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

# make a directory (owned by you) for the volume
export DIR="/tmp/git-data"
mkdir -p $DIR

# run the container (as your own UID)
docker run -d \
    -v $DIR:/tmp/git \
    -u$(id -u):$(id -g) \
    registry/git-sync:tag \
        --repo=https://github.com/kubernetes/git-sync \
        --branch=master \
        --wait=30

# run an nginx container to serve the content
docker run -d \
    -p 8080:80 \
    -v $DIR:/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 $DIR:/tmp/git \
    registry/git-sync:tag \
        --repo=https://github.com/kubernetes/git-sync \
        --branch=master \
        --wait=30 \
        --webhook-url="http://localhost:9090/-/reload"

Primary flags

Flag	Environment Variable	Default	Description
--repo	GIT_SYNC_REPO	(required)	the git repository to clone
--branch	GIT_SYNC_BRANCH	"master"	the git branch to check out
--rev	GIT_SYNC_REV	"HEAD"	the git revision (tag or hash) to check out
--root	GIT_SYNC_ROOT	"$HOME/git"	the root directory for git-sync operations, under which --dest will be created
--dest	GIT_SYNC_DEST	""	the name of (a symlink to) a directory in which to check-out files under --root (defaults to the leaf dir of --repo)
--wait	GIT_SYNC_WAIT	1 (second)	the number of seconds between syncs
--one-time	GIT_SYNC_ONE_TIME	false	exit after the first sync
--max-sync-failures	GIT_SYNC_MAX_SYNC_FAILURES	0	the number of consecutive failures allowed before aborting (the first sync must succeed, -1 will retry forever after the initial sync)
-v	(none)	""	log level for V logs

Flags which control how git runs

Flag	Environment Variable	Default	Description
--depth	GIT_SYNC_DEPTH	0	use a shallow clone with a history truncated to the specified number of commits
--submodules	GIT_SYNC_SUBMODULES	recursive	git submodule behavior: one of 'recursive', 'shallow', or 'off'
--timeout	GIT_SYNC_TIMEOUT	120	the max number of seconds allowed for a complete sync
--sparse-checkout-file	GIT_SYNC_SPARSE_CHECKOUT_FILE	""	the location of an optional sparse-checkout file, same syntax as a .gitignore file.
--git-config	GIT_SYNC_GIT_CONFIG	""	additional git config options in 'key1:val1,key2:val2' format
--git-gc	GIT_SYNC_GIT_GC	"auto"	git garbage collection behavior: one of 'auto', 'always', 'aggressive', or 'off'
--git	GIT_SYNC_GIT	"git"	the git command to run (subject to PATH search, mostly for testing

Flags which configure authentication

Flag	Environment Variable	Default	Description
--username	GIT_SYNC_USERNAME	""	the username to use for git auth
--password	GIT_SYNC_PASSWORD	""	the password or personal access token to use for git auth. (users should prefer --password-file or env vars for passwords)
--password-file	GIT_SYNC_PASSWORD_FILE	""	the path to password file which contains password or personal access token (see --password)
--ssh	GIT_SYNC_SSH	false	use SSH for git operations
--ssh-key-file	GIT_SSH_KEY_FILE	"/etc/git-secret/ssh"	the SSH key to use
--ssh-known-hosts	GIT_KNOWN_HOSTS	true	enable SSH known_hosts verification
--ssh-known-hosts-file	GIT_SSH_KNOWN_HOSTS_FILE	"/etc/git-secret/known_hosts"	the known_hosts file to use
--add-user	GIT_SYNC_ADD_USER	false	add a record to /etc/passwd for the current UID/GID (needed to use SSH with a different UID)
--cookie-file	GIT_COOKIE_FILE	false	use git cookiefile
--askpass-url	GIT_ASKPASS_URL	""	the URL for GIT_ASKPASS callback

Flags which configure hooks

Flag	Environment Variable	Default	Description
--exechook-command	GIT_SYNC_EXECHOOK_COMMAND	""	the command executed with the syncing repository as its working directory after syncing a new hash of the remote repository. it is subject to the sync time out and will extend period between syncs. (doesn't support the command arguments)
--exechook-timeout	GIT_SYNC_EXECHOOK_TIMEOUT	30 (seconds)	the timeout for the sync hook command
--exechook-backoff	GIT_SYNC_EXECHOOK_BACKOFF	3 (seconds)	the time to wait before retrying a failed sync hook command
--webhook-url	GIT_SYNC_WEBHOOK_URL	""	the URL for a webhook notification when syncs complete
--webhook-method	GIT_SYNC_WEBHOOK_METHOD	"POST"	the HTTP method for the webhook
--webhook-success-status	GIT_SYNC_WEBHOOK_SUCCESS_STATUS	200	the HTTP status code indicating a successful webhook (-1 disables success checks to make webhooks fire-and-forget)
--webhook-timeout	GIT_SYNC_WEBHOOK_TIMEOUT	1 (second)	the timeout for the webhook
--webhook-backoff	GIT_SYNC_WEBHOOK_BACKOFF	3 (seconds)	the time to wait before retrying a failed webhook

Flags which configure observability

Flag	Environment Variable	Default	Description
--http-bind	GIT_SYNC_HTTP_BIND	""	the bind address (including port) for git-sync's HTTP endpoint
--http-metrics	GIT_SYNC_HTTP_METRICS	true	enable metrics on git-sync's HTTP endpoint
--http-pprof	GIT_SYNC_HTTP_PPROF	false	enable the pprof debug endpoints on git-sync's HTTP endpoint

Other flags

Flag	Environment Variable	Default	Description
--change-permissions	GIT_SYNC_PERMISSIONS	0	the file permissions to apply to the checked-out files (0 will not change permissions at all)
--error-file	GIT_SYNC_ERROR_FILE	""	the name of a file into which errors will be written under --root