Real-time collaborative markdown editing with CodiMD

Since CodiMD is not built upon the WOPI Protocol (as it happens with Collabora Code), an additional component needs to be deployed alongside the WOPI Server to fill this gap between the application provider and the application itself.

Deploying and configuring the WOPI Bridge

Bridging that gap will be the job for the WOPI Bridge: a sidecar container to translate CodiMD API calls into file operations and vice-versa.

A small configuration patch needs to be applied to an IOP deployment to enable this new component and plug it into the WOPI Server application providers. The main parameters to configure being:

  • The WOPI Server configuration needs to be extended to connect the WOPI Bridge via the config.appProviders.wopibridgeurl parameter.
  • CODIMD_INT_URL connects the bridge and the CodiMD service running inside the cluster.
  • The CODIMD_EXT_URL will be used to generate the URL presented to the end-user when open-file-in-app-provider is called in reva.
      wopibridgeurl: https://<hostname.domain.tld>/wopib
    enabled: true
      APP_ROOT: /wopib
      CODIMD_EXT_URL: https://<hostname.domain.tld>/codimd
      CODIMD_INT_URL: http://meshapps-codimd
      enabled: true
      annotations: nginx "true"
      hostname: <hostname.domain.tld>
      path: /wopib

Note: depending on the ingress controller path-matching policies, you might experience routing issues between requests addressed to the WOPI Server and the Bridge (as their path-s can collide). Review your controller’s path priority policies and use an alternative path in case that could be an issue.

Refer to the chart’s documentation for a complete reference of all the configuration options available. Once ready, the release can be patched with the following command:

helm upgrade -i iop sciencemesh/iop --reuse-values -f wopibridge.yaml

Deploying CodiMD through the sciencemesh/meshapps chart

To deploy the application, the sciencemesh/meshapps umbrella chart already provides a handful of defaults for a lightweight and “stateless” CodiMD installation:

  • Based on a patched codimd container image ( with some extra features to enable this workflow.
  • Enables anonymous access, viewing, and editing.
  • Disables some defaults from the vanilla CodiMD installation:
    • The registration and authentication mechanisms.
    • The image store and PostgreSQL disk persistence, as it will rely on the IOP Storage Providers to read and write all the content, including the attached pictures. The CodiMD pods will maintain ephemeral, in-memory persistence for the time being for its internal use.

The only key aspects left for the user to configure are:

  • The location for the CMD_SAVE_WEBHOOK env. variable: pointing to the /save endpoint of the WOPI Bridge, that will be called when a document is closed.

Note: this webhook needs to be served over HTTPS to work with CodiMD, hence the need to use its external FQDN.

  • A combination of CMD_URL_PATH and an ingress rewrite annotation to strip the base URL (/codimd) from external requests.
  • A postgresql.postgresqlPassword to protect the database that will be used as a temporary cache for the notes.

Note: alternatively, MariaDB can be used instead of PostgreSQL when deploying CodiMD. Refer to the chart’s parameters for all the options available.

Here’s an example codimd.yaml combining all these:

  enabled: true
      domain: <hostname.domain.tld>
      protocolUseSSL: true
      CMD_SAVE_WEBHOOK: https://<hostname.domain.tld>/wopib/save
      CMD_URL_PATH: codimd
    postgresqlPassword: <password>
    annotations: nginx /$2 "true"
    enabled: true
    - host: <hostname.domain.tld>
      - /codimd(/|$)(.*)

After this file is defined, it’s just a matter of upgrading the chart while reusing any previous values, as follows:

helm upgrade -i meshapps sciencemesh/meshapps --reuse-values -f codimd.yaml

Registering the MIME-types and custom file extensions on your Storage Provider

There are three extra steps left for the IOP to integrate with this application. These will require modifying the Revad configuration to identify the files that will be opened by CodiMD:

  1. Append a new set of rules in the appregistry service running on the gateway to identify these files:
"text/markdown" = "iop-gateway:19000"
"application/compressed-markdown" = "iop-gateway:19000"
  1. Optionally, the wopibridge URL might be inserted as part of the appprovider settings on the gateway; to generate a shorter and user-friendlier URL when opening from the reva cli.
wopibridgeurl = "https://<hostname.domain.tld>/wopib"
  1. Add a mapping between the custom .zmd file extension, used to package markdown files together with uploaded images, and the application/compressed-markdown MIME-type used to identify these files. This needs to be done on all the running storageprovider services: whether using a standalone deployment or one based on multiple, decoupled storage providers.
".zmd" = "application/compressed-markdown"
Last modified November 4, 2020: Fix: changes from PR reviews (e0658c4)