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Version: 4.x

Configure File Synchronization

The code synchronization feature of DevSpace allows you to use hot reloading during development. Especially when using programming languages and frameworks that support hot reloading with tools like nodemon, re-building and re-deploying containers is very annoying and time consuming. Therefore, DevSpace uses a smart syncing mechanism that is able to sync local file changes to remote containers directly without the need of rebuilding or restarting the container.

When starting the development mode, DevSpace starts the file sync as configured in the dev.sync section of the devspace.yaml.

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
      - image: john/debugger
dev:
  sync:
  - imageName: backend
    localSubPath: ./
    containerPath: /app
    excludePaths:
    - node_modules/
    - logs/
Start Sync Only

To only start the file sync without the other functions of the development mode, use devspace sync or devspace sync --config=devspace.yaml (to load the config).

Every sync configuration consists of two essential parts:

Pod/Container Selection​

The following config options are needed to determine the container which the file synchronization should be established to:

Combine Otions

If you specify multiple these config options, they will be jointly used to select the pod / container (think logical AND / &&).

Auto Reconnect

If the sync is unable to establish a connection to the selected container or loses it after starting the sync, DevSpace will try to restart the sync several times.

imageName​

The imageName option expects a string with the name of an image from the images section of the devspace.yaml. Using imageName tells DevSpace to select the container based on the referenced image that was last built using DevSpace.

note

If imageName is specified in any of the sync configurations, devspace dev will not rebuild this image because DevSpace assumes that instead of rebuilding the image, the user wants to use the much faster file synchronization. If you still want to force rebuilding all images, run devspace dev -b.

note

When multiple deployments in your devspace.yaml use the same image, you generally want to select the right pod using the labelSelector but you should additionally define the imageName option if you want to enable faster image building (see note above).

Example: Select Container by Image Name​

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - name: container-0
        image: john/devbackend
      - name: container-1
        image: john/debugger
dev:
  sync:
  - imageName: backend
    excludePaths:
    - node_modules/
    - logs/
  - imageName: backend-debugger
    localSubPath: ./debug-logs
    containerPath: /logs

Explanation:

  • The above example defines two images that can be used as imageName: backend and backend-debugger
  • The deployment starts two containers and each of them uses an image from the images section.
  • The imageName option of the first sync configuration in the dev.sync section references backend. That means DevSpace would select the first container for file synchronzation, as this container uses the image: john/devbackend which belongs to the backend image as defined in the images section.
  • The first sync configuration does not define localSubPath, so it defaults to the project's root directory (location of devspace.yaml).
  • The first sync configuration does not define containerPath, so it defaults to the container's working directory (i.e. WORKDIR).
  • The imageName option of the second sync configuration in the dev.sync section references backend-debugger. That means DevSpace would select the second container for file synchronization, as this container uses the image: john/debugger which belongs to the backend-debugger image as defined in the images section.

In consequence, the following sync processes would be started when using the above config example assuming the local project root directoy /my/project/:

  1. localhost:/my/project/ forwards to container-0:$WORKDIR *
  2. localhost:/my/project/debug-logs/ forwards to container-1:/logs

* Changes on either side (local and container filesystem) that occur within the sub-folders node_modules/ and logs/ would be ingored.

labelSelector​

The labelSelector option expects a key-value map of strings with Kubernetes labels.

info

If you are using the labelSelector option, you may want to additionally specify the imageName option to speed up the image building process.

Example: Select Container by Label​

images:
  backend:
    image: john/devbackend
  backend-debugger:
    image: john/debugger
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - name: container-0
        image: john/devbackend
      - name: container-1
        image: john/debugger
dev:
  sync:
  - labelSelector:
      app.kubernetes.io/name: devspace-app
      app.kubernetes.io/component: app-backend
      custom-label: custom-label-value
    containerName: container-0
    localSubPath: ./src
    containerPath: /app/src

Explanation:

  • The labelSelector would select the pod created for the component deployment app-backend.
  • Because the selected pod has two containers, we also need to specify the containerName option which defines the container that should be used for the file synchronization.

containerName​

The containerName option expects a string with a container name. This option is used to decide which container should be selected when using the labelSelector option because labelSelector selects a pod and a pod can have multiple containers.

info

The containerName option is not required if the pod you are selecting using imageName or labelSelector has only one container.

Example​

See "Example: Select Container by Label"

namespace​

The namespace option expects a string with a Kubernetes namespace used to select the container from.

danger

It is generally not needed (nor recommended) to specify the namespace option because by default, DevSpace uses the default namespace of your current kube-context which is usually the one that has been used to deploy your containers to.


Sync Path Mapping​

localSubPath​

The localSubPath option expects a string with a path that is relative to the location of devspace.yaml.

Default Value For localSubPath​

localSubPath: ./ # Project root directory (folder containing devspace.yaml)

Example​

See "Example: Select Container by Image Name"

containerPath​

The containerPath option expects a string with an absolute path on the container filesystem.

Default Value For containerPath​

containerPath: $WORKDIR # working directory, set as WORKDIR in the Dockerfile

Example​

See "Example: Select Container by Image Name"


Exclude Paths​

The config options for excluding paths use the same syntax as .gitignore.

note

An exclude path that matches a folder recursively excludes all files and sub-folders within this folder.

excludePaths​

The excludePaths option expects an array of strings with paths that should not be synchronized between the local filesystem and the remote container filesystem.

Default Value For excludePaths​

excludePaths: [] # Do not exclude anything from file synchronization

Example: Exclude Paths from Synchronization​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    excludePaths:
    - logs/
    - more/logs/
    uploadExcludePaths:
    - node_modules/
    downloadExcludePaths:
    - tmp/

Explanation:

  • Files in logs/ and in more/logs/ would not be synchronized at all.
  • Files in node_modules/ would only be synchronized from the container to the local filesystem but not the other way around.
  • Files in tmp/ would only be synchroniyed from the local to the container filesystem but not the other way around.

downloadExcludePaths​

The downloadExcludePaths option expects an array of strings with paths that should not be synchronized from the remote container filesystem to the local filesystem.

Default Value For downloadExcludePaths​

downloadExcludePaths: [] # Do not exclude anything from file synchronization

Example​

See "Example: Exclude Paths from Synchronization"

uploadExcludePaths​

The uploadExcludePaths option expects an array of strings with paths that should not be synchronized from the local filesystem to the remote container filesystem.

info

This option is often useful if you want to download a dependency folder (e.g. node_modules/) for code completion but you never want to upload anything from there because of compiled binaries that are not portable between local filesystem and container filesystem (e.g. when your local system is Windows but your containers run Linux).

Default Value For uploadExcludePaths​

uploadExcludePaths: [] # Do not exclude anything from file synchronization

Example​

See "Example: Exclude Paths from Synchronization"


Post-Sync Commands​

Sometimes it is useful to execute commands after the sync downloads or uploads files/directories between container and local filesystem.

danger

Make sure that post-sync commands will not trigger a new sync process which could lead to an endless loop.

onUpload.restartContainer​

The restartContainer option expects a boolean which defines if DevSpace should restart the container every time either a single file or even a batch of files have been uploaded to the container using file sync.

Restart Helper Required

Setting restartContainer: true requires to set injectRestartHelper: true for the image that is used to run the affected container. Otherwise, this option does not have any effect.

When not to use this option

Using restartContainer: true is most useful if your application runs based on a compiled language and you are not using a framework or language specific tool which provides hot reloading capabilities. If you are using tools like nodemon or frameworks like React, Rails or Flask, they allow you to enable hot reloading which may be much faster than restarting the entire container. In this case you should disable restartContainer.

Example: Enable Container Restart​

images:
  backend:
    image: john/devbackend
    injectRestartHelper: true
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    onUpload:
      restartContainer: true

onUpload​

The onUpload option defines command(s) that should be executed after a file/directory was uploaded from the local filesystem to the container.

Example: Post-Upload Commands​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    onUpload:
      execRemote:         # These post-sync commands will be executed inside the affected container
        command: chmod    # Command to execute for files and folders
        args:
        - +x
        - {}              # {} will be replaced with the path of the synced file/directory
        onFileChange:     # Command to execute ONLY for files
          command: chmod
          args:
          - +x
          - {}            # {} will be replaced with the path of the synced file/directory
        onDirCreate:      # Command to execute ONLY for newly created directories
          command: chmod
          args:
          - +x
          - {}            # {} will be replaced with the path of the synced file/directory
        onBatch:          # Command to execute after sync has processed a full batch of files and folders
          command: recompile
          args:           # NOTE: {} is NOT available for onBatch
          - assets
          - --minify

onDownload​

The onDownload option defines command(s) that should be executed after a file/directory was downloaded from the container to the local filesystem.

Example: Post-Download Commands​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    onDownload:
      execLocal:          # These post-sync commands will be executed on the local dev machine
        command: chmod    # Command to execute for files and folders
        args:
        - +x
        - {}              # {} will be replaced with the path of the synced file/directory
        onFileChange:     # Command to execute ONLY for files
          command: chmod
          args:
          - +x
          - {}            # {} will be replaced with the path of the synced file/directory
        onDirCreate:      # Command to execute ONLY for newly created directories
          command: chmod
          args:
          - +x
          - {}            # {} will be replaced with the path of the synced file/directory

One-Directional Sync​

These flags allow for local or remote container filesystems to be ignored during synchronization.

disableDownload​

The disableDownload option expects a boolean which enables/disables all synchronization from the remote container filesystem to the local filesystem.

Default Value For disableDownload​

disableDownload: false # Do not ignore remote container files during synchronization

Example: Synchronize Local Filesystem Only​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    disableDownload: true
    excludePaths:
    - logs/
    - more/logs/
    uploadExcludePaths:
    - node_modules/

disableUpload​

The disableUpload option expects a boolean which enables/disables all synchronization from the local filesystem to the remote container filesystem.

Default Value For disableUpload​

disableUpload: false # Do not ignore local files during synchronization

Example: Synchronize Remote Container Filesystem Only​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    disableUpload: true
    excludePaths:
    - logs/
    - more/logs/
    downloadExcludePaths:
    - tmp/

Initial Sync​

initialSync​

The initialSync option expects a string with an initial sync strategy. The following strategies are available:

• mirrorLocal mirrors the local filesystem inside the container (default)​

  1. deletes all files inside the conainer that are not existing on the local filesystem
  2. uploads all files which are existing on the local filesystem but are missing within the container
  3. resolves all file conflicts (different content on local filesystem than in inside the container) by preferring the file on the local filesystem (i.e. all files in the container will be replaced if they are different from on the local filesystem)

• preferLocal is like mirrorLocal but skips step 1.​

• mirrorRemote mirrors the container files to the local filesystem:​

  1. deletes all files on the local filesystem that are not existing inside the container
  2. downloads all files which are existing inside the container but are missing on the local filesystem
  3. resolves all file conflicts (different content on local filesystem than inside the container) by preferring the file within the container (i.e. all files on the local filesystem will be replaced if they are different than inside the container)

• preferRemote is like mirrorRemote but skips step 1.​

• preferNewest merges local and remote filesystem while resolving all conflicts​

  1. uploads all files which are existing on the local filesystem but are missing within the container
  2. downloads all files which are existing inside the container but are missing on the local filesystem
  3. resolves all file conflicts (different content on local filesystem than inside the container) by preferring the newest file (i.e. compares last modified timestamps and replaces all outdated files)

• keepAll merges local and remote filesystem without resolving any conflicts​

  1. uploads all files which are existing on the local filesystem but are missing within the container
  2. downloads all files which are existing inside the container but are missing on the local filesystem

Default Value For initialSync​

initialSync: mirrorLocal

Example: Configuring Initial Sync​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    excludePaths:
    - node_modules/*
  - imageName: backend
    localSubPath: ./node_modules/
    containerPath: /app/node_modules/
    initialSync: preferRemote

Explanation:
With this configuration, devspace dev would do the following:

  • DevSpace would start port-forwarding and file synchronzation.
  • Initial sync would be started automatically.
  • The first sync config section would synchronize all files except files within node_modules/. This means that during initial sync, all remote files that are not existing locally would be deleted and other files would be updated to the most recent version.
  • The second sync config section would only synchronize files within node_modules/ and because of initialSync: preferRemote, DevSpace would download all remote files which are not present on the local filesystem and override all local files which are different than the files within the container.

waitInitialSync​

The waitInitialSync option expects a boolean which defines if DevSpace should wait until the initial sync process has terminated before opening the container terminal or the multi-container log streaming.

Default Value For waitInitialSync​

waitInitialSync: false # Start container terminal or log streaming before initial sync is completed

Example: Wait For Initial Sync To Complete​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    waitInitialSync: true

Explanation:
With the configuration devspace dev would do the following:

  • DevSpace would start port-forwarding and file synchronzation.
  • Initial sync would be started automatically.
  • After the initial sync process is finished, DevSpace starts the multi-container log streaming.

Network Bandwidth Limits​

Sometimes it is useful to throttle the file synchronization, especially when large files or a large number of files are expected to change during development. The following config options provide these capabilities:

bandwidthLimits.download​

The bandwidthLimits.download option expects an integer representing the max file download speed in KB/s, e.g. download: 100 would limit the file sync to a download speed of 100 KB/s.

note

By default, the file synchronization algorithm uses the maximum bandwidth possible to make the sync process as fast as possible.

Example: Limiting Network Bandwidth​

images:
  backend:
    image: john/devbackend
deployments:
- name: app-backend
  helm:
    componentChart: true
    values:
      containers:
      - image: john/devbackend
dev:
  sync:
  - imageName: backend
    bandwidthLimits:
      download: 200
      upload: 100

Explanation:

  • Downloading files from the container to the local filesystem would be limited to a transfer speed of 200 KB/s.
  • Upload files from the local filesystem to the container would be limited to a transfer speed of 100 KB/s.

bandwidthLimits.upload​

The bandwidthLimits.upload option expects an integer representing the max file upload speed in KB/s, e.g. upload: 100 would limit the file sync to a upload speed of 100 KB/s.

note

By default, the file synchronization algorithm uses the maximum bandwidth possible to make the sync process as fast as possible.

Example​

See "Example: Limiting Network Bandwidth"

Useful Commands​

devspace status sync​

To get information about current synchronization activities, simply run:

devspace status sync

Additionally, you can ciew the sync log within .devspace/logs/sync.log to get more detailed information.

devspace sync​

If you want to start file synchronzation on-demand without having to configure it in devspace.yaml and without starting port-forwarding or log streaming etc, you can use the devspace sync command as shown in the examples below:

# Select pod with a picker
devspace sync --local-path=subfolder --container-path=/app

# Select pod and container by name and use current working directory as local-path
devspace sync --pod=my-pod --container=my-container --container-path=/app

FAQ​

How does the sync work?

DevSpace establishes a bi-directional code synchronization between the specified local folders and the remote container folders. It automatically recognizes any changes within the specified folders during the session and will update the corresponding files locally and remotely in the background. It uses a small helper binary that is injected into the target container to accomplish this.

The algorithm roughly works like this:

  1. Inject a small helper binary via kubectl cp into the target container
  2. Run initial sync accoring to the initialSync config option
  3. Watch for file changes on both sides (local and remote) and sync them according to the sync path mappings
  4. After every sync process, restart the container or run other custom post-sync commands (optional)

Are there any requirements for the sync to work?

The tar command has to be present in the container otherwise kubectl cp does not work and the helper binary cannot be injected into the container.

Other than that, no server-side component or special container privileges for code synchronization are required, as the sync algorithm runs completely client-only within DevSpace. The synchronization mechanism works with any container filesystem and no special binaries have to be installed into the containers. File watchers running within the containers like nodemon will also recognize changes made by the synchronization mechanism.


What is the performance impact on using the file sync?

The sync mechanism is normally very reliable and fast. Syncing several thousand files is usually not a problem. Changes are packed together and compressed during synchronization, which improves performance especially for transferring text files. Transferring large compressed binary files is possible, but can affect performance negatively. Remote changes can sometimes have a delay of 1-2 seconds till they are downloaded, depending on how big the synchronized folder is. It should be generally avoided to sync the complete container filesystem.