Geo proxying
Secondaries proxy nearly all HTTP requests through Workhorse to the primary, so users navigating to the
secondary see a read-write UI, and are able to do all operations that they can do on the primary.
High-level components
Proxying of GitLab UI and API HTTP requests is handled by the gitlab-workhorse component. Traffic usually sent to the Rails application on the Geo secondary site is proxied to the internal URL of the primary Geo site instead.
Proxying of Git over HTTP requests is handled by the gitlab-workhorse component, but the decision to proxy or not is handled by the Rails application, taking into account whether the request is push or pull, and whether the desired Git data is up-to-date.
Proxying of Git over SSH traffic is handled by the gitlab-shell component, but the decision to proxy or not is handled by the Rails application, taking into account whether the request is push or pull, and whether the desired Git data is up-to-date.
Request lifecycle
Top-level view
The proxying interaction can be explained at a high level through the following diagram:
sequenceDiagram
actor client
participant secondary
participant primary
client->>secondary: GET /explore
secondary-->>primary: GET /explore (proxied)
primary-->>secondary: HTTP/1.1 200 OK [..]
secondary->>client: HTTP/1.1 200 OK [..]
Proxy detection mechanism
To know whether or not it should proxy requests to the primary, and the URL of the primary (as it is stored in
the database), Workhorse polls the internal API when Geo is enabled. When proxying should be enabled, the internal
API responds with the primary URL and JWT-signed data that is passed on to the primary for every request.
sequenceDiagram
participant W as Workhorse (secondary)
participant API as Internal Rails API
W->API: GET /api/v4/geo/proxy (internal)
loop Poll every 10 seconds
API-->W: {geo_proxy_primary_url, geo_proxy_extra_data}, update config
end
In-depth request flow and local data acceleration compared with proxying
Detailing implementation, Workhorse on the secondary (requested) site decides whether to proxy the data or not. If it
can “accelerate” the data type (that is, can serve locally to save a roundtrip request), it returns the data
immediately. Otherwise, traffic is sent to the primary’s internal URL, served by Workhorse on the primary exactly
as a direct request would. The response is then be proxied back to the user through the secondary Workhorse in the
same connection.
flowchart LR
A[Client]--->W1["Workhorse (secondary)"]
W1 --> W1C[Serve data locally?]
W1C -- "Yes" ----> W1
W1C -- "No (proxy)" ----> W2["Workhorse (primary)"]
W2 --> W1 ----> A
Sign-in
Requests proxied to the primary requiring authorization
sequenceDiagram
autoNumber
participant Client
participant Secondary
participant Primary
Client->>Secondary: `/group/project` request
Secondary->>Primary: proxy /group/project
opt primary not signed in
Primary-->>Secondary: 302 redirect
Secondary-->>Client: proxy 302 redirect
Client->>Secondary: /users/sign_in
Secondary->>Primary: proxy /users/sign_in
Note right of Primary: authentication happens, POST to same URL etc
Primary-->>Secondary: 302 redirect
Secondary-->>Client: proxy 302 redirect
Client->>Secondary: /group/project
Secondary->>Primary: proxy /group/project
end
Primary-->>Secondary: /group/project logged in response (session on primary created)
Secondary-->>Client: proxy full response
Git pull
For historical reasons, the push_from_secondary path is used to forward a Git pull. There is
an issue proposing to rename this route to avoid confusion.
Git pull over HTTP(s)
Accelerated repositories
When a repository exists on the secondary and we detect is up to date with the primary, we serve it directly instead of
proxying.
sequenceDiagram
participant C as Git client
participant Wsec as "Workhorse (secondary)"
participant Rsec as "Rails (secondary)"
participant Gsec as "Gitaly (secondary)"
C->>Wsec: GET /foo/bar.git/info/refs/?service=git-upload-pack
Wsec->>Rsec: <internal API check>
note over Rsec: decide that the repo is synced and up to date
Rsec-->>Wsec: 401 Unauthorized
Wsec-->>C: <response>
C->>Wsec: GET /foo/bar.git/info/refs/?service=git-upload-pack
Wsec->>Rsec: <internal API check>
Rsec-->>Wsec: Render Workhorse OK
Wsec-->>C: 200 OK
C->>Wsec: POST /foo/bar.git/git-upload-pack
Wsec->>Rsec: GitHttpController#git_receive_pack
Rsec-->>Wsec: Render Workhorse OK
Wsec->>Gsec: Workhorse gets the connection details from Rails, connects to Gitaly: SmartHTTP Service, UploadPack RPC (check the proto for details)
Gsec-->>Wsec: Return a stream of Proto messages
Wsec-->>C: Pipe messages to the Git client
Proxied repositories
If a requested repository isn’t synced, or we detect is not up to date, the request will be proxied to the primary, in
order to get the latest version of the changes.
sequenceDiagram
participant C as Git client
participant Wsec as "Workhorse (secondary)"
participant Rsec as "Rails (secondary)"
participant W as "Workhorse (primary)"
participant R as "Rails (primary)"
participant G as "Gitaly (primary)"
C->>Wsec: GET /foo/bar.git/info/refs/?service=git-upload-pack
Wsec->>Rsec: <response>
note over Rsec: decide that the repo is out of date
Rsec-->>Wsec: 302 Redirect to /-/push_from_secondary/2/foo/bar.git/info/refs?service=git-upload-pack
Wsec-->>C: <response>
C->>Wsec: GET /-/push_from_secondary/2/foo/bar.git/info/refs/?service=git-upload-pack
Wsec->>W: <proxied request>
W->>R: <data>
R-->>W: 401 Unauthorized
W-->>Wsec: <proxied response>
Wsec-->>C: <response>
C->>Wsec: GET /-/push_from_secondary/2/foo/bar.git/info/refs/?service=git-upload-pack
note over W: proxied
Wsec->>W: <proxied request>
W->>R: <data>
R-->>W: Render Workhorse OK
W-->>Wsec: <proxied response>
Wsec-->>C: <response>
C->>Wsec: POST /-/push_from_secondary/2/foo/bar.git/git-upload-pack
Wsec->>W: <proxied request>
W->>R: GitHttpController#git_receive_pack
R-->>W: Render Workhorse OK
W->>G: Workhorse gets the connection details from Rails, connects to Gitaly: SmartHTTP Service, UploadPack RPC (check the proto for details)
G-->>W: Return a stream of Proto messages
W-->>Wsec: Pipe messages to the Git client
Wsec-->>C: Return piped messages from Git
Git pull over SSH
As SSH operations go through GitLab Shell instead of Workhorse, they are not proxied through the mechanism used for
Workhorse requests. With SSH operations, they are proxied as Git HTTP requests to the primary site by the secondary
Rails internal API.
Accelerated repositories
When a repository exists on the secondary and we detect is up to date with the primary, we serve it directly instead of
proxying.
sequenceDiagram
participant C as Git client
participant S as GitLab Shell (secondary)
participant I as Internal API (secondary Rails)
participant G as Gitaly (secondary)
C->>S: git pull
S->>I: SSH key validation (api/v4/internal/authorized_keys?key=..)
I-->>S: HTTP/1.1 200 OK
S->>G: InfoRefs:UploadPack RPC
G-->>S: stream Git response back
S-->>C: stream Git response back
C-->>S: stream Git data to push
S->>G: UploadPack RPC
G-->>S: stream Git response back
S-->>C: stream Git response back
Proxied repositories
If a requested repository isn’t synced, or we detect is not up to date, the request will be proxied to the primary, in
order to get the latest version of the changes.
sequenceDiagram
participant C as Git client
participant S as GitLab Shell (secondary)
participant I as Internal API (secondary Rails)
participant P as Primary API
C->>S: git pull
S->>I: SSH key validation (api/v4/internal/authorized_keys?key=..)
I-->>S: HTTP/1.1 300 (custom action status) with {endpoint, msg, primary_repo}
S->>I: POST /api/v4/geo/proxy_git_ssh/info_refs_upload_pack
I->>P: POST $PRIMARY/foo/bar.git/info/refs/?service=git-upload-pack
P-->>I: HTTP/1.1 200 OK
I-->>S: <response>
S-->>C: return Git response from primary
C-->>S: stream Git data to push
S->>I: POST /api/v4/geo/proxy_git_ssh/upload_pack
I->>P: POST $PRIMARY/foo/bar.git/git-upload-pack
P-->>I: HTTP/1.1 200 OK
I-->>S: <response>
S-->>C: return Git response from primary
Git push
Git push over SSH
As SSH operations go through GitLab Shell instead of Workhorse, they are not proxied through the mechanism used for
Workhorse requests. With SSH operations, they are proxied as Git HTTP requests to the primary site by the secondary
Rails internal API.
sequenceDiagram
participant C as Git client
participant S as GitLab Shell (secondary)
participant I as Internal API (secondary Rails)
participant P as Primary API
C->>S: git push
S->>I: SSH key validation (api/v4/internal/authorized_keys?key=..)
I-->>S: HTTP/1.1 300 (custom action status) with {endpoint, msg, primary_repo}
S->>I: POST /api/v4/geo/proxy_git_ssh/info_refs_receive_pack
I->>P: POST $PRIMARY/foo/bar.git/info/refs/?service=git-receive-pack
P-->>I: HTTP/1.1 200 OK
I-->>S: <response>
S-->>C: return Git response from primary
C-->>S: stream Git data to push
S->>I: POST /api/v4/geo/proxy_git_ssh/receive_pack
I->>P: POST $PRIMARY/foo/bar.git/git-receive-pack
P-->>I: HTTP/1.1 200 OK
I-->>S: <response>
S-->>C: return Git response from primary
Git push over HTTP(S)
If a requested repository isn’t synced, or we detect is not up to date, the request will be proxied to the primary, a push redirects to a local path formatted as /-/push_from_secondary/$SECONDARY_ID/*.
Further, requests through this path are proxied to the primary, which will handle the push.
sequenceDiagram
participant C as Git client
participant Wsec as Workhorse (secondary)
participant W as Workhorse (primary)
participant R as Rails (primary)
participant G as Gitaly (primary)
C->>Wsec: GET /foo/bar.git/info/refs/?service=git-receive-pack
Wsec->>C: 302 Redirect to /-/push_from_secondary/2/foo/bar.git/info/refs?service=git-receive-pack
C->>Wsec: GET /-/push_from_secondary/2/foo/bar.git/info/refs/?service=git-receive-pack
Wsec->>W: <proxied request>
W->>R: <data>
R-->>W: 401 Unauthorized
W-->>Wsec: <proxied response>
Wsec-->>C: <response>
C->>Wsec: GET /-/push_from_secondary/2/foo/bar.git/info/refs/?service=git-receive-pack
Wsec->>W: <proxied request>
W->>R: <data>
R-->>W: Render Workhorse OK
W-->>Wsec: <proxied response>
Wsec-->>C: <response>
C->>Wsec: POST /-/push_from_secondary/2/foo/bar.git/git-receive-pack
Wsec->>W: <proxied request>
W->>R: GitHttpController:git_receive_pack
R-->>W: Render Workhorse OK
W->>G: Get connection details from Rails and connects to SmartHTTP Service, ReceivePack RPC
G-->>W: Return a stream of Proto messages
W-->>Wsec: Pipe messages to the Git client
Wsec-->>C: Return piped messages from Git