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張 旭

The for_each Meta-Argument - Configuration Language | Terraform | HashiCorp Developer - 0 views

  • A given resource or module block cannot use both count and for_each
  • The for_each meta-argument accepts a map or a set of strings, and creates an instance for each item in that map or set
  • each.key — The map key (or set member) corresponding to this instance.
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  • each.value — The map value corresponding to this instance. (If a set was provided, this is the same as each.key.)
  • for_each keys cannot be the result (or rely on the result of) of impure functions, including uuid, bcrypt, or timestamp, as their evaluation is deferred during the main evaluation step.
  • The value used in for_each is used to identify the resource instance and will always be disclosed in UI output, which is why sensitive values are not allowed.
  • if you would like to call keys(local.map), where local.map is an object with sensitive values (but non-sensitive keys), you can create a value to pass to for_each with toset([for k,v in local.map : k]).
  • for_each can't refer to any resource attributes that aren't known until after a configuration is applied (such as a unique ID generated by the remote API when an object is created).
  • he for_each argument does not implicitly convert lists or tuples to sets.
  • Transform a multi-level nested structure into a flat list by using nested for expressions with the flatten function.
  • Instances are identified by a map key (or set member) from the value provided to for_each
  • Within nested provisioner or connection blocks, the special self object refers to the current resource instance, not the resource block as a whole.
  • Conversion from list to set discards the ordering of the items in the list and removes any duplicate elements.
張 旭

Syntax - Configuration Language | Terraform | HashiCorp Developer - 0 views

  • the native syntax of the Terraform language, which is a rich language designed to be relatively easy for humans to read and write.
  • Terraform's configuration language is based on a more general language called HCL, and HCL's documentation usually uses the word "attribute" instead of "argument."
  • A particular block type may have any number of required labels, or it may require none
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  • After the block type keyword and any labels, the block body is delimited by the { and } characters
  • Identifiers can contain letters, digits, underscores (_), and hyphens (-). The first character of an identifier must not be a digit, to avoid ambiguity with literal numbers.
  • The # single-line comment style is the default comment style and should be used in most cases.
  • he idiomatic style is to use the Unix convention
  • Indent two spaces for each nesting level.
  • align their equals signs
  • Use empty lines to separate logical groups of arguments within a block.
  • Use one blank line to separate the arguments from the blocks.
  • "meta-arguments" (as defined by the Terraform language semantics)
  • Avoid separating multiple blocks of the same type with other blocks of a different type, unless the block types are defined by semantics to form a family.
  • Resource names must start with a letter or underscore, and may contain only letters, digits, underscores, and dashes.
  • Each resource is associated with a single resource type, which determines the kind of infrastructure object it manages and what arguments and other attributes the resource supports.
  • Each resource type is implemented by a provider, which is a plugin for Terraform that offers a collection of resource types.
  • By convention, resource type names start with their provider's preferred local name.
  • Most publicly available providers are distributed on the Terraform Registry, which also hosts their documentation.
  • The Terraform language defines several meta-arguments, which can be used with any resource type to change the behavior of resources.
  • use precondition and postcondition blocks to specify assumptions and guarantees about how the resource operates.
  • Some resource types provide a special timeouts nested block argument that allows you to customize how long certain operations are allowed to take before being considered to have failed.
  • Timeouts are handled entirely by the resource type implementation in the provider
  • Most resource types do not support the timeouts block at all.
  • A resource block declares that you want a particular infrastructure object to exist with the given settings.
  • Destroy resources that exist in the state but no longer exist in the configuration.
  • Destroy and re-create resources whose arguments have changed but which cannot be updated in-place due to remote API limitations.
  • Expressions within a Terraform module can access information about resources in the same module, and you can use that information to help configure other resources. Use the <RESOURCE TYPE>.<NAME>.<ATTRIBUTE> syntax to reference a resource attribute in an expression.
  • resources often provide read-only attributes with information obtained from the remote API; this often includes things that can't be known until the resource is created, like the resource's unique random ID.
  • data sources, which are a special type of resource used only for looking up information.
  • some dependencies cannot be recognized implicitly in configuration.
  • local-only resource types exist for generating private keys, issuing self-signed TLS certificates, and even generating random ids.
  • The behavior of local-only resources is the same as all other resources, but their result data exists only within the Terraform state.
  • The count meta-argument accepts a whole number, and creates that many instances of the resource or module.
  • count.index — The distinct index number (starting with 0) corresponding to this instance.
  • the count value must be known before Terraform performs any remote resource actions. This means count can't refer to any resource attributes that aren't known until after a configuration is applied
  • Within nested provisioner or connection blocks, the special self object refers to the current resource instance, not the resource block as a whole.
  • This was fragile, because the resource instances were still identified by their index instead of the string values in the list.
  •  
    "the native syntax of the Terraform language, which is a rich language designed to be relatively easy for humans to read and write. "
張 旭

Automated Nginx Reverse Proxy for Docker - 0 views

  • 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.
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  • nginx template can be used to generate a reverse proxy configuration for docker containers using virtual hosts for routing.
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