Browsing

A user of a centralized social network sees it as one big website. He opens this site in a web browser and uses the site’s UI to surf through the social network.

As we said above, Moera is not a single website, it is a web of sites. The best way to surf through it is with an “upgraded” browser. The browser should handle some sort of URIs designating a post, feed or profile in Moera, like

moera:<node name>/<location>

and open this location in a Moera web client.

Unfortunately, it is currently impossible to configure a web browser to handle a different URI scheme. That’s why Moera uses a regular URL instead. The Moera URL has the following form:

https://moera.page/@<node name>/<node host>/<location>

For example:

https://moera.page/@lamed/lamed.moera.blog/post/99d6af7f

Let’s analyze what the URL is built of.

Redirector

The host moera.page used in the URL is the Moera redirector. When a user opens a Moera URL, the moera.page host redirects the browser to a default Moera web client. If the user wants to change the preferred web client, there is a special UI at https://moera.page/set-client?client=<domain name> for doing this. The user’s choice is saved in cookies and moera.page reads the cookies when doing the redirection.

Node Name and Node Host

The web client uses the node name and the node host in the URL to open a correct node. Each of them is optional, but the corresponding element in the URL should be present. If the node name is not known, it should be written as /@/. If the node host is not known, it should be written as /~/.

Essentially, there is enough to know the node name to locate the node. The client just needs to resolve the name through the Moera naming service. But the presence of the host in the URL makes the process faster. If the node host is known, the client tries to open it first. Later, if the hostname returned by the naming service appears to be different, the client opens it instead. The redirector (see the previous chapter) can also put the correct hostname into the URL if it knows it at the moment of redirection.

If the node does not have a registered name, or it is not known, the node host in the URL becomes the only way to locate the node. If the node host is not set as well, the user’s home node is used if it is known to the client.

If the node uses a protocol other than HTTPS or a different port, they should be specified with the host name, like http:localhost:8000.

Virtual Page

The location part of the URL is called a virtual page.

As we said before, Moera REST API may be implemented by any site and sites may have different structures. For example, on one site the “Contacts” page may have location /contact-us.html and on another site — /info/contacts.php, but both correspond to the same Moera virtual page /profile.

All virtual pages have standard names, this simplifies interactions between a client and node. For example, if user Arthur is mentioned in a comment somewhere, and we know that his node hostname is arthur.earth.org, we can link his name to https://moera.page/@Arthur/arthur.earth.org/profile and be sure that the link points to Arthur’s profile. This does not mean the page https://arthur.earth.org/profile exists — that’s why these pages are called virtual.

Discovery

There are two problems with the redirector approach that we need to solve somehow. The first one is the discovery problem:

When you visit some site, you don’t know whether it supports Moera. Even if somehow you find out, you will need to open the Moera client and enter the same address into it.

The problem may be solved by the site itself by displaying the Moera logo somewhere with a Moera link to the site. But we should take into account that

We cannot trust the node because it may open a malicious client.

The solution is to make all Moera-capable sites manifest themselves by adding a special HTTP header (X-Moera) to their HTTP response. A browser extension may detect this header and open a Moera web client automatically.

Single Point of Failure

The second problem is that the redirector becomes a single point of failure. The redirector must be highly-available, secure and handle a lot of traffic. It also puts decentralization in danger.

To mitigate this problem, the Moera URL handling and redirection should happen in the browser itself, without actually sending requests to moera.page host. A browser extension may be used for this task.