Argo CD is largely stateless, all data is persisted as Kubernetes objects, which in turn is stored in Kubernetes' etcd. Redis is only used as a throw-away cache and can be lost. When lost, it will be rebuilt without loss of service.
A set HA of manifests are provided for users who wish to run Argo CD in a highly available manner. This runs more containers, and run Redis in HA mode.
The HA installation will require at least three different nodes due to pod anti-affinity roles in the specs.
argocd-repo-server is responsible for cloning Git repository, keeping it up to date and generating manifests using the appropriate tool.
argocd-repo-serverfork/exec config management tool to generate manifests. The fork can fail due to lack of memory and limit on the number of OS threads. The
--parallelismlimitflag controls how many manifests generations are running concurrently and allows avoiding OOM kills.
argocd-repo-serverensures that repository is in the clean state during the manifest generation using config management tools such as Kustomize, Helm or custom plugin. As a result Git repositories with multiple applications might be affect repository server performance. Read Monorepo Scaling Considerations for more information.
argocd-repo-serverclones repository into
/tmp( of path specified in
TMPDIRenv variable ). Pod might run out of disk space if have too many repository or repositories has a lot of files. To avoid this problem mount persistent volume.
git ls-remoteto resolve ambiguous revision such as
HEAD, branch or tag name. This operation is happening pretty frequently and might fail. To avoid failed syncs use
ARGOCD_GIT_ATTEMPTS_COUNTenvironment variable to retry failed requests.
argocd-repo-serverEvery 3m (by default) Argo CD checks for changes to the app manifests. Argo CD assumes by default that manifests only change when the repo changes, so it caches generated manifests (for 24h by default). With Kustomize remote bases, or Helm patch releases, the manifests can change even though the repo has not changed. By reducing the cache time, you can get the changes without waiting for 24h. Use
--repo-cache-expiration duration, and we'd suggest in low volume environments you try '1h'. Bear in mind this will negate the benefit of caching if set too low.
argocd-repo-serverfork exec config management tools such as
kustomizeand enforces 90 seconds timeout. The timeout can be increased using
argocd_git_request_total- Number of git requests. The metric provides two tags:
repo- Git repo URL;
ARGOCD_ENABLE_GRPC_TIME_HISTOGRAM(v1.8+) - environment variable that enables collecting RPC performance metrics. Enable it if you need to troubleshoot performance issue. Note: metric is expensive to both query and store!
argocd-repo-server to get generated manifests and Kubernetes API server to get actual cluster state.
each controller replica uses two separate queues to process application reconciliation (milliseconds) and app syncing (seconds). Number of queue processors for each queue is controlled by
--status-processors(20 by default) and
--operation-processors(10 by default) flags. Increase number of processors if your Argo CD instance manages too many applications. For 1000 application we use 50 for
--status-processorsand 25 for
The manifest generation typically takes the most time during reconciliation. The duration of manifest generation is limited to make sure controller refresh queue does not overflow. The app reconciliation fails with
Context deadline exceedederror if manifest generating taking too much time. As workaround increase value of
--repo-server-timeout-secondsand consider scaling up
The controller uses
kubectlfork/exec to push changes into the cluster and to convert resource from preferred version into user specified version (e.g. Deployment
extensions/v1beta1). Same as config management tool
kubectlfork/exec might cause pod OOM kill. Use
--kubectl-parallelism-limitflag to limit number of allowed concurrent kubectl fork/execs.
The controller uses Kubernetes watch APIs to maintain lightweight Kubernetes cluster cache. This allows to avoid querying Kubernetes during app reconciliation and significantly improve performance. For performance reasons controller monitors and caches only preferred the version of a resource. During reconciliation, the controller might have to convert cached resource from preferred version into a version of the resource stored in Git. If
kubectl convertfails because conversion is not supported than controller fallback to Kubernetes API query which slows down reconciliation. In this case advice user-preferred resource version in Git.
The controller polls Git every 3m by default. You can increase this duration using
--app-resync secondsto reduce polling.
If the controller is managing too many clusters and uses too much memory then you can shard clusters across multiple controller replicas. To enable sharding increase the number of replicas in
StatefulSetand repeat number of replicas in
ARGOCD_CONTROLLER_REPLICASenvironment variable. The strategic merge patch below demonstrates changes required to configure two controller replicas.
apiVersion: apps/v1 kind: StatefulSet metadata: name: argocd-application-controller spec: replicas: 2 template: spec: containers: - name: argocd-application-controller env: - name: ARGOCD_CONTROLLER_REPLICAS value: "2"
ARGOCD_ENABLE_GRPC_TIME_HISTOGRAM(v1.8+)- environment variable that enables collecting RPC performance metrics. Enable it if you need to troubleshoot performance issue. Note: metric is expensive to both query and store!
argocd_app_reconcile- reports application reconciliation duration. Can be used to build reconciliation duration heat map to get high-level reconciliation performance picture.
argocd_app_k8s_request_total- number of k8s requests per application. The number of fallback Kubernetes API queries - useful to identify which application has a resource with non-preferred version and causes performance issues.
argocd-server is stateless and probably least likely to cause issues. You might consider increasing number of replicas to 3 or more to ensure there is no downtime during upgrades.
ARGOCD_GRPC_MAX_SIZE_MBenvironment variable allows specifying the max size of the server response message in megabytes. The default value is 200. You might need to increase for an Argo CD instance that manages 3000+ applications.
argocd-dex-server uses an in-memory database, and two or more instances would have inconsistent data.
argocd-redis is pre-configured with the understanding of only three total redis servers/sentinels.
Monorepo Scaling Considerations¶
Argo CD repo server maintains one repository clone locally and use it for application manifest generation. If the manifest generation requires to change a file in the local repository clone then only one concurrent manifest generation per server instance is allowed. This limitation might significantly slowdown Argo CD if you have a mono repository with multiple applications (50+).
Enable Concurrent Processing¶
Argo CD determines if manifest generation might change local files in the local repository clone based on config management tool and application settings. If the manifest generation has no side effects then requests are processed in parallel without the performance penalty. Following are known cases that might cause slowness and workarounds:
Multiple Helm based applications pointing to the same directory in one Git repository: ensure that your Helm chart don't have conditional dependencies and create
.argocd-allow-concurrencyfile in chart directory.
Multiple Custom plugin based applications: avoid creating temporal files during manifest generation and and create
.argocd-allow-concurrencyfile in app directory.
Multiple Kustomize or Ksonnet applications in same repository with parameter overrides: sorry, no workaround for now.
Webhook and Manifest Paths Annotation¶
Argo CD aggressively caches generated manifests and uses repository commit SHA as a cache key. A new commit to the Git repository invalidates cache for all applications configured in the repository
that again negatively affect mono repositories with multiple applications. You might use webhooks ⧉ and
CRD annotation to solve this problem and improve performance.
argocd.argoproj.io/manifest-generate-paths contains a semicolon-separated list of paths within the Git repository that are used during manifest generation. The webhook compares paths specified in the annotation
with the changed files specified in the webhook payload. If non of the changed files are located in the paths then webhook don't trigger application reconciliation and re-uses previously generated manifests cache for a new commit.
Installations that use a different repo for each app are not subject to this behavior and will likely get no benefit from using these annotations.
Installations with a large number of apps should also set the
--app-resync flag in the
argocd-application-controller process to a larger value to reduce automatic refreshes based on git polling. The exact value is a trade-off between reduced work and app sync in case of a missed webhook event. For most cases
1800 (30m) or
3600 (1h) is a good trade-off.
Application manifest paths annotation support depends on the git provider used for the Application. It is currently only supported for GitHub, GitLab, and Gogs based repos
- Relative path The annotation might contains relative path. In this case the path is considered relative to the path specified in the application source:
apiVersion: argoproj.io/v1alpha1 kind: Application metadata: name: guestbook namespace: argocd annotations: # resolves to the 'guestbook' directory argocd.argoproj.io/manifest-generate-paths: . spec: source: repoURL: https://github.com/argoproj/argocd-example-apps.git targetRevision: HEAD path: guestbook # ...
- Absolute path The annotation value might be an absolute path started from '/'. In this case path is considered as an absolute path within the Git repository:
apiVersion: argoproj.io/v1alpha1 kind: Application metadata: name: guestbook annotations: argocd.argoproj.io/manifest-generate-paths: /guestbook spec: source: repoURL: https://github.com/argoproj/argocd-example-apps.git targetRevision: HEAD path: guestbook # ...
- Multiple paths It is possible to put multiple paths into the annotation. Paths must be separated with a semicolon (
apiVersion: argoproj.io/v1alpha1 kind: Application metadata: name: guestbook annotations: # resolves to 'my-application' and 'shared' argocd.argoproj.io/manifest-generate-paths: .;../shared spec: source: repoURL: https://github.com/argoproj/argocd-example-apps.git targetRevision: HEAD path: my-application # ...