On joining Twitter

#lifeattwitter

I’ve been settling into my new role at Twitter over the past few months. I’m a Developer Advocate on the Developer and Platform Relations team, based out of a beautiful new London office we opened a few weeks ago.

It has been fantastic so far, learning about the Twitter platform and starting to work with partners and developers trying out the API. I’ve been a small part of a couple of feature launches which I’m incredibly proud to have helped with. We’ve run our first Twitter UK community Friday4Good which I helped to plan. As well as that, I’ve spoken about the Twitter API in the context of the Internet of Things at both Techsylvania in Cluj-Napoca, Romania, and more recently at GOTO in Amsterdam.

In a recent post over on the Twitter Developer blog I’ve written a little bit more about why I was excited to join this amazing team.

Developers embraced Twitter early on, seeing it as an open platform that could enrich apps with contextual information and provide access to public conversations, sentiments and signals. Twitter enabled developers to create cool, new and fun experiences that were never before possible.

Oh, and if you want to follow what we are up to as a team, you should keep an eye on the @TwitterDev and @TwitterAPI handles, as well as @TwitterUK for more UK-centric news!

Latest interviews, and upcoming speaking schedule

Just a quick note to comment that I’ve added links to two recent interviews on the media section of my Speaking and Media page:

I’ve been at QCon London this week and also did a couple more interviews, again one on each of these topics – it may take slightly longer for these to emerge, though. Let me know if you have any feedback on these, always interesting to hear!

It may seem hard to believe, and indeed looking back at my schedule it hardly seems it, but I’ve been avoiding too many speaking gigs since an annoying incident back in December and a need to take a break! Coming up in the next few months, apart from the job change (!), I’m back on the road and I’ll be speaking at the following events:

#newjob

In late 2011, I was contacted by a very charming, smart and persuasive French gentleman who spoke of clouds, platform-as-a-service, and polyglot programming. It took him and his team a couple of months to get me thinking seriously about a career change, after 10 great years at IBM. I’d spent that period with “Big Blue” coding in Java and C, and primarily focused on enterprise application servers, message queueing, and integration – and yet the lure of how easy vmc push[1] made it for me to deploy and scale an app was astounding! Should I make the transition to a crazy new world? Over Christmas that year, I decided it would be a good thing to get in on this hot new technology and join VMware as Developer Advocate on the Cloud Foundry team. I joined the team early in 2012.

The Cloud Foundry adventure has been amazing. The day after I joined the team, the project celebrated its first anniversary, and we announced the BOSH continuous deployment tool; I spent much of that first year with the team on a whirlwind of events and speaking engagements, growing the community. The Developer Relations team that Patrick Chanezon and Adam Fitzgerald put together was super talented, and it was brilliant to be part of that group. Peter, Chris, Josh, Monica, Raja, Rajdeep, Alvaro, Eric, Frank, Tamao, Danny, Chloe, D, Giorgio, friends in that extended team… it was an honour.

A year after I joined, VMware spun out Cloud Foundry, SpringSource and other technologies into a new company, Pivotal – headed up by Paul Maritz. I’ve been privileged to work under him, Rob Mee at Pivotal Labs, and most closely, my good friend James Watters on the Cloud Foundry team. I’ve seen the opening of our new London offices on Old Street, welcomed our partners and customers into that unique collaborative and pairing environment, and observed an explosion of activity and innovation in this space. We launched an amazing productJames Bayer heads up a remarkable group of technologists working full-time on Cloud Foundry, and it has been a pleasure to get to know him and his team. Most recently, I’ve loved every minute working with Cornelia, Ferdy, Matt, Sabha and Scott (aka the Platform Engineering team), another talented group of individuals from whom I’ve learned much.

Over the course of the last two years I’ve seen the Platform-as-a-Service space grow, establish itself, and develop – most recently resulting in my recent talk at bcs Oxfordshire:

Last week, we announced the forthcoming Cloud Foundry Foundation – and one could argue that as a community and Open Source kinda guy, this was the direction I’ve helped to move things in the past two years, although I can claim no credit at all for the Foundation announcement itself. I’ve certainly enjoyed hosting occasional London Cloud Foundry Community meetups and drinks events (note, next London PaaS User Group event has 2 CF talks!), and I’ve made some great friends locally and internationally through the ongoing growth of the project. I’m proud of the Platform event we put on last year, I think the upcoming Cloud Foundry Summit will be just as exciting, and I’m happy to have been a part of establishing and growing the CF community here in Europe.

Cloud Foundry is THE de facto Open Source PaaS standard, the ecosystem is strong and innovative, and that has been achieved in a transparent and collaborative way, respectful to the community, in a good-natured way in the face of competition. Rest assured that I’ll continue to watch the project and use PaaSes which implement it (I upgraded to a paid Pivotal Web Services account just this past week, I tried BlueMix, and I’m an ongoing fan of the Anynines team).

There are many missing shout-outs here… you folks know who you are, and should also know that I’ve deeply enjoyed learning from you and working with you. Thank you, Pivotal team! I do not intend to be a stranger to the Bay Area! In my opinion, Pivotal is positioned brilliantly in offering an end-to-end mobile, agile development, cloud platform and big data story for the enterprise. I look forward to continuing the conversations around that in the next couple of weeks.

[...]

What happens after “the next couple of weeks”? Well, this is as good time as any (!) to close that chapter, difficult though it is to leave behind a team I’ve loved working with, on a product and project that is undoubtedly going to continue to be fantastically successful this year and beyond. So, it is time to announce my next steps, which may or may not be clear from the title of this post… :-)

Joining Twitter!

I joined Twitter as a user on Feb 21 2007. On the same day, seven years later, I accepted a job offer to go and work with the Twitter team as a Developer Advocate, based in London.

If you’ve been a long-term follower of mine either here on this blog, or on Twitter, or elsewhere, you’ll know that Twitter is one of my favourite tools online. It has been transformational in my life and career, and it changed many of my interactions. True story: between leaving IBM and joining VMware I presented at Digital Bristol about social technologies, and I was asked, which one I would miss the most if it went away tomorrow; the answer was simple: Twitter. As an Open Source guy, too, I’ve always been impressed with Twitter’s contributions to the broader community.

I couldn’t be more #excited to get started with the Twitter Developer Relations team in April!

Follow me on Twitter – @andypiper – to learn more about my next adventure…

[1] vmc is dead, long live cf!

Getting inside Cloud Foundry for debug (and profit?)

I’ve recently started to play with some more of the internals of Cloud Foundry than I’ve been used to. This has been made much easier by the advent of bosh-lite, a system for deploying all of Cloud Foundry’s components using the bosh continuous deployment and configuration tool, into a single virtual machine. bosh-lite achieves this by using containers (Cloud Foundry’s own Warden container technology) to “emulate” the individual VMs where jobs would run in a full distributed topology.

bosh-lite has actually been around for a number of months now, but I’ve not had much of a chance to play with it until recently. This is partly due to other activities, and also that my earlier attempts to get an environment up-and-running were hampered by lack of memory. It should be possible to run bosh-lite with a Cloud Foundry deployment in 8Gb of RAM, but given my laptop’s configuration and the amount of other stuff I’m usually running, that was never comfortable – now I’m rocking 16Gb in a MacBook Pro, things are running more smoothly.

I don’t intend to spend this post documenting how to install bosh-lite and get a running single-node Cloud Foundry system. I followed the instructions in the README and things went well on this occasion. One suggestion that I’d make is if you can, to use VMware Fusion (assuming like me, you’re on OS X) and the Vagrant provider for Fusion, seems quite a lot better than Virtualbox. If you do, don’t forget to pass the --provider=vmware_fusion flag when you bring your Vagrant image up (that’s something I do usually forget). One other little thing to mention is that after I started the bosh deployment, the bosh CLI gem timed out and returned a REST error – but the deployment process itself continued without any issues, and I was able to use bosh tasks to check in on the progress. If you are interested, I used cf-release-157 this time around.

Once I had my minty-fresh Cloud Foundry running, I deployed Matt Stine’s handy, simple, Ruby scale demo app and pushed up the number of instances.

So what’s the point of this post? I want to mention two things…

Note: this is not about debugging applications on Cloud Foundry in general – a PaaS is an opinionated system and you generally shouldn’t need to poke around inside it like this. This is for debugging the Cloud Foundry runtime itself, or aspects that might run inside a container. Oh, and I’m sorry about the formatting of some of the shell output examples below!

Peeking at NATS traffic

NATS is the internal, lightweight message bus that Cloud Foundry components use to talk to one another. I’d read blog posts from Cornelia and from Dr Nic about digging into this before.

First of all, I used bosh ssh to access the NATS host:

$ bosh ssh
1. ha_proxy_z1/0
2. nats_z1/0
3. postgres_z1/0
4. uaa_z1/0
5. login_z1/0
6. api_z1/0
7. clock_global/0
8. api_worker_z1/0
9. etcd_leader_z1/0
10. hm9000_z1/0
11. runner_z1/0
12. loggregator_z1/0
13. loggregator_trafficcontroller_z1/0
14. router_z1/0
Choose an instance: 2
Enter password (use it to sudo on remote host): ***
Target deployment is `cf-warden'

Setting up ssh artifacts

Director task 9

Task 9 done
Starting interactive shell on job nats_z1/0

So now I’m on the NATS host – now what? well, strictly speaking I didn’t need to login to that host / container, since of course, as a messaging system, the other hosts can connect to it anyway. The reason I wanted to login to it was to find out how NATS was configured.

$ ps -ef | grep nats
root 1470 1 0 12:09 ? 00:00:12 /var/vcap/packages/gnatsd/bin/gnatsd -V -D -c /var/vcap/jobs/nats/config/nats.conf

$ more /var/vcap/jobs/nats/config/nats.conf

net: "10.244.0.6"
port: 4222

pid_file: "/var/vcap/sys/run/nats/nats.pid"
log_file: "/var/vcap/sys/log/nats/nats.log"

authorization {
user: "nats"
password: "nats"
timeout: 15
}

cluster {
host: "10.244.0.6"
port: 4223

authorization {
user: "nats"
password: "nats"
timeout: 15
}

routes = [

]
}

From this, I can see that NATS is listening on IP 10.244.0.6, port 4222 (the NATS default), and that it is configured for username/password authentication. Handy to know!

I borrowed a little script from Dr Nic, but needed to modify it slightly to talk to authenticated NATS (his original script assumed there was no auth in place):

[update - Dr Nic has provided a more convenient method to do this, in the comments below - check out nats-sub - but this works, as well]

$ ./nats-all.sh
Msg received on [router.register] : '{"host":"10.244.0.134","port":8080,"uris":["login.10.244.0.34.xip.io"],"tags":{"component":"login"},"index":0,"private_instance_id":"e6194fe8-4910-4cb1-9f7c-d5ee7ff3f36b"}'
Msg received on [router.register] : '{"host":"10.244.0.130","port":8080,"uris":["uaa.10.244.0.34.xip.io"],"tags":{"component":"uaa"},"index":0,"private_instance_id":"7713dd5b-3613-41a6-9c67-c48f22a769b4"}'
Msg received on [router.register] : '{"dea":"0-1ba3459ea4cd406db833c1d188a78c02","app":"b8550851-37a0-4bd5-bdce-1d787b087887","uris":["andyp.10.244.0.34.xip.io"],"host":"10.244.0.26","port":61021,"tags":{"component":"dea-0"},"private_instance_id":"b52dfd91d68144cabb14b6c7bae77daae8b493acf1354c99941d49772a1f61fb"}'
Msg received on [router.register] : '{"dea":"0-1ba3459ea4cd406db833c1d188a78c02","app":"b8550851-37a0-4bd5-bdce-1d787b087887","uris":["andyp.10.244.0.34.xip.io"],"host":"10.244.0.26","port":61025,"tags":{"component":"dea-0"},"private_instance_id":"090f5c5aeee94fdfb4a4e0f0afde2553480dcd97c018431db37b4dffdc80fde4"}'
Msg received on [router.register] : '{"dea":"0-1ba3459ea4cd406db833c1d188a78c02","app":"b8550851-37a0-4bd5-bdce-1d787b087887","uris":["andyp.10.244.0.34.xip.io"],"host":"10.244.0.26","port":61028,"tags":{"component":"dea-0"},"private_instance_id":"92e10af77b274836a3f54373c9b7feee025c5b72f41a4c4982bde97d241ebd5b"}'
Msg received on [router.register] : '{"dea":"0-1ba3459ea4cd406db833c1d188a78c02","app":"b8550851-37a0-4bd5-bdce-1d787b087887","uris":["andyp.10.244.0.34.xip.io"],"host":"10.244.0.26","port":61039,"tags":{"component":"dea-0"},"private_instance_id":"86edf0c0a7f84f04b52693b489ad93b7f857f77271b84d568d8f5600b34f7054"}'
Msg received on [router.register] : '{"host":"10.244.0.26","port":34567,"uris":["8b24c0a7d28f4e03aa028a3dc89fb8c3.10.244.0.34.xip.io"],"tags":{"component":"directory-server-0"}}'
Msg received on [dea.advertise] : '{"id":"0-1ba3459ea4cd406db833c1d188a78c02","stacks":["lucid64"],"available_memory":23296,"available_disk":22528,"app_id_to_count":{"b8550851-37a0-4bd5-bdce-1d787b087887":10},"placement_properties":{"zone":"default"}}'
Msg received on [staging.advertise] : '{"id":"0-1ba3459ea4cd406db833c1d188a78c02","stacks":["lucid64"],"available_memory":23296}'
Msg received on [dea.heartbeat] : '{"droplets":[{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"d92d3c0c43ce4b6981e443e5c2064580","index":0,"state":"RUNNING","state_timestamp":1392639135.9526377},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"898e632697e246de9cf6b7330444227c","index":1,"state":"RUNNING","state_timestamp":1392639136.3117783},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"56d023e374aa49d88720daabac58e862","index":2,"state":"RUNNING","state_timestamp":1392639135.2225387},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"f11d86a7f4ad47f1ad554ae1b087d5f6","index":3,"state":"RUNNING","state_timestamp":1392639136.1042},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"c9e6de77f0484e6cae47f73ad6ca778a","index":4,"state":"RUNNING","state_timestamp":1392639135.9426212},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"924c387fc33444289b2db2762eefac42","index":5,"state":"RUNNING","state_timestamp":1392639135.940636},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"69866b260b1a49a09c03e178c4add2c5","index":6,"state":"RUNNING","state_timestamp":1392639135.944143},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"94bc605505d94dc1832e55bf2f671a99","index":7,"state":"RUNNING","state_timestamp":1392639135.4456258},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"8420df9bbe64456385dfa91285641ba4","index":8,"state":"RUNNING","state_timestamp":1392639135.9456131},{"cc_partition":"default","droplet":"b8550851-37a0-4bd5-bdce-1d787b087887","version":"a420d371-0816-4baf-9649-4e21255a66a4","instance":"ed9ad14f6599494c96f90296c59e6041","index":9,"state":"RUNNING","state_timestamp":1392639135.938359}],"dea":"0-1ba3459ea4cd406db833c1d188a78c02"}'
Msg received on [router.register] : '{"host":"10.244.0.10","port":8080,"uris":["loggregator.10.244.0.34.xip.io"]}'
Msg received on [router.register] : '{"host":"10.244.0.138","port":9022,"uris":["api.10.244.0.34.xip.io"],"tags":{"component":"CloudController"},"index":0,"private_instance_id":null}'
Msg received on [router.register] : '{"host":"10.244.0.134","port":8080,"uris":["login.10.244.0.34.xip.io"],"tags":{"component":"login"},"index":0,"private_instance_id":"e6194fe8-4910-4cb1-9f7c-d5ee7ff3f36b"}'

Warden containers and shells

Cloud Foundry’s native container technology is called Warden. When an application is deployed, Cloud Foundry starts up a Warden container based on the limits assigned in terms of memory etc, and the applications run inside that. How can you get “inside” the container to see what is going on?

Well, there are a couple of techniques. Cloud Foundry Loggregator provides streaming access to the standard application logs (stdout/stderr) via the cf logs command. Another option is James Bayer’s cool websocket-based method for getting access to the container. Yet another option is Warden’s own shell, wsh. This does assume you can access the DEA machine with ssh, however.

wsh doesn’t seem to be very well documented, although I knew Cornelia had played around with it – see her excellent blog post on troubleshooting CF and applications, including a great flowchart / graphic suggesting different techniques.

Here’s the secret sauce:

1. Login to the DEA VM (called “runner_z1/0″ in the list provided by bosh ssh).

2. Identify your Warden container… there are a lot showing below, but I happen to know that these are several instances of the same app. The important part is the instance-17ij46hadt2 – the second part or that value maps to the location of the container’s private space on disk.

$ ps -ef | grep warden
root        49    42  1 11:41 ?        00:00:41 /var/vcap/bosh/bin/ruby /var/vcap/bosh/bin/bosh_agent -c -I warden -P ubuntu
root      5390 32634  0 12:12 ?        00:00:00 /var/vcap/data/packages/warden/38.1/warden/src/oom/oom /tmp/warden/cgroup/memory/instance-17ij46hadss
root      5503 32634  0 12:12 ?        00:00:00 /var/vcap/data/packages/warden/38.1/warden/src/oom/oom /tmp/warden/cgroup/memory/instance-17ij46hadsu
root      5697 32634  0 12:12 ?        00:00:00 /var/vcap/data/packages/warden/38.1/warden/src/oom/oom /tmp/warden/cgroup/memory/instance-17ij46hadt3
root      6779 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadsu/bin/iomux-spawn /var/vcap/data/warden/depot/17ij46hadsu/jobs/58 /var/vcap/data/warden/depot/17ij46hadsu/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadsu/run/wshd.sock --user vcap /bin/bash
root      6780  6779  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadsu/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadsu/run/wshd.sock --user vcap /bin/bash
root      6784 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadsu/bin/iomux-link -w /var/vcap/data/warden/depot/17ij46hadsu/jobs/58/cursors /var/vcap/data/warden/depot/17ij46hadsu/jobs/58
root      6930 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadss/bin/iomux-spawn /var/vcap/data/warden/depot/17ij46hadss/jobs/59 /var/vcap/data/warden/depot/17ij46hadss/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadss/run/wshd.sock --user vcap /bin/bash
root      6931  6930  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadss/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadss/run/wshd.sock --user vcap /bin/bash
root      6934 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadss/bin/iomux-link -w /var/vcap/data/warden/depot/17ij46hadss/jobs/59/cursors /var/vcap/data/warden/depot/17ij46hadss/jobs/59
root      6950 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadt3/bin/iomux-spawn /var/vcap/data/warden/depot/17ij46hadt3/jobs/60 /var/vcap/data/warden/depot/17ij46hadt3/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadt3/run/wshd.sock --user vcap /bin/bash
root      6955  6950  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadt3/bin/wsh --socket /var/vcap/data/warden/depot/17ij46hadt3/run/wshd.sock --user vcap /bin/bash
root      6960 32634  0 12:12 ?        00:00:00 /var/vcap/data/warden/depot/17ij46hadt3/bin/iomux-link -w /var/vcap/data/warden/depot/17ij46hadt3/jobs/60/cursors /var/vcap/data/warden/depot/17ij46hadt3/jobs/60
vcap     23713 16807  0 12:26 pts/0    00:00:00 grep --color=auto warden
root     32634     1  0 11:52 ?        00:00:09 ruby /var/vcap/data/packages/warden/38.1/warden/vendor/bundle/ruby/1.9.1/bin/rake warden:start[/var/vcap/jobs/dea_next/config/warden.yml]

3. Head over to the directory for your chosen Warden instance:

$ cd /var/vcap/data/warden/depot/17ij46hadt2

4. Notice that the Warden containers are running as root. If you run wsh now as an unprivileged user, you’ll get a connect: Permission denied error. Time to switch to root, and then run wsh specifying the command to run inside the shell, as a parameter:

$ sudo su -
# cd /var/vcap/data/warden/depot/17ij46hadt2
# bin/wsh /bin/bash

5. At this point, we’re inside the Warden container with a bash shell, and all commands are scoped inside it. So, let’s take a look at what is running:

root@17ij46hadt2:~# ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 12:12 ?        00:00:00 wshd: 17ij46hadt2
vcap        29     1  0 12:12 ?        00:00:00 /bin/bash
vcap        31    29  0 12:12 ?        00:00:00 ruby /home/vcap/app/vendor/bundle/ruby/1.9.1/bin/rackup config.ru -p 61031
vcap        32    31  0 12:12 ?        00:00:00 /bin/bash
vcap        33    31  0 12:12 ?        00:00:00 /bin/bash
vcap        34    32  0 12:12 ?        00:00:00 tee /home/vcap/logs/stdout.log
vcap        35    33  0 12:12 ?        00:00:00 tee /home/vcap/logs/stderr.log
root        39     1  0 12:27 pts/0    00:00:00 /bin/bash
root        52    39  0 12:27 pts/0    00:00:00 ps -ef

This is our Ruby app, running on port 61031, and we can see the logs being written as well.

Hopefully this is useful information for folks wanting to dig around inside bosh-lite and a running Cloud Foundry system!

A little bit of Spring and MQTT

I’ve been involved with Spring (the Java framework, not the season…) for a couple of years now – since I joined VMware in 2012 through the former SpringSource organisation in the UK – and I’ve remained “involved” with it through my transition to Pivotal and the framework’s evolution into Spring 4 / Spring.IO under Pivotal’s stewardship.

To be clear, although I’ve been a “Java guy” / hacker through my time at IBM, I have never been a hardcore JEE coder, and my knowledge of Spring itself has always been limited. My good buddy Josh (MISTER Spring, no less) has done his best to encourage me, I briefly played with Spring Shell last year with @pidster, and the brilliant work done by the Spring Boot guys has been helpful in making me look at Spring again (I spoke about Boot – very briefly, as a newcomer to it – at the London Java Community unconference back in November).

Taking all of that on board, then, I’m still an absolute Spring n00b. I recognise a lot of the benefits, I see the amazing work that has gone into Spring 4, and I’m excited by the message and mission of the folks behind the framework. I would say that though… wouldn’t I? :-)

[considering this is my first blog post in a while, I'm taking a while to get past the preamble...]

This week, I chose to flex my coding muscles (!) with a quick diversion into Spring Integration. With a long history in WebSphere Integration back in my IBM days, this was both something of return to my roots, and also a learning experience!

With the new Spring.IO website (written with Spring, and hosted on Pivotal Web Services Cloud Foundry, fact fans!), the Spring team introduced the new Spring Guides – simple and easy-to-consume starter guides to the different technologies available in the Spring family. I knew that the team had added MQTT support via Eclipse Paho, so I thought I’d take a look at how I could modify a Spring Integration flow to take advantage of MQTT.

Incidentally, there’s complete reference documentation on the MQTT support, which is helpful if you’re already familiar with how Spring Integration works.

The resulting simple project is on Github.

Once I’d figured out that it is useful to ensure the latest versions of the various modules are listed as dependencies in the build.gradle file, it wasn’t too hard to adapt the Guide sample. In the example, the docs lead a developer through creating a new flow which searches Twitter and then passes tweets through a transformer (simply flattening the tweet sender and body into a single line of text), into an outbound file adapter.

The bulk of the changes I made were in the integration.xml file. I wanted to replace the file output with the tweets being published to an MQTT topic. To do that, I added the int-mqtt XML namespace information to the file, and configured an outbound-channel-adapter. It was also necessary to add a clientFactory bean configuration for a Paho MQTT connection. You’ll notice that, by default, my example posts results to the test broker at Eclipse (iot.eclipse.org port 1883 – an instance of mosquitto for public testing). Full information on how to build and test the simple example can be found in the project README file.

Thanks to my colleague Gary Russell for helping me to figure out a couple of things, as I was a Spring Integration newcomer!