Add SMTP server email notification example (#386)

* add email notification example

* add workaround for passing possible files

* Update send-email.py

samples/exit-handler-email/README.md

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+# Email notification via SMTP server
+
+This pipeline demonstrates how to use the exit handler in the Kubeflow pipeline to send email notifications via the SMTP server. The exit component is based on the [send-email](https://github.com/tektoncd/catalog/tree/master/task/sendmail/0.1) Tekton catalog task.
+
+## prerequisites
+- Install [KFP Tekton prerequisites](/samples/README.md)
+- Host or subscribe to a [SMTP server](https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol)
+
+## Instructions
+1. Modify [secret.yaml](secret.yaml) with the following information. Then create the secret under the Kubeflow namespace (for single user) or User namespace (for multi-user).
+
+* **url**: The IP address of the SMTP server
+
+* **port**: The port number of the SMTP server
+
+* **user**: User name for the SMTP server
+
+* **password**: Password for the SMTP server
+
+* **tls**: The tls enabled or not ("True" or "False")
+
+    ```shell
+    NAMESPACE=kubeflow
+    kubectl apply -f secret.yaml -n ${NAMESPACE}
+    ```
+
+2. Create a shared persistent volume claim for passing optional attachment.
+
+    ```shell
+    kubectl apply -f pvc.yaml -n ${NAMESPACE}
+    ```
+
+3. Compile the send-email pipeline using the compiler inside the python code. The kfp-tekton SDK will produce a Tekton pipeline yaml definition in the same directory called `email_pipeline.yaml`.
+    ```shell
+    # Compile the python code
+    python send-email.py
+    ```
+
+Then, upload the `email_pipeline.yaml` file to the Kubeflow pipeline dashboard with Tekton Backend to run this pipeline.
+
+### Pipeline parameters
+
+* **server**: The name of the secret that has the SMTP server information
+
+* **subject**: Email subject (plain text)
+
+* **body**: Email body (plain text)
+
+* **sender**: Email sender email address
+
+* **recipients**: Email recipients email addresses (comma space delimited)
+
+* **attachment_path**: Optional attachment path from the previous path

samples/exit-handler-email/component.yaml

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+name: sendmail
+description: |
+  This task sends a simple email to receivers via SMTP server
+inputs:
+  - {name: server, description: 'secret name for SMTP server information (url, port, password)'}
+  - {name: subject, description: 'plain text email subject'}
+  - {name: body, description: 'plain text email body'}
+  - {name: sender, description: 'sender email address'}
+  - {name: recipients, description: 'recipient email addresses (space delimited list)'}
+  - {name: attachment_path, description: 'email attachment file path'}
+implementation:
+  container:
+    image: docker.io/library/python:3.8-alpine@sha256:c31682a549a3cc0a02f694a29aed07fd252ad05935a8560237aed99b8e87bf77 #tag: 3.8-alpine
+    command:
+    - python3
+    - -u
+    - -c
+    - |
+      #!/usr/bin/env python3
+      import argparse
+      _parser = argparse.ArgumentParser('sendmail inputs')
+      _parser.add_argument("--server", type=str, required=True)
+      _parser.add_argument("--subject", type=str, required=True)
+      _parser.add_argument("--body", type=str, required=True)
+      _parser.add_argument("--sender", type=str, required=True)
+      _parser.add_argument("--recipients", type=str, required=True)
+      _parser.add_argument("--attachment_path", type=str, default='')
+      _parsed_args = _parser.parse_args()
+
+      import smtplib, ssl, os
+      from pathlib import Path
+      from email.mime.multipart import MIMEMultipart
+      from email.mime.base import MIMEBase
+      from email.mime.text import MIMEText
+      from email.utils import COMMASPACE, formatdate
+      from email import encoders
+      port = os.getenv('PORT')
+      smtp_server = os.getenv('SERVER')
+      sender_email = "$(params.sender)"
+      receiver_emails = "$(params.recipients)"
+      user = os.getenv('USER')
+      password = os.getenv('PASSWORD')
+      tls = os.getenv('TLS')
+      path = _parsed_args.attachment_path
+
+      msg = MIMEMultipart()
+      msg['From'] = sender_email
+      msg['To'] = receiver_emails
+      msg['Subject'] = "$(params.subject)"
+      msg.attach(MIMEText("$(params.body)"))
+      if tls == 'True':
+          context = ssl.create_default_context()
+          server = smtplib.SMTP_SSL(smtp_server, port, context=context)
+      else:
+          server = smtplib.SMTP(smtp_server, port)
+      if password != '':
+          server.login(user, password)
+      part = MIMEBase('application', "octet-stream")
+      with open(path, 'rb') as file:
+          part.set_payload(file.read())
+      encoders.encode_base64(part)
+      part.add_header('Content-Disposition',
+                      'attachment; filename="{}"'.format(Path(path).name))
+      msg.attach(part)
+      for receiver in receiver_emails.split(' '):
+          server.sendmail(sender_email, receiver, msg.as_string())
+      server.quit()
+    args: [
+      --server, {inputValue: server},
+      --subject, {inputValue: subject},
+      --body, {inputValue: body},
+      --sender, {inputValue: sender},
+      --recipients, {inputValue: recipients},
+      --attachment_path, {inputValue: attachment_path},
+    ]

samples/exit-handler-email/pvc.yaml

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+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: shared-pvc
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi

samples/exit-handler-email/secret.yaml

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+kind: Secret
+apiVersion: v1
+metadata:
+  name: server-secret
+stringData:
+  url: "smtp.server.com"
+  port: "25"
+  user: "userid"
+  password: "password"
+  tls: "False"

samples/exit-handler-email/send-email.py

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+# Copyright 2020 kubeflow.org
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from kfp import dsl
+import kfp
+from kubernetes import client as k8s_client
+from kfp.components import func_to_container_op
+from kfp import onprem
+import os
+
+
+@func_to_container_op
+def write_file(output_text_path: str):
+    with open(output_text_path, 'w') as writer:
+        writer.write('hello world')
+
+
+def env_from_secret(env_name, secret_name, secret_key):
+    return k8s_client.V1EnvVar(
+        name=env_name,
+        value_from=k8s_client.V1EnvVarSource(
+            secret_key_ref=k8s_client.V1SecretKeySelector(
+                name=secret_name,
+                key=secret_key
+            )
+        )
+    )
+
+
+email_op = kfp.components.load_component_from_file('component.yaml')
+# pvc mount point has to be string, not pipeline param.
+attachment_path = "/tmp/data"
+
+
+@dsl.pipeline(
+    name='email_pipeline',
+    description='email pipeline'
+)
+def email_pipeline(
+    server="server-secret",
+    subject="Hi, again!",
+    body="Tekton email",
+    sender="[email protected]",
+    recipients="[email protected], [email protected]",
+    attachment_filepath="/tmp/data/output.txt"
+):
+    email = email_op(server=server,
+                     subject=subject,
+                     body=body,
+                     sender=sender,
+                     recipients=recipients,
+                     attachment_path=attachment_filepath)
+    email.add_env_variable(env_from_secret('USER', '$(params.server)', 'user'))
+    email.add_env_variable(env_from_secret('PASSWORD', '$(params.server)', 'password'))
+    email.add_env_variable(env_from_secret('TLS', '$(params.server)', 'tls'))
+    email.add_env_variable(env_from_secret('SERVER', '$(params.server)', 'url'))
+    email.add_env_variable(env_from_secret('PORT', '$(params.server)', 'port'))
+    email.apply(onprem.mount_pvc('shared-pvc', 'shared-pvc', attachment_path))
+
+    with dsl.ExitHandler(email):
+        write_file_task = write_file(attachment_filepath).apply(onprem.mount_pvc('shared-pvc', 'shared-pvc', attachment_path))
+
+
+if __name__ == '__main__':
+    from kfp_tekton.compiler import TektonCompiler
+    TektonCompiler().compile(email_pipeline, 'email_pipeline.yaml')