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## Functions

### OnFailure(Status const \&)

Return true if the retry loop should continue after `status`.
This functions are typically used in a retry loop, where they control whether to continue, whether a failure should be retried, and finally how to format the error message.

    std::unique_ptr<RetryPolicy> policy = ....;
    Status status;
    while (!policy->IsExhausted()) {
      auto response = try_rpc();  // typically `response` is StatusOr<T>
      if (response.ok()) return response;
      status = std::move(response).status();
      if (!policy->OnFailure(response->status())) {
        if (policy->IsPermanentFailure(response->status()) {
          return StatusModifiedToSayPermanentFailureCausedTheProblem(status);
        }
        return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);
      }
      // sleep, which may exhaust the policy, even if it was not exhausted in
      // the last call.
    }
    return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);

| **Parameter** ||
|---|---|
| **Name** | **Description** |
| `status` | `Status const &` |

| **Returns** ||
|---|---|
| **Type** | **Description** |
| `bool` |   |

### IsExhausted() const

Return true if the retry policy should stop as the retry limit has been reached.
This functions are typically used in a retry loop, where they control whether to continue, whether a failure should be retried, and finally how to format the error message.

    std::unique_ptr<RetryPolicy> policy = ....;
    Status status;
    while (!policy->IsExhausted()) {
      auto response = try_rpc();  // typically `response` is StatusOr<T>
      if (response.ok()) return response;
      status = std::move(response).status();
      if (!policy->OnFailure(response->status())) {
        if (policy->IsPermanentFailure(response->status()) {
          return StatusModifiedToSayPermanentFailureCausedTheProblem(status);
        }
        return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);
      }
      // sleep, which may exhaust the policy, even if it was not exhausted in
      // the last call.
    }
    return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);

| **Returns** ||
|---|---|
| **Type** | **Description** |
| `bool` |   |

### IsPermanentFailure(Status const \&) const

Return true if `status` is treated as a permanent (and therefore non-retryable) error.
This functions are typically used in a retry loop, where they control whether to continue, whether a failure should be retried, and finally how to format the error message.

    std::unique_ptr<RetryPolicy> policy = ....;
    Status status;
    while (!policy->IsExhausted()) {
      auto response = try_rpc();  // typically `response` is StatusOr<T>
      if (response.ok()) return response;
      status = std::move(response).status();
      if (!policy->OnFailure(response->status())) {
        if (policy->IsPermanentFailure(response->status()) {
          return StatusModifiedToSayPermanentFailureCausedTheProblem(status);
        }
        return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);
      }
      // sleep, which may exhaust the policy, even if it was not exhausted in
      // the last call.
    }
    return StatusModifiedToSayPolicyExhaustionCausedTheProblem(status);

| **Parameter** ||
|---|---|
| **Name** | **Description** |
| `status` | `Status const &` |

| **Returns** ||
|---|---|
| **Type** | **Description** |
| `bool` |   |