Commit graph

95 commits

Author SHA1 Message Date
Joe Duffy 69f5882b97
Fix two closure bugs (#664)
This fixes two closure bugs.

First, we had special cased `__awaiter` from days of yore, when we had
special cased its capture.  I also think we were confused at some point
and instead of fixing the fact that we captured `this` for non-arrow
functions, which `__awaiter` would trigger, we doubled down on this
incorrect hack.  This means we missed a real bonafide `this` capture.

Second, we had a global cache of captured variable objects.  So, if a
free variable resolved to the same JavaScript object, it always resolved
to the first serialization of that object.  This is clearly wrong if
the object had been mutated in the meantime.  The cache is required to
reach a fixed point during mutually recursive captures, but we should
only be using it for the duration of a single closure serialization
call.  That's precisely what this commit does.

Also add a fix for this case.

This fixes pulumi/pulumi#663.
2017-12-07 16:21:28 -08:00
Joe Duffy 16ade183d8
Add a manifest to checkpoint files (#630)
This change adds a new manifest section to the checkpoint files.
The existing time moves into it, and we add to it the version of
the Pulumi CLI that created it, along with the names, types, and
versions of all plugins used to generate the file.  There is a
magic cookie that we also use during verification.

This is to help keep us sane when debugging problems "in the wild,"
and I'm sure we will add more to it over time (checksum, etc).

For example, after an up, you can now see this in `pulumi stack`:

```
Current stack is demo:
    Last updated at 2017-12-01 13:48:49.815740523 -0800 PST
    Pulumi version v0.8.3-79-g1ab99ad
    Plugin pulumi-provider-aws [resource] version v0.8.3-22-g4363e77
    Plugin pulumi-langhost-nodejs [language] version v0.8.3-79-g77bb6b6
    Checkpoint file is /Users/joeduffy/dev/code/src/github.com/pulumi/pulumi-aws/.pulumi/stacks/webserver/demo.json
```

This addresses pulumi/pulumi#628.
2017-12-01 13:50:32 -08:00
joeduffy a4c7c05e27 Simplify RPC changes
This change simplifies the necessary RPC changes for components.
Instead of a Begin/End pair, which complicates the whole system
because now we have the opportunity of a missing End call, we will
simply let RPCs come in that append outputs to existing states.
2017-11-29 12:08:01 -08:00
joeduffy c5b7b6ef11 Bring back component outputs
This change brings back component outputs to the overall system again.
In doing so, it generally overhauls the way we do resource RPCs a bit:

* Instead of RegisterResource and CompleteResource, we call these
  BeginRegisterResource and EndRegisterResource, which begins to model
  these as effectively "asynchronous" resource requests.  This should also
  help with parallelism (https://github.com/pulumi/pulumi/issues/106).

* Flip the CLI/engine a little on its head.  Rather than it driving the
  planning and deployment process, we move more to a model where it
  simply observes it.  This is done by implementing an event handler
  interface with three events: OnResourceStepPre, OnResourceStepPost,
  and OnResourceComplete.  The first two are invoked immediately before
  and after any step operation, and the latter is invoked whenever a
  EndRegisterResource comes in.  The reason for the asymmetry here is
  that the checkpointing logic in the deployment engine is largely
  untouched (intentionally, as this is a sensitive part of the system),
  and so the "begin"/"end" nature doesn't flow through faithfully.

* Also make the engine more event-oriented in its terminology and the
  way it handles the incoming BeginRegisterResource and
  EndRegisterResource events from the language host.  This is the first
  step down a long road of incrementally refactoring the engine to work
  this way, a necessary prerequisite for parallelism.
2017-11-29 07:42:14 -08:00
joeduffy 5762f2d0a6 Merge remote-tracking branch 'origin/resource_parenting' into resource_parenting_lite 2017-11-28 11:03:34 -08:00
joeduffy 41ae40249e Make root resources more general 2017-11-26 12:01:13 -08:00
joeduffy be201739b4 Make some diff formatting changes
* Don't show +s, -s, and ~s deeply.  The intended format here looks
  more like

      + aws:iam/instanceProfile:InstanceProfile (create)
          [urn=urn:pulumi:test::aws/minimal::aws/iam/instanceProfile:InstanceProfile::ip2]
          name: "ip2-079a29f428dc9987"
          path: "/"
          role: "ir-d0a632e3084a0252"

  versus

      + aws:iam/instanceProfile:InstanceProfile (create)
        + [urn=urn:pulumi:test::aws/minimal::aws/iam/instanceProfile:InstanceProfile::ip2]
        + name: "ip2-079a29f428dc9987"
        + path: "/"
        + role: "ir-d0a632e3084a0252"

  This makes it easier to see the resources modified in the output.

* Print adds/deletes during updates as

      - property: "x"
      + property: "y"

  rather than

      ~ property: "x"
      ~ property: "y"

  the latter of which doesn't really tell you what's new/old.

* Show parent indentation on output properties, so they line up correctly.

* Only print stack outputs if not undefined.
2017-11-26 09:39:29 -08:00
joeduffy 8dc9fd027c Add back stack outputs
This change simply prints a stack's output properties at the end of
running the program, since we now no longer actual record the outputs
as part of component registration.  Bringing that back is part of
pulumi/pulumi#340, however it is too risky to add hastily.  So, for
now, we will simply special case Stacks.
2017-11-26 08:14:01 -08:00
joeduffy 86f97de7eb Merge root stack changes with parenting 2017-11-26 08:14:01 -08:00
joeduffy a2ae4accf4 Switch to parent pointers; display components nicely
This change switches from child lists to parent pointers, in the
way resource ancestries are represented.  This cleans up a fair bit
of the old parenting logic, including all notion of ambient parent
scopes (and will notably address pulumi/pulumi#435).

This lets us show a more parent/child display in the output when
doing planning and updating.  For instance, here is an update of
a lambda's text, which is logically part of a cloud timer:

    * cloud:timer:Timer: (same)
          [urn=urn:pulumi:malta::lm-cloud:☁️timer:Timer::lm-cts-malta-job-CleanSnapshots]
        * cloud:function:Function: (same)
              [urn=urn:pulumi:malta::lm-cloud:☁️function:Function::lm-cts-malta-job-CleanSnapshots]
            * aws:serverless:Function: (same)
                  [urn=urn:pulumi:malta::lm-cloud::aws:serverless:Function::lm-cts-malta-job-CleanSnapshots]
                ~ aws:lambda/function:Function: (modify)
                      [id=lm-cts-malta-job-CleanSnapshots-fee4f3bf41280741]
                      [urn=urn:pulumi:malta::lm-cloud::aws:lambda/function:Function::lm-cts-malta-job-CleanSnapshots]
                    - code            : archive(assets:2092f44) {
                        // etc etc etc

Note that we still get walls of text, but this will be actually
quite nice when combined with pulumi/pulumi#454.

I've also suppressed printing properties that didn't change during
updates when --detailed was not passed, and also suppressed empty
strings and zero-length arrays (since TF uses these as defaults in
many places and it just makes creation and deletion quite verbose).

Note that this is a far cry from everything we can possibly do
here as part of pulumi/pulumi#340 (and even pulumi/pulumi#417).
But it's a good start towards taming some of our output spew.
2017-11-26 08:14:01 -08:00
joeduffy 7e48e8726b Add (back) component outputs
This change adds back component output properties.  Doing so
requires splitting the RPC interface for creating resources in
half, with an initial RegisterResource which contains all of the
input properties, and a final CompleteResource which optionally
contains any output properties synthesized by the component.
2017-11-20 17:38:09 -08:00
joeduffy 86267b86b9 Merge root stack changes with parenting 2017-11-20 10:08:59 -08:00
joeduffy 5dc4b0b75c Switch to parent pointers; display components nicely
This change switches from child lists to parent pointers, in the
way resource ancestries are represented.  This cleans up a fair bit
of the old parenting logic, including all notion of ambient parent
scopes (and will notably address pulumi/pulumi#435).

This lets us show a more parent/child display in the output when
doing planning and updating.  For instance, here is an update of
a lambda's text, which is logically part of a cloud timer:

    * cloud:timer:Timer: (same)
          [urn=urn:pulumi:malta::lm-cloud:☁️timer:Timer::lm-cts-malta-job-CleanSnapshots]
        * cloud:function:Function: (same)
              [urn=urn:pulumi:malta::lm-cloud:☁️function:Function::lm-cts-malta-job-CleanSnapshots]
            * aws:serverless:Function: (same)
                  [urn=urn:pulumi:malta::lm-cloud::aws:serverless:Function::lm-cts-malta-job-CleanSnapshots]
                ~ aws:lambda/function:Function: (modify)
                      [id=lm-cts-malta-job-CleanSnapshots-fee4f3bf41280741]
                      [urn=urn:pulumi:malta::lm-cloud::aws:lambda/function:Function::lm-cts-malta-job-CleanSnapshots]
                    - code            : archive(assets:2092f44) {
                        // etc etc etc

Note that we still get walls of text, but this will be actually
quite nice when combined with pulumi/pulumi#454.

I've also suppressed printing properties that didn't change during
updates when --detailed was not passed, and also suppressed empty
strings and zero-length arrays (since TF uses these as defaults in
many places and it just makes creation and deletion quite verbose).

Note that this is a far cry from everything we can possibly do
here as part of pulumi/pulumi#340 (and even pulumi/pulumi#417).
But it's a good start towards taming some of our output spew.
2017-11-20 09:07:53 -08:00
Luke Hoban 96e4b74b15
Support for stack outputs (#581)
Adds support for top-level exports in the main script of a Pulumi Program to be captured as stack-level output properties.

This create a new `pulumi:pulumi:Stack` component as the root of the resource tree in all Pulumi programs.  That resources has properties for each top-level export in the Node.js script.

Running `pulumi stack` will display the current value of these outputs.
2017-11-17 15:22:41 -08:00
CyrusNajmabadi 36a692390d
Properly capture 'arguments' when creating our serialization closure. (#569)
* Simplify how we capture 'this' in our serialization logic.
* Properly capture 'arguments'

* add tests for 'arguments' capture.

* Properly serialize out 'arguments'
* Invert 'with' and function closure.
2017-11-15 11:31:17 -08:00
Luke Hoban af5298f4aa
Initial work on tracing support (#521)
Adds OpenTracing in the Pulumi engine and plugin + langhost subprocesses.

We currently create a single root span for any `Enging.plan` operation - which is a single `preview`, `update`, `destroy`, etc.

The only sub-spans we currently create are at gRPC boundaries, both on the client and server sides and on both the langhost and provider plugin interfaces.

We could extend this to include spans for any other semantically meaningful sections of compute inside the engine, though initial examples show we get pretty good granularity of coverage by focusing on the gRPC boundaries.

In the future, this should be easily extensible to HTTP boundaries and to track other bulky I/O like datastore read/writes once we hook up to the PPC and Pulumi Cloud.

We expose a `--trace <endpoint>` option to enable tracing on the CLI, which we will aim to thread through to subprocesses.

We currently support sending tracing data to a Zipkin-compatible endpoint.  This has been validated with both Zipkin and Jaeger UIs.

We do not yet have any tracing inside the TypeScript side of the JS langhost RPC interface.  There is not yet automatic gRPC OpenTracing instrumentation (though it looks like it's in progress now) - so we would need to manually create meaningful spans on that side of the interface.
2017-11-08 17:08:51 -08:00
Joe Duffy 8d916dc00c
Improve promise leak diagnostics (#508)
This change adds more context information to debuggable promises
to aid with leak detection.  This was super helpful for me just now!
2017-10-31 07:48:59 -07:00
joeduffy b3c4a52933 Add a diagnostics messages for the serialized promise chain 2017-10-31 06:52:42 -07:00
Matt Ellis 67426833a4
Merge pull request #505 from pulumi/FixWindows
Get windows integration tests working again
2017-10-31 00:19:20 -07:00
Matt Ellis 25552b8432 Remove unused import 2017-10-30 23:35:18 -07:00
Joe Duffy 0383c24087
Drain the message queue before exiting (#498)
This change remembers that we failed due to an uncaught exception,
and defers the process.exit(1) until we actually reach the process's
exit event.  This ensures that we drain the message queue before
exiting, which ensures that outbound messages actually reach their
destination.
2017-10-30 11:48:54 -07:00
pat@pulumi.com 8fd2d3e9e0 Fix require paths in closure serialization on Windows.
We were ending up with unescaped backslashes in require paths, which was
causing the requires to fail.
2017-10-30 08:55:18 -07:00
Joe Duffy cdb2c79e8e
Exit with an error code in the face of unhandled errors (#495)
As part of fixing the exit bug recently, we accidentally made errors
lead to zero exit codes.  As a result, the Pulumi CLI thought the
prgoram exited ordinarily, and proceeded to do its usual planning and
deployment, rather than terminating abruptly.

This is a byproduct of how Node's process.uncaughtException handler
works.  It hijacks and replaces all usual error logic, including the
process.exit part.  This change simply adds back the non-zero exit.

I also added a test (and fixed one other that began failing
afterwards), so that we can prevent regressions down the road.
2017-10-28 17:05:05 -07:00
pat@pulumi.com 73baaa2867 Follow up to PR feedback for #475.
- Change a `console.log` to `log.debug`
- Null out gRPC clients after disconnecting.
2017-10-27 13:51:47 -07:00
pat@pulumi.com 97f99d7fa1 Do not disconnect from the engine prematurely.
The `nodejs` language support is implemented as two programs: one that
manages the initial connection to the engine and provides the language
serivce itself, and another that the language service invokes in order
to run a `nodejs` Pulumi program. The latter is responsible for running
the user's program and communicating its resource requests to the
engine. Currently, `run` effectively assumes that the user's program
will run synchronously from start to finish, and will disconnect from
the engine once the user's program has completed. This assumption breaks
if the user's program requires multiple turns of the event loop to
finish its root resource requests. For example, the following program
would fail to create its second resource because the engine will be
disconnected once it reaches its `await`:

```
(async () => {
    let a = new Resource();
    await somePromise();
    let = new Resource();
})();
```

These changes fix this issue by disconnecting from the engine during
process shutdown rather than after the user's program has finished its
first turn through the event loop.
2017-10-26 12:16:32 -07:00
joeduffy c61bce3e41 Permit undefined in more places
The prior code was a little too aggressive in rejected undefined
properties, because it assumed any occurrence indicated a resource
that was unavailable due to planning.  This is a by-produt of our
relatively recent decision to flow undefineds freely during planning.

The problem is, it's entirely legitimate to have undefined values
deep down in JavaScript structures, entirely unrelated to resources
whose property values are unknown due to planning.

This change flows undefined more freely.  There really are no
negative consequences of doing so, and avoids hitting some overly
aggressive assertion failures in some important scenarios.  Ideally
we would have a way to know statically whether something is a resource
property, and tighten up the assertions just to catch possible bugs
in the system, but because this is JavaScript, and all the assertions
are happening at runtime, we simply lack the necessary metadata to do so.
2017-10-23 16:02:28 -07:00
joeduffy 680e73bb97 Add context to "unexpected unknown property" error log 2017-10-23 15:31:45 -07:00
Luke Hoban ba98f5e837 Fix bugs in free variable analysis (#444)
Properties and methods were not being traversed correctly.

Fixes #442.
2017-10-19 23:20:57 -07:00
joeduffy 599ca8ea43 Add accessors to fetch the Pulumi project and stack names
This change adds functions, `pulumi.getProject()` and `pulumi.getStack()`,
to fetch the names of the project and stack, respectively.  These can be
handy in generating names, specializing areas of the code, etc.

This fixes pulumi/pulumi#429.
2017-10-19 08:26:57 -07:00
CyrusNajmabadi d929c169de Enable tslinting of the nodejs sdk. (#433) 2017-10-18 15:03:56 -07:00
CyrusNajmabadi d007f040b9 Move from acorn to TypeScript as the parser we use when computing free variables. (#431) 2017-10-18 13:29:53 -07:00
joeduffy 301739c6b5 Add auto-parenting
This changes a few things about "components":

* Rename what was previously ExternalResource to CustomResource,
  and all of the related fields and parameters that this implies.
  This just seems like a much nicer and expected name for what
  these represent.  I realize I am stealing a name we had thought
  about using elsewhere, but this seems like an appropriate use.

* Introduce ComponentResource, to make initializing resources
  that merely aggregate other resources easier to do correctly.

* Add a withParent and parentScope concept to Resource, to make
  allocating children less error-prone.  Now there's no need to
  explicitly adopt children as they are allocated; instead, any
  children allocated as part of the withParent callback will
  auto-parent to the resource provided.  This is used by
  ComponentResource's initialization function to make initialization
  easier, including the distinction between inputs and outputs.
2017-10-15 04:38:26 -07:00
joeduffy fbfca58a3f Implement components
This change implements core support for "components" in the Pulumi
Fabric.  This work is described further in pulumi/pulumi#340, where
we are still discussing some of the finer points.

In a nutshell, resources no longer imply external providers.  It's
entirely possible to have a resource that logically represents
something but without having a physical manifestation that needs to
be tracked and managed by our typical CRUD operations.

For example, the aws/serverless/Function helper is one such type.
It aggregates Lambda-related resources and exposes a nice interface.
All of the Pulumi Cloud Framework resources are also examples.

To indicate that a resource does participate in the usual CRUD resource
provider, it simply derives from ExternalResource instead of Resource.

All resources now have the ability to adopt children.  This is purely
a metadata/tagging thing, and will help us roll up displays, provide
attribution to the developer, and even hide aspects of the resource
graph as appropriate (e.g., when they are implementation details).

Our use of this capability is ultra limited right now; in fact, the
only place we display children is in the CLI output.  For instance:

    + aws:serverless:Function: (create)
      [urn=urn:pulumi:demo::serverless::aws:serverless:Function::mylambda]
      => urn:pulumi:demo::serverless::aws:iam/role:Role::mylambda-iamrole
      => urn:pulumi:demo::serverless::aws:iam/rolePolicyAttachment:RolePolicyAttachment::mylambda-iampolicy-0
      => urn:pulumi:demo::serverless::aws:lambda/function:Function::mylambda

The bit indicating whether a resource is external or not is tracked
in the resulting checkpoint file, along with any of its children.
2017-10-14 18:30:59 -07:00
joeduffy 65184ec6bd Enable PULUMI_CONFIG envvars, use them
This change adds environment variable fallbacks for configuration
variables, such that you can either set them explicitly, as a specific
variable PULUMI_CONFIG_<K>, or an entire JSON serialized bag via
PULUMI_CONFIG.

This is convenient when simply invoking programs at the command line,
via node, e.g.

    PULUMI_CONFIG_AWS_CONFIG_REGION=us-west-2 node bin/index.js

Our language host also now uses this to communicate config when invoking
a Run RPC, rather than at the command line.  This fixes pulumi/pulumi#336.
2017-10-11 18:41:52 -07:00
Pat Gavlin ee410bfe1e Add a mock resource provider for testing purposes. (#401)
This resource provider accepts a single configuration parameter, `testing:provider:module`, that is the path to a Javascript module that implements CRUD operations for a set of resource types. This allows e.g. a test case to provide its own implementation of these operations that may succeed or fail in interesting ways.

Fixes #338.
2017-10-11 15:27:34 -07:00
CyrusNajmabadi 556345c68e Include environment when computing the hash of closure. (#403)
* Include environment when computing the hash of closure.
2017-10-09 21:46:24 -07:00
joeduffy c5281d29f7 Expose a log module
This exposes the existing runtime logging functionality in a way meant
for 3rd-parties to consume.  This can be useful if we want to introduce
debug logging, warnings, or other things, that fit nicely with the
Pulumi CLI and overall developer workflow.
2017-10-08 12:10:46 -07:00
Luke Hoban 4af1345d4c Move serialization of Closures to JavaScript text to pulumi SDK (#402)
This logic was previously in the `@pulumi/aws` pacakge.  Moving it into the `pulumi` SDK as part of the overall closure serialization logic to make it more broadly accessible, and to centralize this functionality.

Now that it's all in one place, we may decide to remove the publically exposed `Closure` abstraction completely, which may also enable significant simplicifcation to the logic in closure serialization.

Also add one initial test case for this code.

Fixes pulumi/pulumi-aws#14.
2017-10-07 14:29:56 -07:00
joeduffy b7576b9b14 Add a notion of stable properties
This change adds the capability for a resource provider to indicate
that, where an action carried out in response to a diff, a certain set
of properties would be "stable"; that is to say, they are guaranteed
not to change.  As a result, properties may be resolved to their final
values during previewing, avoiding erroneous cascading impacts.

This avoids the ever-annoying situation I keep running into when demoing:
when adding or removing an ingress rule to a security group, we ripple
the impact through the instance, and claim it must be replaced, because
that instance depends on the security group via its name.  Well, the name
is a great example of a stable property, in that it will never change, and
so this is truly unfortunate and always adds uncertainty into the demos.
Particularly since the actual update doesn't need to perform replacements.

This resolves pulumi/pulumi#330.
2017-10-04 08:22:21 -04:00
Matt Ellis ff758e7de6 Merge pull request #370 from pulumi/app-veyor-wip
Get a subset of the build working on Windows
2017-10-02 13:54:09 -07:00
Matt Ellis cb6ac2785e Build, integration tests and publishing on Windows 2017-10-02 13:40:58 -07:00
joeduffy 828d7863fd Implement an invoke runtime function
This wires up the Node.js SDK to the newly added Invoke function
on the resource monitor and provider gRPC interfaces, letting us
expose functions that are implemented by the providers to user code.
2017-09-30 14:53:27 -04:00
Luke Hoban ad5ee5bc04 Support module capture without serialization (#375)
This change adds first class support for capturing objects which are references to loaded Node modules.

If an object to be serialized is found as a loaded module which can be referenced as `require(<name>)`, then is is not serialized and is passed as a new kind of environment entry - `module` which will be de-serialized as a `require` statement.

Supports three cases:
1. built-in modules such as `http` and `path`
2. dependencies in the `node_modules` folder
3. other user-defined modules in the source folder

This allows natural use of `import`s with "inside" code.  For example - note the use of `$` in the outside scope only on the "inside".

```typescript
import * as cloud from "@pulumi/cloud";
import * as $ from "cheerio";
let queue = new pulumi.Topic<string>("sites_to_process");
queue.subscribe("foreachurl", async (url) => {
    let x = $("a", "<a href='foo'>hello</a>");
});
```

Also fixes free variable capture of `this` in arrow functions.

Fixes #342.
2017-09-28 16:44:00 -07:00
Luke Hoban e65348e246 Support for destructing patterns in free variable computation (#365)
Also runs `sdk/nodejs` tests by default during build.
2017-09-25 15:01:31 -07:00
pat@pulumi.com 597db186ec Renames: plan -> preview, deploy -> push.
Part of #353.

These changes also remove all command aliases from the `pulumi` command.
2017-09-22 15:28:03 -07:00
Joe Duffy f6e694c72b Rename pulumi-fabric to pulumi
This includes a few changes:

* The repo name -- and hence the Go modules -- changes from pulumi-fabric to pulumi.

* The Node.js SDK package changes from @pulumi/pulumi-fabric to just pulumi.

* The CLI is renamed from lumi to pulumi.
2017-09-21 19:18:21 -07:00
Luke Hoban c5558e2778 Convert sdk documentation to TypeDoc/JsDoc 2017-09-21 18:15:29 -07:00
Matt Ellis fcc81bac24 Fix nativeruntime module build on Windows
There were two problems:

- node-gyp configure was failing because of different shell syntax
between windows and *nix.
- MSVC 2015 is not smart enough to understand our use of strlen actually
results in a constant value and prevents us from using it to create an
array, move to a macro based solution.
2017-09-21 11:49:03 -07:00
joeduffy 1c2c972d37 Add back Computed<T> as a short-hand
This adds back Computed<T> as a short-hand for Promise<T | undefined>.
Subtly, all resource properties need to permit undefined flowing through
during planning  Rather than forcing the long-hand version, which is easy
to forget, we'll keep the convention of preferring Computed<T>.  It's
just a typedef and the runtime type is just a Promise.
2017-09-20 09:59:32 -07:00
joeduffy f8ee6c570e Eliminate Computed/Property in favor of Promises
As part of pulumi/pulumi-fabric#331, we've been exploring just using
undefined to indicate that a property value is absent during planning.
We also considered blocking the message loop to simplify the overall
programming model, so that all asynchrony is hidden.

It turns out ThereBeDragons 🐲 anytime you try to block the
message loop.  So, we aren't quite sure about that bit.

But the part we are convicted about is that this Computed/Property
model is far too complex.  Furthermore, it's very close to promises, and
yet frustratingly so far away.  Indeed, the original thinking in
pulumi/pulumi-fabric#271 was simply to use promises, but we wanted to
encourage dataflow styles, rather than control flow.  But we muddied up
our thinking by worrying about awaiting a promise that would never resolve.

It turns out we can achieve a middle ground: resolve planning promises to
undefined, so that they don't lead to hangs, but still use promises so
that asynchrony is explicit in the system.  This also avoids blocking the
message loop.  Who knows, this may actually be a fine final destination.
2017-09-20 09:59:32 -07:00