The past month of work on Kernl has seen a lot of great infrastructure improvements as well as a few customer facing features that I’m pretty excited about.
Customer Facing Features
- Direct Uploads to AWS S3 – When Kernl was originally created all file uploads were stored directly on Kernl’s servers. As we grew, this became an unsustainable solution, so the process changed to just use Kernl’s servers as temporary holding space before putting the file on S3. This month we made this process even better by having files upload directly to S3. For you, this means faster uploads and less time waiting to get updates out to your customers.
- Expiring Purchase Codes – You can now create purchase codes that expire on a specific date. This allows you to sell your updates over time, instead of having to give them away for free for the life of the plugin or theme.
- Max Download Purchase Code Flag – You can configure a purchase code to only allow a certain number of update downloads. This will help resolve any issues with customers sharing purchase codes amongst themselves or across multiple installations.
- plugin_update_check.php Bug Fixes – There was an edge-case bug where some code in this file would collide with an old version of WP-Updates plugin update check file. This happens when a customer has your plugin and also has a really old version of somebody else’s plugin installed. This update takes care of that collision permanently.
- Client-side JS Errors – A few minor miscellaneous bug fixes were performed on the front-end of Kernl.
- MongoDB – The month started off with Kernl’s database moving to it’s own server. This was a temporary step that aimed to make the move to a highly available setup easier.
- Mongo Replica Sets – After the first MongoDB move, the next step was to make the setup highly available. Kernl now has 3 Mongo databases (1 master + 2 replicas). In the event that the master database goes down, Kernl automatically fails over to one of the replicas with no downtime.
- Memcache – Memcache was moved to it’s own server to make it easier to increase the number of items that Kernl caches over time. This piece of the setup doesn’t need to be highly available. If for some reason it goes down, Kernl will continue to operate fine.
- Nginx – Nginx is used by Kernl both as a front-door to the application as well as load balancer between the app servers. This was moved to it’s own server which allows it scale up when we need additional capacity. In the future (hopefully soon), we’ll use a floating IP address to give this portion of the infrastructure the ability to fail over to a backup Nginx server.
- Multiple App Servers – Kernl’s app servers can now scale horizontally. We’re currently running 3 app servers which Nginx load balances traffic to. This setup allows us to add app servers easily as our traffic grows.
- Automated Deployment – Kernl can now be deployed with a single command.
- Caching the repository list that you see when you set up CI builds.
- Get a rich text editor set up on the installation and description fields.
- Theme change logs.
- Wrap up infrastructure work.
- Sign in / Sign up with BitBucket & GitHub.
- Slack Integration.
- HipChat Integration.
Since last month I’ve been working hard on getting a few features out the door. They are:
- All new files are now hosted on S3 – Part of the work to make Kernl highly available is to get files hosted elsewhere. When you upload a new version to Kernl, or push a change via webhooks, the deliverable now lives on S3. Existing versions were a bit complicated, so thats going to be a task for May.
- SSL and domain renewed – The SSL cert and domain for Kernl were renewed this month. This should have been a completely transparent change.
- Editable version fields – For plugins, you can now edit a few fields on a version once it has been created. This was a pre-requisite for getting changelogs implemented nicely.
- Plugin changelog API – You can now programmatically add, get, and remove changelog entries from you plugins. Documentation on this feature is available at https://kernl.us/documentation/api#changelog-api and full examples are available at https://github.com/vital101/Kernl-API-Examples
- Plugin changelog tab – The changelog tab in the plugin detail update window is now populated automatically and looks like the wordpress.org version.
So whats on backlog for May?
- Moving the legacy version files to S3.
- Moving the database to its own server + adding a replica.
- Moving Memcache to its own server.
Over the past 4 months we’ve been making a lot of progress on many different fronts with Kernl. After 4 new features, 5 feature updates, 3 infrastructure changes, and numerous bug fixes, Kernl is better than ever. Check out the detailed info below, and leave a comment or reach out if you have questions.
- Purchase Code API – A long requested feature has been the ability to add and remove purchase codes from Kernl via an API. This has always been supported, but there wasn’t any documentation or examples of how to do it. We now have detailed documentation for the Purchase Code API available at https://kernl.us/documentation/api.
- WebHook Build Log – For customers using BitBucket and GitHub integration, it could be frustrating to figure why your build failed. To help with that, we added a WebHook Build Log on the continuous integration page. It can be found at https://kernl.us/app/#/dashboard/continuous-integration
- Envato Purchase Code Validation – Another often requested feature was the ability to validate against Envato purchase codes. You can read about how to use and enable this functionality at https://kernl.us/documentation#envato-purchase-code-validation.
- Caching – Since the beginning of the year, Kernl’s traffic has more than doubled and isn’t showing any signs of slowing down. To keep response times and server load down, update check results are now cached for 10 seconds. What this means for you is that after you upload a new version or make any changes in the ‘edit’ modal, Kernl will take a maximum of 10 seconds to reflect those changes on the update check API endpoints.
- PHP Update Check File Timeout – In the plugin_update_check.php and theme_update_check.php files that you include in your plugin and themes, the timeout value for fetching data from Kernl is set really high by default (10 seconds). If you want the update to fail fast in the event that Kernl is down, you can now configure this value using the remoteGetTimeout property. Depending on how close your client’s server are to Kernl and how fast Kernl responds, you could likely lower this value significantly. You should exercise caution using this though. The documentation has been updated here and here to reflect the change. You will also need to publish a new build with the updated PHP files.
- Email Notification Settings – You can now enable/disable email notifications from Kernl. There are two types: General and Build. General email notifications are all emails Kernl sends to you that aren’t build emails. Build notifications are the emails you receive when a webhook event from BitBucket or GitHub triggers a build. You can modify these settings in your profile.
- Failed Build Email Notifications – You will now receive an email notification when your BitBucket/GitHub webhook push fails to build in an unexpected way. For instance if the version number in your kernl.version file doesn’t follow semantic versioning, the build would fail and send you an email notification.
- Indeterminate Spinner for Version Uploads – Depending on the size of your deliverable and the speed of your connection, the Kernl interface didn’t give a lot of great feedback when you were uploading a file. An indeterminate spinner now shows while your file is being uploaded. Copy has also been updated to reflect that this action can take a little while.
- Filterable Select on Repository Select Drop Downs – When trying to select a repository for continuous integration, it could be a real pain if you had lots of repositories. A filterable select field is now in place that allows you to search large lists easily.
- Capacity Increases – In mid March we had about 4 minutes of downtime in the wee hours of the morning while we upgraded our server capacity. Current capacity should hold until we double or triple our traffic levels.
- Mandrill to SendGrid Migration – Since the beginning of Kernl we used Mandrill as our transactional email provider. As I’m sure some of you know, Mandrill sort of screwed it’s customers by making their free low-volume plan cost $30 per month. Since this isn’t really something we wanted (or needed) to pay for, we migrated to SendGrid.
- Apache to Nginx Migration – As our traffic numbers started to rise, Apache started to fall over on us. A migration to Nginx as our reverse-proxy was high in the backlog, so instead of tweaking Apache we just did a quick migration to Nginx. With the default configuration, load levels dropped from 1 – 1.5 to 0.3 – 07 with no configuration tweaking. *high five nginx*
- Multi-tier Server Architecture – Kernl started out as a fun side project. As a side project, keeping things simple as long as possible is almost always the right choice. Now that Kernl has a growing number of paying customers, and those customers have lots of paying customers, it’s time for Kernl’s server architecture to grow as well. Over the next month or two, we’ll be teasing apart Kernl’s current infrastructure to support horizontal scaling and automatic failover in case any node in the stack goes down.
- Better Change Log Support – The current change log support on Kernl is… meh, at best. A big goal for the next month or two is try and get better change log support out the door.
- Analytics – Having some insights into your clients has always been a goal of Kernl. Doing this efficiently and cost effectively is tough, but we’re 60% there already. Infrastructure work has a higher priority than this right now, but getting this out the door in the next few months is a priority.
- Bug Fixes – As always, bug fixes come first.
When you log in to Kernl, near the top you see a few boxes with general stats in them. The ‘update pings’ stat is going to be off for awhile until the new analytics work is complete. This is due to the naive way that we currently calculate update pings not being compatible with how we cache. The ‘update downloads’ stat is still accurate since we do not cache the download endpoints.