git-sync

git-sync is a simple command that pulls a git repository into a local directory. It is a perfect "sidecar" container in Kubernetes - it can periodically pull files down from a repository so that an application can consume them.

git-sync can pull one time, or on a regular interval. It can pull from the HEAD of a branch, from a git tag, or from a specific git hash. It will only re-pull if the target of the run has changed in the upstream repository. When it re-pulls, it updates the destination directory atomically. In order to do this, it uses a git worktree in a subdirectory of the --root and flips a symlink.

git-sync can pull over HTTP(S) (with authentication or not) or SSH.

git-sync can also be configured to make a webhook call upon successful git repo synchronization. The call is made after the symlink is updated.

Building it

We use docker buildx to build images.

# build the container
make container REGISTRY=registry VERSION=tag

# build the container behind a proxy
make container REGISTRY=registry VERSION=tag \
    HTTP_PROXY=http://<proxy_address>:<proxy_port> \
    HTTPS_PROXY=https://<proxy_address>:<proxy_port>

# build the container for an OS/arch other than the current (e.g. you are on
# MacOS and want to run on Linux)
make container REGISTRY=registry VERSION=tag \
    GOOS=linux GOARCH=amd64

Usage

# run the container
docker run -d \
    -v /tmp/git-data:/tmp/git \
    registry/git-sync:tag \
        --repo=https://github.com/kubernetes/git-sync \
        --branch=master \
        --root=/tmp/git/root \
        --period=30s

# run an nginx container to serve the content
docker run -d \
    -p 8080:80 \
    -v /tmp/git-data:/usr/share/nginx/html \
    nginx

Webhooks

Webhooks are executed asynchronously from the main git-sync process. If a webhook-url is configured, when a change occurs to the local git checkout a call is sent using the method defined in webhook-method (default to POST). git-sync will continually attempt this webhook call until it succeeds (based on webhook-success-status). If unsuccessful, git-sync will wait webhook-backoff (default 3s) before re-attempting the webhook call.

Usage

A webhook is configured using a set of CLI flags. At its most basic only webhook-url needs to be set.

docker run -d \
    -v /tmp/git-data:/tmp/git \
    registry/git-sync:tag \
        --repo=https://github.com/kubernetes/git-sync \
        --branch=master \
        --root=/tmp/git/root \
        --period=30s \
        --webhook-url="http://localhost:9090/-/reload"

Parameters

Environment Variable	Flag	Description	Default
GIT_SYNC_REPO	--repo	the git repository to clone	""
GIT_SYNC_BRANCH	--branch	the git branch to check out	"master"
GIT_SYNC_REV	--rev	the git revision (tag or hash) to check out	"HEAD"
GIT_SYNC_DEPTH	--depth	use a shallow clone with a history truncated to the specified number of commits	0
GIT_SYNC_SUBMODULES	--submodules	git submodule behavior: one of 'recursive', 'shallow', or 'off'	recursive
GIT_SYNC_ROOT	--root	the root directory for git-sync operations, under which --link will be created	""
GIT_SYNC_LINK	--link	the name of a symlink, under --root, which points to a directory in which --repo is checked out (defaults to the leaf dir of --repo)	""
GIT_SYNC_PERIOD	--period	how long to wait between syncs, must be >= 10ms	"10s"
GIT_SYNC_SYNC_TIMEOUT	--sync-timeout	the total time allowed for one complete sync, must be >= 10ms	"120s"
GIT_SYNC_ONE_TIME	--one-time	exit after the first sync	false
GIT_SYNC_MAX_SYNC_FAILURES	--max-sync-failures	the number of consecutive failures allowed before aborting (the first sync must succeed, -1 will retry forever after the initial sync)	0
GIT_SYNC_PERMISSIONS	--change-permissions	the file permissions to apply to the checked-out files (0 will not change permissions at all)	0
GIT_SYNC_HOOK_COMMAND	--sync-hook-command	an optional command to be executed after syncing a new hash of the remote repository
GIT_SYNC_WEBHOOK_URL	--webhook-url	the URL for a webook notification when syncs complete	""
GIT_SYNC_WEBHOOK_METHOD	--webhook-method	the HTTP method for the webhook	"POST"
GIT_SYNC_WEBHOOK_SUCCESS_STATUS	--webhook-success-status	the HTTP status code indicating a successful webhook (-1 disables success checks to make webhooks fire-and-forget)	200
GIT_SYNC_WEBHOOK_TIMEOUT	--webhook-timeout	the timeout for the webhook	1 (second)
GIT_SYNC_WEBHOOK_BACKOFF	--webhook-backoff	the time to wait before retrying a failed webhook	3 (seconds)
GIT_SYNC_USERNAME	--username	the username to use for git auth	""
GIT_SYNC_PASSWORD	--password	the password or personal access token to use for git auth (prefer env vars for passwords)	""
GIT_SYNC_SSH	--ssh	use SSH for git operations	false
GIT_SSH_KEY_FILE	--ssh-key-file	the SSH key to use	"/etc/git-secret/ssh"
GIT_KNOWN_HOSTS	--ssh-known-hosts	enable SSH known_hosts verification	true
GIT_SSH_KNOWN_HOSTS_FILE	--ssh-known-hosts-file	the known_hosts file to use	"/etc/git-secret/known_hosts"
GIT_SYNC_ADD_USER	--add-user	add a record to /etc/passwd for the current UID/GID (needed to use SSH with a different UID)	false
GIT_COOKIE_FILE	--cookie-file	use git cookiefile	false
GIT_ASKPASS_URL	--askpass-url	the URL for GIT_ASKPASS callback	""
GIT_SYNC_GIT	--git	the git command to run (subject to PATH search, mostly for testing	"git"
GIT_SYNC_HTTP_BIND	--http-bind	the bind address (including port) for git-sync's HTTP endpoint	""
GIT_SYNC_HTTP_METRICS	--http-metrics	enable metrics on git-sync's HTTP endpoint	true
GIT_SYNC_HTTP_PPROF	--http-pprof	enable the pprof debug endpoints on git-sync's HTTP endpoint	false