Add docs / samples for Sequence (#1481)

* sequence with broker

* add sequence -> sequence sample

* sequence wired to event display

* terminal sequence

* first two examples moved to new v1beta1 services + cascading changes

* fix sequence2sequence to use v1beta services / default ns

* fix broker example to use v1beta1 service + default ns

* Address PR feedback

* add a pointer to vaikas-google/transformer sample

* update transformer image refs to latest

* address PR feedback

* move overview before prerequisites, add link to main sequence page

docs/eventing/samples/sequence/sequence-reply-to-event-display/README.md

@@ -0,0 +1,197 @@
+---
+title: "Sequence Wired to event-display"
+weight: 20
+type: "docs"
+---
+
+# Using Sequences in series
+
+## Overview
+
+We are going to create the following logical configuration. We create a CronJobSource,
+feeding events to a (`Sequence`)[../../../sequence.md], then taking the output of that `Sequence` and
+displaying the resulting output.
+
+![Logical Configuration](./sequence-reply-to-event-display.png)
+
+## Prerequisites
+
+For this example, we'll assume you have set up an `InMemoryChannel`
+as well as Knative Serving (for our functions). The examples use `default`
+namespace, again, if you want to deploy to another Namespace, you will need
+to modify the examples to reflect this.
+
+If you want to use different type of `Channel`, you will have to modify the
+`Sequence.Spec.ChannelTemplate` to create the appropriate Channel resources.
+
+
+## Setup
+
+### Create the Knative Services
+
+Change `default` below to create the steps in the Namespace where you want resources
+created.
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+---
+```
+
+
+```shell
+kubectl -n default create -f ./steps.yaml
+```
+
+### Create the Sequence
+
+The `sequence.yaml` file contains the specifications for creating the Sequence. If you are using a different type of Channel, you need to change the
+spec.channelTemplate to point to your desired Channel.
+
+```yaml
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Service
+    apiVersion: serving.knative.dev/v1beta1
+    name: event-display
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you want the
+resources to be created.
+```shell
+kubectl -n default create -f ./sequence.yaml
+```
+
+
+### Create the Service displaying the events created by Sequence
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: event-display
+spec:
+  template:
+    spec:
+      containers:
+      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you want your resources
+to be created.
+
+```shell
+kubectl -n default create -f ./event-display.yaml
+```
+
+### Create the CronJobSource targeting the Sequence
+
+This will create a CronJobSource which will send a CloudEvent with {"message": "Hello world!"} as
+the data payload every 2 minutes.
+
+```yaml
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: sequence
+```
+
+```shell
+kubectl -n default create -f ./cron-source.yaml
+```
+
+### Inspecting the results
+
+You can now see the final output by inspecting the logs of the event-display pods.
+
+```shell
+kubectl -n default get pods
+```
+
+Then look at the logs for the event-display pod:
+
+
+```shell
+kubectl -n default logs -l serving.knative.dev/service=event-display -c user-container
+☁️  cloudevents.Event
+Validation: valid
+Context Attributes,
+  cloudEventsVersion: 0.1
+  eventType: samples.http.mod3
+  source: /transformer/2
+  eventID: df52b47e-02fd-45b2-8180-dabb572573f5
+  eventTime: 2019-06-18T14:18:42.478140635Z
+  contentType: application/json
+Data,
+  {
+    "id": 0,
+    "message": "Hello world! - Handled by 0 - Handled by 1 - Handled by 2"
+  }
+```
+
+And you can see that the initial Cron Source message ("Hello World!") has been appended to it by each
+of the steps in the Sequence.

docs/eventing/samples/sequence/sequence-reply-to-event-display/cron-source.yaml

@@ -0,0 +1,11 @@
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: sequence

docs/eventing/samples/sequence/sequence-reply-to-event-display/event-display.yaml

@@ -0,0 +1,9 @@
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: event-display
+spec:
+  template:
+    spec:
+      containers:
+      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display

docs/eventing/samples/sequence/sequence-reply-to-event-display/sequence.yaml

@@ -0,0 +1,25 @@
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Service
+    apiVersion: serving.knative.dev/v1beta1
+    name: event-display

docs/eventing/samples/sequence/sequence-reply-to-event-display/steps.yaml

@@ -0,0 +1,40 @@
+apiVersion: serving.knative.dev/v1alpha1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1alpha1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1alpha1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+---

docs/eventing/samples/sequence/sequence-reply-to-sequence/README.md

@@ -0,0 +1,271 @@
+---
+title: "Sequence Wired to another Sequence"
+weight: 20
+type: "docs"
+---
+
+# Using Sequences in series
+
+## Overview
+
+We are going to create the following logical configuration. We create a CronJobSource,
+feeding events to a (`Sequence`)[../../../sequence.md], then taking the output of that `Sequence` and sending
+it to a second `Sequence` and finally displaying the resulting output.
+
+![Logical Configuration](./sequence-reply-to-sequence.png)
+
+## Prerequisites
+
+For this example, we'll assume you have set up a an `InMemoryChannel`
+as well as Knative Serving (for our functions). The examples use `default`
+namespace, again, if you want to deploy to another Namespace, you will need to
+modify the examples to reflect this.
+
+If you want to use different type of `Channel`, you will have to modify the
+`Sequence.Spec.ChannelTemplate` to create the appropriate Channel resources.
+
+
+## Setup
+
+### Create the Knative Services
+
+Change `default` below to create the steps in the Namespace where you want resources
+created.
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: fourth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "3"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: fifth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "4"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: sixth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "5"
+---
+```
+
+
+```shell
+kubectl -n default create -f ./steps.yaml
+```
+
+### Create the first Sequence
+
+The `sequence1.yaml` file contains the specifications for creating the Sequence. If you are using a different type of
+Channel, you need to change the spec.channelTemplate to point to your desired Channel.
+
+```yaml
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: first-sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Sequence
+    apiVersion: messaging.knative.dev/v1alpha1
+    name: second-sequence
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you  want
+your resources created.
+
+```shell
+kubectl -n default create -f ./sequence1.yaml
+```
+
+
+### Create the second Sequence
+
+The `sequence2.yaml` file contains the specifications for creating the Sequence. If you are using a different type of
+Channel, you need to change the spec.channelTemplate to point to your desired Channel.
+
+```yaml
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: second-sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: fourth
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: fifth
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: sixth
+  reply:
+    kind: Service
+    apiVersion: serving.knative.dev/v1beta1
+    name: event-display
+```
+
+
+### Create the Service displaying the events created by Sequence
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: event-display
+spec:
+  template:
+    spec:
+      containerers:
+      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you want your resources
+created.
+
+```shell
+kubectl -n default create -f ./event-display.yaml
+```
+
+### Create the CronJobSource targeting the first Sequence
+
+This will create a CronJobSource which will send a CloudEvent with {"message": "Hello world!"} as
+the data payload every 2 minutes.
+
+```yaml
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: first-sequence
+```
+
+```shell
+kubectl -n default create -f ./cron-source.yaml
+```
+
+### Inspecting the results
+
+You can now see the final output by inspecting the logs of the event-display pods.
+
+```shell
+kubectl -n default get pods
+```
+
+Then look at the logs for the event-display pod:
+
+```shell
+kubectl -n default logs -l serving.knative.dev/service=event-display -c user-container
+☁️  cloudevents.Event
+Validation: valid
+Context Attributes,
+  cloudEventsVersion: 0.1
+  eventType: samples.http.mod3
+  source: /transformer/5
+  eventID: 7628a147-ec74-43d5-a888-8384a1b6b005
+  eventTime: 2019-06-18T13:57:20.279354375Z
+  contentType: application/json
+Data,
+  {
+    "id": 0,
+    "message": "Hello world! - Handled by 0 - Handled by 1 - Handled by 2 - Handled by 3 - Handled by 4 - Handled by 5"
+  }
+```
+
+And you can see that the initial Cron Source message ("Hello World!") has been appended to it by each
+of the steps in the Sequence.

docs/eventing/samples/sequence/sequence-reply-to-sequence/cron-source.yaml

@@ -0,0 +1,11 @@
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: first-sequence

docs/eventing/samples/sequence/sequence-reply-to-sequence/event-display.yaml

@@ -0,0 +1,9 @@
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: event-display
+spec:
+  template:
+    spec:
+      containers:
+      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display

docs/eventing/samples/sequence/sequence-reply-to-sequence/sequence1.yaml

@@ -0,0 +1,25 @@
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: first-sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Sequence
+    apiVersion: messaging.knative.dev/v1alpha1
+    name: second-sequence

docs/eventing/samples/sequence/sequence-reply-to-sequence/sequence2.yaml

@@ -0,0 +1,25 @@
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: second-sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: fourth
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: fifth
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: sixth
+  reply:
+    kind: Service
+    apiVersion: serving.knative.dev/v1alpha1
+    name: event-display

docs/eventing/samples/sequence/sequence-reply-to-sequence/steps.yaml

@@ -0,0 +1,80 @@
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: fourth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "3"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: fifth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "4"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: sixth
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "5"
+---

docs/eventing/samples/sequence/sequence-terminal/README.md

@@ -0,0 +1,257 @@
+title: "Sequence terminal"
+weight: 20
+type: "docs"
+---
+
+# Using Sequences in series
+
+## Overview
+
+We are going to create the following logical configuration. We create a CronJobSource,
+feeding events to a (`Sequence`)[../../../sequence.md]. Sequence can then do either external work, or 
+out of band create additional events.
+
+![Logical Configuration](./sequence-terminal.png)
+
+## Prerequisites
+
+For this example, we'll assume you have set up an `InMemoryChannel`
+as well as Knative Serving (for our functions). The examples use `default`
+namespace, again, if you want to deploy to another Namespace, you will need
+to modify the examples to reflect this.
+
+If you want to use different type of `Channel`, you will have to modify the
+`Sequence.Spec.ChannelTemplate` to create the appropriate Channel resources.
+
+
+## Setup
+
+### Create the Knative Services
+
+First create the 3 steps that will be referenced in the Steps.
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+---
+```
+
+
+```shell
+kubectl -n default create -f ./steps.yaml
+```
+
+### Create the Sequence
+
+The `sequence.yaml` file contains the specifications for creating the Sequence. If you are using a different type of Channel, you need to change the
+spec.channelTemplate to point to your desired Channel.
+
+```yaml
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you want the
+resources to be created.
+```shell
+kubectl -n default create -f ./sequence.yaml
+```
+
+
+### Create the CronJobSource targeting the Sequence
+
+This will create a CronJobSource which will send a CloudEvent with {"message": "Hello world!"} as
+the data payload every 2 minutes.
+
+```yaml
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: sequence
+```
+
+Here, if you are using different type of Channel, you need to change the
+spec.channelTemplate to point to your desired Channel. 
+
+```shell
+kubectl -n default create -f ./cron-source.yaml
+```
+
+### Inspecting the results
+
+You can now see the final output by inspecting the logs of the event-display pods. Note that since
+we set the `CronJobSource` to emit every 2 minutes, it might take some time for the events to show
+up in the logs.
+
+```shell
+kubectl -n default get pods
+```
+
+Let's look at the logs for the first `Step` in the `Sequence`:
+
+```shell
+kubectl -n default logs -l serving.knative.dev/service=first -c user-container
+Got Event Context: Context Attributes,
+  specversion: 0.2
+  type: dev.knative.cronjob.event
+  source: /apis/v1/namespaces/default/cronjobsources/cronjob-source
+  id: 2fdf69ec-0480-463a-92fb-8d1259550f32
+  time: 2019-06-18T14:38:00.000379084Z
+  contenttype: application/json
+Extensions,
+  knativehistory: sequence-kn-sequence-0-kn-channel.default.svc.cluster.local
+2019/06/18 14:38:14 http: superfluous response.WriteHeader call from github.com/vaikas-google/transformer/vendor/github.com/cloudevents/sdk-go/pkg/cloudevents/transport/http.(*Transport).ServeHTTP (transport.go:446)
+
+Got Data: &{Sequence:0 Message:Hello world!}
+Got Transport Context: Transport Context,
+  URI: /
+  Host: first.default.svc.cluster.local
+  Method: POST
+  Header:
+    X-Request-Id: 9b51bcaa-10bc-97a5-a288-dde9b97f6e1e
+    Content-Length: 26
+    K-Proxy-Request: activator
+    X-Forwarded-For: 10.16.3.77, 127.0.0.1, 127.0.0.1
+    X-Forwarded-Proto: http
+    Ce-Knativehistory: sequence-kn-sequence-0-kn-channel.default.svc.cluster.local
+    X-B3-Spanid: 42bcd58bd1ea8191
+    X-B3-Parentspanid: c63efd989dcf5dc5
+    X-B3-Sampled: 0
+    X-B3-Traceid: 4a1da6622ecbbdea0c75ae32e065cfcb
+
+----------------------------
+```
+
+
+Then we can look at the output of the second Step in the `Sequence`:
+
+```shell
+kubectl -n default logs -l serving.knative.dev/service=second -c user-container
+Got Event Context: Context Attributes,
+  cloudEventsVersion: 0.1
+  eventType: samples.http.mod3
+  source: /transformer/0
+  eventID: 5a9ec173-5224-41a2-9c83-50786651bcd5
+  eventTime: 2019-06-18T14:38:14.657008072Z
+  contentType: application/json
+
+Got Data: &{Sequence:0 Message:Hello world! - Handled by 0}
+Got Transport Context: Transport Context,
+  URI: /
+  Host: second.default.svc.cluster.local
+  Method: POST
+  Header:
+    X-Forwarded-For: 10.16.3.77, 127.0.0.1, 127.0.0.1
+    X-Forwarded-Proto: http
+    Content-Length: 48
+    X-B3-Sampled: 0
+    Ce-Knativehistory: sequence-kn-sequence-1-kn-channel.default.svc.cluster.local
+    X-B3-Parentspanid: 4fba491a605b2391
+    K-Proxy-Request: activator
+    X-B3-Spanid: 56e4150c4e1d679b
+    X-B3-Traceid: fb468aa8ec035a66153ce3f4929aa2fe
+    X-Request-Id: d60e7109-3853-9ca1-83e2-c70f8cbfbb93
+
+----------------------------
+```
+
+And you can see that the initial Cron Source message ("Hello World!") has now been modified by the
+first step in the Sequence to include " - Handled by 0". Exciting :)
+
+Then we can look at the output of the last Step in the `Sequence`:
+
+```shell
+kubectl -n default logs -l serving.knative.dev/service=third -c user-container
+Got Event Context: Context Attributes,
+  cloudEventsVersion: 0.1
+  eventType: samples.http.mod3
+  source: /transformer/1
+  eventID: 5747fb77-66a2-4e78-944b-43192aa879fb
+  eventTime: 2019-06-18T14:38:32.688345694Z
+  contentType: application/json
+
+Got Data: &{Sequence:0 Message:Hello world! - Handled by 0 - Handled by 1}
+Got Transport Context: Transport Context,
+  URI: /
+  Host: third.default.svc.cluster.local
+  Method: POST
+  Header:
+    X-B3-Sampled: 0
+    X-B3-Traceid: 64a9c48c219375476ffcdd5eb14ec6e0
+    X-Forwarded-For: 10.16.3.77, 127.0.0.1, 127.0.0.1
+    X-Forwarded-Proto: http
+    Ce-Knativehistory: sequence-kn-sequence-2-kn-channel.default.svc.cluster.local
+    K-Proxy-Request: activator
+    X-Request-Id: 505ff620-2822-9e7d-8855-53d02a2e36e2
+    Content-Length: 63
+    X-B3-Parentspanid: 9e822f378ead293c
+    X-B3-Spanid: a56ee81909c767e6
+
+----------------------------
+```
+
+And as expected it's now been handled by both the first and second Step as reflected by
+the Message being now: "Hello world! - Handled by 0 - Handled by 1"

docs/eventing/samples/sequence/sequence-terminal/cron-source.yaml

@@ -0,0 +1,11 @@
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: Sequence
+    name: sequence

docs/eventing/samples/sequence/sequence-terminal/sequence.yaml

@@ -0,0 +1,21 @@
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third

docs/eventing/samples/sequence/sequence-terminal/steps.yaml

@@ -0,0 +1,40 @@
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+---

docs/eventing/samples/sequence/sequence-with-broker-trigger/README.md

@@ -0,0 +1,227 @@
+---
+title: "Sequence with Broker and Trigger"
+weight: 20
+type: "docs"
+---
+
+# Using Sequence with Broker and Trigger
+
+## Overview
+
+We are going to create the following logical configuration. We create a CronJobSource,
+feeding events into the Broker, then we create a `Filter` that wires those events
+into a (`Sequence`)[../../../sequence.md] consisting of 3 steps. Then we take the end of the Sequence and
+feed newly minted events back into the Broker and create another Trigger which 
+will then display those events.
+
+**NOTE** [TODO: Fix this](https://github.com/knative/eventing/issues/1421)
+So, currently as set up, the events emitted by the Sequence do not make it into
+the Broker.
+
+## Prerequisites
+
+For this example, we'll assume you have set up a `Broker` and an `InMemoryChannel`
+as well as Knative Serving (for our functions). The examples use `default`
+namespace, again, if your broker lives in another Namespace, you will need to
+modify the examples to reflect this.
+
+If you want to use different type of `Channel`, you will have to modify the
+`Sequence.Spec.ChannelTemplate` to create the appropriate Channel resources.
+
+![Logical Configuration](./sequence-with-broker-trigger.png)
+
+
+## Setup
+
+### Create the Knative Services
+
+Change `default` below to create the steps in the Namespace where you have configured your
+`Broker`
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+            env:
+            - name: STEP
+              value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+            env:
+            - name: STEP
+              value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+            env:
+            - name: STEP
+              value: "2"
+
+---
+```
+
+
+```shell
+kubectl -n default create -f ./steps.yaml
+```
+
+### Create the Sequence
+
+The `sequence.yaml` file contains the specifications for creating the Sequence. If you are using a different type of Channel,
+you need to change the spec.channelTemplate to point to your desired Channel.
+
+Also, change the spec.reply.name to point to your `Broker`
+
+```yaml
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Broker
+    apiVersion: eventing.knative.dev/v1alpha1
+    name: broker-test
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you have configured your
+`Broker`. 
+
+```shell
+kubectl -n default create -f ./sequence.yaml
+```
+
+
+### Create the CronJobSource targeting the Broker
+
+This will create a CronJobSource which will send a CloudEvent with {"message": "Hello world!"} as
+the data payload every 2 minutes.
+
+```yaml
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: eventing.knative.dev/v1alpha1
+    kind: Broker
+    name: broker-test
+```
+
+Here, if you are using different type of Channel, you need to change the
+spec.channelTemplate to point to your desired Channel. Also, change the
+spec.reply.name to point to your `Broker`
+
+Change `default` below to create the `Sequence` in the Namespace where you have configured your
+`Broker`. 
+
+```shell
+kubectl -n default create -f ./cron-source.yaml
+```
+
+### Create the Trigger targeting the Sequence
+
+```yaml
+apiVersion: eventing.knative.dev/v1alpha1
+kind: Trigger
+metadata:
+  name: sequence-trigger
+spec:
+  filter:
+    sourceAndType:
+      type: dev.knative.cronjob.event
+  subscriber:
+    ref:
+      apiVersion: messaging.knative.dev/v1alpha1
+      kind: Sequence
+      name: sequence
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you have configured your
+`Broker`. 
+
+```shell
+kubectl -n default create -f ./trigger.yaml
+
+```
+
+### Create the Service and Trigger displaying the events created by Sequence
+
+**NOTE** This does not work yet because the events created by the Sequence in the last step
+are filtered. [TODO: Fix this](https://github.com/knative/eventing/issues/1421)
+
+```yaml
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: sequence-display
+spec:
+  template:
+    spec:
+      containers:
+      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
+---
+apiVersion: eventing.knative.dev/v1alpha1
+kind: Trigger
+metadata:
+  name: sequence-trigger
+spec:
+  filter:
+    sourceAndType:
+      type: samples.http.mod3
+  subscriber:
+    ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: sequence-display
+---
+```
+
+Change `default` below to create the `Sequence` in the Namespace where you have configured your
+`Broker`. 
+
+```shell
+kubectl -n default create -f ./display-trigger.yaml
+```
+

docs/eventing/samples/sequence/sequence-with-broker-trigger/cron-source.yaml

@@ -0,0 +1,11 @@
+apiVersion: sources.eventing.knative.dev/v1alpha1
+kind: CronJobSource
+metadata:
+  name: cronjob-source
+spec:
+  schedule: "*/2 * * * *"
+  data: '{"message": "Hello world!"}'
+  sink:
+    apiVersion: eventing.knative.dev/v1alpha1
+    kind: Broker
+    name: broker-test

docs/eventing/samples/sequence/sequence-with-broker-trigger/display-trigger.yaml

@@ -0,0 +1,27 @@
+apiVersion: serving.knative.dev/v1alpha1
+kind: Service
+metadata:
+  name: sequence-display
+spec:
+  runLatest:
+    configuration:
+      revisionTemplate:
+        spec:
+          container:
+            image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
+---
+apiVersion: eventing.knative.dev/v1alpha1
+kind: Trigger
+metadata:
+  name: display-trigger
+spec:
+  broker: broker-test
+  filter:
+    sourceAndType:
+      type: samples.http.mod3
+  subscriber:
+    ref:
+      apiVersion: serving.knative.dev/v1alpha1
+      kind: Service
+      name: sequence-display
+---

docs/eventing/samples/sequence/sequence-with-broker-trigger/sequence.yaml

@@ -0,0 +1,25 @@
+apiVersion: messaging.knative.dev/v1alpha1
+kind: Sequence
+metadata:
+  name: sequence
+spec:
+  channelTemplate:
+    apiVersion: messaging.knative.dev/v1alpha1
+    kind: InMemoryChannel
+  steps:
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: first
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: second
+  - ref:
+      apiVersion: serving.knative.dev/v1beta1
+      kind: Service
+      name: third
+  reply:
+    kind: Broker
+    apiVersion: eventing.knative.dev/v1alpha1
+    name: broker-test

docs/eventing/samples/sequence/sequence-with-broker-trigger/steps.yaml

@@ -0,0 +1,41 @@
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: first
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "0"
+
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: second
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "1"
+---
+apiVersion: serving.knative.dev/v1beta1
+kind: Service
+metadata:
+  name: third
+spec:
+  template:
+    spec:
+      containers:
+      - image: us.gcr.io/probable-summer-223122/cmd-03315b715ae8f3e08e3a9378df706fbb@sha256:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
+        env:
+        - name: STEP
+          value: "2"
+
+---

docs/eventing/samples/sequence/sequence-with-broker-trigger/trigger.yaml

@@ -0,0 +1,14 @@
+apiVersion: eventing.knative.dev/v1alpha1
+kind: Trigger
+metadata:
+  name: sequence-trigger
+spec:
+  broker: broker-test
+  filter:
+    sourceAndType:
+      type: dev.knative.cronjob.event
+  subscriber:
+    ref:
+      apiVersion: messaging.knative.dev/v1alpha1
+      kind: Sequence
+      name: sequence

docs/eventing/sequence.md

@@ -0,0 +1,85 @@
+---
+title: "Sequence"
+weight: 20
+type: "docs"
+---
+
+Sequence CRD provides a way to define an in-order list of functions that will
+be invoked. Each step can modify, filter or create a new kind of an event.
+Sequence creates `Channel`s and `Subscription`s under the hood.
+
+## Usage
+
+### Sequence Spec
+
+Sequence has three parts for the Spec:
+
+1. `Steps` which defines the in-order list of `Subscriber`s, aka, which functions
+are executed in the listed order. These are specified using the
+`eventingv1alpha1.SubscriberSpec` just like you would when creating `Subscription`.
+Each step should be `Callable`.
+1. `ChannelTemplate` defines the Template which will be used to create `Channel`s
+between the steps. 
+1. `Reply` (Optional) Reference to where the results of the final step in the 
+sequence are sent to.
+
+### Sequence Status
+
+Sequence has four parts for the Status:
+
+1. Conditions which detail the overall Status of the Sequence object
+1. ChannelStatuses which convey the Status of underlying `Channel` resources that
+are created as part of this Sequence. It is an array and each Status corresponds to the Step number,
+so the first entry in the array is the Status of the `Channel` before the first Step.
+1. SubscriptionStatuses which convey the Status of underlying `Subscription` resources that
+are created as part of this Sequence. It is an array and each Status corresponds to the Step number, so
+the first entry in the array is the `Subscription` which is created to wire the first channel to the
+first step in the `Steps` array.
+1. AddressStatus which is exposed so that Sequence can be used where Addressable can be used. Sending
+to this address will target the `Channel` which is fronting the first Step in the Sequence.
+
+
+## Examples
+
+For each of these examples below, we'll use
+[`CronJobSource`](https://knative.dev/docs/eventing/samples/cronjob-source/)
+as the source of events.
+
+We also use a very simple [transformer](https://github.com/vaikas-google/transformer) which
+performs very trivial transformation of the incoming events to demonstrate they have passed
+through each stage.
+
+### (Sequence with no reply (terminal last Step))[./samples/sequence/sequence-terminal/README.md)
+
+For the first example, we'll use a 3 Step `Sequence` that is wired directly into the `CronJobSource`.
+Each of the steps simply tacks on "- Handled by <STEP NUMBER>", for example the first Step in the
+`Sequence` will take the incoming message and append "- Handled by 0" to the incoming message.
+
+### [Sequence with reply (last Step produces output)](./samples/sequence/sequence-reply-to-event-display/README.md)
+
+For the next example, we'll use the same 3 Step `Sequence` that is wired directly into the `CronJobSource`.
+Each of the steps simply tacks on "- Handled by <STEP NUMBER>", for example the first Step in the
+`Sequence` will take the incoming message and append "- Handled by 0" to the incoming message.
+
+The only difference is that we'll use the `Subscriber.Spec.Reply` field to wire the output of the
+last Step to an event display pod.
+
+### [Chaining Sequences together](./samples/sequence/sequence-reply-to-sequence/README.md)
+
+For the next example, we'll use the same 3 Step `Sequence` that is wired directly into the `CronJobSource`.
+Each of the steps simply tacks on "- Handled by <STEP NUMBER>", for example the first Step in the
+`Sequence` will take the incoming message and append "- Handled by 0" to the incoming message.
+
+The only difference is that we'll use the `Subscriber.Spec.Reply` field to wire the output of the
+last Step to another `Sequence` that does the smae message modifications as the first pipeline (with
+different steps however).
+
+### [Using Sequence with Broker/Trigger model](./samples/sequence/sequence-with-broker-trigger/README.md)
+
+You can also create a Trigger which targets `Sequence`. This time we'll wire `CronJobSource` to send
+events to a `Broker` and then we'll have the `Sequence` emit the resulting Events back into the Broker
+so that the results of the `Sequence` can be observed by other `Trigger`s.
+
+
+
+