K
Q

How to access external SMTP server from within Kubernetes cluster with Istio Service Mesh

4/11/2019

I have a kubernetes cluster that has applications running in an Istio service mesh. In one application I am trying to send an email using SMTP. How do I set up Istio rules to allow my applications to use my external SMTP server?

Initially I was getting an exception "Could not connect to SMTP host: in-v3.mailjet.com, port: 587, response: -1." as detailed here. After visiting this site I realized I needed to provide egress rules which I did as per below

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: mailjet
spec:
  hosts:
  - "in-v3.mailjet.com"
  location: MESH_EXTERNAL
  ports:
  - number: 587
    name: tls
    protocol: TLS
  resolution: DNS
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: mailjet
spec:
  hosts:
  - "*.mailjet.com"
  tls:
  - match:
    - port: 587
      sni_hosts:
      - "*.mailjet.com"
    route:
    - destination:
        host: "*.mailjet.com"
        port:
          number: 587
      weight: 100

I am no longer getting the "Could not connect to SMTP host" exception but I am getting a SocketTieoutException

[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1487)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1378)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at java.lang.Thread.run(Thread.java:748)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55) Caused by: javax.mail.MessagingException: Exception reading response;
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)   nested exception is:
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  java.net.SocketTimeoutException: Read timed out
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:2460)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2187)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:740)
[0m[31m06:56:39,048 ERROR [stderr] (default task-55)  at javax.mail.Service.connect(Service.java:366)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at javax.mail.Service.connect(Service.java:246)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at javax.mail.Service.connect(Service.java:267)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at org.keycloak.email.DefaultEmailSenderProvider.send(DefaultEmailSenderProvider.java:138)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  ... 73 more
[0m[31m06:56:39,049 ERROR [stderr] (default task-55) Caused by: java.net.SocketTimeoutException: Read timed out
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.net.SocketInputStream.socketRead0(Native Method)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.net.SocketInputStream.read(SocketInputStream.java:171)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.net.SocketInputStream.read(SocketInputStream.java:141)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at com.sun.mail.util.TraceInputStream.read(TraceInputStream.java:126)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.io.BufferedInputStream.fill(BufferedInputStream.java:246)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at java.io.BufferedInputStream.read(BufferedInputStream.java:265)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at com.sun.mail.util.LineInputStream.readLine(LineInputStream.java:106)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:2440)
[0m[31m06:56:39,049 ERROR [stderr] (default task-55)  ... 79 more
[0m[31m06:56:39,049 ERROR [org.keycloak.services.resources.admin.RealmAdminResource] (default task-55) Failed to send email
 javax.mail.MessagingException: Exception reading response;
  nested exception is:
        java.net.SocketTimeoutException: Read timed out

What do I need to do to successfully send an email within a Kubernetes cluster with an Istio service mesh?

-- Khetho Mtembo
istio
kubernetes
mailjet
smtp

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1 Answer

4/11/2019

After comparing with Mesh-external service entry for an external MySQL instance I managed to get this working using TCP as per below. I tried TLS with the IP address but that did not work. It would be nice however if I did not have to specify the IP address

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: mailjet
spec:
  hosts:
  - in-v3.mailjet.com
  addresses:
  - 104.199.96.85/32
  ports:
  - name: tls
    number: 587
    protocol: tcp
  location: MESH_EXTERNAL
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: mailjet
spec:
  hosts:
  - in-v3.mailjet.com
  tcp:
  - match:
    - port: 587
    route:
    - destination:
        host: in-v3.mailjet.com
        port:
          number: 587 
---
-- Khetho Mtembo
Source: StackOverflow