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張 旭

Rate Limits - Let's Encrypt - Free SSL/TLS Certificates - 0 views

letsencrypt.org/...rate-limits

server https security

shared by 張 旭 on 03 Jun 17 - No Cached
  • If you have a lot of subdomains, you may want to combine them into a single certificate, up to a limit of 100 Names per Certificate.
  • A certificate with multiple names is often called a SAN certificate, or sometimes a UCC certificate
  • The main limit is Certificates per Registered Domain (20 per week).
  • ...12 more annotations...
  • A certificate is considered a duplicate of an earlier certificate if they contain the exact same set of hostnames, ignoring capitalization and ordering of hostnames.
  • We also have a Duplicate Certificate limit of 5 certificates per week.
  • a Renewal Exemption to the Certificates per Registered Domain limit.
  • The Duplicate Certificate limit and the Renewal Exemption ignore the public key and extensions requested
  • You can issue 20 certificates in week 1, 20 more certificates in week 2, and so on, while not interfering with renewals of existing certificates.
  • Revoking certificates does not reset rate limits
  • If you’ve hit a rate limit, we don’t have a way to temporarily reset it.
  • get a list of certificates issued for your registered domain by searching on crt.sh
  • Revoking certificates does not reset rate limits
  • If you have a large number of pending authorization objects and are getting a rate limiting error, you can trigger a validation attempt for those authorization objects by submitting a JWS-signed POST to one of its challenges, as described in the ACME spec.
  • If you do not have logs containing the relevant authorization URLs, you need to wait for the rate limit to expire.
  • having a large number of pending authorizations is generally the result of a buggy client
張 旭

Guide to Service Discovery with Docker - 0 views

docs.datadoghq.com/...servicediscovery

docker service system server dns

shared by 張 旭 on 23 Apr 17 - No Cached
  • The Service Discovery feature watches for Docker events like when a container is created, destroyed, started or stopped. When one of these happens, the Agent identifies which service is impacted, loads the configuration template for this image, and automatically sets up its checks.
  • Configuration templates can be defined by simple template files or as single key-value stores using etcd or Consul.
張 旭

Automated Nginx Reverse Proxy for Docker - 0 views

jasonwilder.com/...nginx-reverse-proxy-for-docker

docker nginx proxy haproxy system web server

shared by 張 旭 on 04 Dec 15 - No Cached
  • Docker containers are assigned random IPs and ports which makes addressing them much more complicated from a client perspsective
  • Binding the container to the hosts port can prevent multiple containers from running on the same host. For example, only one container can bind to port 80 at a time.
  • Docker provides a remote API to inspect containers and access their IP, Ports and other configuration meta-data.
  • ...1 more annotation...
  • nginx template can be used to generate a reverse proxy configuration for docker containers using virtual hosts for routing.
張 旭

MetalLB, bare metal load-balancer for Kubernetes - 0 views

metallb.universe.tf

kubernetes network

shared by 張 旭 on 14 Apr 21 - No Cached
  • Kubernetes does not offer an implementation of network load-balancers (Services of type LoadBalancer) for bare metal clusters
  • If you’re not running on a supported IaaS platform (GCP, AWS, Azure…), LoadBalancers will remain in the “pending” state indefinitely when created.
  • Bare metal cluster operators are left with two lesser tools to bring user traffic into their clusters, “NodePort” and “externalIPs” services.
張 旭

Storage Classes | Kubernetes - 0 views

kubernetes.io/...storage-classes

kubernetes storage

shared by 張 旭 on 20 Apr 21 - No Cached
  • A StorageClass provides a way for administrators to describe the "classes" of storage they offer.
  • Kubernetes itself is unopinionated about what classes represent.
  • Each StorageClass contains the fields provisioner, parameters, and reclaimPolicy, which are used when a PersistentVolume belonging to the class needs to be dynamically provisioned.
  • ...2 more annotations...
  • The name of a StorageClass object is significant, and is how users can request a particular class.
  • Administrators can specify a default StorageClass only for PVCs that don't request any particular class to bind to
張 旭

Introduction to MongoDB - MongoDB Manual - 0 views

docs.mongodb.com/...introduction

database mongodb

shared by 張 旭 on 20 Apr 21 - No Cached
  • MongoDB is a document database designed for ease of development and scaling
  • MongoDB offers both a Community and an Enterprise version
  • A record in MongoDB is a document, which is a data structure composed of field and value pairs.
  • ...12 more annotations...
  • MongoDB documents are similar to JSON objects.
  • The values of fields may include other documents, arrays, and arrays of documents.
  • reduce need for expensive joins
  • MongoDB stores documents in collections.
  • Collections are analogous to tables in relational databases.
  • Read-only Views
  • Indexes support faster queries and can include keys from embedded documents and arrays.
  • MongoDB's replication facility, called replica set
  • A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and increasing data availability.
  • Sharding distributes data across a cluster of machines.
  • MongoDB supports creating zones of data based on the shard key.
  • MongoDB provides pluggable storage engine API
張 旭

Logging Architecture | Kubernetes - 0 views

kubernetes.io/...logging

kubernetes log

shared by 張 旭 on 27 May 21 - No Cached
  • Application logs can help you understand what is happening inside your application
  • container engines are designed to support logging.
  • The easiest and most adopted logging method for containerized applications is writing to standard output and standard error streams.
  • ...26 more annotations...
  • In a cluster, logs should have a separate storage and lifecycle independent of nodes, pods, or containers. This concept is called cluster-level logging.
  • Cluster-level logging architectures require a separate backend to store, analyze, and query logs
  • Kubernetes does not provide a native storage solution for log data.
  • use kubectl logs --previous to retrieve logs from a previous instantiation of a container.
  • A container engine handles and redirects any output generated to a containerized application's stdout and stderr streams
  • The Docker JSON logging driver treats each line as a separate message.
  • By default, if a container restarts, the kubelet keeps one terminated container with its logs.
  • An important consideration in node-level logging is implementing log rotation, so that logs don't consume all available storage on the node
  • You can also set up a container runtime to rotate an application's logs automatically.
  • The two kubelet flags container-log-max-size and container-log-max-files can be used to configure the maximum size for each log file and the maximum number of files allowed for each container respectively.
  • The kubelet and container runtime do not run in containers.
  • On machines with systemd, the kubelet and container runtime write to journald. If systemd is not present, the kubelet and container runtime write to .log files in the /var/log directory.
  • System components inside containers always write to the /var/log directory, bypassing the default logging mechanism.
  • Kubernetes does not provide a native solution for cluster-level logging
  • Use a node-level logging agent that runs on every node.
  • implement cluster-level logging by including a node-level logging agent on each node.
  • the logging agent is a container that has access to a directory with log files from all of the application containers on that node.
  • the logging agent must run on every node, it is recommended to run the agent as a DaemonSet
  • Node-level logging creates only one agent per node and doesn't require any changes to the applications running on the node.
  • Containers write stdout and stderr, but with no agreed format. A node-level agent collects these logs and forwards them for aggregation.
  • Each sidecar container prints a log to its own stdout or stderr stream.
  • It is not recommended to write log entries with different formats to the same log stream
  • writing logs to a file and then streaming them to stdout can double disk usage.
  • If you have an application that writes to a single file, it's recommended to set /dev/stdout as the destination
  • it's recommended to use stdout and stderr directly and leave rotation and retention policies to the kubelet.
  • Using a logging agent in a sidecar container can lead to significant resource consumption. Moreover, you won't be able to access those logs using kubectl logs because they are not controlled by the kubelet.
張 旭

Upgrading kubeadm clusters | Kubernetes - 0 views

kubernetes.io/...kubeadm-upgrade

kubernetes system

shared by 張 旭 on 02 Jun 21 - No Cached
  • Swap must be disabled.
  • read the release notes carefully.
  • back up any important components, such as app-level state stored in a database.
  • ...16 more annotations...
  • All containers are restarted after upgrade, because the container spec hash value is changed.
  • The upgrade procedure on control plane nodes should be executed one node at a time.
  • /etc/kubernetes/admin.conf
  • kubeadm upgrade also automatically renews the certificates that it manages on this node. To opt-out of certificate renewal the flag --certificate-renewal=false can be used.
  • Manually upgrade your CNI provider plugin.
  • sudo systemctl daemon-reload sudo systemctl restart kubelet
  • If kubeadm upgrade fails and does not roll back, for example because of an unexpected shutdown during execution, you can run kubeadm upgrade again.
  • To recover from a bad state, you can also run kubeadm upgrade apply --force without changing the version that your cluster is running.
  • kubeadm-backup-etcd contains a backup of the local etcd member data for this control plane Node.
  • the contents of this folder can be manually restored in /var/lib/etcd
  • kubeadm-backup-manifests contains a backup of the static Pod manifest files for this control plane Node.
  • the contents of this folder can be manually restored in /etc/kubernetes/manifests
  • Enforces the version skew policies.
  • Upgrades the control plane components or rollbacks if any of them fails to come up.
  • Creates new certificate and key files of the API server and backs up old files if they're about to expire in 180 days.
  • backup folders under /etc/kubernetes/tmp
張 旭

Quick start - 0 views

terragrunt.gruntwork.io/...quick-start

devops terraform

shared by 張 旭 on 15 Jun 21 - No Cached
  • Terragrunt will forward almost all commands, arguments, and options directly to Terraform, but based on the settings in your terragrunt.hcl file
  • the backend configuration does not support variables or expressions of any sort
  • the path_relative_to_include() built-in function,
  • ...9 more annotations...
  • The generate attribute is used to inform Terragrunt to generate the Terraform code for configuring the backend.
  • The find_in_parent_folders() helper will automatically search up the directory tree to find the root terragrunt.hcl and inherit the remote_state configuration from it.
  • Unlike the backend configurations, provider configurations support variables,
  • if you needed to modify the configuration to expose another parameter (e.g session_name), you would have to then go through each of your modules to make this change.
  • instructs Terragrunt to create the file provider.tf in the working directory (where Terragrunt calls terraform) before it calls any of the Terraform commands
  • large modules should be considered harmful.
  • it is a Bad Idea to define all of your environments (dev, stage, prod, etc), or even a large amount of infrastructure (servers, databases, load balancers, DNS, etc), in a single Terraform module.
  • Large modules are slow, insecure, hard to update, hard to code review, hard to test, and brittle (i.e., you have all your eggs in one basket).
  • Terragrunt allows you to define your Terraform code once and to promote a versioned, immutable “artifact” of that exact same code from environment to environment.
張 旭

Keep your Terraform code DRY - 0 views

terragrunt.gruntwork.io/...keep-your-terraform-code-dry

terraform devops

shared by 張 旭 on 15 Jun 21 - No Cached
  • Each root terragrunt.hcl file (the one at the environment level, e.g prod/terragrunt.hcl) should define a generate block to generate the AWS provider configuration to assume the role for that environment.
  • The include block tells Terragrunt to use the exact same Terragrunt configuration from the terragrunt.hcl file specified via the path parameter.
  • 張 旭 on 15 Jun 21
     
    "Each root terragrunt.hcl file (the one at the environment level, e.g prod/terragrunt.hcl) should define a generate block to generate the AWS provider configuration to assume the role for that environment. "
張 旭

Locals - 0 views

terragrunt.gruntwork.io/...locals

terraform devops

shared by 張 旭 on 15 Jun 21 - No Cached
  • common_vars = yamldecode(file(find_in_parent_folders("common_vars.yaml")))
  • 張 旭 on 15 Jun 21
     
    "common_vars = yamldecode(file(find_in_parent_folders("common_vars.yaml")))"
張 旭

Override Files - Configuration Language - Terraform by HashiCorp - 0 views

www.terraform.io/...override.html

terraform devops

shared by 張 旭 on 15 Jun 21 - No Cached
  • In both the required_version and required_providers settings, each override constraint entirely replaces the constraints for the same component in the original block.
  • If both the base block and the override block both set required_version then the constraints in the base block are entirely ignored.
  • Terraform normally loads all of the .tf and .tf.json files within a directory and expects each one to define a distinct set of configuration objects.
  • ...14 more annotations...
  • If two files attempt to define the same object, Terraform returns an error.
  • a human-edited configuration file in the Terraform language native syntax could be partially overridden using a programmatically-generated file in JSON syntax.
  • Terraform has special handling of any configuration file whose name ends in _override.tf or _override.tf.json
  • Terraform initially skips these override files when loading configuration, and then afterwards processes each one in turn (in lexicographical order).
  • merges the override block contents into the existing object.
  • Over-use of override files hurts readability, since a reader looking only at the original files cannot easily see that some portions of those files have been overridden without consulting all of the override files that are present.
  • When using override files, use comments in the original files to warn future readers about which override files apply changes to each block.
  • A top-level block in an override file merges with a block in a normal configuration file that has the same block header.
  • Within a top-level block, an attribute argument within an override block replaces any argument of the same name in the original block.
  • Within a top-level block, any nested blocks within an override block replace all blocks of the same type in the original block.
  • The contents of nested configuration blocks are not merged.
  • If more than one override file defines the same top-level block, the overriding effect is compounded, with later blocks taking precedence over earlier blocks
  • The settings within terraform blocks are considered individually when merging.
  • If the required_providers argument is set, its value is merged on an element-by-element basis, which allows an override block to adjust the constraint for a single provider without affecting the constraints for other providers.
  • 張 旭 on 15 Jun 21
     
    "In both the required_version and required_providers settings, each override constraint entirely replaces the constraints for the same component in the original block. "
張 旭

Configuration Blocks and Attributes - 0 views

terragrunt.gruntwork.io/...config-blocks-and-attributes

terraform devops

shared by 張 旭 on 16 Jun 21 - No Cached
  • The generate block can be used to arbitrarily generate a file in the terragrunt working directory (where terraform is called).
  • This can be used to generate common terraform configurations that are shared across multiple terraform modules.
  • 張 旭 on 16 Jun 21
     
    "The generate block can be used to arbitrarily generate a file in the terragrunt working directory (where terraform is called). "
張 旭

Database Profiler - MongoDB Manual - 0 views

docs.mongodb.com/...manage-the-database-profiler

database mongodb

shared by 張 旭 on 16 Apr 21 - No Cached
  • The database profiler collects detailed information about Database Commands executed against a running mongod instance.
  • The profiler writes all the data it collects to the system.profile collection, a capped collection in the admin database.
  • db.setProfilingLevel(2)
  • ...10 more annotations...
  • The slowms and sampleRate profiling settings are global. When set, these settings affect all databases in your process.
  • db.setProfilingLevel(1, { slowms: 20 })
  • db.setProfilingLevel(0, { slowms: 20 })
  • show profile
  • The system.profile collection is a capped collection with a default size of 1 megabyte.
  • By default, sampleRate is set to 1.0, meaning all slow operations are profiled.
  • When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.
  • The slowms field indicates operation time threshold, in milliseconds, beyond which operations are considered slow.
  • You cannot enable profiling on a mongos instance.
  • profiler logs information about database operations in the system.profile collection.
張 旭

MongoDB Performance - MongoDB Manual - 0 views

docs.mongodb.com/...analyzing-mongodb-performance

database mongodb performance

shared by 張 旭 on 20 Apr 21 - No Cached
  • MongoDB uses a locking system to ensure data set consistency. If certain operations are long-running or a queue forms, performance will degrade as requests and operations wait for the lock.
  • performance limitations as a result of inadequate or inappropriate indexing strategies, or as a consequence of poor schema design patterns.
  • performance issues may be temporary and related to abnormal traffic load.
  • ...9 more annotations...
  • Lock-related slowdowns can be intermittent.
  • If globalLock.currentQueue.total is consistently high, then there is a chance that a large number of requests are waiting for a lock.
  • If globalLock.totalTime is high relative to uptime, the database has existed in a lock state for a significant amount of time.
  • For write-heavy applications, deploy sharding and add one or more shards to a sharded cluster to distribute load among mongod instances.
  • Unless constrained by system-wide limits, the maximum number of incoming connections supported by MongoDB is configured with the maxIncomingConnections setting.
  • When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.
  • At higher logLevel settings, all operations appear in the diagnostic log regardless of their latency with the following exception
  • Full Time Diagnostic Data Collection (FTDC) mechanism. FTDC data files are compressed, are not human-readable, and inherit the same file access permissions as the MongoDB data files.
  • mongod processes store FTDC data files in a diagnostic.data directory under the instances storage.dbPath.
  • 張 旭 on 20 Apr 21
     
    "MongoDB uses a locking system to ensure data set consistency. If certain operations are long-running or a queue forms, performance will degrade as requests and operations wait for the lock."
張 旭

Production Notes - MongoDB Manual - 0 views

docs.mongodb.com/...production-notes

mongodb database performance

shared by 張 旭 on 29 Apr 21 - No Cached
  • mongod will not start if dbPath contains data files created by a storage engine other than the one specified by --storageEngine.
  • mongod must possess read and write permissions for the specified dbPath.
  • WiredTiger supports concurrent access by readers and writers to the documents in a collection
  • ...9 more annotations...
  • Journaling guarantees that MongoDB can quickly recover write operations that were written to the journal but not written to data files in cases where mongod terminated due to a crash or other serious failure.
  • To use read concern level of "majority", replica sets must use WiredTiger storage engine.
  • Write concern describes the level of acknowledgement requested from MongoDB for write operations.
  • With stronger write concerns, clients must wait after sending a write operation until MongoDB confirms the write operation at the requested write concern level.
  • By default, authorization is not enabled, and mongod assumes a trusted environment
  • The HTTP interface is disabled by default. Do not enable the HTTP interface in production environments.
  • Avoid overloading the connection resources of a mongod or mongos instance by adjusting the connection pool size to suit your use case.
  • ensure that each mongod or mongos instance has access to two real cores or one multi-core physical CPU.
  • The WiredTiger storage engine is multithreaded and can take advantage of additional CPU cores
張 旭

The differences between Docker, containerd, CRI-O and runc - Tutorial Works - 0 views

www.tutorialworks.com/ocker-containerd-runc-crio-oci

docker container devops

shared by 張 旭 on 28 Jun 21 - No Cached
  • Docker isn’t the only container contender on the block.
  • Container Runtime Interface (CRI), which defines an API between Kubernetes and the container runtime
  • Open Container Initiative (OCI) which publishes specifications for images and containers.
  • ...20 more annotations...
  • for a lot of people, the name “Docker” itself is synonymous with the word “container”.
  • Docker created a very ergonomic (nice-to-use) tool for working with containers – also called docker.
  • docker is designed to be installed on a workstation or server and comes with a bunch of tools to make it easy to build and run containers as a developer, or DevOps person.
  • containerd: This is a daemon process that manages and runs containers.
  • runc: This is the low-level container runtime (the thing that actually creates and runs containers).
  • libcontainer, a native Go-based implementation for creating containers.
  • Kubernetes includes a component called dockershim, which allows it to support Docker.
  • Kubernetes prefers to run containers through any container runtime which supports its Container Runtime Interface (CRI).
  • Kubernetes will remove support for Docker directly, and prefer to use only container runtimes that implement its Container Runtime Interface.
  • Both containerd and CRI-O can run Docker-formatted (actually OCI-formatted) images, they just do it without having to use the docker command or the Docker daemon.
  • Docker images, are actually images packaged in the Open Container Initiative (OCI) format.
  • CRI is the API that Kubernetes uses to control the different runtimes that create and manage containers.
  • CRI makes it easier for Kubernetes to use different container runtimes
  • containerd is a high-level container runtime that came from Docker, and implements the CRI spec
  • containerd was separated out of the Docker project, to make Docker more modular.
  • CRI-O is another high-level container runtime which implements the Container Runtime Interface (CRI).
  • The idea behind the OCI is that you can choose between different runtimes which conform to the spec.
  • runc is an OCI-compatible container runtime.
  • A reference implementation is a piece of software that has implemented all the requirements of a specification or standard.
  • runc provides all of the low-level functionality for containers, interacting with existing low-level Linux features, like namespaces and control groups.
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