus API in a loop and await a matching status for N length of time.
+
+Code for the gate container is located at [github.com/iancoffey/prometheus-gate](https://github.com/iancoffey/prometheus-gate).
+
+## Strategy
+
+Currently, it is possible to enforce that a returned range query values all meet min, max and equals comparisons. Soon, p95 and p99 will be added as well.
+
+- *`min`* - enforce a minimum value for the time period
+- *`max`* - enforce value does not exceed target during time period
+- *`equals`* - enforce a target equals value for the entire time period
+
+## Range Query
+
+The gate can make use of any valid [range query](https://prometheus.io/docs/prometheus/latest/querying/api/#range-queries). This approach works best when the dataset returned is tighly scoped via the range query itself. The gate considers an empty dataset as a failure to be retried.
+
+### Parameters
+
+* **prometheus_endpoint:**: Prometheus API endpoint
+* **range_query:**: The range query to use to define SLO
+* **range_time:**: The time we want to assert fits the SLO`
+* **target_value:**: The target value to assert
+* **target_strategy:**: min, max or equals. p95/99 not supported yet
+* **timeout:**: Maximum ticker time for gate
+* **tick_time:**: How often to try to assert the desired SLO

task/prometheus-gate/0.1/prometheus-gate.yaml

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+---
+apiVersion: tekton.dev/v1beta1
+kind: Task
+metadata:
+  name: prometheus-gate
+  labels:
+    app.kubernetes.io/version: "0.1"
+  annotations:
+    tekton.dev/pipelines.minVersion: "0.12.1"
+    tekton.dev/tags: gate
+    tekton.dev/displayName: prometheus gate
+spec:
+  description: >-
+    A gate task which will query the prometheus API in a loop and await a matching status for N length of time.
+
+  params:
+  - name: prometheus_endpoint
+    type: string
+    description: Prometheus API endpoint
+  - name: range_query
+    type: string
+    description: range query to use to define SLO
+  - name: range_time
+    type: string
+    description: time we want to assert fits the SLO
+    default: "-10m"
+  - name: target_value
+    type: string
+    description: value we will use as threshold
+    default: "1"
+  - name: target_strategy
+    type: string
+    description: The target_strategy is min,max or equal
+    default: "min"
+  - name: timeout
+    type: string
+    description: timeout of the gate
+    default: "3600"
+  - name: tick_time
+    type: string
+    description: how often to draw data from prometheus
+    default: "1m"
+  steps:
+  - name: gate
+    image: iancoffey/prometheus-gate-cf7c3e662ede0a4e9bc24d37d2af86d6@sha256:c3df9d8400aef7acb76f409d1e347c5ecaa6f28a69df50981c14bfe87add85d7
+    env:
+    - name: "PROMETHEUS_ENDPOINT"
+      value: $(params.prometheus_endpoint)
+    - name: "RANGE_QUERY"
+      value: $(params.range_query)
+    - name: "RANGE_TIME"
+      value: $(params.range_time)
+    - name: "TARGET_VALUE"
+      value: $(params.target_value)
+    - name: "TARGET_STRATEGY"
+      value: $(params.target_strategy)
+    - name: "TIMEOUT"
+      value: $(params.timeout)
+    - name: "TICK_TIME"
+      value: $(params.tick_time)

task/prometheus-gate/0.1/samples/README.md

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+# Prometheus Gate Example
+
+When provided with a valid Prometheus API endpoint and an event sink, the sample Pipeline will await there being 0 *kube_endpoint_address_not_ready* metrics for 5 minutes before proceding to the second step, which sends a CloudEvent.
+
+## Params
+
+**prometheus_endpoint**: The API endpoint of your local (or remote) Prometheus API. The gate will use this endpoint to submit a range query every minute.
+
+**promotion_sink**: The URI to an event endpoint that can recieve events.
+
+## PipelineRun
+
+Edit the provided Pipeline run `gated-pipeline-run` to contain your prometheus API endpoint URI and an event sink promotion_sink.
+
+Once it is accurate, run the pipleine with `kubectl apply -f ./pipelinerun.yaml`.

task/prometheus-gate/0.1/samples/pipeline.yaml

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+---
+apiVersion: tekton.dev/v1beta1
+kind: Pipeline
+metadata:
+  name: gated-pipeline
+spec:
+  params:
+    - name: prometheus_endpoint
+      type: string
+      description: The triggers endpoint to send out completion CloudEvent
+      default: ""
+    - name: promotion_sink
+      type: string
+      description: The triggers endpoint to send out promotion CloudEvent
+      default: ""
+  tasks:
+    - name: gate-slo
+      taskRef:
+        name: prometheus-gate
+      params:
+      - name: range_time
+        value: "-5m"
+      - name: target_value
+        value: "0"
+      - name: prometheus_endpoint
+        value: "$(params.prometheus_endpoint)"
+      - name: range_query
+        value: kube_endpoint_address_not_ready{namespace="default"}
+      - name: target_strategy
+        value: equals
+    - name: send-promotion-events
+      taskRef:
+        name: cloudevent
+      params:
+      - name: sink
+        value: $(params.promotion_sink)
+      - name: eventID
+        value: "success.1234"
+      - name: eventType
+        value: "promoted.event"
+      - name: source
+        value: "development-pipeline"
+      - name: data
+        value: '{"message": "The gate succeeded. Woo"}'

task/prometheus-gate/0.1/samples/pipelinerun.yaml

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+---
+apiVersion: tekton.dev/v1beta1
+kind: PipelineRun
+metadata:
+  name: gated-pipeline-run
+spec:
+  serviceAccountName: git-rebase-service-account
+  pipelineRef:
+    name: gated-pipeline
+  params:
+  - name: prometheus_endpoint
+    value: your.prometheus.endpoint:9090
+  - name: promotion_sink
+    value: replace-with-your-uri