Migrate Sirupsen to sirupsen.

vendor/github.com/gravitational/trace/LICENSE

@@ -0,0 +1,201 @@
+Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
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+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
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+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright 2015 Gravitational, Inc.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

vendor/github.com/gravitational/trace/errors.go

@@ -0,0 +1,448 @@
+/*
+Copyright 2015 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package trace
+
+import (
+	"crypto/x509"
+	"fmt"
+	"io"
+	"net"
+	"net/url"
+	"os"
+)
+
+// NotFound returns new instance of not found error
+func NotFound(message string, args ...interface{}) error {
+	return WrapWithMessage(&NotFoundError{
+		Message: fmt.Sprintf(message, args...),
+	}, message, args...)
+}
+
+// NotFoundError indicates that object has not been found
+type NotFoundError struct {
+	Message string `json:"message"`
+}
+
+// IsNotFoundError returns true to indicate that is NotFoundError
+func (e *NotFoundError) IsNotFoundError() bool {
+	return true
+}
+
+// Error returns log friendly description of an error
+func (e *NotFoundError) Error() string {
+	if e.Message != "" {
+		return e.Message
+	}
+	return "object not found"
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (e *NotFoundError) OrigError() error {
+	return e
+}
+
+// IsNotFound returns whether this error is of NotFoundError type
+func IsNotFound(e error) bool {
+	type nf interface {
+		IsNotFoundError() bool
+	}
+	err := Unwrap(e)
+	_, ok := err.(nf)
+	if !ok {
+		return os.IsNotExist(err)
+	}
+	return ok
+}
+
+// AlreadyExists returns a new instance of AlreadyExists error
+func AlreadyExists(message string, args ...interface{}) error {
+	return WrapWithMessage(&AlreadyExistsError{
+		fmt.Sprintf(message, args...),
+	}, message, args...)
+}
+
+// AlreadyExistsError indicates that there's a duplicate object that already
+// exists in the storage/system
+type AlreadyExistsError struct {
+	Message string `json:"message"`
+}
+
+// Error returns log friendly description of an error
+func (n *AlreadyExistsError) Error() string {
+	if n.Message != "" {
+		return n.Message
+	}
+	return "object already exists"
+}
+
+// IsAlreadyExistsError indicates that this error of the AlreadyExistsError type
+func (AlreadyExistsError) IsAlreadyExistsError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (e *AlreadyExistsError) OrigError() error {
+	return e
+}
+
+// IsAlreadyExists returns whether this is error indicating that object
+// already exists
+func IsAlreadyExists(e error) bool {
+	type ae interface {
+		IsAlreadyExistsError() bool
+	}
+	_, ok := Unwrap(e).(ae)
+	return ok
+}
+
+// BadParameter returns a new instance of BadParameterError
+func BadParameter(message string, args ...interface{}) error {
+	return WrapWithMessage(&BadParameterError{
+		Message: fmt.Sprintf(message, args...),
+	}, message, args...)
+}
+
+// BadParameterError indicates that something is wrong with passed
+// parameter to API method
+type BadParameterError struct {
+	Message string `json:"message"`
+}
+
+// Error returns log friendly description of an error
+func (b *BadParameterError) Error() string {
+	return b.Message
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (b *BadParameterError) OrigError() error {
+	return b
+}
+
+// IsBadParameterError indicates that this error is of BadParameterError type
+func (b *BadParameterError) IsBadParameterError() bool {
+	return true
+}
+
+// IsBadParameter returns whether this error is of BadParameterType
+func IsBadParameter(e error) bool {
+	type bp interface {
+		IsBadParameterError() bool
+	}
+	_, ok := Unwrap(e).(bp)
+	return ok
+}
+
+// CompareFailed returns new instance of CompareFailedError
+func CompareFailed(message string, args ...interface{}) error {
+	return WrapWithMessage(&CompareFailedError{Message: fmt.Sprintf(message, args...)}, message, args...)
+}
+
+// CompareFailedError indicates a failed comparison (e.g. bad password or hash)
+type CompareFailedError struct {
+	// Message is user-friendly error message
+	Message string `json:"message"`
+}
+
+// Error is debug - friendly message
+func (e *CompareFailedError) Error() string {
+	if e.Message != "" {
+		return e.Message
+	}
+	return "compare failed"
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (e *CompareFailedError) OrigError() error {
+	return e
+}
+
+// IsCompareFailedError indicates that this is CompareFailedError
+func (e *CompareFailedError) IsCompareFailedError() bool {
+	return true
+}
+
+// IsCompareFailed detects if this error is of CompareFailed type
+func IsCompareFailed(e error) bool {
+	type cf interface {
+		IsCompareFailedError() bool
+	}
+	_, ok := Unwrap(e).(cf)
+	return ok
+}
+
+// AccessDenied returns new instance of AccessDeniedError
+func AccessDenied(message string, args ...interface{}) error {
+	return WrapWithMessage(&AccessDeniedError{
+		Message: fmt.Sprintf(message, args...),
+	}, message, args...)
+}
+
+// AccessDeniedError indicates denied access
+type AccessDeniedError struct {
+	Message string `json:"message"`
+}
+
+// Error is debug - friendly error message
+func (e *AccessDeniedError) Error() string {
+	if e.Message != "" {
+		return e.Message
+	}
+	return "access denied"
+}
+
+// IsAccessDeniedError indicates that this error is of AccessDeniedError type
+func (e *AccessDeniedError) IsAccessDeniedError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (e *AccessDeniedError) OrigError() error {
+	return e
+}
+
+// IsAccessDenied detects if this error is of AccessDeniedError type
+func IsAccessDenied(e error) bool {
+	type ad interface {
+		IsAccessDeniedError() bool
+	}
+	_, ok := Unwrap(e).(ad)
+	return ok
+}
+
+// ConvertSystemError converts system error to appropriate trace error
+// if it is possible, otherwise, returns original error
+func ConvertSystemError(err error) error {
+	innerError := Unwrap(err)
+
+	if os.IsExist(innerError) {
+		return WrapWithMessage(&AlreadyExistsError{Message: innerError.Error()}, innerError.Error())
+	}
+	if os.IsNotExist(innerError) {
+		return WrapWithMessage(&NotFoundError{Message: innerError.Error()}, innerError.Error())
+	}
+	if os.IsPermission(innerError) {
+		return WrapWithMessage(&AccessDeniedError{Message: innerError.Error()}, innerError.Error())
+	}
+	switch realErr := innerError.(type) {
+	case *net.OpError:
+		return WrapWithMessage(&ConnectionProblemError{
+			Message: realErr.Error(),
+			Err:     realErr}, realErr.Error())
+	case *os.PathError:
+		message := fmt.Sprintf("failed to execute command %v error:  %v", realErr.Path, realErr.Err)
+		return WrapWithMessage(&AccessDeniedError{
+			Message: message,
+		}, message)
+	case x509.SystemRootsError, x509.UnknownAuthorityError:
+		return wrapWithDepth(&TrustError{Err: innerError}, 2)
+	}
+	if _, ok := innerError.(net.Error); ok {
+		return WrapWithMessage(&ConnectionProblemError{
+			Message: innerError.Error(),
+			Err:     innerError}, innerError.Error())
+	}
+	return err
+}
+
+// ConnectionProblem returns new instance of ConnectionProblemError
+func ConnectionProblem(err error, message string, args ...interface{}) error {
+	return WrapWithMessage(&ConnectionProblemError{
+		Message: fmt.Sprintf(message, args...),
+		Err:     err,
+	}, message, args...)
+}
+
+// ConnectionProblemError indicates a network related problem
+type ConnectionProblemError struct {
+	Message string `json:"message"`
+	Err     error  `json:"-"`
+}
+
+// Error is debug - friendly error message
+func (c *ConnectionProblemError) Error() string {
+	if c.Err == nil {
+		return c.Message
+	}
+	return c.Err.Error()
+}
+
+// IsConnectionProblemError indicates that this error is of ConnectionProblemError type
+func (c *ConnectionProblemError) IsConnectionProblemError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (c *ConnectionProblemError) OrigError() error {
+	return c
+}
+
+// IsConnectionProblem returns whether this error is of ConnectionProblemError
+func IsConnectionProblem(e error) bool {
+	type ad interface {
+		IsConnectionProblemError() bool
+	}
+	_, ok := Unwrap(e).(ad)
+	return ok
+}
+
+// LimitExceeded returns whether new instance of LimitExceededError
+func LimitExceeded(message string, args ...interface{}) error {
+	return WrapWithMessage(&LimitExceededError{
+		Message: fmt.Sprintf(message, args...),
+	}, message, args...)
+}
+
+// LimitExceededError indicates rate limit or connection limit problem
+type LimitExceededError struct {
+	Message string `json:"message"`
+}
+
+// Error is debug - friendly error message
+func (c *LimitExceededError) Error() string {
+	return c.Message
+}
+
+// IsLimitExceededError indicates that this error is of ConnectionProblem
+func (c *LimitExceededError) IsLimitExceededError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (c *LimitExceededError) OrigError() error {
+	return c
+}
+
+// IsLimitExceeded detects if this error is of LimitExceededError
+func IsLimitExceeded(e error) bool {
+	type ad interface {
+		IsLimitExceededError() bool
+	}
+	_, ok := Unwrap(e).(ad)
+	return ok
+}
+
+// TrustError indicates trust-related validation error (e.g. untrusted cert)
+type TrustError struct {
+	// Err is original error
+	Err     error `json:"error"`
+	Message string
+}
+
+// Error returns log-friendly error description
+func (t *TrustError) Error() string {
+	return t.Err.Error()
+}
+
+// IsTrustError indicates that this error is of TrustError type
+func (*TrustError) IsTrustError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (t *TrustError) OrigError() error {
+	return t
+}
+
+// IsTrustError returns if this is a trust error
+func IsTrustError(e error) bool {
+	type te interface {
+		IsTrustError() bool
+	}
+	_, ok := Unwrap(e).(te)
+	return ok
+}
+
+// OAuth2 returns new instance of OAuth2Error
+func OAuth2(code, message string, query url.Values) Error {
+	return WrapWithMessage(&OAuth2Error{
+		Code:    code,
+		Message: message,
+		Query:   query,
+	}, message)
+}
+
+// OAuth2Error defined an error used in OpenID Connect Flow (OIDC)
+type OAuth2Error struct {
+	Code    string     `json:"code"`
+	Message string     `json:"message"`
+	Query   url.Values `json:"query"`
+}
+
+//Error returns log friendly description of an error
+func (o *OAuth2Error) Error() string {
+	return fmt.Sprintf("OAuth2 error code=%v, message=%v", o.Code, o.Message)
+}
+
+// IsOAuth2Error returns whether this error of OAuth2Error type
+func (o *OAuth2Error) IsOAuth2Error() bool {
+	return true
+}
+
+// IsOAuth2 returns if this is a OAuth2-related error
+func IsOAuth2(e error) bool {
+	type oe interface {
+		IsOAuth2Error() bool
+	}
+	_, ok := Unwrap(e).(oe)
+	return ok
+}
+
+// IsEOF returns true if the passed error is io.EOF
+func IsEOF(e error) bool {
+	return Unwrap(e) == io.EOF
+}
+
+// Retry return new instance of RetryError which indicates a transient error type
+func Retry(err error, message string, args ...interface{}) error {
+	return WrapWithMessage(&RetryError{
+		Message: fmt.Sprintf(message, args...),
+		Err:     err,
+	}, message, args...)
+}
+
+// RetryError indicates a transient error type
+type RetryError struct {
+	Message string `json:"message"`
+	Err     error  `json:"-"`
+}
+
+// Error is debug-friendly error message
+func (c *RetryError) Error() string {
+	if c.Err == nil {
+		return c.Message
+	}
+	return c.Err.Error()
+}
+
+// IsRetryError indicates that this error is of RetryError type
+func (c *RetryError) IsRetryError() bool {
+	return true
+}
+
+// OrigError returns original error (in this case this is the error itself)
+func (c *RetryError) OrigError() error {
+	return c
+}
+
+// IsRetryError returns whether this error is of ConnectionProblemError
+func IsRetryError(e error) bool {
+	type ad interface {
+		IsRetryError() bool
+	}
+	_, ok := Unwrap(e).(ad)
+	return ok
+}

vendor/github.com/gravitational/trace/httplib.go

@@ -0,0 +1,129 @@
+package trace
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+// WriteError sets up HTTP error response and writes it to writer w
+func WriteError(w http.ResponseWriter, err error) {
+	if IsAggregate(err) {
+		for i := 0; i < maxHops; i++ {
+			var aggErr Aggregate
+			var ok bool
+			if aggErr, ok = Unwrap(err).(Aggregate); !ok {
+				break
+			}
+			errors := aggErr.Errors()
+			if len(errors) == 0 {
+				break
+			}
+			err = errors[0]
+		}
+	}
+	writeError(w, err)
+}
+
+// ErrorToCode returns an appropriate HTTP status code based on the provided error type
+func ErrorToCode(err error) int {
+	if IsNotFound(err) {
+		return http.StatusNotFound
+	} else if IsBadParameter(err) || IsOAuth2(err) {
+		return http.StatusBadRequest
+	} else if IsCompareFailed(err) {
+		return http.StatusPreconditionFailed
+	} else if IsAccessDenied(err) {
+		return http.StatusForbidden
+	} else if IsAlreadyExists(err) {
+		return http.StatusConflict
+	} else if IsLimitExceeded(err) {
+		return http.StatusTooManyRequests
+	} else if IsConnectionProblem(err) {
+		return http.StatusGatewayTimeout
+	}
+	return http.StatusInternalServerError
+}
+
+func writeError(w http.ResponseWriter, err error) {
+	replyJSON(w, ErrorToCode(err), err)
+}
+
+// ReadError converts http error to internal error type
+// based on HTTP response code and HTTP body contents
+// if status code does not indicate error, it will return nil
+func ReadError(statusCode int, re []byte) error {
+	var e error
+	switch statusCode {
+	case http.StatusNotFound:
+		e = &NotFoundError{Message: string(re)}
+	case http.StatusBadRequest:
+		e = &BadParameterError{Message: string(re)}
+	case http.StatusPreconditionFailed:
+		e = &CompareFailedError{Message: string(re)}
+	case http.StatusForbidden:
+		e = &AccessDeniedError{Message: string(re)}
+	case http.StatusConflict:
+		e = &AlreadyExistsError{Message: string(re)}
+	case http.StatusTooManyRequests:
+		e = &LimitExceededError{Message: string(re)}
+	case http.StatusGatewayTimeout:
+		e = &ConnectionProblemError{Message: string(re)}
+	default:
+		if statusCode < 200 || statusCode > 299 {
+			return Errorf(string(re))
+		}
+		return nil
+	}
+	return unmarshalError(e, re)
+}
+
+func replyJSON(w http.ResponseWriter, code int, err error) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(code)
+
+	var out []byte
+	if IsDebug() {
+		// trace error can marshal itself,
+		// otherwise capture error message and marshal it explicitly
+		var obj interface{} = err
+		if _, ok := err.(*TraceErr); !ok {
+			obj = message{Message: err.Error()}
+		}
+		out, err = json.MarshalIndent(obj, "", "    ")
+		if err != nil {
+			out = []byte(fmt.Sprintf(`{"message": "internal marshal error: %v"}`, err))
+		}
+	} else {
+		innerError := err
+		if terr, ok := err.(Error); ok {
+			innerError = terr.OrigError()
+		}
+		out, err = json.Marshal(message{Message: innerError.Error()})
+	}
+	w.Write(out)
+}
+
+type message struct {
+	Message string `json:"message"`
+}
+
+func unmarshalError(err error, responseBody []byte) error {
+	if len(responseBody) == 0 {
+		return err
+	}
+	var raw RawTrace
+	if err2 := json.Unmarshal(responseBody, &raw); err2 != nil {
+		return err
+	}
+	if len(raw.Traces) != 0 && len(raw.Err) != 0 {
+		// try to capture traces, if there are any
+		err2 := json.Unmarshal(raw.Err, err)
+		if err2 != nil {
+			return err
+		}
+		return &TraceErr{Traces: raw.Traces, Err: err, Message: raw.Message}
+	}
+	json.Unmarshal(responseBody, err)
+	return err
+}

vendor/github.com/gravitational/trace/log.go

@@ -0,0 +1,240 @@
+/*
+Copyright 2015 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package trace implements utility functions for capturing logs
+package trace
+
+import (
+	"bytes"
+	"fmt"
+	"regexp"
+	rundebug "runtime/debug"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+
+	"runtime"
+)
+
+const (
+	// FileField is a field with code file added to structured traces
+	FileField = "file"
+	// FunctionField is a field with function name
+	FunctionField = "func"
+	// LevelField returns logging level as set by logrus
+	LevelField = "level"
+	// Component is a field that represents component - e.g. service or
+	// function
+	Component = "trace.component"
+	// ComponentFields is a fields component
+	ComponentFields = "trace.fields"
+	// DefaultComponentPadding is a default padding for component field
+	DefaultComponentPadding = 11
+	// DefaultLevelPadding is a default padding for level field
+	DefaultLevelPadding = 4
+)
+
+// TextFormatter is logrus-compatible formatter and adds
+// file and line details to every logged entry.
+type TextFormatter struct {
+	// DisableTimestamp disables timestamp output (useful when outputting to
+	// systemd logs)
+	DisableTimestamp bool
+	// ComponentPadding is a padding to pick when displaying
+	// and formatting component field, defaults to DefaultComponentPadding
+	ComponentPadding int
+}
+
+// Format implements logrus.Formatter interface and adds file and line
+func (tf *TextFormatter) Format(e *log.Entry) (data []byte, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			data = append([]byte("panic in log formatter\n"), rundebug.Stack()...)
+			return
+		}
+	}()
+	var file string
+	if frameNo := findFrame(); frameNo != -1 {
+		t := newTrace(frameNo, nil)
+		file = t.Loc()
+	}
+
+	w := &writer{}
+
+	// time
+	if !tf.DisableTimestamp {
+		w.writeField(e.Time.Format(time.RFC3339))
+	}
+
+	// level
+	w.writeField(strings.ToUpper(padMax(e.Level.String(), DefaultLevelPadding)))
+
+	// component, always output
+	componentI, ok := e.Data[Component]
+	if !ok {
+		componentI = ""
+	}
+	component, ok := componentI.(string)
+	if !ok {
+		component = fmt.Sprintf("%v", componentI)
+	}
+	padding := DefaultComponentPadding
+	if tf.ComponentPadding != 0 {
+		padding = tf.ComponentPadding
+	}
+	if w.Len() > 0 {
+		w.WriteByte(' ')
+	}
+	if component != "" {
+		component = fmt.Sprintf("[%v]", component)
+	}
+	component = strings.ToUpper(padMax(component, padding))
+	if component[len(component)-1] != ' ' {
+		component = component[:len(component)-1] + "]"
+	}
+	w.WriteString(component)
+
+	// message
+	if e.Message != "" {
+		w.writeField(e.Message)
+	}
+
+	// rest of the fields
+	if len(e.Data) > 0 {
+		w.writeMap(e.Data)
+	}
+
+	// file, if present, always last
+	if file != "" {
+		w.writeField(file)
+	}
+
+	w.WriteByte('\n')
+	data = w.Bytes()
+	return
+}
+
+// JSONFormatter implements logrus.Formatter interface and adds file and line
+// properties to JSON entries
+type JSONFormatter struct {
+	log.JSONFormatter
+}
+
+// Format implements logrus.Formatter interface
+func (j *JSONFormatter) Format(e *log.Entry) ([]byte, error) {
+	if frameNo := findFrame(); frameNo != -1 {
+		t := newTrace(frameNo, nil)
+		new := e.WithFields(log.Fields{
+			FileField:     t.Loc(),
+			FunctionField: t.FuncName(),
+		})
+		new.Time = e.Time
+		new.Level = e.Level
+		new.Message = e.Message
+		e = new
+	}
+	return (&j.JSONFormatter).Format(e)
+}
+
+var r = regexp.MustCompile(`github\.com/(S|s)irupsen/logrus`)
+
+func findFrame() int {
+	for i := 3; i < 10; i++ {
+		_, file, _, ok := runtime.Caller(i)
+		if !ok {
+			return -1
+		}
+		if !r.MatchString(file) {
+			return i
+		}
+	}
+	return -1
+}
+
+type writer struct {
+	bytes.Buffer
+}
+
+func (w *writer) writeField(value interface{}) {
+	if w.Len() > 0 {
+		w.WriteByte(' ')
+	}
+	w.writeValue(value)
+}
+
+func (w *writer) writeValue(value interface{}) {
+	stringVal, ok := value.(string)
+	if !ok {
+		stringVal = fmt.Sprint(value)
+	}
+	if !needsQuoting(stringVal) {
+		w.WriteString(stringVal)
+	} else {
+		w.WriteString(fmt.Sprintf("%q", stringVal))
+	}
+}
+
+func (w *writer) writeKeyValue(key string, value interface{}) {
+	if w.Len() > 0 {
+		w.WriteByte(' ')
+	}
+	w.WriteString(key)
+	w.WriteByte(':')
+	w.writeValue(value)
+}
+
+func (w *writer) writeMap(m map[string]interface{}) {
+	if len(m) == 0 {
+		return
+	}
+	keys := make([]string, 0, len(m))
+	for key := range m {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	for _, key := range keys {
+		if key == Component {
+			continue
+		}
+		switch val := m[key].(type) {
+		case log.Fields:
+			w.writeMap(val)
+		default:
+			w.writeKeyValue(key, val)
+		}
+	}
+}
+
+func needsQuoting(text string) bool {
+	for _, r := range text {
+		if !strconv.IsPrint(r) {
+			return true
+		}
+	}
+	return false
+}
+
+func padMax(in string, chars int) string {
+	switch {
+	case len(in) < chars:
+		return in + strings.Repeat(" ", chars-len(in))
+	default:
+		return in[:chars]
+	}
+}

vendor/github.com/gravitational/trace/trace.go

@@ -0,0 +1,381 @@
+/*
+Copyright 2015 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package trace implements utility functions for capturing debugging
+// information about file and line in error reports and logs.
+package trace
+
+import (
+	"encoding/json"
+	"fmt"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync/atomic"
+
+	"golang.org/x/net/context"
+)
+
+var debug int32
+
+// SetDebug turns on/off debugging mode, that causes Fatalf to panic
+func SetDebug(enabled bool) {
+	if enabled {
+		atomic.StoreInt32(&debug, 1)
+	} else {
+		atomic.StoreInt32(&debug, 0)
+	}
+}
+
+// IsDebug returns true if debug mode is on, false otherwize
+func IsDebug() bool {
+	return atomic.LoadInt32(&debug) == 1
+}
+
+// Wrap takes the original error and wraps it into the Trace struct
+// memorizing the context of the error.
+func Wrap(err error, args ...interface{}) Error {
+	if len(args) > 0 {
+		format := args[0]
+		args = args[1:]
+		return WrapWithMessage(err, format, args...)
+	}
+	return wrapWithDepth(err, 2)
+}
+
+// Unwrap unwraps error to it's original error
+func Unwrap(err error) error {
+	if terr, ok := err.(Error); ok {
+		return terr.OrigError()
+	}
+	return err
+}
+
+// UserMessage returns user-friendly part of the error
+func UserMessage(err error) string {
+	if err == nil {
+		return ""
+	}
+	if wrap, ok := err.(Error); ok {
+		return wrap.UserMessage()
+	}
+	return err.Error()
+}
+
+// DebugReport returns debug report with all known information
+// about the error including stack trace if it was captured
+func DebugReport(err error) string {
+	if err == nil {
+		return ""
+	}
+	if wrap, ok := err.(Error); ok {
+		return wrap.DebugReport()
+	}
+	return err.Error()
+}
+
+// WrapWithMessage wraps the original error into Error and adds user message if any
+func WrapWithMessage(err error, message interface{}, args ...interface{}) Error {
+	trace := wrapWithDepth(err, 3)
+	if trace != nil {
+		trace.AddUserMessage(message, args...)
+	}
+	return trace
+}
+
+func wrapWithDepth(err error, depth int) Error {
+	if err == nil {
+		return nil
+	}
+	var trace Error
+	if wrapped, ok := err.(Error); ok {
+		trace = wrapped
+	} else {
+		trace = newTrace(depth+1, err)
+	}
+
+	return trace
+}
+
+// Errorf is similar to fmt.Errorf except that it captures
+// more information about the origin of error, such as
+// callee, line number and function that simplifies debugging
+func Errorf(format string, args ...interface{}) (err error) {
+	err = fmt.Errorf(format, args...)
+	trace := wrapWithDepth(err, 2)
+	trace.AddUserMessage(format, args...)
+	return trace
+}
+
+// Fatalf - If debug is false Fatalf calls Errorf. If debug is
+// true Fatalf calls panic
+func Fatalf(format string, args ...interface{}) error {
+	if IsDebug() {
+		panic(fmt.Sprintf(format, args))
+	} else {
+		return Errorf(format, args)
+	}
+}
+
+func newTrace(depth int, err error) *TraceErr {
+	var pc [32]uintptr
+	count := runtime.Callers(depth+1, pc[:])
+
+	traces := make(Traces, count)
+	for i := 0; i < count; i++ {
+		fn := runtime.FuncForPC(pc[i])
+		filePath, line := fn.FileLine(pc[i])
+		traces[i] = Trace{
+			Func: fn.Name(),
+			Path: filePath,
+			Line: line,
+		}
+	}
+	return &TraceErr{
+		err,
+		traces,
+		"",
+	}
+}
+
+// Traces is a list of trace entries
+type Traces []Trace
+
+// SetTraces adds new traces to the list
+func (s Traces) SetTraces(traces ...Trace) {
+	s = append(s, traces...)
+}
+
+// Func returns first function in trace list
+func (s Traces) Func() string {
+	if len(s) == 0 {
+		return ""
+	}
+	return s[0].Func
+}
+
+// Func returns just function name
+func (s Traces) FuncName() string {
+	if len(s) == 0 {
+		return ""
+	}
+	fn := filepath.ToSlash(s[0].Func)
+	idx := strings.LastIndex(fn, "/")
+	if idx == -1 || idx == len(fn)-1 {
+		return fn
+	}
+	return fn[idx+1:]
+}
+
+// Loc points to file/line location in the code
+func (s Traces) Loc() string {
+	if len(s) == 0 {
+		return ""
+	}
+	return s[0].String()
+}
+
+// String returns debug-friendly representaton of trace stack
+func (s Traces) String() string {
+	if len(s) == 0 {
+		return ""
+	}
+	out := make([]string, len(s))
+	for i, t := range s {
+		out[i] = fmt.Sprintf("\t%v:%v %v", t.Path, t.Line, t.Func)
+	}
+	return strings.Join(out, "\n")
+}
+
+// Trace stores structured trace entry, including file line and path
+type Trace struct {
+	// Path is a full file path
+	Path string `json:"path"`
+	// Func is a function name
+	Func string `json:"func"`
+	// Line is a code line number
+	Line int `json:"line"`
+}
+
+// String returns debug-friendly representation of this trace
+func (t *Trace) String() string {
+	dir, file := filepath.Split(t.Path)
+	dirs := strings.Split(filepath.ToSlash(filepath.Clean(dir)), "/")
+	if len(dirs) != 0 {
+		file = filepath.Join(dirs[len(dirs)-1], file)
+	}
+	return fmt.Sprintf("%v:%v", file, t.Line)
+}
+
+// TraceErr contains error message and some additional
+// information about the error origin
+type TraceErr struct {
+	Err     error `json:"error"`
+	Traces  `json:"traces"`
+	Message string `json:"message,omitemtpy"`
+}
+
+type RawTrace struct {
+	Err     json.RawMessage `json:"error"`
+	Traces  `json:"traces"`
+	Message string `json:"message"`
+}
+
+// AddUserMessage adds user-friendly message describing the error nature
+func (e *TraceErr) AddUserMessage(formatArg interface{}, rest ...interface{}) {
+	newMessage := fmt.Sprintf(fmt.Sprintf("%v", formatArg), rest...)
+	if len(e.Message) == 0 {
+		e.Message = newMessage
+	} else {
+		e.Message = strings.Join([]string{e.Message, newMessage}, ", ")
+	}
+}
+
+// UserMessage returns user-friendly error message
+func (e *TraceErr) UserMessage() string {
+	if e.Message != "" {
+		return e.Message
+	}
+	return e.Err.Error()
+}
+
+// DebugReport returns develeoper-friendly error report
+func (e *TraceErr) DebugReport() string {
+	return fmt.Sprintf("\nERROR REPORT:\nOriginal Error: %T %v\nStack Trace:\n%v\nUser Message: %v\n", e.Err, e.Err.Error(), e.Traces.String(), e.Message)
+}
+
+// Error returns user-friendly error message when not in debug mode
+func (e *TraceErr) Error() string {
+	if IsDebug() {
+		return e.DebugReport()
+	}
+	return e.UserMessage()
+}
+
+// OrigError returns original wrapped error
+func (e *TraceErr) OrigError() error {
+	err := e.Err
+	// this is not an endless loop because I'm being
+	// paranoid, this is a safe protection against endless
+	// loops
+	for i := 0; i < maxHops; i++ {
+		newerr, ok := err.(Error)
+		if !ok {
+			break
+		}
+		if newerr.OrigError() != err {
+			err = newerr.OrigError()
+		}
+	}
+	return err
+}
+
+// maxHops is a max supported nested depth for errors
+const maxHops = 50
+
+// Error is an interface that helps to adapt usage of trace in the code
+// When applications define new error types, they can implement the interface
+// So error handlers can use OrigError() to retrieve error from the wrapper
+type Error interface {
+	error
+	// OrigError returns original error wrapped in this error
+	OrigError() error
+	// AddMessage adds formatted user-facing message
+	// to the error, depends on the implementation,
+	// usually works as fmt.Sprintf(formatArg, rest...)
+	// but implementations can choose another way, e.g. treat
+	// arguments as structured args
+	AddUserMessage(formatArg interface{}, rest ...interface{})
+
+	// UserMessage returns user-friendly error message
+	UserMessage() string
+
+	// DebugReport returns develeoper-friendly error report
+	DebugReport() string
+}
+
+// NewAggregate creates a new aggregate instance from the specified
+// list of errors
+func NewAggregate(errs ...error) error {
+	// filter out possible nil values
+	var nonNils []error
+	for _, err := range errs {
+		if err != nil {
+			nonNils = append(nonNils, err)
+		}
+	}
+	if len(nonNils) == 0 {
+		return nil
+	}
+	return wrapWithDepth(aggregate(nonNils), 2)
+}
+
+// NewAggregateFromChannel creates a new aggregate instance from the provided
+// errors channel.
+//
+// A context.Context can be passed in so the caller has the ability to cancel
+// the operation. If this is not desired, simply pass context.Background().
+func NewAggregateFromChannel(errCh chan error, ctx context.Context) error {
+	var errs []error
+
+Loop:
+	for {
+		select {
+		case err, ok := <-errCh:
+			if !ok { // the channel is closed, time to exit
+				break Loop
+			}
+			errs = append(errs, err)
+		case <-ctx.Done():
+			break Loop
+		}
+	}
+
+	return NewAggregate(errs...)
+}
+
+// Aggregate interface combines several errors into one error
+type Aggregate interface {
+	error
+	// Errors obtains the list of errors this aggregate combines
+	Errors() []error
+}
+
+// aggregate implements Aggregate
+type aggregate []error
+
+// Error implements the error interface
+func (r aggregate) Error() string {
+	if len(r) == 0 {
+		return ""
+	}
+	output := r[0].Error()
+	for i := 1; i < len(r); i++ {
+		output = fmt.Sprintf("%v, %v", output, r[i])
+	}
+	return output
+}
+
+// Errors obtains the list of errors this aggregate combines
+func (r aggregate) Errors() []error {
+	return []error(r)
+}
+
+// IsAggregate returns whether this error of Aggregate error type
+func IsAggregate(err error) bool {
+	_, ok := Unwrap(err).(Aggregate)
+	return ok
+}

vendor/github.com/gravitational/trace/udphook.go

@@ -0,0 +1,112 @@
+package trace
+
+import (
+	"encoding/json"
+	"net"
+	"time"
+
+	"github.com/jonboulle/clockwork"
+	log "github.com/sirupsen/logrus"
+)
+
+const (
+	// UDPDefaultAddr is a default address to emit logs to
+	UDPDefaultAddr = "127.0.0.1:5000"
+	// UDPDefaultNet is a default network
+	UDPDefaultNet = "udp"
+)
+
+// UDPOptionSetter represents functional arguments passed to ELKHook
+type UDPOptionSetter func(f *UDPHook)
+
+// NewUDPHook returns logrus-compatible hook that sends data to UDP socket
+func NewUDPHook(opts ...UDPOptionSetter) (*UDPHook, error) {
+	f := &UDPHook{}
+	for _, o := range opts {
+		o(f)
+	}
+	if f.Clock == nil {
+		f.Clock = clockwork.NewRealClock()
+	}
+	if f.clientNet == "" {
+		f.clientNet = UDPDefaultNet
+	}
+	if f.clientAddr == "" {
+		f.clientAddr = UDPDefaultAddr
+	}
+	addr, err := net.ResolveUDPAddr(f.clientNet, f.clientAddr)
+	if err != nil {
+		return nil, Wrap(err)
+	}
+	conn, err := net.ListenPacket("udp", ":0")
+	if err != nil {
+		return nil, Wrap(err)
+	}
+	f.addr = addr
+	f.conn = conn.(*net.UDPConn)
+	return f, nil
+}
+
+type UDPHook struct {
+	Clock      clockwork.Clock
+	clientNet  string
+	clientAddr string
+	addr       *net.UDPAddr
+	conn       *net.UDPConn
+}
+
+type Frame struct {
+	Time    time.Time              `json:"time"`
+	Type    string                 `json:"type"`
+	Entry   map[string]interface{} `json:"entry"`
+	Message string                 `json:"message"`
+	Level   string                 `json:"level"`
+}
+
+// Fire fires the event to the ELK beat
+func (elk *UDPHook) Fire(e *log.Entry) error {
+	// Make a copy to safely modify
+	entry := e.WithFields(nil)
+	if frameNo := findFrame(); frameNo != -1 {
+		t := newTrace(frameNo-1, nil)
+		entry.Data[FileField] = t.String()
+		entry.Data[FunctionField] = t.Func()
+	}
+	data, err := json.Marshal(Frame{
+		Time:    elk.Clock.Now().UTC(),
+		Type:    "trace",
+		Entry:   entry.Data,
+		Message: entry.Message,
+		Level:   entry.Level.String(),
+	})
+	if err != nil {
+		return Wrap(err)
+	}
+
+	conn, err := net.ListenPacket("udp", ":0")
+	if err != nil {
+		return Wrap(err)
+	}
+	defer conn.Close()
+
+	resolvedAddr, err := net.ResolveUDPAddr("udp", "127.0.0.1:5000")
+	if err != nil {
+		return Wrap(err)
+	}
+
+	_, err = (conn.(*net.UDPConn)).WriteToUDP(data, resolvedAddr)
+	return Wrap(err)
+
+}
+
+// Levels returns logging levels supported by logrus
+func (elk *UDPHook) Levels() []log.Level {
+	return []log.Level{
+		log.PanicLevel,
+		log.FatalLevel,
+		log.ErrorLevel,
+		log.WarnLevel,
+		log.InfoLevel,
+		log.DebugLevel,
+	}
+}